ATN IPS Guidance Material
ACP/WGI WP 711
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
64th MEETING OF WORKING GROUP I
MontrealMontréal, CanadaCanada 022-067 JuneDecember 20087
|Agenda Item : 4 |Guidance Material |
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ATN IPS Guidance Material
(Presented by Kelly KitchensEivan Cerasi)
|SUMMARY |
|This working paper provides an includes comments on the IPS Guidance Material presented at WGI 3update of |
|the Guidance Material. |
TABLE OF CONTENTS
1 Introduction - 4 -
1.1 Background - 4 -
2 Elements of IPS Guidance Material - 4 -
2.1 Transport layer - 4 -
2.1.1 Generality - 4 -
2.1.2 Connection oriented and connectionless transmission - 5 -
2.1.3 Transport layer addressing - 5 -
2.1.4 Application interface to the transport layer - 5 -
2.1.5 Congestion avoidance - 6 -
2.1.6 Error detection and recovery - 6 -
2.2 Network layer - 7 -- 6 -
2.2.1 Rationale for selecting IPv6 in ATN - 7 -- 6 -
2.2.2 Network layer addressing - 7 -
2.2.3 Inter-domain routing - 8 -- 7 -
2.2.4 Traffic type segregation - 8 -- 7 -
2.2.5 Qos management - 8 -
2.2.6 Application interface to the network layer - 9 -- 8 -
3 IPV6 Addressing Scheme - 9 -- 8 -
3.1 Purpose - 9 -- 8 -
3.2 Important Définitions - 10 -- 9 -
3.2.1 Allocation - 10 -- 9 -
3.2.2 Sub-allocation - 10 -- 9 -
3.2.3 Assignment - 10 -9
3.3 IPv6 Addressing Scheme - 10 -9
3.4 Basic IPV6 Address Space Assignments and BGP as Numbers - 11 -11
3.5 EXAMPLE - 13 -12
4 Transit Traffic 1615
4.1 ISSUES 1615
5 QoS/CoS Definition 1716
5.1 Discussion 1716
5.2 ATN/IPS QoS 2120
5.3 Summary 2221
6 IPS Security Guidance Material 2322
6.1 IPsec Authentication Header and Encapsulating Security Payload 2322
6.2 Authentication Header 2423
6.3 Encapsulating Security Payload 2524
6.4 IPsec Transport and Tunnel Modes 2625
6.5 IPsec Key Management 2726
6.5.1 Manual Key Management 2726
6.5.2 Dynamic Key Management 2726
6.5.3 Describe configuration options 2726
7 Alternatives to IPv6 Security 2827
7.1 Security at Different Layers 2827
7.1.1 Criteria Which Differentiate Between Security Solutions At Different Layers 2827
7.2 Alternatives/Compliments to IPsec 3130
7.3 Need for Security at Multiple Levels in Aviation Environment 3231
9 Annex 1 Example Implementation Guide 3433
9.1 Scope of this document 3433
9.2 Differences to previous edition 3433
9.3 Use of the Document 3433
9.4 General context 3534
9.5 Organisation of the Document 3534
9.6 Symbols Used 3736
9.6.1 Link to the ATM 2000+ Strategy 3837
9.7 Reference Documents 3837
9.8 Communication Protocols Requirements 4039
9.9 Introduction 4039
9.10 IP Version 4039
9.11 Data Link Layer 4039
9.11.1 Ethernet Frame Format 4140
9.11.2 IPv4 Addressing 4241
9.11.3 IPv6 Addressing 4342
9.12 Network Layer 4443
9.13 Internet Protocol version 4 4443
9.13.2 Internet Protocol version 6 47
9.13.3 ICMP 5049
9.14 Transport layer 5150
9.14.1 4.5.1 Addressing 5150
9.14.2 UDP checksum 5150
9.15 Limitation of maximum size of messages 5251
10 SPECIFIC CONFIGURATION REQUIREMENTS 5251
10.1 Surveillance Data Transmitter 5251
10.1.1 Common (IPv4 and IPv6) configuration requirements 5251
10.1.2 IP version 4 specific configuration requirements 52
10.1.3 P version 6 specific configuration requirements 5352
10.2 Surveillance Data Receiver 5453
10.2.1 Common (IPv4 and IPv6) configuration requirements 5453
10.2.2 IP version 4 specific configuration requirement 5554
10.2.3 IP version 6 specific configuration requirements 5554
10.3 System Configuration Examples 5554
10.3.1 Single Attached Multicast Receiver with one Incoming Flow per Interface 5554
10.3.2 Multi-homed Multicast Receiver with one Incoming Flow per Interface 56
10.3.3 Receivers with Multiple Incoming Flows per Received Interface and Multihomed Transmitters 57
10.3.4 Multi-homed Transmitters and multiple transmissions of the same flow 58
11 Abbreviation List 68
12 Multicast Service 70
12.1 Planned European Deployments 70
1 Introduction 3
1.1 Background 4
1.2 Reference Document 4
1.3 Abbreviations 4
2 General Guidance 4
2.1 ATN Policy 4
2.2 Transition between IPv4 and IPv6 5
3 Physical and Link Layer Guidance 6
4 Network Layer 6
4.1 Address Plan 6
4.2 Application interface to the network layer 6
4.3 Inter-domain routing 6
4.3.1 AS numbering plan 6
4.3.2 ATN/IPS Router Ids 6
5 Transport Layer 7
5.1 Transmission Control Protocol 7
5.2 User Datagram Protocol (UDP) 8
5.3 Transport Layer Addressing 8
5.4 Application Interface to the Transport Layer 9
5.5 Congestion Avoidance 9
5.6 Error Detection and Recovery 9
5.7 Performance Enhancing Proxies (PEPs) 10
6 Transition Mechanisms 10
6.1 Tunnelling 10
6.2 Dual Stack 11
6.3 Translation 12
6.4 Combining of the Mechanisms 12
6.5 FMTP/OLDI 12
6.5.1 OLDI 12
6.5.2 FMTP 13
6.5.3 Testing 13
7 Security Guidance 13
7.1 Ground-Ground Network Layer Security 13
7.1.1 Ground-Ground IPsec 14
7.2 Air-Ground Security 14
7.2.1 Access Network Security 14
7.2.2 Air-Ground IPsec 14
7.2.3 Air-Ground Transport Layer Security 15
7.2.4 Air-Ground Application Layer Security 15
8 Voice over Internet Protocol (VoIP) 15
8.1 Standards and Protocols 16
8.1.1 H323 16
8.1.2 Multimedia 17
8.1.3 Data Transfer 17
8.1.4 Signalling 17
8.2 MGCP/MEGACO 18
FOREWORD
The material contained in this document supplements the Standards and Recommended Practices (SARPs) and the Manual for Detailed Technical Specifications. This document is to be used to assist in the deployment of IPS systems of the Aaeronautical tTelecommunication Nnetwork (ATN) as defined in Annex 10 — Aeronautical Telecommunications, Volume III — Communication Systems and Part I — Digital Data Communication Systems. and the IPS Mmanual on Detailed Technical Specification for the IPS ATN Doc 9896XXXX. The purpose of this document is to support the deployment of ATN network components in ICAO Regions.
In December 1997, the Air Navigation Commission (ANC) agreed that detailed technical provisions for the ATN should be published as an ICAO manual (to be updated annually, if necessary), while retaining its SARPs-style language. The ANC will review the status of the material contained in this document, after sufficient implementation and operational experience has been gained and the requirements for the extent of standardization of ATN and other complex aeronautical systems have been better ascertained.
This document consists of nine Sub-Chapters
Chapter 1 — Elements for IPS Guidance Material
Chapter 2 — Eurocontrol IPv6 Addressing Scheme
Chapter 3 — Transit Traffic
Chapter 4 — IP Multicast
Chapter 5 — QOS for IPS
Chapter 6 — IPS Security Guidance
Chapter VII — Directory Services (DIR)
Chapter VIII — Security (SEC)
Chapter IX — Registration (REG)
In line with the agreement by the ANC that the document should be updated on a yearly basis (if deemed necessary), the Third Edition has been published to incorporate changes necessitated by continuing validation and implementation activities.
Introduction
The Aeronautical Telecommunication Network Internet Protocol Suite (ATN /IPS) Guidance Document contains information to assist member states in the deployment of an harmonized IPS network for their state infrastructure to support the delivery of ICAO Air Traffic Management (ATM) services. The following minimum core services should be provided by ATN/IPS:
• Interface registry
• Directory and naming
• Flight Information
• IP network services
• Security
• Infrastructure management
• Global information exchange
These core services enable ATN IPS applications to provideto exchange voice and data services with the appropriate priority and security over a an underlying transport networks with the required quality and class of serviceQoS and CoS technology.
The protocols discussed in this document are referred to based on the open system interconnect reference model (OSI). However, since IPS uses only 4 layers the mapping is not consistent with the reference model. Figure 1.1 depicts the OSI reference model and the relationship between the ISO ATN and the IPS protocols.
[pic]
Figure 1.1 Protocol Reference Model
1.1
Background
Background
The ICAO/ATN has established with the specific goals of providing a commercial off the shelf for modernizing global ATM servicesystems. Currently, ATN services can be provided using the ISO based ICAO protocols as documented is ICAO Standards 9705/9880. This document along with the ICAO ATN/IPS Standard 9896 [1] is an additionala new technical approachconcept for networking, and will enable member state to have an additional resource for providing ATM servicesbased upon an open, flexible, modular, manageable, and secure architecture that is transparent to the stakeholders.
1.2 Reference Document
ICAO Document 9705 Manual of Technical Provisions for the ATN V2
ICAO Document 9880 Manual of Technical Provisions for the ATN VX
1.3 This approach provides value by using industry networking products thereby reducing costs and risks, enabling new capabilities and enhancing legacy services.
Elements of IPS Guidance Material
This section contains general guidance information about TCP/IP and also provides information for implementation of IP services for the ATN.Abbreviations
ATN Aeronautical Telecommunications Network
ATM Air Traffic Management
BGP Border Gateway Protocol
IPS Internet Protocol Suite
ICAO International Civil Aviation Organization
IPv4 Internet Protocol Version 4
IPv6 Internet Protocol Version 6
ISO International Organization for Standardization
MOA Memorandum of Agreement
General Guidance
This section contains general guidance information about the implementation of IPS for ATN services. This document only discusses IPS based services for detailed information on ISO standards based ATN services refer to document 9705/9880.
The current recommendation of ICAO is to deploy IPv6 protocols and services but that does not preclude a member state network from supporting or deploying IPv4 services. However, these services must remain transparent from the IPv6 portion of the network. All transaction over the ICAO ATN must be done using ICAO standards 9705/9880 or 9896.
This document focuses on the network, transport and application services; physical and link services are to be negotiated on a service need basis by the implementing state.
ATN Administration
The administration of the ATN shall be performed by the member state and the their appointed service provider. However, that does not preclude agreements between member states that form a federation in the interest of providing ATM services.
2.1 ATN Policy
The purpose of this section is to define the operating polices for the ATN.
Transit Traffic
The ATN IPS manual does not specify which routes are to be advertised between ATN IPS routers nor basic traffic management policies for a dynamically routed environment.
ATN IPS routers will exchange information about their internal network prefixes with its immediate neighbor routers but may also forward routing information about other network prefixes learned from other BGP neighbors.
As a result, traffic between two Administrative Domains may be relayed by an number of intermediate Administrative Domains. Such traffic being carried on behalf of two others is termed transit traffic.
All Administrative Domains that participate to the ATN IPS must ensure the proper handling of transit traffic on the following basis:
• An Administrative Domain shall not advertise a network prefix if it is not prepared to accept incoming traffic to that network prefix destination;
• When establishing the interconnections between two Administrative domains a charging mechanism may be agreed to support implicit corresponding transit policy;
• Administrative Domains that relay transit traffic shall ensure that the associated security and QoS policies of the traffic is maintained
2.2 Transition between IPv4 and IPv6
Current ground communications are generally handled through appropriate protocol profiles that are based on IPv4. For technical, economical and strategic reasons, transition to IPv6 will be made gradually and appropriate transition path need to be defined:
RFC 4213 - Basic Transition Mechanisms for IPv6 Hosts and Routers
This RFC discusses dual stack approaches as well as tunnelling IPv6 traffic through existing IPv4 networks. The three main interoperability cases are as follows:
1) IPv6 nodes that require to communicate over an IPv4 sub network
2) IPv4 nodes that require to communicate over an IPv6 sub network
3) An IPv4 node that requires to communicate with an IPv6 node
Case 1 can be resolved by relying on common IPv6 over IPv4 tunnels. Although this does create additional overhead it would allow early deployment of ATN/IPS applications.
Case 2 could be resolved by relaying on IPv4 over IPv6 tunnels. If the two autonomous IPv4 domains overlap in terms of routing and addressing; interoperability may not be achieved. A dual stack approach is recommended to ensure that ATN systems can natively interface over the ATN/IPS without having to resort to such tunnelling techniques which may not be appropriate.
Case 3 can be the result of legacy applications that have not been updated to IPv6 or no longer maintained. In the ATN context, this issue needs to be considered as some application vendors (e.g. AMHS) do not have a dual stack solution and only support IPv4 profiles. This case can be handled through the use of network address translation from IPv4 to IPv6:
RFC 2766 - Network Address Translation - Protocol Translation (NAT-PT)
The benefit of NAT-PT and other similar mechanisms allow an IPv4-only system to behave as an IPv6 system and communicate over the ATN/IPS.
All ATN/IPS systems are recommended to adopt a dual stack approach in order to ensure native inter-working over the ATN/IPS and local IPv4 environments without having to rely on the use of external tunnelling or translation devices.
• Physical and Link Layer Guidance
• Physical and link layer issues will be determined by the required service and member state connections. The physical and link layer issues will be on service need basis and should be contained in a memorandum of agreement (MOA).
Network Layer
The IPS ATN addressing is performed using IPv6, which uses 128 bits long address block versus 32 bits in IPv4.
4.1 Address Plan
The address plan is to be supported by the member state allocation as assigned by IANA.
