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RFC 3033 - The Assignment of the Information Field and Protocol


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Network Working Group                                          M. Suzuki
Request for Comments: 3033                                           NTT
Category: Standards Track                                   January 2001

    The Assignment of the Information Field and Protocol Identifier
   in the Q.2941 Generic Identifier and Q.2957 User-to-user Signaling
                       for the Internet Protocol

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

   The purpose of this document is to specify the assignment of the
   information field and protocol identifier in the Q.2941 Generic
   Identifier and Q.2957 User-to-user Signaling for the Internet
   protocol.

   The assignment, that is specified in section 4 of this document, is
   designed for advanced B-ISDN signaling support of the Internet
   protocol, especially the B-ISDN signaling support for the connection
   that corresponds to the session in the Internet protocol which is
   clarified in section 2.  This specification provides an indispensable
   framework for the implementation of long-lived session and QoS-
   sensitive session transfers over ATM.

1. Purpose of Document

   The purpose of this document is to specify the assignment of the
   information field and protocol identifier in the Q.2941 Generic
   Identifier and Q.2957 User-to-user Signaling for the Internet
   protocol.

   The assignment, that is specified in section 4 of this document, is
   designed for advanced B-ISDN signaling support of the Internet
   protocol, especially the B-ISDN signaling support for the connection
   that corresponds to the session in the Internet protocol which is

   clarified in section 2.  Needless to say, the purpose of this
   specification is not limited to this support, and it should also be
   applicable to other purposes.

   This specification provides an indispensable framework for the
   implementation of long-lived session and QoS-sensitive session
   transfers over ATM.  Note that this document only specifies the
   assignment of the information field and protocol identifier, and that
   it may not specify complete protocol that enables interoperable
   implementation.  This is because it is beyond the scope of this
   document and will be specified in a separate document.

2. Session-related ATM Connection

   With the development of new multimedia applications on the current
   Internet, the demands for multimedia support are increasing in the IP
   network, which currently supports best effort communications.  In
   particular, demands to support QoS guaranteed communications are
   increasing with the development of voice, audio, and video
   communications applications.  And it may also be necessary to
   introduce the mechanism that can efficiently transfer the huge volume
   of traffic expected with these applications.

   The major features of B-ISDN are high speed, logical multiplexing
   with the VP/VC, and flexible QoS management per VC, so it is quite
   natural to use these distinctive functions of B-ISDN to implement a
   multimedia support mechanism in the IP network.  The flexible QoS
   management and logical multiplexing functions in B-ISDN are the
   expected method of implementing the QoS guaranteed communications in
   the Internet.  And when a long-lived session is supported by a
   particular VC, efficient packet forwarding may be possible using the
   high speed and logical multiplexing of B-ISDN.

   This section clarifies B-ISDN signaling functions that are required
   when the session is supported by the VC, for advanced B-ISDN
   signaling support of the Internet protocol.

2.1 Long-lived Session Signaling

   An example scenario for establishing a VC for a long-lived session is
   shown in Fig. 2.1.

         IP Router      ATM SW         ATM SW       IP Router
+----+                        Default VC                        +----+
| WS |   +------+  UNI  +-----+        +-----+  UNI  +------+   | WS |
+--+-+   |   /->|<------+-\-/-+--------+-\-/-+------>|<-\   |   +-+--+
   |.....|__/   |===||==|  X  |========|  X  |==||===|   \__|.....|
         |      |       | / \ |        | / \ |       |      |
         +------+       +-----+        +-----+       +------+

         A. New session initially forwarded over a default VC.

         IP Router      ATM SW         ATM SW       IP Router
+----+                        Default VC                        +----+
| WS |   +------+  UNI  +-----+        +-----+  UNI  +------+   | WS |
+--+-+   |   /->|<------+-\-/-+--------+-\-/-+------>|<-\   |   +-+--+
   |.....|__/   |===||==|  X  |========|  X  |==||===|   \__|.....|
         |      |<------+-/-\-+--------+-/-\-+------>|      |
         +------+       +-----+        +-----+       +------+
                            New VC is set up

          B. New VC is set up for the long-lived session.

         IP Router      ATM SW         ATM SW       IP Router
+----+                        Default VC                        +----+
| WS |   +------+  UNI  +-----+        +-----+  UNI  +------+   | WS |
+--+-+   |      |<------+-\-/-+--------+-\-/-+------>|      |   +-+--+
   |.....|__    |===||==|  X  |========|  X  |==||===|    __|.....|
         |  \-->|<------+-/-\-+--------+-/-\-+------>|<--/  |
         +------+       +-----+        +-----+       +------+
                                New VC

           C. Transfer of the long-lived session to a new VC.

      Fig. 2.1: Example scenario for establishing a VC for a long-lived
                session.

