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rfc:rfc2351

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:
  1. Applications have not been migrated.
  2. 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:
  1. TCP/IP is the standard protocol of UNIX based applications
  2. TCP/IP stacks are inexpensive
  3. 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:
  1. TYPE A Host / Terminal
  2. TYPE A Host / TYPE A host
  3. 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:
  1. A1,A2 only are used and H1H2 is set to 0000.
  2. H1,H2 identify the session and A1A2 the ASCU inside the session.
  3. 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:
  1. Subtype of traffic for TYPE A (Type A host to host or Type A

conversational )

  1. Multiplexing used (for Type A)
  2. Data header
  3. 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:
  1. Session Open (SO) to open a session.
  2. Open Confirm (OC) to confirm the SO command.
  3. Session close (SC) to close the current session.
 A MATIP session can be up only if the associated TCP connection is
 up.  However it is not mandatory to close the TCP connection when
 closing the associated MATIP session.
 Typical exchange is:
                    TCP session establishment
           Session Open --------->
                          <-----------   Open confirm
                        data exchange
           ---------------------->

Robert Informational [Page 8] RFC 2351 MATIP May 1998

                           <-------------------------
                           .
                           .
                           .
  Session Close ----------------->
                           .
                           .
                           .
                            <-------------------------   Session Open
 Open confirm ------------------->
                      data exchange
                             <-------------------------
           ---------------------->
 The Session Open command may contain configuration elements. An
 Session Open command received on a session already opened (i.e., same
 IP address and port number) will automatically clear the associated
 configuration and a new configuration will be set up according to the
 information contained in the new open session command.
 As illustrated above, the open and close commands are symmetrical.
 For type A conversational traffic, the SO and OC commands contain
 information for the identification of the ASCUs and the session.
 ASCUs are identified within a session by two or 4 bytes. A flag is
 set to indicate if the ASCU is identified by 4 bytes (H1H2A1A2) or by
 2 bytes (A1A2). In the latter case, H1H2 is reserved for session
 identification.
 The SO command is sent to open the MATIP session. In Type A
 conversational it may contains the list of ASCUs configured in this
 session.
 The OC command confirms the SO command. It can refuse or accept it,
 totally or conditionally. In Type A, it contains the list of the
 ASCUs either rejected or configured in the session.

7. OVERALL PACKET FORMAT FOR TYPE A & TYPE B

 The first 4 bytes of the MATIP header follow the following rules.
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |C|     Cmd     |            length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Robert Informational [Page 9] RFC 2351 MATIP May 1998

 Ver
 The `Ver' (Version) field represents the version of the MATIP. It
 must contain the value 001 otherwise the packet is considered as
 invalid.
 C
 Identifies a CONTROL packet.
   When set to 1, the packet is a Control packet
   When set to 0, the packet is a Data packet
 Cmd
 This field identifies the control command if the flag C is set to 1.
 Length
 This field indicates the number of bytes of the whole packet, header
 included.
 Notes : Fields identified as optional (Opt) are not transmitted if
 not used.

8. MATIP FORMAT FOR TYPE A CONVERSATIONAL TRAFFIC

8. 1 Control Packet Format

 There are 3 control packets to open or close the session at the MATIP
 level.

8.1.1 Session Open format (SO)

 To be able to identify the session and before sending any data
 packets, a Session Open command is sent. It can be initiated by
 either side. In case of collision, the open session from the side
 having the lower IP address is ignored.
     0                   1                   2                   3
     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0|0|0|0|0| Ver |1|1 1 1 1 1 1 0|           length              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |0 0|0 1|0| CD  | STYP  |0 0 0 0|       RFU     |MPX|HDR| PRES. |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |      H1       |      H2       |           RFU                 |
    |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Reserved    |              RFU              | Nbr of ASCUs  |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Nbr of ASCUs |        ASCU list (opt)                        |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Robert Informational [Page 10] RFC 2351 MATIP May 1998