4.2 Application interface to the network layer
Although applications generally accede to the communication service at the transport layer, it is sometime necessary to transmit and receive datagrams at the network level. This is granted by some socket API extensions specified in:
RFC 3542 - Advanced Sockets Application Program Interface (API) for IPv6
4.3 Inter-domain routing
This section discusses inter-domain routing that will enable member state networks to interconnect while maintaining state or federation autonomy. The protocol to be used shall be the border gateway protocol (BGP).
4.3.1 AS numbering plan
AS numbers need to be assigned and configured in ATN/IPS routers to announce their autonomous systems within the routed domain. The AS numbering plan is presented in (To be added).
4.3.2 ATN/IPS Router Ids
In order to establish BGP between two neighbour, each BGP peer must define a router id. If two routers make use of the same router-id value, BGP cannot be established. As the router id is a 32 bit field, it is usually on the IPv4 address of the router.
As ATN IPS routers may not have Ipv4 interfaces a scheme needs to be recommended. Although global uniqueness of these values is not a pre-requisite, to ease implementation of the ATN IPS the following scheme is recommended (based on draft-dupont-durand-idr-ipv6-bgp-routerid-01.txt):
• 4 bits set to one,
• 16 bits set to the AS number (a global AS number plan is part of this Document)
• 12 bits manually allocated within the domain. (allows for 4096 different router IDs in each routing domain)
4.3.2.1 Routing Advertisement
ATN IPS routers should advertise network prefixes based on consistent prefix lengths or aggregate route prefixes;
4.3.2.2 Traffic type segregation
BGP-4 does not natively allow setting up different set of routes for different traffic to the same destination.
ATN IPS requirement on traffic type segregation may be fulfilled by appropriate provisions in the ATN addressing plan: if the ATN address incorporates an indication of the traffic type, BGP-4 will transparently flood segregated route information for the various traffics.
4.3.2.3 Differentiated Service
Differentiated Service (RFC 2474) provides a mean for specifying and implementing QOS handling consistently in IPS network. This specification is made on a per node basis, specifying behaviour of individual nodes concerning QOS (Per Hop behaviour).
The general framework / current practices is depicted in details in:
RFC 2475 - Architecture for Differentiated Services
4.3.2.4 Traffic Priority
Historically, network layer priority was selected explicitly by the sending application through the TOS field. Although Differentiated Service (RFC 2474) preserves the IP precedence semantic of the TOS field, this approach is now deprecated. This is partly because the IP precedence has been superseded by the Per-Hop-Behaviour strategy inside Differentiated service, but also because network administrators usually don’t trust QOS specification coming from the application.
ATN application traffics can be identified / prioritised according to the destination port of data grams when they enter the network:
• This provides transparent and safe identification of traffics, because the destination port is always a trusted information (otherwise the traffic will never reach its destination).
• But this requires specification of a distinct port for every ATN application (proliferation of ports would unnecessarily complexity administration of routers, and incurs their performance).
• During transit in the IPS network, corresponding data grams could be marked using the Differentiated Service field, in respect to the practices indicated in RFC 2475.
• Transport Layer
Transport layer
The transport layer protocols are used to provide reliable or unreliable communicationa variety of services over the ATN. There are two mandatory transport protocols, TCP and UDP. TCP is used to provide reliable transport services and UDP is used to provide best effort service. Other transport protocols may be used but can not affect ATN communications or services.
5.1 Transmission Control Protocol
Generality
TCP and UDP were naturallyare adopted by ATN because as they are the have been recognised and intensively used for a while as general purpose end-to-end transmission protocols standardized by in the Internet Society P comm(ISOC) for all IP enabled devicesunity.
In order to ease inter-connection between IPS systems over theof public internetsystems, the ISOC has published P community provides some guidance on using the IPS suite of protocols. A particularthe following RFC focuses on the transport (and above) layerswhich can also be used within a private network environment such as the ATN:
RFC 1122 - Requirements for Internet Hosts -- Communication Layers
Connection oriented and connectionless transmission
The Internet Protocol (IP) works by exchanging groups of information called packets. Packets are short sequences of bytes consisting of a header and a body. The header describes the packet's routing information, which routers on the Internet use to pass the packet along in the right direction until it arrives at its final destination. The body contains the application information. TCP is optimized for accurate delivery rather than timely delivery, TCP sometimes incurs long delays while waiting for out-of-order messages or retransmissions of lost messages, and it is not particularly suitable for real-time applications like Voice over IP. Real time applications will require protocols like the Real-time Transport Protocol (RTP) running over the User Datagram Protocol (UDP).
TCP is a reliable stream delivery service that guarantees to deliver a stream of data sent from one host to another without duplication or losing data. Since packet transfer is not reliable, a technique known as positive acknowledgment with retransmission, is used to guarantee reliability of packet transfers. This fundamental technique requires the receiver to respond with an acknowledgment message as it receives the data. The sender keeps a record of each packet it sends, and waits for acknowledgment before sending the next packet. The sender also keeps a timer from when the packet was sent, and retransmits a packet if the timer expires. The timer is needed in case a packet becomes lost or corrupt.
In the event of congestion, the IP can discard packets, and, for efficiency reasons, two consecutive packets on the internet can take different routes to the destination. Then, the packets can arrive at the destination in the wrong order.
The TCP software libraries use the IP and provides a simpler interface to applications by hiding most of the underlying packet structures, rearranging out-of-order packets, minimizing network congestion, and re-transmitting discarded packets. Thus, TCP very significantly simplifies the task of writing network applications.
TCP provides a connection-oriented service with a reliable semantic. It operates above thea network layer that which does not necessarily detect and report alls errors (e.g. corruption, misrouting). For this purpose, it provides:
• Error detection based on a checksum covering the transport header and payload as well as some vital network layer information.
• Recovery from error based on retransmission of erroneous or lost packets.
TCP is also designed for to detect and managing manage end-to-end network efficiently congestion and maximum user data segment sizes insides IP nodes and subnetworks. This is essential for operation over hetereogeneousheterogeneous subnetworkssub networks with some low bandwidth / high latency trunks, such as the actual ATN Air/Ground subnetworkssub networks.
5.2 User Datagram Protocol (UDP)
UDP provides a connectionless service with limited error detection and no recovery, nor congestion management mechanisms. It is naturally dedicated for light data exchanges, where undetected occasional loss or corruption of packets is acceptable, and when simplicity of use is a goal.
5.3 Transport Llayer Aaddressing
Transport layer addressing relies on port numbers (16 bits integer values) that are associated with source and destinations endpoints to identify separate data streams.
Ports are classified in three categories with associated range of values:
• Well-known ports are those from 0 through 1023 and are assigned by IANA. On most systems these ports can only be used by system (or root) processes or by programs executed by privileged users. Such pre-defined well-known port numbers associated to distinct TCP and/or UDP server applications, makesing them visible (“well-known”) to client applications without specific knowledge / configuration. Using one of these ports usually requires special privilege from the application. Values in this range are assigned to application by IANA.
• Registered ports are those from 1024 through 49151 and are registered by IANA following user request. number eEssentially such ports plays the same role as well-known ports but for less critical or widespreadserver applications. In particular,The useing of such ports does not require specific privileges. Values in this range are also assigned by IANA.
• Dynamic and/or private ports are those from 49152 through 65535. They may be used freely by applications.
Port assignment is obtained on request to IANA. An up-to-date image of the port registry is available at:
This assignment plan is compulsory over the public Internet. It should be made applicable to ATN IPS (at least concerning well-known ports) in order to avoid conflicts between standard IPS applications (that may be used in ATN IPS environment) and ATN applications.
ATN/IPS hosts will require to support the following port numbers:
• tcp 102 for ATSMHS
• tcp 8500 for FMTP
5.4 Application I interface to the Ttransport L layer
The application interface to the TCP and UDP transport layers is provided consistently on a wide range of platform / operating systems according to the specification made in:
RFC 3493 - Basic Socket Interface Extensions for IPv6
This RFC extends the socket interface (originally developed by the Berkeley University for supporting IPv4 in their BSD Unix distribution) to IPv6.
5.5 Congestion Aavoidance
In order to adapt to variables conditions for draining traffic in sub networks, TCP implements basically 4 mechanisms: slow-start, congestion-avoidance, fast-retransmit and fast-recovery. These are specified in:
RFC 2581 - TCP Congestion Control
The two first mechanisms aims at preventing important loss of packets when congestion occurs, while the two others attempt to shorten the delay for retransmitting the lost packets. These mechanisms are implemented independently in every end systems.
Although they provide great performances over usual ground subnetworks, they don’t completely avoid loss of packets.
In the case of low bandwidth sub networks (e.g. ATN Air/Ground sub networks), TCP applications may make Uuse of the Explicit Congestion Notification mechanism over low bandwidth subnetworks (e.g. ATN Air/Ground subnetworks) will more likely provide a significant benefit. It is specified by:
RFC 3168 - The Addition of Explicit Congestion Notification (ECN) to IP
This feature anticipates congestion, hence significantly reducing avoidingpacket loss of packets for this reason. However, But it impacts the transport and network layers, and requires participation of a significant numbers of routers in the networks (preferentially, the routers at the edge of low speeds / high latency sub networks).
5.6 Error Detection and Recovery
TCP error detection relies on lack of timely received acknowledgement. Recovery is performed through retransmission of (supposed) lost packets.
Loss of a large numbers of packets in a short period of time may heavily incur the TCP connection throughput (hence performance). This may become critical for high latency sub networks (e.g. ATN Air/Ground sub networks).
Support of TCP selective acknowledge option may mitigate this problem by allowing selective retransmission of lost packets only (instead of the whole sequence from the first to the last packet lost).
This option is specified in:
RFC 2018 - TCP Selective Acknowledgment Options
5.7 Performance Enhancing Proxies (PEPs)
Performance Enhancing Proxies (PEPs) are often employed to improve severely degraded TCP performance caused by different link characteristics in heterogeneous environments, e.g. in wireless or satellite environments that are common in aeronautical communications. Transport layer or application layer PEPs are applied to adapt the TCP parameters to the different link characteristics.
RFC3135 “Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations” is a survey of PEP performance enhancement techniques, and describes some of the implications of using Performance Enhancing Proxies. Most implications of using PEPs result from the fact that the end-to-end semantics of connections are usually broken. In particular, PEPs disable the use of end-to-end IPsec encryption and have implications on mobility and handoff procedures.
Transition Mechanisms
IPv6 has been adopted by the IETF and the internet authorities to cope with the ever increasing growth rate of the global internet. IPv6 solves many of the technical problems associated with IPv4, in particular the limited IPv4 address space.
The global implementation of IPv6 has already begun. It is the building block of the next generation internet which will enable a flexible means to roll-out new technologies and services. For this reason, the ATN IPS is based on IPv6 to take immediate advantage of new commercial off-the-shelf products and technologies.
The implementation of the ATN IPS will be gradual over a significant period of time. Many organizations will be required to go through multiple steps to ensure that ATN IPS end-systems and routers are integrated into their existing environment in particular for those that have deployed legacy ATN/OSI CLNP (primarily over Ethernet or “X.25”) and IPv4 systems.
Three transitions mechanisms can assist organisations deploying the ATN IPS in a heterogeneous environment:
o Tunnelling: one protocol being encapsulated in another
o Dual stack: an environment in which multiple protocols operate simultaneously
o Translation: the conversion from one protocol to another
An in-depth description of the first two mechanisms can be found in RFC4213 (Basic Transition Mechanisms for IPv6 Hosts and Routers). The applicability of above three mechanisms to the ATN IPS are further described.
6.1 Tunnelling
IPv6 has been specified to operate over a variety of lower layer interfaces such as Frame Relay, ATM, HDLC, PPP and LAN technologies. Tunneling implies that a given protocol is encapsulated into another, meaning that IPv6 would be encapsulated into another functionally equivalent network protocol. With regard to the ATN IPS, the key benefit of this mechanism would be for aeronautical organizations that already operate IPv4 networks to allow the ATN IPS hosts and routers communicate between each other over such an underlying IPv4 network. Furthermore, if the interconnecting infrastructure between two ATN IPS administrative domains is limited to IPv4, this mechanism can be applied.
It is recalled that IPv6 cannot operate over X.25; an IPv6 tunnel over IPv4 can be in turn tunneled over an X.25 network. A specific tunneling mechanism termed IP SNDCF is defined for ATN/OSI applications, it is to be noted that this enables interoperability between ATN/OSI applications over an IP network but does not enable interoperability with ATN/IPS applications.
Tunnelling mechanisms lead to an increase of protocol overhead and the segregation of the two routed domains creates additional network management e.g. an IPv6 routed domain over an underlying IPv4 routed domain that needs to be managed in terms of QoS, security, and route optimization. In addition, this mechanism only foresees interoperability between ATN IPS systems as it does not enable interoperability between ATN OSI systems nor other IPv4 systems within the organization. Nevertheless, it may provide an effective way to enable the ATN IPS within and between two administrative domains.
The tunneling mechanism is best suited to resolve lower layer communication issues between ATN IPS IPv6 hosts and routers but does not provide interoperability with non-compliant ATN IPS systems.
6.2 Dual Stack
The dual stack mechanism implies that an implementation handles more than one communications protocol for a given application or function. Within the internet domain a significant number of communication applications have been dual stacked e.g. HTTP, FTP, SSH, DNS, SMTP etc. by supporting both IPv4 and IPv6 protocols. However, in the context of the ATN IPS the purpose of dual stacking is to resolve similar yet different issues.
The concept of dual stacking is ideally suited for systems that need to support ATN applications for both OSI and IPS. In such environments, the applications are designed in an abstract fashion to be independent of the lower layers, in other words they are unaware which lower layer communications protocol (OSI or IP) is being used to communicate with their peer. X.400 vendors have taken this approach to support both OSI and IP environments avoiding the need to develop complex ad-hoc lower layer communication gateways. Usually such implementations rely on some form of directory or lookup table associating a high-level address with a specific communications protocol address.
The concept of dual stack can be extended to multiple stack. ATN AMHS manufacturers usually support operation over multiple protocols such as OSI, TCP/IP and X.25 .
