ACP WGN04 – WP28
11/10/2004
AERONAUTICAL COMMUNICATIONS PANEL (ACP)
WorkinG group N (NETWORKING) – 4th meeting
New Orleans (U.S.A.), 10th – 19th November 2004
Development of TCP/IP Protocol for Aeronautical Telecommunications Network (ATN)
Ground-to-Ground Telecommunication Service
Working Paper
Prepared by USA/FAA
Presented by Steve Dash
Summary
This paper presents the FAA strategic and tactical position regarding the ATN technology direction and on-going ATN router and ATS Message Handling Service (AMHS) implementation activities.
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Schedule of New Orleans ACP WGN meeting (November 2004) Devel of TCP / IP protocol for the ATN
1. Introduction
This paper presents the strategic and tactical positions of the FAA regarding the ATN technology direction and on-going ATN router and AMHS implementation activities.
2. Background
The original ATN concept was predicated upon the need to provide a global Air Traffic Management (ATM) network capable of supporting seamless fixed and mobile intercommunication for envisioned Air-to-Ground (A-G) and Ground-to-Ground (G-G) applications across International communication boundaries and sub-networks. This need stemmed from several key drivers:
· The predicted increase in international air traffic;
· The envisioned development of new applications such as Controller Pilot Data Link Communications (CPDLC), Automatic Dependent Surveillance (ADS), Flight Information Service (FIS), ATS Message Handling Service (AMHS), and ATS Interfacility Data Communications (AIDC) Service;
· Sustainability issues surrounding the existing Aeronautical Fixed Telecommunication Network (AFTN) switching service; and
· The economic advantages of integrating Air Traffic, Airline, and Other General Aviation traffic on a single network
The development of the ATN standards started in 1989 and was predicated on the predominant networking technology of that time, the OSI/ISO protocol suite. Since then, significant changes have occurred in the technology arena and in the Air Traffic operational outlook. Technologically, the worldwide acceptance of the Internet Protocol (IP) Suite as internetworking protocol has led industry away from providing OSI-based commercial products. This has resulted in numerous aviation technical organizations like the AEEC and Boeing, and ICAO member states to review their planned implementation of the OSI/ISO protocols; this has also been the genesis for the current ICAO debate whether and how to include IP Suite in the standards documentation. Operationally, the Air Traffic environment and outlook has changed, effectively resulting in the delay of many of the original ATN concept drivers.
· Air-to-Ground applications have been slowed, delaying the need for Air-to-Ground mobile services (the FAA currently forecasts initial CPDLC deployment in the 2009 timeframe)
· Ground-to-ground applications have not developed with the exception of AMHS, delaying the need for and economic benefits of an integrated world-wide ATN network
· International air traffic has not exceeded current telecommunications capacity, also contributing to the delayed economic benefits of an integrated world-wide ATN network
3. Assessment
In light of these dynamics, the only immediate operational need for implementing ATN is to address the sustainability of the Aeronautical Fixed Telecommunications Network switching service. Additionally, investment in any additional ATN infrastructure (in accordance with the current ICAO standards) might well prove to be throwaway, if the international standards development bodies adopt the IP Suite. Accordingly, a strategic and tactical reassessment of the FAA investment approach to ATN is required.
Strategically – From a strategic stand-point, the key question of IP Suite versus OSI/ISO (or some hybrid) has been of primary concern, both in terms of if/how it can accommodate the ICAO ATN Air Traffic requirements (e.g. specifically the air-to-ground mobility piece), and what impacts it has technically and economically in terms of industry support and the availability of commercial products. Generally, the FAA agrees in principle to the development of IP based standards in the form of SARPs (Standards of Recommended Practice), and recognizes there may be potential mobility limitations that need to be investigated. The FAA also recognizes that, at this time, the need for the mobility component of the ATN has not materialized and likely will not do so within the near future (at least 5 years within the FAA). Given the uncertainty of the requirement and the technology, the FAA thinks it is prudent to separate the mobility component at this time in order to facilitate the decision making process for the G-G network piece of the ATN.
