rfc2351.txt

<VC++网络游戏建摸与实现>源代码

Network Working Group                                          A. Robert
Request for Comments: 2351                                          SITA
Category: Informational                                         May 1998


              Mapping of Airline Reservation, Ticketing,
                     and Messaging Traffic over IP

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Security Disclaimer:

   This document fails to adequately address security concerns.  The
   protocol itself does not include any security mechanisms.  The
   document notes that traffic can be authenticated based on external
   mechanisms that use static identifiers or what are apparently clear-
   text passwords, neither of which provide sound security.  The
   document notes in general terms that traffic can be secured using
   IPSEC, but leaves this form of sound security strictly optional.

Abstract

   This memo specifies a protocol for the encapsulation of the airline
   specific protocol over IP.

Table of Conents

   1. INTRODUCTION                                                    2
   2. TERMINOLOGY & ACRONYMS                                          4
   3. LAYERING                                                        7
   4. TRAFFIC IDENTIFICATION                                          7
   5. TCP PORT ALLOCATION                                             8
   6. MATIP SESSION ESTABLISHMENT                                     8
   7. OVERALL PACKET FORMAT FOR TYPE A & TYPE B                       9
   8. MATIP FORMAT FOR TYPE A CONVERSATIONAL TRAFFIC                 10
    8.1 Control Packet Format                                        10
     8.1.1 Session Open format (SO)                                  10
     8.1.2 Open Confirm format (OC)                                  12
     8.1.3 Session Close (SC)                                        14
    8.2 Data Packet Format                                           14



Robert                       Informational                      [Page 1]

RFC 2351                         MATIP                          May 1998


   9. MATIP FORMAT FOR TYPE A HOST-TO-HOST TRAFFIC                   15
    9. 1 Control Packet Format                                       15
     9.1.1 Session Open format (SO)                                  15
     9.1.2 Open Confirm format (OC)                                  17
     9.1.3 Session Close (SC)                                        17
    9.2 Data Packet Format                                           18
   10. MATIP FORMAT FOR TYPE B TRAFFIC                               19
    10.1 Control packet format                                       19
     10.1.1 Session Open format (SO)                                 19
     10.1.2 Open confirm format (OC)                                 20
     10.1.3 Session Close (SC)                                       21
    10.2 Data packet format                                          21
   11. SECURITY CONSIDERATIONS                                       22
   12. AUTHOR'S ADDRESS                                              22
   13. FULL COPYRIGHT STATEMENT                                      23

1. Introduction

   The airline community has been using a worldwide data network for
   over 40 years, with two main types of traffic:

    Transactional traffic

      This is used typically for communication between an airline office
      or travel agency and a central computer system for seat
      reservations and ticket issuing. A dumb terminal or a PC accesses
      the central system (IBM or UNISYS) through a data network.

      This traffic is also called TYPE A and is based on real-time
      query/response with limited protection, high priority and can be
      discarded. The user can access only one predetermined central
      computer system. In case of no response (data loss), the user can
      duplicate the request.

    Messaging

      This is an e-mail application where real-time is not needed.
      However a high level of protection is required. The addressing
      scheme uses an international format defined by IATA and contains
      the city and airline codes.

      This traffic is also called TYPE B and is transmitted with a high
      level of protection, multi-addressing and 4 levels of priority.

   The detailed formats for TYPE A and TYPE B messages are defined in
   the IATA standards.





Robert                       Informational                      [Page 2]

RFC 2351                         MATIP                          May 1998


   At the bottom level, synchronous protocols have been built since
   1960's and well before the OSI and SNA standards.

   At present, there is a big number of legacy equipment installed in
   thousands of airline offices around the world. Many airlines do not
   have immediate plans to replace their terminals with more modern
   equipment using open standards. They are in search of more economical
   ways for connecting these terminals to the present reservation
   system.

   Most airlines are willing to migrate from airline specific protocols
   to standardized protocols in order to benefit from the lower cost of
   new technologies, but the migration has been slow done to the
   following factors:

   - Applications have not been migrated.
   - Dumb terminals using airline protocols P1024B (IBM ALC) or P1024C
     (UNISYS UTS) are still numerous.

   There are currently many different proprietary solutions based on
   gateways available to take advantage of low cast networking, but they
   are not scalable and cannot interact.

   In the future, TCP/IP will be more commonly used as a common
   transport means for traffic types because:

   - TCP/IP is the standard protocol of UNIX based applications
   - TCP/IP stacks are inexpensive
   - TCP/IP is used on intranets.

   The purpose of this RFC is to define the mapping of the airline
   traffic types over TCP/IP. The airlines implementing it in their
   systems should have a TCP/IP stack to enable the traffic exchange
   below:

















Robert                       Informational                      [Page 3]

RFC 2351                         MATIP                          May 1998


     !----!          (            )
     !    !----------(            )
     !----!          (            )
     Type B HOST     (   NETWORK  )
                     (            )
                     (            )            !---o
     !----!          (            )--------! D !---o Type A stations
     !----!----------(            )            !---o
     !----!          (            )
     TYPE A HOST           !
                           !
                           !
                           !
                        --------
                       !       !
                        --------
                      Network Messaging System


      (D) : Gateway TYPE A router

   The different airline traffic flows concerned by this RFC are:

     - TYPE A Host / Terminal
     - TYPE A Host / TYPE A host
     - TYPE B Host / Network messaging System

   In the case of dumb terminals, a conversion is required on the
   terminal side in order to have an IP connection between the host and
   the router. However, the IP connection is directly between the
   central airline host and the intelligent workstation if the latter
   has a direct connection to the network, a TCP/IP stack and a terminal
   emulation

2. Terminology & Acronyms

   ALC
   Airline Line Control: IBM airline specific protocol (see P1024B)

   ASCII
   American Standard Code for Information Interchange

   ASCU
   Agent Set Control Unit: Cluster at the user side.