The dual stack mechanism is best suited to provide the maximum level of interoperability with peers while reducing the complexity of lower layer communication protocol gateways and additional single points of failure. It is ideally suited for applications such as AMHS whereby some systems have already been implemented on the basis of OSI and others on TCP/IP. A dual stack approach can be a valid for air-ground datalink ground systems to support CPDLC over multiple datalink services such as ATN OSI and ATN IPS.
6.3 Translation
Translation mechanisms imply the conversion from one protocol to another. This mechanism can be interpreted as a lower layer communications gateway between two protocols that share a high degree of commonality. Several translators have been developed in the context of the transition from IPv4 to IPv6 as both versions share a number of common features.
Within the overall transition from IPv4 to IPv6, it was envisaged that some systems may be only capable of communicating with IPv4 and others with IPv6. Considering global internet scalability issues and the fact that most internet applications and systems have become dual stacked, the need for translators has declined.
However, translators may play an important short-term role in the case of the ATN IPS. For example, although existing AMHS systems operate on dual stack operating systems, none of them have upgraded their application code to make use of IPv6. In other words, RFC1006 is supported but not RFC2126. In such particular cases and in view of the limited number of systems, the deployment of translators provides a short-term measure for such systems to comply with the ATN IPS and inter-work with RFC2126 enabled systems.
IPv4/IPv6 translators increase the complexity of the IP infrastructure and its management. A dual stack approach is to be preferred but in specific cases translators may be the only short-term measure to provide compliance with the ATN IPS.
6.4 Combining of the Mechanisms
As the ATN IPS implementation will be gradual it is understandable that a combination of the above three mechanisms will be applied.
Specific combinations of the above mechanisms can be deployed to better fit within the environment of the administrative domain environment.
6.5 FMTP/OLDI
On-Line Data Interchange (OLDI) combined with the Flight Message Transfer Protocol (FMTP) is a means to enable AIDC operational requirements for the co-ordination and transfer of aircraft between adjacent air traffic control units.
6.5.1 OLDI
The OLDI specification does not mandate the implementation of OLDI messages but specifies the requirements that need to be met when implementing such facilities. If OLDI messages are implemented as the result of regulatory provisions, or based on bilateral agreement between Air Traffic Control Units, then the requirements outlined as mandatory in this specification for those messages become mandatory for implementation. This is required in order to meet the purpose of the messages and to ensure interoperability between systems.
The co-ordination procedure requires that systems identify whether or not transfers are in accordance with Letters of Agreements (LoAs).
The process which checks such compliance is referred to in the OLDI Specification as "the filter". The database used for the filter will include the following, if required:
• agreed co-ordination points;
• eligible (or ineligible) flight levels which may also be associated with the co-ordination points;
• aerodromes of departure;
• destinations;
• agreed direct routes ;
• time and/or distance limits prior to the COP, after which any co-ordination message is considered non-standard;
• any other conditions, as bilaterally agreed.
All items in this list may be combined to define more complex conditions.
The format of the messages (ICAO PANS/RAC 4444 or EUROCONTROL ADEXP) to be transmitted and received has to be agreed bilaterally.
The address of the ATS units providing the services has to be agreed and has to be different from the addresses of the other units to which the ATS units are already connected or planned to be connected. The ATS unit addresses are part of the OLDI message.
6.5.2 FMTP
The Flight Message Transfer Protocol is a communications stack based on TCP/IPv6. FMTP is a state machine that handles connection establishment and session management. Each FMTP system requires to be assigned with an identification value that is to be exchanged during connection establishment. The identification values have to be bilaterally agreed and must be different from the values of the other units to which the ATS units are already connected or planned to be connected.
The FMTP specification assumes the transfer of ASCII characters but implementations of the protocol may wish to extend this support to other character sets or binary transfers. Further guidance material on FMTP is available from EUROCONTROL at the following website:
6.5.3 Testing
EUROCONTROL has developed a test tool named ETIC to validate OLDI/FMTP implementations and build test scenarios. The tool can be made available to FMTP implementation projects upon request. Request for further should be addressed to EUROCONTROL.
Network layer
The IPS ATN addressing is performed using IPv6. The network layer provides the functionality that allows different types of networks to be joined and share a common addressing scheme.
Rationale for selecting IPv6 in ATN
IPv6 has been preferred to IPv4 in the ATN IPS context mainly for the following reasons:
Official IPv4 address resources are limited, difficult to obtain for the global long term requirements of the ATN/IPS
The internet community is planning the transition from IPv4 to IPv6 and some ICAO regions have already deployed IPv6 network services
A large number of IPv4 deployments make use of the same private address ranges preventing their inter-connectivity
IPv6t provides a large addressing space, allowing setting up a hierarchical addressing plan; inter-domain routing may easily take advantage of this feature to optimise routing information diffusion (aggregating / reducing network address prefixes).
IPv6 provides extended addressing functionality such as:
• Native support for unicast, anycast and multicast (provisions for anycast).
• Address autoconfiguration in nodes.
• DHCP prefix delegation.
• Neighbour discovery (versatile, extensible).
← Improved support of mobility:
• Better integration of mobility / optimisation of routes in IPv6.
• Support mobility of a whole network (Nemo).
As for the hosts system, the IP internet community provides some guidance on using IPv6 in:
RFC 4294 - IPv6 Node Requirements (note: may also reference NIST IPv6 profile here).
Network layer addressing
ATN IPS addressing plan
(TBD)
Transition between IPv4 and IPv6
Current ground communications are generally handled through appropriate profiles based on IPv4. For technical, economical and strategic reasons, transition to IPv6 will be made gradually and appropriate transition path need to be defined:
RFC 4213 - Basic Transition Mechanisms for IPv6 Hosts and Routers
This RFC discusses dual stack approaches as well as tunnelling IPv6 traffic through existing IPv4 networks. The three main interoperability cases are as follows:
1. IPv6 nodes that require to communicate over an IPv4 subnetwork
2. IPv4 nodes that require to communicate over an IPv6 subnetwork
3. An IPv4 node that requires to communicate with an IPv6 node
Case 1 can be resolved by relying on common IPv6 over IPv4 tunnels. Although this does create additional overhead it would allow early deployment of ATN/IPS applications.
Case 2 could be resolved by relaying on IPv4 over IPv6 tunnels. Indeed, if the two autonomous IPv4 domains overlap in terms of routing and addressing interoperability may not be achieved. A dual stack approach is recommended to ensure that ATN systems can natively interface over the ATN/IPS without having to resort to such tunnelling techniques which may not be appropriate.
Case 3 can be the result of legacy applications that have not been updated to IPv6 or no longer maintained. In
In the ATN context, a symmetrical this issue needs to be considered as some application vendors issue exists: the core network is IPv6 while some application (e.g. AMHS) do not have a dual stack solution and only support only supports IPv4 profiles. This case may can be handled through the use of “IPv4-compatible IPv6 address” and “IPv4-mapped IPv6 address” as stated innetwork address translation from IPv4 to IPv6:
RFC 27663513 - Network Address Translation - Protocol Translation (NAT-PT)Basic Transition Mechanisms for IPv6 Hosts and Routers.
The benefit of NAT-PT and An aother similar mechanisms allow an IPv4-only system to behave as an IPv6 system and communicate over the ATN/IPSlternate solution consists in making appropriate provisions for supporting IPv4 systems when specifying the ATN addressing plan. This solution improves consistency between all categories of ATN systems addresses.
All ATN/IPS systems are recommended to adopt a dual stack approach in order to ensure native inter-working over the ATN/IPS and local IPv4 environements without having to rely on the use of external tunnelling or translation devices.
Network Addressing
Definitions
Allocation
This is the address space that is set aside by a Regional Internet Registry (RIPE) for a Local Internet Registry (LIR).
Sub-allocation
This is the address space that is set aside by a Local Internet Registry for an LIR's downstream customer or organisation.
Assignment
Address space taken from the LIR allocation and given to the End User or to the LIR’s infrastructure.
IPv6 Addressing Scheme
The ATN/IPv6 addressing scheme is based on the allocation of a prefix to ICAO. In turn, ICAO can sub-allocate the address space to the ATN/IPS administrative domains. The Administrative Domains assign IPv6 addresses to the ATN/IPS subnetworks and nodes.
For example, within the European region in which the EUROCONTROL Agency has become an LIR and received the allocation of address prefix 2001:4b50::/32 as indicated in the database.
inet6num: 2001:4b50::/32
org: ORG-EitE1-RIPE
netname: BE-EUROCONTROL-20050131
descr: EUROCONTROL, the European Organisation for the Safety of Air Navigation
country: BE
admin-c: EJC2-RIPE
tech-c: EJC2-RIPE
status: ALLOCATED-BY-RIR
mnt-by: RIPE-NCC-HM-MNT
mnt-lower: EURO-HQ-MNT
mnt-routes: EURO-HQ-MNT
source: RIPE # Filtered
Acting as LIR, EUROCONTROL then sub-allocates /32 address space to its stakeholders and assigns IPv6 /48 prefixes on its behalf:
inet6num: 2001:4B50:0940::/48
netname: RO-ROMATSA-OR-1
descr: Assignment for site RO-ROMATSA-OR-1
country: RO
admin-c: CA1732-RIPE
tech-c: CD1668-RIPE
status: ASSIGNED
mnt-by: EURO-HQ-MNT
source: RIPE # Filtered
This assignment policy is based on the following IPv6 addressing scheme that is applicable within the European region.
[pic]
• The 3 bits of Field F1 are assigned as follows;
|F1 Assignment |Binary |Hex |Network Name |
|1 |000 |0 |National/Regional Entities |
|2 |001 |1 |Pan-European Organisations and Entities |
• The 7 bits of the fixed “Net. Prefix” field are used to number each ANSP, organisation or infrastructure that can be considered as a single entity; the high order bit of the “Net. Prefix” is set to 0 for national entities and 1 for regional entities;
• The 1 bit of the v4/v6 field is a toggle bit to indicate if IP address translation is required at the network border.
• The 5 bits of F2 field are assigned sequentially to provide multiple /48 per network prefix, the bit assignment follows RFC 3531 (A Flexible Method for Managing the Assignment of Bits of an IPv6 Address Block).
|F2 Assignment |Binary |Hex |Network Name |
|1 |00000 |0 |First Operational |
|2 |10000 |10 |First Pre-Operational |
|3 |01000 |8 |Second Operational |
|4 |11000 |18 |Second Pre-Operational |
|5 |00100 |4 |Third Operational |
|6 |10100 |14 |Third Pre-Operational |
|7 |01100 |C |…. |
|8 |11100 |1C |…. |
|9 |00010 |2 |…. |
|…. |…. | | |
|…. |…. | | |
|32 |11111 |1F |…. |
Stakeholders assign the remaining 80 bits of the address based on their own policies but advised to consider RFC 3531 (A Flexible Method for Managing the Assignment of Bits of an IPv6 Address Block); typically the first 16 bits (SLA ID) are used to represent location related information.
Inter-domain routing
AS numbering plan
(TBD)AS numbers need to be assigned and configured in ATN/IPS routers to announce their autonomous systems within the routed domain. The AS numbering plan is presented in Annex 1.
ATN/IPS Router Ids
In order to establish BGP between two neighbour, each BGP peer must define a router id. If two routers make use of the same router-id value, BGP cannot be established. As the router id is a 32 bit field, it is usually on the IPv4 address of the router.
As ATN IPS routers may not have IPv4 interfaces a scheme needs to be recommended. Although global uniqueness of these values is not a pre-requisite, to ease implementation of the ATN IPS the following scheme is recommended (based on draft-dupont-durand-idr-ipv6-bgp-routerid-01.txt):
4 bits set to one,
16 bits set to the AS number (a global AS number plan is part of this Document)
12 bits manually allocated within the domain. This allows for 4096 different router IDs in each routing domain.
Routing Advertisement
ATN IPS routers should advertise network prefixes based on consistent prefix lengths or aggregate route prefixes;
Traffic type segregation
BGP-4 does not natively allow setting up different set of routes for different traffic to the same destination.
ATN IPS requirement on traffic type segregation may be fulfilled by appropriate provisions in the ATN addressing plan: if the ATN address incorporates an indication of the traffic type, BGP-4 will transparently flood segregated route information for the various traffics.
Qos management
Differentiated Service
Differentiated Service (RFC 2474) provides a mean for specifying and implementing Qos handling consistently in IPS network. This specification is made on a per node basis, specifying behaviour of individual nodes concerning Qos (Per Hop behaviour).
The general framework / current practices is depicted in details in:
RFC 2475 - Architecture for Differentiated Services
Traffic Priority
Historically, network layer priority was selected explicitly by the sending application through the TOS field. Although Differentiated Service (RFC 2474) preserves the IP precedence semantic of the TOS field, this approach is now deprecated. This is partly because the IP precedence has been superseded by the Per-Hop-Behaviour strategy inside Differentiated service, but also because network administrators usually don’t trust QOS specification coming from the application.
ATN application traffics can be identified / prioritised according to the destination port of datagrams when they enter the network:
• This provides transparent and safe identification of traffics, because the destination port is always a trusted information (otherwise the traffic will never reach its destination).
• But this requires specification of a distinct port for every ATN application (proliferation of ports would unnecessarily complexity administration of routers, and incurs their performance).
• During transit in the IPS network, corresponding datagrams could be marked using the Differentiated Service field, in respect to the practices indicated in RFC 2475.
Application interface to the network layer
Although applications generally accede to the communication service at the transport layer, it is sometime necessary to transmit and receive datagrams at the network level. This is granted by some socket API extensions specified in:
RFC 3542 - Advanced Sockets Application Program Interface (API) for IPv6
IPV6 Addressing Scheme
Purpose
The purpose of this document is to describe the current EUROCONTROL IPv6 addressing scheme and BGP Autonomous System Number (ASN) assignments.
The EUROCONTROL Agency has been requested to perform IPv6 address management for European ATS applications and services until an overall decision with regard to the management of a new Pan-European Network service is made.
