ICAO. CIRCULAR 261-ANlf 55 CIRCULAR A PLANNING GUIDE FOR THE EVOLUTIONARY DEVELOPMENT OF THE DATA INTERCHANGE PORTION OF THE AERONAUTICAL FIXED SERVICE Approved by the Secretary General and pished under his autorify INTERNATIONAL CIVIL AVIATION ORGAUIZAT ION MONTREAL CANADA
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FOREWORD This circular was prepared by the Aeronautical Fixed Servfce AFS Systems Planning for Data Interchange Panel WSPP in response to the Air Navigation Commission's ANC directed work programme to provide States with a wbrld-wide planning document for transition from the current AFS to the future system. The objective of this circular is to provide guidance on the transition to the aeronauticd Me- communication network Am for the ground-ground, store and forward segment of the AFS. Other segments of the AFS and mobile communication segments are not addressed in this circular. The work programme for the ATN Panel ATNP includes the fomulation of a comprehensive "planning document for the world-wide evolutionary implementation of the Am. That planning document will include transition guidehes for the entire aeronautical data communication system, encompassing both bed and mobfle comunicatrons. Until the enbe world-wide plan- ning documentation is available, the guidance in this circular should be considered as infor- mation to support near-term transition actjvities related to the AFS. SUMMARY The Aeronautical Fixed Service Systems Planning for Data Interchange Panel AsPP. in accordance with its terms of reference, has developed this world-wide planning document to define the participants and plans for the aeronautical ked service AFS migration from the current aeronautical fmed telecommunication network 0 to the future aeronautical tele- communication network Am. The future air traffic management AW applications operate over the Am internetwork. An internetwork is comprised of the interconnection of computers with routers via real subnetworks. The purpose of this document is to provide Reglonal Planning Groups and Individual States with an over-all planning document to promote the harmonious migration to and development of a global AFS data communications internetwork to satisfy ATM operational requirements. In order to fully utlllze automated ATM systems, a global data networking infrastructure must be im- plemented which supports the intemrking of state-of-the-art computer systems operating in fixed ground-based and mobile aircraft-based locations. Improved airborne and ground cornmunlcation systems need to be developed and used in a complementary fashion to facilitate and rnardrnize the efficient use of airport and airspace resources. The total benefit of AES ground systems can only be achieved through their full im- plementation at the regional level. In order fur the civil aviation community to realize the advantages which can be afforded to both users and providers of air trd3c control ATC services. close co-operation and participation by States for the implementation of new global systems are
ii A Planning Guide for the Evolutionary Development of the Data Interchange Portion of the Aeronautical Fixed Service most important. This planning document serves as the framework for the progressive and orderly implementation of ground ATM systems in a cost-effective manner, on a flexible timetable achievable in all regions. The document is not intended to substitute for regional plans, but to provide general guidelines that serve as the basis for ATN-related regional planning activities and the production of the detailed implementation plans. The realization of a system capable of satisfjrlng the above principles requires the adaptation of existing procedures and facilities, as well as the development of new ones. This document ident- ifies the current and future data communication requirements for ATM systems. Also, various strategies to be considered by the regions for improving the network infrastructure in support of the future environment and applications are identified. Guidance is provided for a variety of alternative configurations for both the current and planned network and application environ- ments to support the transition, and interoperability between the existing and future ATM . systems. These guidelines should be used by Regional Planning Groups and individual States to migrate to the ATN. Transi-tion considerations for the various system and operational configurations are identified. These considerations encompass regional and interregional issues and interdependencies. It may be essential for regional offices and States to co-ordinate between themselves when iden-g the proposed strategy for the definition and implementation of AFTN/ATN gateways and ATN routers. These actions need to occur prior to and during the decision-making process for the selection of a regional configuration plan. It is necessary to identi the methods and mechanisms to be used to carry existing AFTN messages over the ATN internetwork and to deflne a migration strategy applicable to AFTN environments. The AFTN/ATN gateway is one component that is needed during the transition period from the present technical environment proprietary software and equipment to a more modem communications system. The gateway provides each State with the flexibility for a mixed AFTN and ATN environment and the freedom to implement its own individual transition schedule. This document illustrates the various gateway configurations available to States. The ATN router is another component to be utilized for the expansion of the ATN internetwork. Ideally. States should have the ability to interconnect new open systems interconnection OSI compliant ATM processors directly to the ATN with the deployment of these routers, bypassing the need to use any non-ATN or proprietary protocols. Policy-routing principles need to be established between administrations when ATN routers are deployed between States. The inter- domain routing exchange protocol controls which inter-domain exchanges are permitted. ATN connectivity, which is dependent upon which strategy i.e. unilateral, bilateral, trilateral or mixed is selected between neighbouring States, is an example that requires early consideration and co-ordination. Alternative considerations, administrative matters and network management information, which are essential for any State addressing the numerous aspects of this development effort, are also identified. While implementation details may vary around the world, the different elements of the AFS ground systems must be treated as integral parts of the global systems.