 RFU
 Reserved for future use. Must be set to zero.
 CD
 This field specifies the Coding
    000 : 5 bits (padded baudot)
    010 : 6 bits (IPARS)
    100 : 7 bits (ASCII)
    110 : 8 bits (EBCDIC)
    xx1 : R.F.U
 STYP
 This is the traffic subtype (type being TYPE A).
    0001 : TYPE A Conversational
 MPX
 This flag specifies the multiplexing used within the TCP session.
 Possible values are:
    00 : Group of ASCU with 4 bytes identification per ASCU (H1H2A1A2)
    01 : Group of ASCUs with 2 bytes identification per ASCU (A1A2)
    10 : single ASCU inside the TCP session.
 HDR
 This field specifies which part of the airline's specific address is
 placed ahead of the message texts transmitted over the session.
 Possible values are:
    00 : ASCU header = H1+H2+A1+A2
    01 : ASCU Header = A1+A2
    10 : No Header
    11 : Not used
 The MPX and HDR must be coherent. When ASCUs are multiplexed, the data
 must contain the ASCU identification. The table below summarizes the
 allowed combinations:
     +--------------------------+
     |       MPX | 00 | 01 | 10 |
     +--------------------------+
     | HDR       |              |
     | 00        | Y  | Y  | Y  |
     | 01        | N  | Y  | Y  |
     | 10        | N  | N  | Y  |
     +--------------------------+

Robert Informational [Page 11] RFC 2351 MATIP May 1998

 PRES
 This field indicates the presentation format
    0001 : P1024B presentation
    0010 : P1024C presentation
    0011 : 3270 presentation
 H1 H2
 These fields can logically identify the session if MPX is not equal to
 00. When this field is not used, it must be set to 0. If used in
 session (MPX <> 0) with HDR=00, H1H2 in data packet must have the same
 value as set in SO command.
 Nbr of ASCUs
 Nbr_of_ASCUs field is mandatory and gives the number of ASCUs per
 session. A 0 (zero) value means unknown. In this case the ASCU list is
 not present in the `Open Session' command and must be sent by the
 other end in the `Open Confirm' command.
 ASCU LIST
 Contains the list of identifier for each ASCU. If MPX=00 it has a
 length of four bytes (H1H2A1A2) for each ASCU, otherwise it is two
 bytes (A1A2).

8.1.2 Open Confirm format (OC)

 The OC (Open Confirm) command is a response to an SO (Session Open)
 command and is used to either refuse the session or accept it
 conditionally upon checking hte configuration of each ASCU.
 In case of acceptance, the OC indicates the number and the address of
 the rejected ASCUs, if any. Alternatively, it indicates the list of
 ASCUs configured for that MATIP session if the list provided by the
 SO command was correct or the number of ASCUs configured in the
 session was unknown (n. of ASCU equals 0).

8.1.2.1 Refuse the connection

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     cause     |
   +-+-+-+-+-+-+-+-+
 Cause
 This field indicates the reason for the MATIP session refusal:

Robert Informational [Page 12] RFC 2351 MATIP May 1998

     0 0 0 0 0 0 0 1 : No Traffic Type matching between Sender &
         Recipient
     0 0 0 0 0 0 1 0 : Information in SO header incoherent
     1 0 0 0 0 1 0 0
         up to       : Application dependent
     1 1 1 1 1 1 1 1
     Other values reserved.

8.1.2.2 Accept the connection

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 1|            length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 R 0 0 0 0 0| Nbr of ASCUs  |Nbr of ASCU(opt|  ASCU LIST    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 R
 Flag indicating an error in the ASCU configuration provided in the SO
 command.
 NBR of ASCUs
 If the MPX value is equal to 00 in the SO command, this field is two
 bytes long. Otherwise, it is one byte.
 If the R flag is set, the Nbr_of_ASCUs field represents the number of
 ASCUs in error. Otherwise, it indicates the number of ASCUs configured
 for that MATIP session.
 Notes: The length of this field is either one or two bytes. In the SO
 command, the length is always two bytes. This discrepancy comes from
 backward compatibility with AX25 (see chapter 4). In the SO command,
 it is possible to use a free byte defined in the AX25 call user data.
 Unfortunately, there is no such free byte in the AX25 clear user
 data.
 ASCU LIST
 Depending on the R flag, this field indicates the list of ASCUs  (A1A2
 or H1H2A1A2) either in error or within the session.