In order to co-ordinate the management of address space a Local Internet Registry (LIR) is required. November 2004, EUROCONTROL submitted a request to RIPE (the Regional Internet Registry covering Europe) to become a LIR. This was accepted in December 2004 and in January 2005, EUROCONTROL requested its first IPv6 allocation and received a standard LIR /32 allocation:
inet6num: 2001:4b50::/32
org: ORG-EitE1-RIPE
netname: BE-EUROCONTROL-20050131
descr: EUROCONTROL, the European Organisation for the Safety of Air Navigation
country: BE
admin-c: EJC2-RIPE
tech-c: EJC2-RIPE
status: ALLOCATED-BY-RIR
notify: eivan.cerasi@eurocontrol.int
mnt-by: RIPE-NCC-HM-MNT
mnt-lower: EURO-HQ-MNT
mnt-routes: EURO-HQ-MNT
changed: hostmaster@ 20050131
source: RIPE
The above data is extracted from the RIPE database ().
LIRs with in the geographical coverage of RIPE must follow the policies defined in “IPv6 Allocation and Assignment Policy” document (ripe-267). It should be noted that this policy may be reviewed by RIPE through its experiences of allocations and assignments and may vary per RIR.
Important Definitions
Allocation
This is the address space that is set aside by a Regional Internet Registry (RIPE) for an LIR.
Sub-allocation
This is the address space that is set aside by a Local Internet Registry (EUROCONTROL Agency) for an LIR's downstream customer or organisation.
Assignment
Address space taken from the LIR allocation and given to the End User or to the LIR’s infrastructure.
IPv6 Addressing Scheme
The IPv6 addressing scheme builds on the RIPE allocation in order to provide /48 assignments.
The IPv6 addressing scheme had been developed within the context of the former EUROCONTROL iPAX Task Force which is illustrated in Figure 1. This is the scheme that is being deployed.
[pic]
The iPAX addressing scheme is structured according to following principles:
The first 32 bits are fixed to 2001:4b50 (RIPE allocation);
The 3 bits of Field F1 are assigned as follows;
|F1 Assignment |Binary |Hex |Network Name |
|1 |000 |0 |National/Regional Entities |
|2 |001 |1 |Pan-European Organisations and Entities |
The 7 bits of the fixed “Net. Prefix” field are used to number each ANSP, organisation or infrastructure that can be considered as a single entity; the high order bit of the “Net. Prefix” is set to 0 for national entities and 1 for regional entities;
The 1 bit of the v4/v6 field is a toggle bit to indicate if IP address translation is required at the network border.
The 5 bits of F2 field are assigned sequentially to provide multiple /48 per network prefix, the bit assignment follows RFC 3531 (A Flexible Method for Managing the Assignment of Bits of an IPv6 Address Block).
|F2 Assignment |Binary |Hex |Network Name |
|1 |00000 |0 |First Operational |
|2 |10000 |10 |First Pre-Operational |
|3 |01000 |8 |Second Operational |
|4 |11000 |18 |Second Pre-Operational |
|5 |00100 |4 |Third Operational |
|6 |10100 |14 |Third Pre-Operational |
|7 |01100 |C |…. |
|8 |11100 |1C |…. |
|9 |00010 |2 |…. |
|…. |…. | | |
|…. |…. | | |
|32 |11111 |1F |…. |
It is to be notedt that the current ATN/IPS applications do not require such an interface. Stakeholders assign the remaining 80 bits of the address based on their own policies but should note the advice provided in RFC 3531 (A Flexible Method for Managing the Assignment of Bits of an IPv6 Address Block); typically the first 16 bits (SLA ID) are used to represent location related information.
In order to address direct interconnections between stakeholders, the future PEN backbone or regional networks, additional address space has been planned.
Basic IPV6 Address Space Assignments and BGP as Numbers
Each stakeholder is initially assigned with a network prefix. On the basis of this network prefix, each organisation can advertise the associated /42 IPv6 address prefix at their network border.
EUROCONTROL enters this information into the RIPE database and indicate the address space as being “sub-allocated”.
Then two /48 prefixes (one for real v6 nodes and the other to represent virtual v4 nodes) for operational networks and another two for pre-operational networks will be assigned. This will correspond to 2 values of the F2 field complemented by the v4/v6 toggle bit.
EUROCONTROL will enter this information into the RIPE database on behalf of the organisation. These 4 assignments are referred to as the “basic assignment”.
This process will provide the same address space to all organisations irrespective of their size. In reality, some organisations may be operating multiple, very large or regional networks. As a consequence, the basic assignment may be insufficient or inappropriate. In such cases an alternative assignment can be made within the organisations range as long as it remains within the RIPE policy and does not compromise the overall addressing scheme.
Private BGP AS numbers within the range [64512 to 65535] are defined on the basis of the first IPv6 address assignment (v4/v6 bit and F2 set to 0). More precisely, an algorithm based on 4 hexadecimal values (nibbles) that immediately follow the /32 assignment:
• when the first nibble equals zero, the AS number is equal to the sum of decimal value 64600 and the decimal value of the following two nibbles; assignments with such values correspond to national/local networks and entities.
• when the first nibble equals one, the AS number is equal to the sum of decimal value 65100 and the decimal value of the following two nibbles; assignments with such values correspond to regional networks and entities.
• when the first nibble equals two, the AS number is equal to the sum of decimal value 65200 and the decimal value of the following two nibbles; assignments with such values correspond to pan-European networks and entities.
EXAMPLE
ROMATSA has been assigned with the Network Prefix of binary value 0100101 As a result, they have been sub-allocated with IPv6 network prefix 2001:4B50:0940::/42 which they can advertise at their border.
ROMATSA has been assigned with the following /48 network prefixes to number their systems. These addresses are indicated as being maintained by the EUROCONTROL Agency.
|inet6num: 2001:4B50:0940::/48 |Inet6num: 2001:4B50:0960::/48 |
|netname: RO-ROMATSA-OR-1 |netname: RO-ROMATSA-OV-1 |
|descr: Assignment for site RO-ROMATSA-OR-1 |descr: Assignment for site RO-ROMATSA-OV-1 |
|country: RO |country: RO |
|admin-c: CA1732-RIPE |admin-c: CA1732-RIPE |
|tech-c: CD1668-RIPE |tech-c: CD1668-RIPE |
|status: ASSIGNED |status: ASSIGNED |
|mnt-by: EURO-HQ-MNT |mnt-by: EURO-HQ-MNT |
|source: RIPE # Filtered |source: RIPE # Filtered |
|inet6num: 2001:4B50:0950::/48 |Inet6num: 2001:4B50:0970::/48 |
|netname: RO-ROMATSA-PR-1 |netname: RO-ROMATSA-PV-1 |
|descr: Assignment for site RO-ROMATSA-PR-1 |descr: Assignment for site RO-ROMATSA-PV-1 |
|country: RO |country: RO |
|admin-c: CA1732-RIPE |admin-c: CA1732-RIPE |
|tech-c: CD1668-RIPE |tech-c: CD1668-RIPE |
|status: ASSIGNED |status: ASSIGNED |
|mnt-by: EURO-HQ-MNT |mnt-by: EURO-HQ-MNT |
|source: RIPE # Filtered |source: RIPE # Filtered |
The associated BGP AS number is 64748 (64600 + decimal (94h) ).
| | | | |Operational /48 ASSIGNMENTS | | |Pre-Operational /48 ASSIGNMENTS |
| | |
|Application |Service and application theft; Database & document read, modify, insertion; wildlife(viruses, worms, Trojan Horses, |
| |etc.); Administrator services (Accts., privilege enhancement, etc.) |
|Presentation |Message-level encryption attack, |
| |copying of user display contents |
|Session |Password theft |
|Transport |Transit attacks (vs. 3rd party networks); |
| |Back/trap doors; Port scanning; Buffer overflows; NAKs |
|Network |Address spoofing, routing table corruption |
|Mac |DoS, Bulk encryption, EDAC, RX, Location |
| |attacks, key theft |
|Physical |Radio intercept, Eavesdropping, Jamming, Traffic Analysis, Physical damage |
Location of Threats
Another criterion is the location of threats. If a particular threat can occur at any point in the communication path, then it is unlikely that a data link security solution protecting a particular physical link will do the job. Security experts are notoriously paranoid people and therefore typically favor end-to-end security over hop-by-hop security for this reason. End-to-end security is most closely associated with application layer security solutions, although this is a simplification – in some circumstances transport and even network security solutions can provide security that is “end-to-end enough” (the gap in WAP is an example of transport security that was not “end-to-end enough”), whereas in other circumstances even application security solutions are not really “end-to-end” (think about using the ATN application security solution to secure GACS).
Type of Security Service
Another criterion is the type of security service required. On the one hand, there are services like non-repudiation which are best supplied by application layer security solutions – since true non-repudiation requires that the user knows what is signed when it is signed – something that is easier to ensure when only application data is involved. On the other hand, there are services like anonymity which are best supplied by lower layer security solutions – since protecting more of the bits on the wire makes it less likely that the users identity will be given away, perhaps by addressing information that appears in layer headers. Other relevant services include replay protection and message re-ordering protection – for example the IP network layer protocol does not provide guarantees to deliver messages in order and hence it is problematic to provide message effective re-ordering protection at the network layer within TCP/IP network.
Type of Data
Another criterion is the type of data to be protected. Data specific to a particular layer will not be protected by security solutions which operate at a higher layer. The ATN provides a good example here. One of the threats considered important to prevent was the possibility of injection of false information into routing tables. The ATN handles routing table updates via the IDRP protocol, which operates at the network layer. Simply put, application and transport security solution are of no use in this scenario since they will not protect the network layer IDRP information.
Efficiency
A final important criterion that must not be overlooked is efficiency. Efficiency is a broad term that can apply in different ways in different situations. For example:
• Efficiency can mean minimizing developmental overhead – which may result in a desire to use a lower layer security solution so that security does not have to be added to each application.
• Efficiency can mean minimizing the administrative overhead involved in operating a security solution – which may result in a desire to use a lower layer security solution and run packets for a number of applications through a single secure pipe.
• Efficiency can mean minimizing computational overhead.
• Efficiency can mean minimizing the bits on the wire. Interestingly the desire to minimize the bits on the wire pushed the ATN towards an application layer security solution in order to leverage the existing relationship between the CM application and other application entities.
Alternatives/Compliments to IPsec
▪ Data Link Layer
▪ Point-to-Point Tunneling Protocol (PPTP)
▪ Layer 2 Tunneling Protocol (L2TP)
▪ Layer 2 Forwarding
▪ Transport Layer
▪ Transport Layer Security (TLS)
▪ Application Layer
▪ Secure Shell (SSH)
▪ Application Specific protocols (e.g. e-mail)
▪ ATN Application Security
Need for Security at Multiple Levels in Aviation Environment
Consider a CAA-provided CPDLC service. Two of the primary threats are the introduction of hazardous information by an attacker at any point in the data’s communications path with the purpose of misleading either the pilot or the controller, and the penetration and hacking of the CAA’s network via the CPDLC communications path. No security solution at a single layer will address both these threats – end-to-end security (for example via an application layer security solution) is needed to prevent CPDLC messages being altered or injected, while perimeter protection (for example via a network layer security solution or firewall) is needed to prevent penetration of other systems within the CAA’s network. End-to-end security does not prevent penetration into other systems since the target systems do not implement CPDLC security, and perimeter security does not prevent CPDLC messages being altered or injected within the CAA’s network perimeter.Voice over Internet Protocol (VoIP)
The key advantages associated with the use of a packet network for the transmission of digitized voice are:
• Bandwidth allocation efficiency
• Ability to use modern voice compression methods
• Associate economics with shared network use
• Reduce costs
• Enhanced reliability of packet networks
• Ability to use multiple logical connections over a single physical circuit.
8.1 Standards and Protocols
There are two standardized frame works for implementing VoIP, H.323 and SIP. Although both protocols may be used for VoIP applications, the original focus of each protocol is different. The focus of H.323 has been to handle voice and multimedia calls, including supplementary services, while SIP was designed as a generic transaction protocol for session initiation not bound to any specific media (e.g., audio or video). Details of relevant protocols are described in the following subsection:
8.1.1 H323
As shown in Figure 8.1, H.323 operates in the application layer to support multimedia, data and signalling protocols. Also depicted in Figure 7.1 are the various protocols used to convey multimedia traffic over TCP/UDP/IP networks.
Multimedia Data Transfer Signalling
1 Figure 8.1 H.323 Core Architecture
2
8.1.2 Multimedia
This group of protocols converts between analog (e.g., voice) and digital signals, which are fed into, or picked from, the UDP/IP network. Some of these protocols include:
• Audio codecs – These compress digital voice for low bandwidth transmission, and decompress digital voice received from the network for feeding to the user audio device (e.g., speaker, headphone).
• Video codecs – These compress digital video for constrained bandwidth, and decompress digital video received from the network for feeding to the user video device.
• RTP (Real-Time Transport Protocol) and RTP Control Protocol (RTCP) – These are control protocols for the payloads fed into the network. RTP regulates the end-to-end delivery of audio and video in real time over IP networks. RTCP regulates the control services in multimedia transmissions, and monitors the quality of its distribution, including synchronization of receivers.
8.1.3 Data Transfer
This class of protocols provides real-time, multi-point data communications and application services over IP networks (e.g., collaborative decision making with video, voice, and data exchange). Data transfers between generic applications and the IP network are processed by the T.120 protocol, which can operate over various transports, including PSTN and ISDN.
T.130 is a protocol still under development for controlling audiovisual sessions for real-time multimedia conferencing, and ensure high QoS.
8.1.4 Signalling
H.225.0 call signalling is used to set up connections and exchange call signalling between H.323 endpoints (terminals and gateways), which are transported as real-time data and carried over the TCP/UDP/IP network. H.225.0 uses Q.931 for call setup and teardown.
H.245 control signalling is used to exchange end-to-end messages between H.323 endpoints. The control messages are carried over H.245 logical control channels, which are relayed between conference session endpoints.
H.235 provides security services within the H.323 framework, such as authentication, encryption, integrity and no-repudiation.
