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Versions: 00 RFC 2351

INTERNET DRAFT          EXPIRES SEPT 1998       INTERNET DRAFT
N.S.C Working Group                                             A.Robert
INTERNET DRAFT                                                      SITA
Category: Informational                                       March 1998




                      MAPPING OF AIRLINE TRAFFIC OVER IP
                        <draft-rfced-info-matip-00.txt>


Status of This Memo

This document is an Internet-Draft.  Internet-Drafts are working
documents of the Internet Engineering Task Force (IETF), its
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Distribution of this document is unlimited.


Abstract

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


Contents



. INTRODUCTION                                                         3


2. TERMINOLOGY & ACRONYMS                                              5


3. LAYERING                                                            7


4. TRAFFIC IDENTIFICATION                                              8


5. TCP PORT ALLOCATION                                                 8


6. MATIP SESSION ESTABLISHMENT                                         8






SITA                                                           [Page 1]

7. OVERALL PACKET FORMAT FOR TYPE A & TYPE B                          10


8. MATIP FORMAT FOR TYPE A CONVERSATIONAL TRAFFIC                     11

 8. 1 Control Packet Format                                           11
  8.1.1 Session Open format (SO)                                      11
  8.1.2 Open Confirm format (OC)                                      13
  8.1.3 Session Close (SC)                                            14

 8.2 Data Packet Format                                               15


9. MATIP FORMAT FOR TYPE A HOST-TO-HOST TRAFFIC                       16

 9. 1 Control Packet Format                                           16
  9.1.1 Session Open format (SO)                                      16
  9.1.2 Open Confirm format (OC)                                      18
  9.1.3 Session Close (SC)                                            19

 9.2 Data Packet Format                                               19


10. MATIP FORMAT FOR TYPE B TRAFFIC                                   20

 10.1 Control packet format                                           20
  10.1.1 Session Open format (SO)                                     20
  10.1.2 Open confirm format (OC)                                     21
  10.1.3 Session Close (SC)                                           22

 10.2 Data packet format                                              23


11. SECURITY                                                          23


12. AUTHOR ADDRESS                                                    24















SITA                                                           [Page 2]

. 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.

  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:




SITA                                                           [Page 3]

  - 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 memo 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 :



  !----!          (            )
  !    !----------(            )
  !----!          (            )
  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 memo are :
     - TYPE A Host / Terminal
     - TYPE A Host / TYPE A host
     - TYPE B Host / Network messaging System




SITA                                                           [Page 4]

  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)

  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




SITA                                                           [Page 5]

  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)

  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)





SITA                                                           [Page 6]

  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)




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               |
  +-------------------------------+




SITA                                                           [Page 7]

  |            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.


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:





SITA                                                           [Page 8]

     - 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.
  - Open Confirm (OC) to confirm the SO command.
  - 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
          ---------------------->
                          <-------------------------
                          .
                          .
                          .
 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




SITA                                                           [Page 9]

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             |
  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

  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.





SITA                                                           [Page 10]

  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)                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


  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




SITA                                                           [Page 11]

  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  |
      +--------------------------+


  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.





SITA                                                           [Page 12]

  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 :

      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.




SITA                                                           [Page 13]

  As specified in chapter 6, an already opened session is closed in this
  case.



      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.


    8.1.3 Session Close (SC)

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




SITA                                                           [Page 14]

     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.


  +------------------------------+-------------------------------+
  |HDR |  PRES = P1024B and 3270 |     PRES = P1024C             |
  +------------------------------+-------------------------------+
  |00  |ID = 4 bytes H1-H2-A1-A2 | ID = 5 bytes H1-H2-A1-0x01-A2 |




SITA                                                           [Page 15]

  +------------------------------+-------------------------------+
  |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




SITA                                                           [Page 16]

  Reserved for future use. Must be set to zero.


  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  |
      +---------------------+







SITA                                                           [Page 17]

  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).


    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|




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     +-+-+-+-+-+-+-+-+



    9.1.3 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


  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




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  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            |
  +-------------------------------+



  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           |




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     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       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'

  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)




SITA                                                           [Page 21]

  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


      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  |




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     +-+-+-+-+-+-+-+-+

  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.


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





11. Security

  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.





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  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 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
                 @



























SITA                                                           [Page 24]
INTERNET DRAFT          EXPIRES SEPT 1998       INTERNET DRAFT


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