Robert Informational [Page 13] RFC 2351 MATIP May 1998

8.1.3 Session Close (SC)

 The SC (Session Close) command is used to close an existing MATIP
 session.
   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Close  Cause  |
   +-+-+-+-+-+-+-+-+
 Close Cause
 Indicates the reason for the session closure:
     0 0 0 0 0 0 0 0 : Normal Close
     1 0 0 0 0 1 0 0
          up to      : Application dependent
     1 1 1 1 1 1 1 1
     Other values reserved.

8.2 Data Packet Format

   0                   1                   2                   3
   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |0|0 0 0 0 0 0 0|          length               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         ID (optional)                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         Payload                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ID
 This field is optional and has a different length and format
 according to the value of HDR, PRES indicated during the session
 establishment.

Robert Informational [Page 14] RFC 2351 MATIP May 1998

   +------------------------------+-------------------------------+
   |HDR |  PRES = P1024B and 3270 |     PRES = P1024C             |
   +------------------------------+-------------------------------+
   |00  |ID = 4 bytes H1-H2-A1-A2 | ID = 5 bytes H1-H2-A1-0x01-A2 |
   +------------------------------+-------------------------------+
   |01  |ID = 2 bytes A1-A2       | ID = 3 bytes A1-0x01-A2       |
   +------------------------------+-------------------------------+
   |10  |ID = 0 bytes             | ID = 0 bytes                  |
   +------------------------------+-------------------------------+
 H1, H2 value must match the value given in the SO command if MPX is
 different from 0.
 Payload
 payload begins with the terminal identification:
    - One byte Terminal identifier (TA) in P1024B
    - Two bytes SID/DID Terminal identifier in P1024C.

9. MATIP FORMAT FOR TYPE A HOST-TO-HOST TRAFFIC

9. 1 Control Packet Format

 There are 3 control packets to open or close the session at the MATIP
 level.

9.1.1 Session Open format (SO)

 To be able to identify the session and before sending any data
 packet, a Session Open command is sent. It can be initiated by either
 side. In case of collision, the open session from the side having the
 lower IP address is ignored.
    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 1 0|     length                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0|0 1|0| CD  | STYP  |0 0 0 0|       RFU     |MPX|HDR|0 0 0 0|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      H1       |      H2       |           RFU                 |
   |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Flow ID(opt)|
   +-+-+-+-+-+-+-+-+
 RFU
 Reserved for future use. Must be set to zero.

Robert Informational [Page 15] RFC 2351 MATIP May 1998

 CD
 This field specifies the Coding, as defined in section 8.1.1.1.
 STYP
 This is the traffic subtype (type being Type A).
 0010 : TYPE A IATA Host to Host
 1000 : SITA Host to Host
 MPX
 This flag specifies the multiplexing used within the MATIP session in
 TYPE A SITA host to host. Possible values are:
 00 : irrelevant
 01 : multiple flow inside the TCP connection
 10 : single flow inside the TCP connection
 HDR
 This field specifies which part of the airline's specific address is
 placed ahead of the message text transmitted over the session.
 Possible values are:
 00 : used in TYPE A SITA Host to Host Header = H1+H2+Flow ID
 01 : used in TYPE A SITA Host to Host Header = Flow ID
 10 : No Header (default for IATA host to Host)
 11 : Not used
 The MPX and HDR must be coherent. When flow are multiplexed, the data
 must contain the flow identification. The table below summarizes the
 possible combinations:
       +---------------------+
       |       MPX | 01 | 10 |
       +---------------------+
       | HDR       |    |    |
       | 00        | Y  | Y  |
       | 01        | Y  | Y  |
       | 10        | N  | Y  |
       +---------------------+
 H1 H2
 These fields can be used to identify the session. When this field is
 not used, it must be set to 0. If HDR=00, H1H2 in data packet must
 have the same value as set in SO command.
 Flow ID
 This field is optional and indicates the Flow ID (range 3F - 4F Hex).