H.450.1 deals with the procedures and signalling protocol between H.323 entities for the control of supplementary services. Other protocols within the H.450 series (i.e. H.450.2-12) provide specific supplementary services (e.g., call transfer, call hold, call waiting, call priority).
8.2 MGCP/MEGACO
Shown in Figure 8.2 is the SIP Protocol Suite. SIP is an application layer control protocol that provides advanced signalling and control functionality for large range multimedia communications. SIP is an alternative to H.323, which establishes, modifies, and terminates multimedia sessions, which can be used for IP telephony. SIP is an important component in the context of other protocols to enable complete multimedia architecture, as shown in Figure 4. These include RTP for real time data transport and QoS assurance, RTSP for controlling streaming media, MEGACO for controlling gateways to the PSTN, Figure 8.3, and SDP for describing multimedia sessions. These sessions include Internet multimedia conferences, Internet telephone calls, and multimedia distribution over TCP/UDP/IPv4, or IPv6, as shown in Figure 8.4.
Figure 8.2 SIP Protocol Suite
[pic]
[pic]
Annex 1 Example Implementation Guide
In order to ensure a uniform and consistent implementation of the ATN across state or regional boundaries an implementation guide should be developed to document the minimum network services, protocol provisioning parameters, and implementation sequence that should be performed to maintain the integrity of the network. The following document is an example Implementation Guide
1.
Scope of this document
2.
3. The document describes requirements of the various communications protocols to ensure transmission and reception of surveillance data in an IP network environment. These requirements are presented in the form of a Protocol Requirements List (PRL)
4. A Protocol Implementation Conformance Statements (PICS) proforma is attached as Annex 1 to facilitate the interaction with potential suppliers.
5. The purpose of this document is to ensure compatibility of different IPv4 multicast implementations of surveillance data transmission over an IPv4 network service and to ensure compatibility of different IPv6 multicast implementations of surveillance data transmission over an IPv6 network service.
6. Other networking techniques that achieve the same multicast objective may consider certain provisions within this implementation guide but are not further considered within the scope of this document.
7. It is the intention of the concerned ANSPs that the procurement of a system based on commercial-of-the-shelf (COTS) products will provide the maximum benefit/cost ratio with the minimum risk of timescale overrun. The organisation and content of this document and the instructions are designed to facilitate the interaction with potential suppliers.
8.
Differences to previous edition
9.
10. This new edition of the implementation guide clarifies the content and scope of the IP versions 4 and 6.
11. Since the previous edition, significant technical progress has been made in the field of IP multicast, namely source specific multicast (SSM). SSM provides added simplicity and resiliency to the routing of IP multicast traffic, which is of particular interest for inter-ANSP communications. SSM is recommended within this guideline for that purpose.
12. In this new edition of the guideline, the default maximum message size has been reduced from 512 bytes to 256 bytes.
13.
Use of the Document
14.
15. This document can be used for a different purposes, including the following:
16. a) As a checklist by the protocol implementers, to reduce the risk of failure during surveillance data exchanges in IP multicast;
17. b) As a detailed specification of the requirements, to assist the procurement of an IP multicast implementation for surveillance data exchange;
18. c) As a basis for initially checking the possibility of interworking with another implementation. (Note that, while interworking can never be guaranteed, failure to interwork can often be predicted from incompatible PICS);
19. d) As the basis for selecting appropriate tests by a protocol tester, to assess the conformance of the implementation.
20. This implementation guide describes the characteristics of transmitters and receivers using an IP multicast network.
21. Furthermore, this implementation guide facilitates the introduction of multicast within an international context through the use of source specific multicast (SSM).
22. Mandatory capabilities are denoted with the terms “shall” or “must”; desired capabilities are denoted with the term “should”. Suppliers are encouraged to propose COTS systems that provide all the mandatory capabilities and as many desired capabilities that are available with a minimum amount of development.
23. The terms "SHALL", "SHALL NOT", “MUST”, “MUST NOT”, "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY" and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
24.
General context
25.
26. A transmitter or receiver using IP multicast technology shall implement a set of protocols as described below:
27.
28. a) Data link layer: For the end-users of surveillance data distribution in IP multicast, this implementation guide assumes that end-user system is connected to Ethernet local area network (LAN).
29. b) Network layer: The compliant systems shall implement the IPv4 and IPv6 protocols (as well as ICMP and ICMPv6) as described in the references presented in this document.
30. c) Transport layer: User Datagram Protocol (UDP) shall be the transport layer for IP multicast services. (TCP is used by surveillance systems but is not within the scope of this implementation guide).
31.
32. These specifications are independent of the network point of attachment of the transmitters and receivers.
33.
Organisation of the Document
34. This document is composed of the following sections.
35. Section 1: provides an introduction including information about the document structure, instructions to Suppliers, conformance with the ECAC Strategy and reference documents.
36. Section 2: describes the "Communication protocols" and the associated technical requirements.
37. Section 3: describes the "Implementation requirements" (interface between applicative layer et communication layer)
38. Annex 1 provides Protocol Implementation Conformance Statements (PICS) proforma to facilitate the process of technical offers by Suppliers.
39. Annex 2 provides an abbreviation list of terms used within the document.
40.
Symbols Used
41.
|The following symbols are used in the present document: |
|RDPRL_n | |A scheme to number each requirement in this implementation guideline |
|M |: |Mandatory capability (or field) |
|! |: |Logical negation, applied to a conditional item symbol |
|O |: |Optional capability (or field) |
|O. |: |Optional capability (or field), but at least one of the group of options labeled by the same numeral |
| | |is required |
|O/ |: |Optional field/ capability, but one and only one of the group of options labeled by the same numeral |
| | |is required |
|X |: |Prohibited capability (or field) |
| : | |simple-predicate condition, dependent on the support marked for |
|*: | |AND-predicate condition, the requirement shall be met if both optional items are implemented |
| | | |
| |The ECAC strategy for the 1990s, containing the overall objective “to provide increasing airspace and |
| |control capacity urgently while maintaining a high level of safety”, was adopted by the ECAC Transport |
| |Ministers in 1990. In addition to the overall objective, the ECAC Strategy specified five implementation |
| |objectives, addressing radar, communications, airspace management, common standards and specifications, |
| |and human factors. To achieve these objectives, the European Air Traffic Control Harmonisation and |
| |Implementation Programme (EATCHIP) was created. |
| | |A second ECAC Strategy, addressing capacity at airports and in terminal areas, was adopted by the ECAC |
| | |Transport Ministers in 1992, and resulted in the creation of the Airport and Air Traffic Services |
| | |Interface (APATSI) programme. A subsequent decision by the ECAC Transport Ministers has resulted in the |
| | |absorption of this programme into EATCHIP, in a philosophy known as “gate-to-gate”. |
| | |The first phase of EATCHIP was one of appraising the current situation in order to obtain, for the first |
| | |time, a complete picture of the European ATC services, systems and procedures. This was followed by a |
| | |programme development phase in which the deficiencies and problems identified in the first phase were |
| | |addressed. |
| | |As a result of this second phase, two complementary programmes were established; the EATCHIP Work |
| | |Programme (EWP) and the Convergence And Implementation Programme (CIP). The aim of these programmes is |
| | |the accomplishment of the third phase of EATCHIP, to operationally integrate the European ATM system. |
| | |The basis for the harmonisation and integration process is the Convergence and Implementation Programme |
| | |Document (CIPD) which provides a reference and a framework for national and multi-national plans. The |
| | |CIPD contains CIP Objectives for which functional performance levels are defined, the applicability of |
| | |which is dependent upon the subject airspace complexity. |
| | |Complementary to the CIP, as part of the EATCHIP Work Programme, operational requirements, CNS/ATM |
| | |architecture, and technical specifications are being defined as a means of realisation of the CIP |
| | |Objectives |
Link to the ATM 2000+ Strategy
42. In order to cope with the increase level of traffic and to bring further substantial gains in ATM capacity and efficiency to meet this predicted future demand, a uniform European ATM Strategy for the year 2000+ has been developed. This strategy is built on the previous work and results of the EATMS, EATCHIP and APATSI.
43. This ATM2000+ Strategy has led to the development of the EATMP Programme, which is described in the EATMP Work Programme (EWP) and to the revision of the CIP Process. New requirements emerging from EATMP after having successfully passed the validation process and judged sufficiently matured were introduced in this document.
44. An EATMP Communication Strategy Document has been released on 13 Jan. 2003 as version 4.2. This document is an updated version of the original EATCHIP Communication Strategy released in 1998. This implementation guideline is fully in line with this strategy.
45.
Reference Documents
a) ICAO Annex10 Volumes I and II.
b) EATMP Communications Strategy, Volumes 1 and 2, Released Issue 13 Jan. 2003.
c) Eurocontrol EGIS Part 5 Communication & Navigation Specifications Chapter 12 Surveillance Distribution Over Ipv4 Multicast Profile Requirement List (PRL) Edition 1 dated 23/06/2003.
d) STNA document reference 8CR02032 dated 08/11/02 available from STNA sub-division 8/CR.
e) IEEE 802.3 "Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specification" dated 2005.
f) Electronic Industries Alliance/Telecommunications Industry Association "Commercial Building Telecommunications Cabling Standard" (EIA/TIA 568-B) dated 01 Apr. 2001
g) Internet Society "User Datagram Protocol" (STD0006/RFC768) dated 01 Aug. 1980
h) Internet Society "Internet Protocol" (STD0005/RFC791) dated 01 Sep. 1981.
i) Internet Society "Internet Control Message Protocol" (STD0005/RFC792) dated 01 Sep. 1981.
j) Internet Society "A Standard for the Transmission of IP Datagrams over Ethernet Networks" (STD0041/RFC894) dated 01 Apr. 1984.
k) Internet Society "Internet Standard Subnetting Procedure" (STD0005/RFC950) dated 01 Aug. 1985.
l) Internet Society "Host Extensions for IP Multicasting" (RFC1112) dated 01 Aug. 1989
m) Internet Society "Requirements for Internet Hosts - Communication Layers" (STD0003/RFC1122) dated 01 Oct. 1989
n) Internet Society “Key words for use in RFCs to Indicate Requirement Level”(BCP14/RCF2119) dated March 1997
o) Internet Society “Internet Protocol, Version 6 (IPv6) Specification” (Draft Standard / RFC 2460) dated December 1998.
p) Internet Society “Neighbour Discovery for IP version 6 (IPv6)” (Draft Standard / RFC 2461) dated December 1998
q) Internet Society “IPv6 Stateless Address Autoconfiguration” (Draft Standard / RFC 2462) dated December 1998
r) Internet Society “Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers” (Proposed Standard / RFC 2474) dated December 1998
s) Internet Society “Unicast-Prefix-based IPv6 Multicast Addresses” (Draft Standard / RFC 3306) dated August 2002
t) Internet Society “Allocation Guidelines for IPv6 Multicast Addresses” (Proposed Standard / RFC 3307) dated August 2002.
u) Internet Society “Default Address Selection for Internet Protocol version 6 (IPv6)” (Proposed Standard / RFC 3484) dated February 2003.
v) Internet Society “Basic Socket Interface Extensions for IPv6” (Informational / RFC 3493) dated February 2003
w) Internet Society “An Overview of Source-Specific Multicast (SSM)” (Informational / RFC 3569) dated July 2003
x) Internet Society “Source Address Selection for the Multicast Listener Discovery (MLD) Protocol” (Draft Standard / RFC 3590) dated September 2003
y) Internet Society “Multicast Listener Discovery Version 2 (MLDv2) for IPv6” (Proposed Standard / RFC 3810) dated June 2004
z) Internet Society “IP version 6 Addressing Architecture” (Draft Standard / RFC 4291) dated February 2006.
aa) Internet Society “IPv6 Node Requirements” (Informational / RFC 4294) dated April 2006
bb) Internet Society “Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification” (Draft Standard / RFC 4443) dated March 2006
cc) Internet Society “Source-Specific Multicast for IP” (Draft Standard / RFC 4607) dated August 2006.
Communication Protocols Requirements
46.
Introduction
47.
48. The former EUROCONTROL iPAX Task Force identified the difficulty to
49. introduce IP pan-European network services between ANSPs in view of the
50. current IPv4 implementations.
51.
52. In its conclusions, it clearly recommended the introduction of IPv6 for inter
53. ANSP data exchanges which are typically cross-border. These conclusions
54. were applicable to both unicast and multicast network services.
55.
56. As source specific multicast (SSM) is particularly suited to inter-ANSP data exchanges, this document describes the use of IPv6 in conjunction with SSM.
57.
IP Version
58.
59. RDPRL_1. The surveillance data flows that cross national borders are required to use the IPv6 protocol due to the architecture of the trans-national backbone network. Surveillance data flows that remain inside national borders use either IPv4 or IPv6 depending on the architecture of the national network infrastructure.
60. RDPRL_2. All surveillance data transmitters or receivers that are intended to send or receive data beyond the local domain, ie across national borders, should be IPv6-compliant.
61. Note: non IPv6-compliant surveillance data transmitters or receivers that are intended to send or receive cross-border data, will require the use of an application layer gateway (ALG) to convert the IPv4 surveillance data stream to IPv6. The description of the ALG is beyond the scope of this document and at the time of writing the existence of such implementations has not been identified.
62.
Data Link Layer
RDPRL_3. All IPv4-compliant systems shall be able to send and receive IPv4 packets using RFC 894 encapsulation (item n° 1.2.1.1 of Annex 1).
RDPRL_4. All IPv4-compliant systems shall conform to the recommendations in section 2 of the RFC 1122 as listed in Annex 1 when sending and receiving IPv4 packets.
RDPRL_5. All IPv6-compliant systems shall be able to send and receive IPv6 packets using RFC 2464 encapsulation (item n° 1.2.2.1 of Annex 1).
RDPRL_6. All IPv6-compliant systems shall conform to the recommendations in section 3 of the RFC 4294 (IPv6 Node Requirements) as listed in Annex 1 when sending and receiving IPv6 packets.
