IPv6 integration with the ATN

Tony WhymanHelios Information Services Ltd

Current Status

The ATN SARPs specify the OSI Protocol Suite

CLNP, TP4, ES-IS, IDRPMandatory for Government Procurements in early 1990s

Aeronautical Industry working with IP protocol suite

For Airline Passenger ServicesPossibly some Operational ServicesAEEC Project 664 Aircraft Data Networks (ADN)

What is the Issue?

OSI Standards no longer being developedIP Ground Networks “cheap” and availableAPC Services to use IP ProtocolsIPv6 becoming availableConsiderable Industry investment in the ATN Specification

Need for Change

ATN must accommodate ground IP networks

X.25 ceasing to be supportedIPv4 in short termIPv6 in medium to long term

ATN should be able to co-exist with airborne ADN IP systemsLong Term Strategy needed

Otherwise issue will keep reappearing

IP vs OSIInternet Protocol (IP)

Transmission Control Protocol (TCP)User Datagram Protocol (UDP)Routing Protocols

ARP, RIP, OSPF, BGP-4

AddressingInterface based4 byte addresses (IPv4)16 byte addresses (IPv6)

Connectionless Network Protocol (CLNP)Transport Protocol (TP4)

Connectionless Transport Protocol (CLTP)Routing Protocols

ES-IS, IS-IS, IDRP

Addressing20 byte System Addresses

Key Differences

Protocols are not mutually intelligibleInformation is encoded differently

CLNP has a much bigger address spaceTransport connection semantics are different

TCP has a graceful release optionTP4 is both message and stream oriented

Options for Convergence (1)Replace OSI ATN with IP ATN

Community investment lostDelays introduction of datalink servicesInvalidates current operational services

Use IP as an ATN SubnetworkGround Only at presentAn Encapsulation Strategy (CLNP inside of IP)Permits use of IP Networks as part of ATNDoes not affect existing AvionicsOr Ground End Systems

Options for Convergence (2)

IP to CLNP Protocol ConversionPermits a gradual replacement of CLNP with IPIndependent of end-to-end communications (implies TP4 over IP)Full migration requires Application Change

Transport RelaysTCP to TP4 not possible in generalATN Dialogue Service TCP/TP4 gateway possibleSingle Point of Failure Issues

The Ground Environment

ATC Centre

CLNP

IPv4 or IPv6 Internet

CLNPATC Centre

IPv4 or IPv6 Internet

ATC Centre

CLNP inEnd System

The IP SNDCFCLNP

IP SNDCF

IP Network

Other IP ServiceUsers e.g. TCP/UDP

Data Link Servicese.g. Ethernet, PPP, etc.

Other SNDCFs

ES-IS

IP SNDCF Benefits

Simple to implementCan support both IPv4 and IPv6No impact on rest of ATNAllows COTS IP Networks to be part of the ATNGives maximum benefit for least investmentSpecification being presented to ATNP

Eurocontrol and STNA validating specification

Air/Ground Environment

Expensively produced avionicsDO178B Level C Software DevelopmentCertified for Operational UseLong in service lifetime

Support for Aircraft Mobility neededSecurity Requirements Include

Separation from Passenger SystemsResistent to external threats

Mobility ScenariosAircraft only uses a single A/G Service Provider

No network roaming requirement

Aircraft serially uses multiple A/G Service Providers

Strategy Required to manage transition

Aircraft concurrently uses multiple A/G Service Providers

Strategy required to manage use and route traffic according to policy and application requirements

Current ATN Mobility

Extends standard Routing ProtocolsAdds information on route QoS and A/G networksMeets all ScenariosNeeds a big address space - mobility at top of addressing hierarchy

SecurityLeverages off existing “web of trust” routing model

Mobile IP

The Internet

Home Agent

Host Computer

Foreign Agent

Mobile Network

Mobile System

Mobile IP and ATN

Supports only serial use of multiple A/G Service ProvidersSecurity

Complex dynamic three way trust modelRequires a network wide Public Key Infrastructure

Potential for single point of failureRejected by ATNP as a model for ATN Mobility

Airborne Convergence Options (1)

No ChangeRetains strong separation between ATC and passenger communicationsCompatible with use of IP Ground Networks

Make use of ADN IP networks where appropriate

Extend use of IP SNDCFRespects differences in equipment lifecyclesFirewalls can maintain strong separation

Airborne Convergence Options (2)

Replace CLNP with IPv6 in new systemsRequires new SARPs developmentAssumes Ground Systems MigrationTranslation of ATN Mobile Routing to IPRequires development of new certified systemsRequires more complex firewallsCompatibility with passenger systems potentially limited by product lifecycle differencesCurrently not under consideration

Conclusion

ATN will include IP Networks in its scope

IP SNDCF is first stepMeets most of the real requirement

Co-existence with ADN IP SystemsCurrently under considerationLong Term Strategy to follow