Robert Informational [Page 16] RFC 2351 MATIP May 1998

9.1.2 Open Confirm format (OC)

 The OC (Open Confirm) command is a response to an SO (Session Open)
 command and is used to either refuse the session or accept it.

9.1.2.1 Refuse the connection

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     cause     |
   +-+-+-+-+-+-+-+-+
 Cause
 This field indicates the reason for the MATIP session refusal
     0 0 0 0 0 0 0 1 : No Traffic Type matching between Sender &
          Recipient
     0 0 0 0 0 0 1 0 : Information in SO header incoherent
     1 0 0 0 0 1 0 0
          up to      : Application dependent
     1 1 1 1 1 1 1 1
     Other values reserved.

9.1.2.2 Accept the connection

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+

9.1.3 Session Close (SC)

 The SC (Session Close) command is used to close an existing MATIP
 session.

Robert Informational [Page 17] RFC 2351 MATIP May 1998

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Close  Cause  |
   +-+-+-+-+-+-+-+-+
 Close Cause
 Indicates the reason for the session closure:
     0 0 0 0 0 0 0 0 : Normal Close
     1 0 0 0 0 1 0 0
          up to      : Application dependent
     1 1 1 1 1 1 1 1
     Other values reserved

9.2 Data Packet Format

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |0|0 0 0 0 0 0 0|          length               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         ID (optional)                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         Payload                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 ID
 This field is optional and has a different length and format
 according to the value of   HDR indicated during the session
 establishment.
   +-------------------------------+
   |HDR |        I.D.              |
   +-------------------------------+
   |00  |ID = 3 bytes H1-H2 FLOW ID|
   +-------------------------------+
   |01  |ID = FLOW ID              |
   +-------------------------------+
   |10  |ID nor present            |
   +-------------------------------+

Robert Informational [Page 18] RFC 2351 MATIP May 1998

 Payload packet
 The payload format is relevant to the MATIP layer. It is formatted
 according to the IATA host to host specifications and agreed
 bilaterally by the sender and the receiver.

10. MATIP FORMAT FOR TYPE B TRAFFIC

10.1 Control packet format

 There are 3 control packets used to open or close the session at the
 MATIP level for exchanging Type B data

10.1.1 Session Open format (SO)

 Before sending any data packets, it is recommended to let the systems
 establishing a session check that they are indeed able to communicate
 (i.e., Both systems agree on the characteristics of the traffic that
 will cross the connection). For this purpose, a two way handshake,
 using the Session commands defined hereafter, is performed
 immediately after the establishment of the TCP level connection.
 Either side can initiate this procedure. In case of collision, the
 open session from the side having the lower IP address is ignored.
    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 1 0|            length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0| C D | PROTEC| BFLAG |          Sender HLD           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       Recipient HLD           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Length
 This field indicates the number of bytes of the whole command, header
 included. The only possible values are equal to 6 bytes or 10 bytes.
 CD
 This field specifies the Coding, as defined in section 8.1.1.1.
 PROTEC
 Identifies the end to end Messaging Responsibility Transfer protocol
 used.
 0010: BATAP
 All other values available.
 BFLAG (X means `do not care'

Robert Informational [Page 19] RFC 2351 MATIP May 1998

 X X 0 0 means that the fields `Sender HLD, Recipient HLD' do not exist
      in this packet. In this case, the exact length of the packet is 6
      Bytes.
 X X 1 0 means that the `Sender HLD, Recipient HLD' are carried
      respectively in bytes 9,10 and 11,12 of this packet. In this
      case, the exact length of the packet is 10 Bytes.
 0 0 X X means that the connection request has been transmitted from a
 host (Mainframe system)
 0 1 X X means that the connection request has been transmitted from a
 gateway)
 Sender HLD
 HLD of the Type B System sending the Session Open.
 Recipient HLD
 HLD of the Type B system to which session opening is destined.