RDPRL_7. IEEE 802.3 standard specifies a rate of transmission going from 1 to 1 000 Mega bits per second. However, surveillance data distribution is speed transmission independent. Thus, these specifications shall be applied to 10 Mbps infrastructures (item n° 1.1.1 of Annex 1) as well as on 100 Mbps infrastructures (item n ° 1.1.2 of Annex 1) and 1000 Mbps infrastructures (item n° 1.1.3 of Annex 1).
Ethernet Frame Format
RDPRL_8. All frames exchanged by systems shall be in conformity with the format presented in the diagram 2.1.1 below.
Figure: 2.1.1: Frame format
IPv4 Addressing
RDPRL_15. The destination address of Ethernet frames (DMAC) shall be derived from the IPv4 multicast destination address. (item no 1.3.1.1 of Annex 1). This derived destination Ethernet address is also called multicast address.
RDPRL_16. The IPv4 implementations of this document shall be in conformity with sections 6.4 and 7.4 of RFC 1112 according to their system role (transmitter and/or receiver).
RDPRL_17. The following diagram presents an example of the multicast MAC address that is derived from IPv4 multicast destination address: IPv4 Multicast Address = 239.255.0.1
[pic]
Figure: 2.3.2: Example of the Derived Multicast MAC Address for IPv4
IPv6 Addressing
RDPRL_18. All systems shall support the neighbour discovery protocol functions described in RFC 4294 section 4.2 (items no 2.2.1.2 to 2.2.1.9 of Annex 1)
RDPRL_19. The destination address of Ethernet frames (DMAC) shall be derived from the IPv6 multicast destination address. (item no 1.3.2.2 of Annex 1). This derived destination Ethernet address is also called multicast address.
The Ethernet MAC is derived by the four low-order octets of the IPv6 address OR'ed with the MAC 33:33:00:00:00:00, so for example the IPv6 address FF3E::8000:1 would map to the Ethernet MAC address 33:33:80:00:00:01
[pic]
Figure: 2.3.3: Example of the Derived Multicast MAC Address for IPv6
Network Layer
Internet Protocol version 4
An IPv4-compliant UDP/IP multicast implementation shall be in conformity with
the following referenced documents:
RDPRL_22. a) RFC 791: which defines the IPv4 protocol;
RDPRL_23. b) RFC 792: which defines ICMP (supplementary functionalities described further);
RDPRL_24. c) RFC 950: which defines an addressing extension;
RDPRL_25. d) RFC 1112: which provides the necessary recommendations for
multicast.
RDPRL_26. Section 3 of RFC 1122 shall prevail in case of any discrepancy between
The referenced documents.
RDPRL_27. The following diagram presents the IPv4 packet header:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live | Protocol | Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Options | Padding |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
(Diagram 14.2.1. : IPv4 datagram header (extract from RFC 791)
a) Version
RDPRL_28. In the case of IPv4, the version is 4. (items n° 2.1 and 2.1.5 of Annex 1)
b) Internet Header Length (IHL) – in 32 bits words
RDPRL_29. Within the context of surveillance data distribution over IP multicast, this field
should have value 5 as no IP options are used (section 2.2.2).
c) Type of service (TOS)
RDPRL_30. The surveillance data transmitter systems (in IP multicast) shall allow the
setting of this field (item n° 3.1.1.16 of Annex 1).
RDPRL_31. Recommendations of the RFC 795 shall not be followed.
RDPRL_32. For receiver systems, the value of this field may be passed up to transport and
applicative layer (item n° 2.1.14) but this value shall not be taken into account
for a possible filtering.
d) Total length
RDPRL_33. The field “Total Length” indicates the full IP packet length including header and
data, measured in bytes.
e) Identification
RDPRL_34. An identification value shall be assigned by the transmitter in order to identify
the IP fragments of a same datagram.
f) Flags
RDPRL_35. This three-bit encoded field shall be used in conformity with the specification
of the RFC 791.
RDPRL_36. The use of the first bit (in big-endian bit order, so bit 0) is reserved: its value
shall be null.
RDPRL_37. The two other bits are named DF (Don’t Fragment) and MF (More fragments)
bits in conformity with the RFC 791.
RDPRL_38. Within surveillance data distribution, systems connected to local area networks
(whether they are transmitters or receivers) do not have to manage
fragmentation2. So, the value of this field filled by the transmitter is null (all bits
set to 0). However, the DF bit, used in order to forbid fragmentation may be
positioned to 1 according to the transmitter system parameters setting (item n°
3.1.1.16 of Annex 1).
g) Fragment Offset
RDPRL_39. This field indicates the shift of the first byte of the fragment in reference to the
complete datagram. This relative position is measured with 8 byte (64 bits)
blocks. The shift of the first fragment is worth zero.
RDPRL_40. Transmitter and receiver systems that comply to this guideline do not have to
manage fragmentation2. So, the value of this field filled by the transmitter is
null (all bits set to 0).
h) Time to live
RDPRL_41. The systems transmitting or receiving surveillance data in IP multicast shall enable this field value setting.
RDPRL_42. For receiver systems, this field shall not be taken into account.
i) Protocol
RDPRL_43. Surveillance data distribution makes use of UDP datagrams, therefore the
value of this field is 17 (decimal).
Note : For ICMP packets, the value of this field is 1.
j) Header checksum
RDPRL_44. For transmitters, this field shall be filled in conformity with the indications of the
RFC 791.
RDPRL_45. For receivers, this field shall be checked. When a packet is received with a
bad checksum, the packet shall be discarded (item n° 3.1.1.8 of Annex 1).
k) Source address
RDPRL_46. The value of this field is chosen by the transmitting applicative layer:
parameters setting enable to fix the source address used when packets are
sent (item n° 3.1.1.13 of Annex 1).
RDPRL_47. A surveillance data receiver shall not filter the received packets with this field:
all source IP addresses are valid for receiving IP multicast packets.
l) Destination address
RDPRL_48. The value of this field is chosen by the transmitting applicative layer:
parameters setting enable to fix the destination address used for sending
packets (item of Annex 1 n° 3.1.1.16).
RDPRL_49. An IP multicast receiver system shall ensure that layer 3 IP multicast address
information is forwarded to the application that requested to join a specific IP
multicast group (item n° 2.1.31 of Annex 1)
Note : This is essential if the receiver subscribes to multiple IP group
addresses.
P options
RDPRL_50. For surveillance data distribution, IP options shall not be used.
ICMP
RDPRL_51. Implementations of the protocol described in the RFC 792 shall be in
conformity with section 3.2.2 of the RFC 1122.
RDPRL_52. When an “Echo request” ICMP message is received by a surveillance data
transmitter (radar, conversion module, etc.), an answer shall be returned («
Echo reply » ICMP message) in conformity with RFC 792 and section 3.2.2.6
of the RFC 1122.
RDPRL_53. In response to an “Echo request” ICMP message, the ”Echo reply” message is
sent :
RDPRL_54. • By using a source IP address corresponding to:
RDPRL_55. a) the destination IP address used for sending the «Echo Request»
message, when it is a unicast address;
RDPRL_56. b) the IP address associated with the network interface on which the
message had been received, when it is a multicast or broadcast
address;
RDPRL_57. • By using a destination address corresponding to the source IP address
used for sending the « Echo Request » message;
RDPRL_58. • By using the same data as those received in the «Echo Request»
message.
RDPRL_59. Concerning the implementation of ICMP “Echo Reply” message, system
configuration shall allow the user to:
RDPRL_60. • Suppress of all transmission of these messages;
RDPRL_61. • Limit the send data size in the “Echo Reply” message (from 0 to 65 500
octets).
IGMP
RDPRL_62. The system should support the IGMP3 protocol as described in Appendix 1 of
the RFC 1112. (item n° 2.1.2.1 of Annex 1).
RDPRL_63. If IGMP is implemented, the system shall support IGMP version 2 and allow
the disabling of this protocol.
RDPRL_64. The IPv4 network infrastructure may statically forward multicast surveillance
data to the LAN on which the receiver system is located. If this is the case,
then the receiver is not required to support IGMP.
RDPRL_65. If the IPv4 network infrastructure does not statically forward the multicast
surveillance data to the LAN on which the receiver system is located, then the
receiver must support IGMP as described in RDPRL_62.
Internet Protocol version 6
An IPv6-compliant UDP/IP multicast implementation shall be in conformity with
the following referenced documents:
RDPRL_66. a) RFC 2460: which defines the IPv6 protocol;
RDPRL_67. b) RFC 4443 which defines ICMP for IPv6 (supplementary functionalities
described further);
RDPRL_68. c) RFC 4291 which defines the IPv6 addressing architecture.
RDPRL_69. d) RFC 4294 section 4.
RDPRL_70. e) Path MTU discovery should be supported. If Path MTU discovery is not supported, IPv6 packets sent must be no larger than 1280 bytes.
RDPRL_71. The following diagram presents the IPv6 packet header:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14.4.2.1: IPv6 header format (extract from RFC 2460)
a) Version
RDPRL_72. In the case of IPv6, the version is 6. (items n° 2.2 and 2.2.2.1 of Annex 1)
b) Traffic Class
RDPRL_73. The surveillance data transmitter systems (in IP multicast) shall allow the
setting of this field (item n° 3.1.2.13 of Annex 1).
Note – Network operators may overwrite this setting for management
purposes.
RDPRL_74. For receiver systems, the value of this field can be passed up to transport and
applicative layer (item n°2.2.2.9) but this value shall not be taken into account
for a possible filtering.
c) Flow Label
RDPRL_75. The “Flow Label” field shall be set to 0.
d) Payload Length
RDPRL_76. Length of the IPv6 payload, i.e., the rest of the packet following the IPv6
header, in octets.
e) Next Header
RDPRL_77. Identifies the type of header immediately following the IPv6 header. The values are compatible with those specified for the IPv4 protocol field as described in
the IANA database. If there are no extension headers (see i) below), the value of this field shall be 17 (decimal), corresponding to the UDP protocol.
f) Hop Limit
RDPRL_78. The systems transmitting or receiving surveillance data in IPv6 multicast shall enable setting this field value.
g) Source address
RDPRL_79. The value of this field shall be chosen by the transmitting application layer:
parameter setting enabling the selection of the source address used when
packets are sent (item n° 3.1.2.11 of Annex 1).
RDPRL_80. An IPv6 multicast receiver system shall ensure that layer 3 IPv6 source
address information is forwarded to the application that requested to join a
specific IPv6 source specific multicast channel (item n°2.2.2.13 of Annex 1)
Note: This is essential if the receiver subscribes to multiple IPv6 multicast
channels.
h) Destination address
RDPRL_81. The value of this field shall be chosen by the transmitting application layer:
parameter setting enabling the selection of the destination address used for
sending packets (item of Annex 1 n° 3.1.2.13).
RDPRL_82. An IPv6 multicast receiver system shall ensure that layer 3 IPv6 multicast
address information is forwarded to the application that requested to join a
specific IPv6 multicast group (item n° 2.2.2.13 of Annex 1)
Note: This is essential if the receiver subscribes to multiple IPv6 group
addresses.
i) Extension header
RDPRL_83. In IPv6, optional internet-layer information is encoded in separate headers that may be placed between the IPv6 header and the upper- layer header in a packet. A surveillance data IPv6 packet may carry a fragment header.
In that case the extension header value is 44.
RDPRL_84. The fragment header, if present, must conform to RFC 2460 sections 4.1 and 4.5. (item n° 2.2.2.5 of Annex 1).
RDPRL_85. Surveillance data distribution makes use of UDP datagrams, therefore the value of the “next header” field in the fragment header is 17 (decimal).
ICMP
RDPRL_86. When an “Echo request” ICMP message is received by a surveillance data transmitter (radar, conversion module, etc.), an answer shall be returned («
Echo reply » ICMP message) as required in section 4.1 of RFC 4443.
RDPRL_87. In response to an “Echo request” ICMP message, the ”Echo reply” message shall contain the following fields:
RDPRL_88. • The IPv6 source address shall correspond to :
RDPRL_89. a) the destination IPv6 address used for sending the “Echo Request”
message, when it is a unicast address;
RDPRL_90. b) the IPv6 address associated with the network interface on which the
message had been received, when it is a multicast or broadcast
address;
RDPRL_91. • The destination IPv6 address shall correspond to the source IP address
used for sending the « Echo Request » message;
RDPRL_92. • The data received in the “Echo Request” message shall be returned
entirely and unmodified in the ”Echo reply” message
RDPRL_93. Concerning the implementation of ICMP “Echo Reply” message, system
configuration shall allow the user to:
RDPRL_94. • Suppress all transmission of these messages;
RDPRL_95. • Limit the sent data size in the “Echo Reply” message (from 0 to 65 500
octets).
MLD
RDPRL_96. The system should support the Multicast Listener Discovery protocol version 2 (MLDv2) as described in RFC 3810 (item n° 2.2.4.1 of Annex 1).
RDPRL_97. The system should implement the source address selection mechanism for the MLDv2 protocol described in RFC 3810 sections 5.1.13 and 5.2.13.(item
n° 2.2.4.2 of Annex 1).
RDPRL_98. The IPv6 network infrastructure may statically forward multicast surveillance data to the LAN on which the receiver system is located. If this is the case, then the receiver is not required to support MLDv2.
RDPRL_99. If the IPv6 network infrastructure does not statically forward the multicast
surveillance data to the LAN on which the receiver system is located, then the
receiver must support MLDv2 as described in RDPRL_96 and RDPRL_97.
Transport layer
RDPRL_100. Surveillance data distribution over IP multicast is based on the use of the UDP transport protocol. Systems shall be in full conformance with the RFC 768.
RDPRL_101. The following figure presents the UDP datagram:
[pic]
Figure 14.3: UDP Header and Data
4.5.1 Addressing
RDPRL_102. UDP transport layer addressing is based on source and destination port numbers.
RDPRL_103. If an IPv6 datagram arrives addressed to a UDP port for which there is no pending LISTEN call, the IPv6-compliant UDP/IP multicast layer implementations shall send an ICMP Destination Unreachable message with code 4 (Port Unreachable) as described in section 3.1 of RFC 4443
RDPRL_104. IPv4-compliant UDP/IP multicast layer implementations shall be in conformity with section 4.1.3.1 of the RFC 1122.
