ACP - WGN06-WPxx

AERONAUTICAL COMMUNICATIONS PANEL (ACP)

Working Group N – NETWORKING

6th MEETING – BRUSSELS, BELGIUM, 3 – 7 July 2006

AFTN AIDC

over

ATN ICS or IPS

Prepared by AEROTHAI

Summary

This paper proposes an alternative to implementation of the ATN AIDC Application as defined in ICAO Doc 9705. The alternative is to adapt the AFTN AIDC application to be block oriented so that it may run over the ATN OSI-based Internet Communications Service or the Internet Protocol Suite.

1. Introduction

The ATS Interfacility Data Communications (AIDC) application exchangesinformation between ATS Units (ATSUs) for support of critical Air Traffic Control(ATC) functions including:

  • Notification of flights approaching a Flight Information Region (FIR) boundary,
  • Coordination of boundary conditions and
  • Transfer of control and communications authority.

2. AIDC Variants in the Asia/Pacific Region

There are two variants of AIDC defined for the Asia/Pacific Region.

a)AFTN-based AIDC Protocol

The latest version 2.0 as documented in the Asia/Pacific Regional Interface Control Document (ICD) for ATS Interfacility Data Communications (AIDC), Version 2.0 – September 2003

b)ATN-based AIDC Protocol

This variant is under development based on Edition 3 of ICAO Doc 9705. It is not yet submitted for approval by Bangkok ICAO Regional Office

3. Key Differences in the AIDC Variants in the Asia/Pacific Region

3.1 Control Logic

Control Logic is the rules governing the sequencing of messaging. The control logic for AFTN AIDC is in the ATC Application and is depicted in Figure 1.

The control logic for ATN AIDC is in the Control Function of the Application Entity and is depicted in Figure 2.

Figure 1 – AFTN AIDC Control Logic

Figure 2 – ATN AIDC Control Logic

3.2 Message Format and Encoding

AFTN AIDC messages are defined and encoded using standard AFTN text encoding while ATN AIDC messages have a distinct abstract syntax (ASN.1) and PER encoding rules.

Figure 3 depicts the AFTN environment and Figure 4 depicts the ATN AIDC environment.

Figure 3 - AFTN AIDC Architecture

Figure 4 – ATN AIDC Architecture

4. Current progress in the development of AIDC

At the present, OPLINK panel has amended relevant information regarding AIDC at the OPLINKP1 meeting on September 2005. The new architecture of AIDC has not been incorporated in the ATN AIDC material in the technical manual.

5. Proposed Architecture – AFTN AIDC over ATN ICS

Rather than implement the ATN AIDC Upper Layer Architecture, an AFTN AIDC-like architecture could be used.The concept is basically to run AFTN AIDC over the OSI Internet Communications Service (over TP4/CLNP). Figure 5 depicts this environment.

Figure 5 - AFTN AIDC over ATN ICS

The AIDC application in this case would be block oriented i.e. from the Transport Layer perspective it would look like an OSI upper layer application. The advantage of this approach is that it could readily operate in an IPS environment using RFC 1006. Thus if the Asia/Pacific region were to eventually migrate to an IPS or dual IPS/OSI infrastructure the application would be isolated from change.

5. Recommendation

The working group is invited to comment on the proposed AIDC approach.