10.1.2 Open confirm format (OC)

 The OC (Open Confirm) command is a response to an SO (Session Open)
 command and is used to either refuse the session or accept it.

10.1.2.1 Refuse the connection

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|1|   Cause   |
   +-+-+-+-+-+-+-+-+
 Length of this packet is 5 Bytes.
 Cause
 Indicates the cause of the rejection
     0 0 0 0 0 1 : No Traffic Type matching between Sender & Recipient
     0 0 0 0 1 0 : Information in SO header incoherent
     0 0 0 0 1 1 : Type of Protection mechanism are different
     0 0 0 1 0 0 up to 1 1 1 1 1 1 : R.F.U

Robert Informational [Page 20] RFC 2351 MATIP May 1998

10.1.2.2 Accept the connection

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 1|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0 0 0 0 0 0 0 0|
   +-+-+-+-+-+-+-+-+
 Length of this packet is 5 Bytes.

10.1.3 Session Close (SC)

 The SC (Session Close) command is used to close an existing MATIP
 session.
    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |1|1 1 1 1 1 0 0|0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 1|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Close  Cause  |
   +-+-+-+-+-+-+-+-+
 Close Cause
 Indicates the reason for the session closure:
 0 0 0 0 0 0 0 0 : Normal Close
 1 0 0 0 0 1 0 0 up to 1 1 1 1 1 1 1 1 : Application dependent
 Other values reserved

10.2 Data packet format

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |0|0|0|0|0| Ver |0|0 0 0 0 0 0 0|            length             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                         Payload                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 Length
 This field indicates the number of bytes of the whole packet, header
 included.

Robert Informational [Page 21] RFC 2351 MATIP May 1998

 Payload
 Type B message formatted according to the IATA standard and
 conforming to the rules of the accessed TYPE B service

11. Security Considerations

 The security is a very sensitive point for airline industry. Security
 for the MATIP users can take place at different levels:
 The ASCU must be defined to enable the session with the host
 application. The control can be achieved in two ways: either the ASCU
 address (H1 H2 A1 A2) is defined at the application level by the
 means of a static configuration, or the ASCU is identified by a User
 ID / password. In most cases, the User ID and Password are verified
 by a dedicated software running in the central host. But they can
 also be checked by the application itself.
 The MATIP sessions being transported over TCP/IP, It can go through a
 firewall. Depending on the firewall level, the control can be
 performed at network (IP addresses) or TCP application layer.
 For higher level of security all compliant implementations MAY
 implement IPSEC ESP for securing control packets.  Replay protection,
 the compulsory cipher suite for IPSEC ESP, and NULL encryption MAY be
 implemented. Optionally, IPSEC AH MAY also be supported.  All
 compliant implementations MAY also implement IPSEC ESP for protection
 of data packets. Replay prevention and integrity protection using
 IPSEC ESP mandated cipher suit MAY be implemented.  NULL encryption
 also MAY be supported. Other IPSEC ESP required ciphers MAY also be
 supported.

12. Author's Address

 Alain Robert
 S.I.T.A.
 18, rue Paul Lafargue
 92904 PARIS LA DEFENSE 10
 FRANCE
 Phone: 33 1 46411491
 Fax: 33 1 46411277
 EMail: arobert@par1.par.sita.int

Robert Informational [Page 22] RFC 2351 MATIP May 1998

13. Full Copyright Statement

 Copyright (C) The Internet Society (1998).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Robert Informational [Page 23]

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