UDP checksum
RDPRL_105. All systems shall implement the generation and the validation of UDP
checksums.
• Surveillance data transmitter system:
RDPRL_106. The UDP checksum value shall be put into the corresponding field.
When the checksum value is 0, the source shall transmit an UDP segment
with all bits of the checksum field set to 1 (65535 - decimal).
• Surveillance data receiver system:
RDPRL_107. The receiver system shall verify that the specified value is valid. In this case, the data is passed to the upper layer application.
RDPRL_108. When an invalid UDP datagram is received, it shall be discarded.
RDPRL_109. When a UDP segment is received with a no checksum (value zero), data shall be discarded and an error shall be reported to the upper layer application.
RDPRL_110. When a UDP segment is received with a no checksum (value zero) in an IPv4 packet, data shall be passed up to the applicative layer.
Limitation of maximum size of messages
RDPRL_111. To ensure migration and compatibility with legacy telecommunication
equipment and technologies (which does not permit fragmentation or is non-IP
based), the limitation of the UDP data size shall be a system parameter.
RDPRL_112. Transmitter systems should be capable of limiting the data size as low as 256 bytes. A default maximum size value of 256 bytes should be configured4.
RDPRL_113. However, this is transparent to the receiver systems. Receiver systems shall not limit the size of incoming UDP datagrams.
SPECIFIC CONFIGURATION REQUIREMENTS
This section describes the specific configuration requirements for the development of surveillance data distribution systems over IP Multicast. This chapter does not take into account all the parameters that shall be configurable (such parameters are indicated in the reference documents). A LAN connected system shall be at least one of the following :
RDPRL_114. • a surveillance data transmitter;
RDPRL_115. • a surveillance data receiver;
Note: A transmitter system may be the originator of several radar flows, hence,
the source of several IP multicast groups.
Surveillance Data Transmitter
Common (IPv4 and IPv6) configuration requirements
RDPRL_116. When the application layer is used for sending radar data, there shall be a mechanism (configuration or parameter setting) enabling to specify, per radar
and for per physical interface, the following elements:
RDPRL_117. • For multi-homed systems, the source address to use (items n° 3.1.1.16 and 3.1.2.13 of Annex 1);
RDPRL_118. • destination UDP port number (items n° 3.1.1.16 and 3.1.2.13 of Annex 1):
all port numbers from 1024 to 65535 shall be configurable – default value :
8600.
The default port number associated with ASTERIX content is 8600 which is
registered with IANA.
RDPRL_119. When the same sensor is capable of providing more than one surveillance data flow, different multicast addresses should be defined within the transmitter.
IP version 4 specific configuration requirements
RDPRL_120. When the application layer is used for sending radar data, there shall be a mechanism (configuration or parameter setting) enabling to specify, per radar
and for per physical interface, the following elements:
RDPRL_121. • Data message maximum size (item n° 4.1.1 of Annex 1), possible values (in bytes): 256, 512, 1472 (maximum message size for a non-fragmented
Ethernet frame), 1497 (maximum message size for a MAC/LLC1 frame),
others (paragraph2.6) – default proposed value: 256 bytes.
RDPRL_122. • The data IP multicast address group: all class D addresses (address range 224.0.0.0/8) shall be configurable (items n° 3.1.1.16 and n° 2.1.31 of Annex
1) ;
RDPRL_123. • TTL field value (item n° 2.1.31 of Annex 1), from 1 to 255 (hexadecimal) – default proposed value: 32;
RDPRL_124. • TOS/DS field value (item n° 2.1.31 of Annex 1), all allowed values by RFC 791 and RFC 2474 shall be configurable – default proposed value: 0;
RDPRL_125. • authorization or not to fragment datagrams (DF bit value : item n° 2.1.31 of Annex 1) – default value : Authorization to fragment (DF bit = 0);
RDPRL_126. For a given multicast group, a multicast source shall never retransmit the same surveillance data message on the same interface in order to avoid duplicates at the receiver end.
RDPRL_127. For a given multicast group, a multicast source may use different interfaces to transmit as long as each surveillance data message is transmitted only once.
RDPRL_128. For a given multicast group, a multicast source may retransmit the same surveillance data message on different interfaces for resiliency purposes if the
local network access routers are capable of suppressing the duplicate
messages. .
P version 6 specific configuration requirements
RDPRL_129. The surveillance data is delivered using the source specific multicast (SSM) service. A data channel is defined by the combination of destination multicast
address and source unicast address, and contains a single surveillance data flow.
RDPRL_130. The IPv6 multicast destination address shall be a source specific multicast address as specified in RFC 3306 section 6 and RFC 4607 section 1.
RDPRL_131. The scope of IPv6 multicast destination address shall be global, as specified in RFC 4291 section 2.7.
RDPRL_132. The following figure shows such an IPv6 multicast address:
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+
|11111111|0011|1110|00000000|00000000| 000……………………000 | group ID |
+--------+----+----+--------+--------+----------------+----------+
Figure 15.1: SSM Multicast IPv6 address with global scope
RDPRL_133. The IPv6 multicast group ID shall be in the range 0x8000000 to 0xFFFFFFFF allowed for dynamic assignment by a host, as specified in RFC 3307 section 4.3 and RFC 4607 section 1.
RDPRL_134. The resulting available IPv6 SSM address range is FF3E::8000:0/97
(FF3E:0:0:0:0:0:8000:0 / 97).
RDPRL_135. Every multicast group ID identifies a particular surveillance data flow (a radar station may produce more than one surveillance data flow).
RDPRL_136. When the application layer is used for sending radar data, there shall be a mechanism (configuration or parameter setting) enabling to specify, per radar
and for per physical interface, the following elements:
RDPRL_137. • Data message maximum size (item n° 4.1.1 of Annex 1), possible values (in bytes): 256, 512, 1232 (message size corresponding to a minimum size
IPv6 packet, ie 1280 bytes), 1452 (maximum message size for an Ethernet
frame), 1497 (maximum message size for a MAC/LLC1 frame), others
(paragraph2.6) – default proposed value: 256 bytes.
RDPRL_138. • The data IPv6 multicast address: all addresses in range FF3E::8000:0/97 shall be available except FF3E::8000:0 (items n° 3.1.2.13 and n° 2.2.2.13 of Annex 1) ;
RDPRL_139. • Hop Limit field value (item n° 2.2.2.13 of Annex 1), from 1 to 255
(hexadecimal) – default proposed value: 32;
RDPRL_140. • Traffic Class field value (item n° 2.2.2.13 of Annex 1), all allowed values by RFC 2460 and RFC 2474 shall be configurable – default proposed value:
0;
RDPRL_141. For a given multicast channel, a multicast source shall never retransmit the same surveillance data message on the same interface in order to avoid
duplicates at the receiver end.
RDPRL_142. For a given multicast channel, a multicast source may use different interfaces to transmit as long as each surveillance data message is transmitted only once.
RDPRL_143. For a given multicast channel, a multicast source may retransmit the same surveillance data message on different interfaces for resiliency purposes if the
local network access routers are capable of suppressing the duplicate
messages.
Surveillance Data Receiver
Common (IPv4 and IPv6) configuration requirements
RDPRL_144. When an application layer is used for receiving radar data, there shall be a mechanism (configuration or parameter setting) enabling to specify, per radar,
the following elements:
RDPRL_145. • destination UDP port number (items n° 3.1.2.13 and n° 2.2.2.13 of Annex 1) all port numbers from 1024 to 65535 shall be configurable – default
value : 8600.
RDPRL_146. • The interface used to receive the data (items n° 3.1.1.16 and 3.1.2.13)
RDPRL_147. The receiver application shall be capable of receiving several surveillance data flows from the same source (same source address, different destination addresses).
RDPRL_148. A receiver connected to several LANs shall be able to receive surveillance data flows on different interfaces from the same MAC address (item n° 1.3.3 of Annex 1).
RDPRL_149. A receiver receiving the same flow on 2 different interfaces shall be able to distinguish between the data received on each interface in order to avoid
duplication of data (items n° 3.1.1.16 and 3.1.2.13 of Annex 1).
IP version 4 specific configuration requirement
RDPRL_150. When an application layer is used for receiving radar data, there shall be a mechanism (configuration or parameter setting) enabling to specify, per radar, the destination IP multicast address: all class D addresses shall be
configurable (items n° 3.1.1.16 and n° 2.1.31 of Annex 1);
RDPRL_151. For a given multicast group, a multicast receiver shall be able to handle
duplicate datagrams5.
IP version 6 specific configuration requirements
RDPRL_152. When an application layer is used for receiving radar data, there shall be a mechanism (configuration or parameter setting) enabling to specify, per radar,
the following elements:
RDPRL_153. • The data IPv6 multicast address: all addresses in range FF3E::8000:0/97 shall be available except FF3E::8000:0 (items n° 3.1.2.13 and n° 2.2.2.13 of Annex 1) ;
RDPRL_154. • The IP unicast source address: all global scope IPv6 addresses shall be available (items n° 3.1.2.13 and n° 2.2.2.13 of Annex 1);
RDPRL_155. For a given multicast channel, a multicast receiver shall be able to handle duplicate datagrams5.
System Configuration Examples
In below configuration examples the IP multicast source is the radar. The below examples are also valid for other configurations where the IP multicast source is a separate device connected to the radar LAN. The below configuration examples are based on flows, each flow being a specific IP multicast group/channel associated with a surveillance data stream.
Single Attached Multicast Receiver with one Incoming Flow per Interface
It is the case where the receiver has a single interface to the network. A multicast address group is defined to which the receiver can subscribe in order to receive the radar flow.
[pic]
[pic]
Multi-homed Multicast Receiver with one Incoming Flow per Interface
For this case, the receiver is multi-homed. The receiver has single interfaces to separate LANs and a single multicast address group is defined to which the receiver can subscribe in order to receive the radar data flow.
[pic]
An alternative to the above configuration is the case where the transmitter is also multi-homed. The transmitter has multiple interfaces to the network. In this case it is possible to define different multicast addresses to select the same flow via different receiver interfaces or network paths.
[pic]
Receivers with Multiple Incoming Flows per Received Interface and Multihomed Transmitters
In this case, the transmitter is multi-homed. The transmitter has single interfaces to separate LANs. Two multicast address groups are defined to identify the two possible flows from the radar. The receiver can subscribe to multiple multicast address groups per interfaces in order to receive the same radar flow twice.
[pic]
[pic]
Multi-homed Transmitters and multiple transmissions of the same flow
In this case, the transmitter is multi-homed and transmits the same flow (same multicast group address and same source IP address) on 2 different interfaces. For each data message, the transmitter chooses which interface to use for transmission, so that each message is sent only once on the network.
[pic]
[pic]
63. ANNEX 1
EUROCONTROL GUIDELINES FOR IMPLEMENTATION SUPPORT (EGIS)
Part 5 - COMMUNICATION AND NAVIGATION SPECIFICATIONS
CHAPTER 12
SURVEILLANCE DISTRIBUTION OVER IP MULTICAST PROFILE
REQUIREMENT LIST (PRL)
TEMPLATE FOR PROTOCOL IMPLEMENTATION CONFORMANCE
STATEMENTS (PICS)
[pic]
[pic]
[pic]
[pic]
[pic]
[pic]
[pic]
[pic]
[pic]
[pic]
[pic]
Abbreviation List
A
ANSP(s) - Air Navigation Service Provider(s)
ATC - Air Traffic Control
ATM - Air Traffic Management
C
COTS - Commercial Off The Shelf
D
DFS - Detailed Functional Specification
E
EATMP - European ATM Programme
ECAC - European Civil Aviation Conference
EGIS - EUROCONTROL Guidelines for Implementation Support
EIS - EATMP Implementation Support
I
IANA - Internet Assigned Numbers Authority
ICAO - International Civil Aviation Organisation
ICMP - Internet Control Message Protocol
IGMP - Internet Group Management Protocol
IEEE - Institute of Electrical and Electronics Engineers Inc.
IHL - Internet Header Length
IP - Internet Protocol
IPv4 - Internet Protocol Version 4
IPv6 - Internet Protocol Version 6
L
LAN - Local Area Network
LLC - Logical Link Control
M
MAC - Medium Access Control
MLD - Multicast Listener Discovery
P
PICS - Protocol Implementation Conformance Statement
PRL - Profile Requirements List
R
RFC - Request for Comment
S
SSM - Source Specific Multicast
STD - Standard
T
TX - Transmit
ToS - Type of Services
U
UDP - User Datagram Protocol
Multicast Service for Surveillance Services
64. General
The need to send the same information to multiple receivers is one of the main requirements of surveillance data distribution. This requirement can be supported by the Internet Protocol versions 4 and 6 (IPv4 and IPv6 respectively) multicast services. Other networking techniques that achieve the same multicast objective are not further considered within the scope of this document.
A limited number of European States have deployed national IPv4 multicast services for surveillance data distribution . However, the limited range of the IPv4 multicast address space inhibits the deployment of scalable multicast service within the ATN/IPS. Furthermore, at present, there are no gateways to allow interworking between IPv4 and IPv6 multicast implementations.
In recent years, significant technical progress has been made in the field of IP multicast, namely source specific multicast (SSM). Contrary to existing deployments on the basis of PIM-SM (Protocol Independent Multicast--Sparse Mode), source specific multicast (SSM) provides added simplicity and resiliency to the routing of IP multicast traffic and is ideally suited for surveillance needs.
At present, there are no gateways to allow interworking between IPv4 and IPv6 multicast implementations.It is recommended to deploy IPv6 source specific multicast (SSM) within the ATN IPS.
Guidelines prepared by EUROCONTROL entitled : “EUROCONTROL GUIDELINES FOR IMPLEMENTATION SUPPORT (EGIS) Part 5: COMMUNICATION & NAVIGATION SPECIFICATIONS, Chapter 12, SURVEILLANCE DISTRIBUTION OVER IP MULTICAST PROFILE REQUIREMENT LIST (PRL)” can be used as a basis to deploy such a multicast service (). These guidelines recognize that IPv4 multicast may be used locally but IPv6 source specific multicast (SSM) is to be used internationally or between ATN IPS Administrative Domains.