Consistent with this reasoning and to accommodate the pressing need to move forward on the AMHS deployment (to address the AFTN switching sustainability issue), the FAA has framed its position on the IP Suite issue around the Ground-to-Ground component of ATN only. The FAA position supports the inclusion of a standalone IP Suite in a SARP documentation format as a full native stack for both routers and G-G applications as opposed to the OSI/ISO over IP encapsulation approach or a dual stack approach. The basis for this position is that the benefit of migrating to an IP Suite is not the use of the protocol itself, but the economic benefit derived from leveraging the vast commercial product, service, and support base. Moving to an OSI/ISO over IP encapsulation approach or dual stack approach would require modifications to commercial off-the-shelf (COTS) products, increases technical complexity for the sake of protocol interoperability, and hence diffuses the full economic benefit. From an application perspective, the benefit is similar in that most development platforms, workstations, and servers come with IP Suite kernels “built” into the Operating System negating the need to develop specialized software as would be the case for OSI/ISO-based or encapsulated applications. This benefit also extends to the supportability aspect as well, in that support for native IP Suite applications and routers are far more available and prevalent in today’s commercial world than support services for OSI/ISO-based applications and routers.
Having stated its strategic position on the Ground-to-Ground component of ATN, the FAA is committed to supporting the final decision determined within the International Civil Aviation Organization (ICAO) Air Navigation Commission (ANC). A challenge in doing so, however, is determining what to do with the current ATN application and router development and implementation activities previously initiated between the FAA and other regional boundaries. Preliminary research by the FAA has concluded that continuing the development, implementation, and testing of ATN routers and applications given the uncertainty of the OSI/ISO technology and the lack of immediate operation or economic drivers will not result in the best return on investment for the U.S. National Airspace System (NAS). Continuation of this development may lead down a technological path that limits future flexibility and interoperability; additionally, it will mean continued expenditure of funds that may prove un-leveragable in the future. Therefore, the FAA recommends a strategy of minimizing development and implementation activities and associated spending as appropriate, until a clear technological direction is achieved by the ICAO ANC and the operational and economic benefits mature.
Tactically – The FAA has been engaged in a prototype trial of AMHS connection over ATN routers with Japan. An AMHS switching application and an ATN compliant router was developed and implemented as part of this trial effort. In addition, the FAA has agreements with several other countries for less formal test/proof of concept activities. The FAA is also in the process of re-hosting its AFTN Switching Platform (the National Airspace Data Interchange Network (NADIN) Message Switched Network).
In light of the strategic recommendation documented in this paper, the FAA proposes to take the results and lessons learned from the AMHS trial and integrate the AMHS application with the MSN switch (NADIN I) re-host activity over the next 1 to 2 years. In doing so, the FAA will be capable of supporting both IP Suite and OSI protocol stacks, although operationally, the IP Suite would be our preferred approach. During the 1 to 2 year development time, the FAA proposes to minimize any additional development, implementation, and/or testing of ATN infrastructure until a firm direction is achieved within ICAO regarding the technology decision. This course of action effectively addresses the AFTN switch replacement issue, ensures support of either IP Suite or X.25 (PSN) technology, and minimizes potential throwaway investment impacts. This approach will also provide a migration path for legacy users to migrate to an IP Suite as required in the future.
4. CONCLUSION
In summary, the FAA is anxious to work within the ICAO to address the IP Suite SARPs, and the pending resolution of this issue. At the same time, the FAA must keep investments to a minimum while focusing on providing the necessary operational aviation services. Consistent with these objectives the FAA has adopted the following plan of action:
· Support the incorporation of IP Suite into a SARPs document for the G-G network component of the ATN. To realize substantial benefit from such incorporation, the FAA believes it should support a full migration of applications and routers to a native IP Suite protocol stack as opposed to an encapsulation or dual stack technique.
· Move forward with a plan to support the AFTN switch sustainability by re-hosting the trial AMHS application onto the NADIN MSN platform.
· Move forward in coordination with other regional boundaries with a strategy to minimize any additional development, implementation, and testing of ATN applications and routers until the technology decision is firm.
5. Recommendation
The meeting is invited to note the FAA plan to migrate from OSI to TCP/IP protocol platform for ground-to-ground telecommunication service.
The FAA supports the update activity of the ICAO Document 9705 and its related documents to include the TCP/IP protocol.
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