   AX.25
   Airline X.25: Airline application of the X.25 OSI model (published by
   IATA)



Robert                       Informational                      [Page 4]

RFC 2351                         MATIP                          May 1998


   BAUDOT
   Alphabet defined in ITU-T Number 5. BAUDOT uses 5 bits. Padded BAUDOT
   uses 7 bits with the Most significant bit (bit 7) for the parity and
   the bit 6 equal to 1.

   BATAP
   Type B Application to Application Protocol. Protocol to secure the
   TYPE B traffic. It was specified by SITA and is now published by IATA
   (SCR Vol. 3)

   EBCDIC
   Extended Binary Coded Decimal Interchange Code

   Flow ID Traffic
   Flow identifier used in host to host traffic  to differentiate
   traffic flow types.

   HLD
   High Level Designator: Indicates the entry or exit point of a block
   in the network.

   IA
   Interchange Address: ASCU identifier in P1024B protocol.

   IATA
   International Air Transport Association

   IP
   Internet Protocol

   IPARS
   International Program Airline Reservation System: IPARS code is used
   in ALC

   HTH
   Host to Host (traffic).

   LSB
   Least Significant Bit

   MATIP
   Mapping of Airline Traffic over Internet Protocol

   MSB
   Most Significant Bit

   OC
   Open Confirm (MATIP command)



Robert                       Informational                      [Page 5]

RFC 2351                         MATIP                          May 1998


   OSI
   Open Standard Interface

   P1024B
   SITA implementation of the ALC, the IBM airlines specific protocol.
   It uses 6-bit padded characters (IPARS) and IA/ TA for physical
   addressing.

   P1024C
   SITA implementation of the UTS, the UNISYS terminal protocol. It uses
   7-bit (ASCII) characters and RID/ SID for physical addressing.

   RFU
   Reserved for Future Use

   RID
   Remote Identifier: ASCU identifier in P1024C protocol.

   SC
   Session Close (MATIP command)

   SCR
   System and Communication Reference. (IATA document)

   SID
   Station Identifier: Terminal identifier in P1024C protocol.

   SITA
   Societe International de Telecommunications Aeronautiques

   SO
   Session Open (MATIP command)

   TA
   Terminal Address: Terminal identifier in P1024B protocol.

   TCP
   Transport Control Protocol

   TYPE A Traffic
   Interactive traffic or host to host

   TYPE B Traffic
   Messaging traffic in IATA compliant format with high level of
   reliability

   UTS
   Universal Terminal System by Unisys: (see P1024C)



Robert                       Informational                      [Page 6]

RFC 2351                         MATIP                          May 1998


3. LAYERING

   MATIP is an end to end protocol. Its purpose is to have a mapping
   standard between the TCP layer and the airline application without
   any routing element.

     +-------------------------------+
     |Airline TYPE A | Airline TYPE B|
     |               |   Application |
     |               |---------------|
     | Application   |   BATAP       |
     +-------------------------------+
     |   MATIP A     |   MATIP B     |
     +-------------------------------+
     |            T.C.P              |
     +-------------------------------+
     |             I.P               |
     +-------------------------------+
     |            MEDIA              |
     +-------------------------------+

4. TRAFFIC IDENTIFICATION

   In TYPE A conversational traffic, the airline host application
   recognizes the ASCU due to 4 bytes (H1, H2, A1, A2). These bytes are
   assigned by the host and are unique per ASCU. Thus, a host can
   dynamically recognize the ASCU independent of IP address.

   H1 H2 A1 A2 bytes follow one of the three cases below:

     - A1,A2 only are used and H1H2 is set to 0000.
     - H1,H2 identify the session and A1A2 the ASCU inside the session.
     - H1,H2,A1,A2 identify the ASCU.

   The first two cases are fully compatible with the AX.25 mapping where
   H1H2 may be equivalent to the HLD of the concentrator, i.e., 2 bytes
   hexadecimal. The third rule allows more flexibility but is not
   compatible with AX.25.

   In TYPE A host to host traffic the identification field is also
   present and is equal to 3 bytes H1 H2 Flow ID (optional). H1H2 are
   reserved for remote host identification (independently of the IP
   address) and must be allocated bilaterally.

   In Type B traffic, identification of End Systems may be carried out
   by the use of HLDs, or directly by the pair of IP addresses.





Robert                       Informational                      [Page 7]

RFC 2351                         MATIP                          May 1998


5. TCP PORT ALLOCATION

   IANA (Internet Assigned Numbers Authority) has allocated the
   following ports for MATIP TYPE A and TYPE B traffic:
     MATIP Type A TCP port = 350
     MATIP Type B TCP port = 351

   Therefore the traffic type A or B is selected according to the TCP
   port.

6. MATIP SESSION ESTABLISHMENT

   Prior to any exchange between two applications, a single MATIP
   session is established above the TCP connection in order to identify
   the traffic characteristic such as:

     - Subtype of traffic for TYPE A (Type A host to host or Type A
       conversational )
     - Multiplexing used (for Type A)
     - Data header
     - Character set

   A separate session and TCP connection must be established for each
   set of parameters (e.g., P1024B, P1024C traffic between two points
   needs two separate sessions).

   The establishment of a MATIP session can be initiated by either side.
   No keep-alive mechanism is defined at MATIP level. Session time out
   relies on the TCP time-out parameters.

   There are three commands defined to manage the MATIP session:

   - Session Open (SO) to open a session.