Planned European DeploymentMulticast Addressings
As early as 2001, Eurocontrol and its Member States identified the need to introduce IPv6 for inter-ANSP data exchanges (which are typically cross-border) for both unicast and multicast network services.
Indeed, surveillance data flows that cross national borders are required to use the IPv6 protocol due to the architecture of the trans-national backbone network. Surveillance data flows that remain inside national borders use either IPv4 or IPv6 depending on the architecture of the national network infrastructure.
As source specific multicast (SSM) is particularly suited to inter-ANSP data exchanges, it use over IPv6 is recommended in a Eurocontrol guideline entitled “EUROCONTROL GUIDELINES FOR IMPLEMENTATION SUPPORT (EGIS) Part 5: COMMUNICATION & NAVIGATION SPECIFICATIONS, Chapter 12, SURVEILLANCE DISTRIBUTION OVER IP MULTICAST PROFILE REQUIREMENT LIST (PRL)”. Eurocontrol will indicate the URL of the above document once it is on-line.
Furthermore it is recommended that all surveillance data transmitters or receivers that are intended to send or receive data beyond the local domain, ie across national borders, should be IPv6-compliant.
The fundamental pre-requirsuite for a successful deployment of a multicast service is the addressing scheme. As described in the above, surveillance data is delivered using the source specific multicast (SSM) service. A data channel is defined by the combination of destination multicast
address and source unicast address, and contains a single surveillance data flow.
The following figure shows such an IPv6 multicast address:
| 8 | 4 | 4 | 8 | 8 | 64 | 32 |
+--------+----+----+--------+--------+----------------+----------+
|11111111|0011|1110|00000000|00000000| 000……………………000 | group ID |
+--------+----+----+--------+--------+----------------+----------+
Figure 1: SSM Multicast IPv6 address with global scope
The IPv6 multicast group ID shall be in the range 0x8000000 to 0xFFFFFFFF allowed for dynamic assignment by a host, as specified in RFC 3307 section 4.3 and RFC 4607 section 1.
The resulting available IPv6 SSM address range is FF3E::8000:0/97 (FF3E:0:0:0:0:0:8000:0 / 97).
Assuming the appropriate access to the service, to receive a SSM (source specific multicast) stream one requires three parameters:
• Source-address (unicast address)
• Multicast address (as indicated by the source application)
• Port (default is 8600 for ASTERIX surveillance data in Europe)
We can delete above sections 8 and 9 if we directly point to the EGIS document
65. Annex 1 : AS numbering plan
ICAO RegionCountry/Organisation/LocationASNICAO RegionCountry/Organisation/LocationASNMIDAfghanistan 64512EUR/NATIreland 64688APACAmerican Samoa 64513EUR/NATItaly 64692ESAFAngola 64514EUR/NATKazakhstan 64696NACCAnguilla I. (U.K.) 64515EUR/NATKyrgyzstan 64700NACCAntigua and Barbuda 64516EUR/NATLatvia 64704SAMArgentina 64517EUR/NATLiechtenstein64706NACCAruba (Netherlands) 64518EUR/NATLithuania 64708WACAFAscension and St Helena Is. (U.K.)64519EUR/NATLuxembourg 64712APACAustralia 64520EUR/NATThe former Yugoslav Republic of Macedonia 64716NACCBahamas 64521EUR/NATMalta 64720APACBangladesh 64522EUR/NATMonaco 64724NACCBarbados 64523EUR/NATMontenegro64725NACCBelize 64524EUR/NATMorocco 64726WACAFBenin 64525EUR/NATNetherlands 64728NACCBermuda (U.K.) 64526EUR/NATNorway 64732APACBhutan 64527EUR/NATPoland 64736SAMBolivarian Republic of Venezuela 64528EUR/NATPortugal 64740SAMBolivia 64529EUR/NATRepublic of Moldova 64744ESAFBotswana 64530EUR/NATRomania 64748SAMBrazil 64531EUR/NATSerbia64752ESAFBritish Indian Ocean Territory 64532EUR/NATRussian Federation 64756APACBrunei Darussalam 64533EUR/NATSan Marino 64758WACAFBurkina Faso 64534EUR/NATSlovak Republic 64760ESAFBurundi 64535EUR/NATSlovenia 64764APACCambodia 64536EUR/NATSpain 64768WACAFCameroon 64537EUR/NATSweden 64772NACCCanada 64538EUR/NATTajikistan 64776WACAFCape Verde 64539EUR/NATSwitzerland 64780NACCCayman Is. (U.K.) 64540EUR/NATThe Holy See64781WACAFCentral African Republic 64541EUR/NATTunisia 64782WACAFChad 64542EUR/NATTurkey 64784SAMChile 64543EUR/NATTurkmenistan 64788APACChina 64544EUR/NATUkraine 64792SAMColombia 64545EUR/NATUnited Kingdom 64796WACAFCongo 64546EUR/NATUzbekistan 64800APACCook Islands 64547EUR/NATRegional - Benelux/Germany65108NACCCosta Rica 64548EUR/NATRegional - Central Europe65112WACAFCôte d'Ivoire 64549EUR/NATEUROCONTROL65208NACCCuba 64550EUR/NATEUROCONTROL65212APACDemocratic People's Republic of Korea 64551EUR/NATEUROCONTROL65216WACAFDemocratic Republic of the Congo 64552EUR/NATEUROCONTROL65220APACDemocratic Republic of Timor-Leste 64553EUR/NATEUROCONTROL65224ESAFDjibouti 64554EUR/NATEUROCONTROL65228NACCDominica 64555EUR/NATEUROCONTROL65232NACCDominican Republic 64556EUR/NATEUROCONTROL65236APACEaster Island (Chile)64557WACAFMauritania 65237SAMEcuador 64558ESAFMauritius 65238MIDEgypt 64559NACCMexico 65239NACCEl Salvador 64560APACMicronesia, Federated States of 65240WACAFEquatorial Guinea 64561APACMidway Is. (U.S.) 65241ESAFEritrea 64562APACMongolia 65242ESAFEthiopia 64563NACCMontserrat I. (U.K.) 65243SAMFalklands Is. (U.K.) 64564ESAFMozambique 65244NACCFrench Antilles (?)64565APACMyanmar 65245WACAFGabon 64566ESAFNamibia 65246WACAFGambia 64567APACNauru 65247WACAFGhana 64568APACNepal 65248NACCGrenada 64569NACCNetherlands Antilles 65249APACGuam (U.S.) ?64570APACNew Caledonia 65250NACCGuatemala 64571APACNew Zealand 65251WACAFGuinea 64572NACCNicaragua 65252WACAFGuinea-Bissau 64573WACAFNiger 65253SAMGuyana 64574WACAFNigeria 65254SAMGuyane Francaise 64575APACNiue Island (New Zealand) 65255NACCHaiti 64576MIDOman 65256SAMHonduras 64577MIDPakistan 65257APACHong Kong Special Administrative Region of China 64578APACPalau 65258APACIles Wallis Et Futuna (France)64579Palestinian Territory, occupied 65259APACIndia 64580APACPalmyra Is. (U.S.)65260APACIndonesia 64581SAMPanama 65261MIDIran, Islamic Republic of 64582APACPapua New Guinea 65262MIDIraq 64583SAMParaguay 65263MIDIsrael 64584SAMPeru 65264NACCJamaica 64585APACPhilippines 65265APACJapan 64586APACPitcairn Island (U.K.)65266APACJohnston I. (U.S.) 64587APACPolynesie Francaise 65267MIDJordan 64588NACCPuerto Rico 65268ESAFKenya 64589MIDQatar 65269MIDKingdom of Bahrain 64590APACRepublic of Korea 65270APACKingman Reef (U.S.) ?64591APACRepublic of the Fiji Islands 65271APACKiribati 64592ESAFRwanda 65272MIDKuwait 64593NACCSaint Kitts and Nevis 65273ESAFLa Reunion (France) 64594NACCSaint Lucia 65274APACLao People's Democratic Republic 64595NACCSaint Vincent and the Grenadines 65275MIDLebanon 64596APACSamoa 65276ESAFLesotho 64597WACAFSao Tome and Principe 65277WACAFLiberia 64598MIDSaudi Arabia 65278MIDLibyan Arab Jamahiriya 64599WACAFSenegal 65279APACMacao Special Administrative Region of China 64600ESAFSeychelles 65280ESAFMadagascar 64601WACAFSierra Leone 65281ESAFMalawi 64602APACSingapore 65282APACMalaysia 64603APACSolomon Islands 65283APACMaldives 64604ESAFSomali Republic 65284WACAFMali 64605ESAFSouth Africa 65285APACMariana Is. (U.S.) 64606APACSri Lanka 65286APACMarshall Islands 64607MIDSudan 65287EUR/NATAlbania 64608SAMSuriname 65288EUR/NATAlgeria 64609ESAFSwaziland 65289EUR/NATAndorra 64610MIDSyrian Arab Republic 65290EUR/NATArmenia 64612APACThailand 65291EUR/NATAustria 64616WACAFTogo 65292EUR/NATRepublic of Azerbaijan 64620APACTonga 65293EUR/NATBelarus 64624NACCTrinidad And Tobago 65294EUR/NATBelgium 64628NACCTurks And Caicos Islands (U.K.) 65295EUR/NATBosnia and Herzegovina 64632APACTuvalu 65296EUR/NATBulgaria 64636ESAFUganda 65297EUR/NATCroatia 64640ESAFUnion of the Comoros 65298MIDCyprus 64644MIDUnited Arab Emirates 65299EUR/NATCzech Republic 64648ESAFUnited Republic of Tanzania 65300EUR/NATDenmark 64652NACCUnited States of America 65301EUR/NATEstonia 64656SAMUruguay 65302EUR/NATFinland 64660APACVanuatu 65303EUR/NATFrance 64664APACViet Nam 65304EUR/NATGeorgia 64668NACCVirgin Islands (U.K.) 65305EUR/NATGermany 64672NACCVirgin Islands (U.S.) 65306Gibraltar 64674APACWake I. (U.S.) 65307EUR/NATGreece 64676Western Sahara 65308Greenland 64678MIDYemen 65309EUR/NATHungary 64680ESAFZambia 65310EUR/NATIceland 64684ESAFZimbabwe 65311
-----------------------
3
13
13
3
13
16
64
FP
TLA ID
Sub-TLA
Res.
NLA ID
SLA ID
Interface ID
variable bits
variable bits
F2
Site
Location
LAN
ESI
64 bits
Net.
Prefix
5 bits
7 bits
v4/
v6
1 bit
F1
3 bits
Local Authority
(80 bits)
Common Responsibility
(EUROCONTROL Agency)
(16 bits)
3
RIPE Responsibilty
(32 bits)
The first 4 bits of the IP header constitute the IP version number. RDPRL_20. An UDP/IP multicast implementation should support both the IPv4 and IPv6 protocols as described below. RDPRL_21. An UDP/IP multicast implementation must support at least one of the 2 above-
Ethernet layer Ethernet data Ethernet layer Destination Address Source Address Type IP Packet Padding FCS 6 bytes 6 bytes 2 bytes n bytes 4 bytes
RDPRL_9. The IP packet format is described in the section 2.4. RDPRL_10. Type, coded on two bytes (Type field), indicates the data type conveyed in the Ethernet frame. The values of this field are allocated by IANA1 . The hexadecimal value 0x0800 indicates that the data corresponds to an IPv4 packet (item n° 1.2.1.1 of Annex 1). The hexadecimal value 0x86DD indicates that data corresponds to an IPv6 packet (item n° 1.2.2.1 of Annex 1). RDPRL_11. For Ethernet frames with a type field equal to 0x0800 (IPv4), the requirements in sections 2.3.2 and 2.4.1 apply. RDPRL_12. For Ethernet frames with a type field equal to 0x086DD (IPv6), the requirements in sections 2.3.3 and 2.4.2 apply. RDPRL_13. The Ethernet standard limits the maximum frame length. The implementation shall enable the exchange of an IP packet whose size reaches the maximum length of the Ethernet frame (1518 bytes). Thus, it shall be possible to receive packets whose size can reach 1500 bytes. For sending data, the implementation shall take into account section 2.6 of this document (item n° 5.1.14 of Annex 1). RDPRL_14. Frames received with a FCS error or whose length is not included within the lower and higher limits defined in the reference documents shall be ignored (item n° 1.1.5 of Annex 1).
3
13
13
3
13
16
64
FP
TLA ID
Sub-TLA
Res.
NLA ID
SLA ID
Interface ID
variable bits
variable bits
F2
Site
Location
LAN
ESI
64 bits
Net.
Prefix
5 bits
7 bits
v4/
v6
1 bit
F1
3 bits
Local Authority
(80 bits)
Common Responsibility
(EUROCONTROL Agency)
(16 bits)
3
RIPE Responsibilty
(32 bits)
X.25 PLP
ES-IS/CLNP
SNDCF
Physical Layer (e. g., EIA-232, V.35, X.21)
LAP B (HDLC)
Consolidated Application Services (e.g., SMTP, SNMPv3, FTP, X.400 and Telnet)
TCP/UDP
IPv6 & ICMPv6
LLC/MAC
Physical Layer (e.g., FDDI, 802.X)
Fast-byte
Transport Layer Class 4
ATN Applications (e.g., CMIP, X.400)
Fast-byte
ATN IPSTCP/IP
ATN ISO /Protocols
OSI Reference Model
Presentation Layer 6
Physical Layer 1
Link Layer 2
Network Layer 3
Transport Layer 4
Session Layer 5
Application Layer 7
Audio
Codecs
G.711
G.728
G.729
RTCP
(Real Time TransportControl Protocol)
RTP
T.120
(Real Time)
T.130
(Audio- Visual
Control)
H.225.0
RAS
Q.931
(Call Signalling)
H.235 (Security)
H.245
(Control
Signalling)
UDP (User Datagram Protocol)
TCP (Transfer Control Protocol)
IP (Internet Protocol) v4 or v6
H.450.1 Series
(Supplementary Services)
Video
Codecs
H.261
H.263
[pic]
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