   First, a session is multiplexed into the default VC connecting the
   routers.  Then, if a router detects that it is a long-lived session,
   it sets up a new VC for the session.  If the new VC is established
   successfully, the long-lived session is moved to the new VC.

   In this procedure involving an ATM VC setup, the B-ISDN signaling
   entity in the called side router must detect that the incoming call
   corresponds to a session of the Internet protocol and notify that
   fact to the IP layer entity.  Based on this information, the IP layer
   entity moves the session to the new VC.

   Therefore, to implement this signaling procedure, the B-ISDN
   signaling must include an session identifier as an information
   element.  The B-LLI, B-HLI, User-user, and Generic Identifier
   information elements are all capable of transferring this
   information.  Considering the original purposes of these information
   elements, the most appropriate one to use is the Generic Identifier
   information element.

2.2 QoS-sensitive Session Signaling

   The major difference between QoS-sensitive session signaling and
   long-lived session signaling is that call setup is not initiated by
   the detection of a long-lived session, but is explicitly initiated by
   the setup protocol such as RSVP.  To implement QoS-sensitive session
   signaling using ATM, the ATM network between the routers must forward
   not only the session identifier but also the setup protocol.

   There are two schemes for forwarding the setup protocol.  One is to
   multiplex the protocol into a default VC connecting the routers, or
   to forward the protocol through a particular VC.  In this case, the
   QoS-sensitive session and the ATM VC are established sequentially.
   The second scheme is to forward the setup protocol as an information
   element in the B-ISDN signaling.  In this case, the QoS-sensitive
   session and the ATM VC are established simultaneously.  The latter
   scheme has the following advantages compared with the former one.

   o Easier to implement.

     - Admission control is simplified, because admission control for
       the IP and ATM layers can be done simultaneously.

     - Watchdog timer processing is simplified, because there is no need
       to watch the IP layer establishment and ATM layer establishment
       sequentially.

   o If the setup protocol supports negotiation, then an ATM VC whose
     QoS is based on the result of negotiation can be established.

   However, the latter scheme, at least, cannot support a case where a
   PVC is used to support a QoS-sensitive session.  Therefore, both
   procedures should be taken into account.

   An example of a message sequence that simultaneously establishes a
   QoS-sensitive session and an ATM VC is shown in Fig. 2.2.

         IP Router      ATM SW         ATM SW       IP Router
+----+                     B-ISDN Signaling                     +----+
| WS |   +------+  UNI  +-----+ Setup  +-----+  UNI  +------+   | WS |
+--+-+   |   /->|<------+-\-/--Protocol--\-/-+------>|<-\   |   +-+--+
   |.....|__/   |===||==|  X  |========|  X  |==||===|   \__|.....|
         |  \-->|<------+-/-\-+--------+-/-\-+------>|<--/  |
         +------+       +-----+  Data  +-----+       +------+
                                QoS VC
 N-CONNECT |                                              |
---------->|  |             |            |             |  |
           |->|    SETUP    |            |             |  |
           |  |------------>|            |             |  |
           |  |<------------|            |             |  |
           |  |  CALL PROC  |----------->|    SETUP    |  |
           |  |             |            |------------>|  |
           |  |             |            |             |->| N-CONNECT
           |  |             |            |             |  |---------->
           |  |             |            |             |  |<----------
           |  |             |            |    CONN     |<-| N-CONNECT-ACK
           |  |             |            |<------------|  |
           |  |             |            |------------>|  |
           |  |    CONN     |<-----------|  CONN ACK   |->|
           |  |<------------|            |             |  |
           |  |------------>|            |             |  |
           |<-|  CONN ACK   |            |             |  |
<----------|  |             |            |             |  |
 N-CONNECT |                                              |
      -ACK

      Fig. 2.2: Example procedure for simultaneous QoS-sensitive session
                and ATM VC establishment.

   RSVP is currently proposed for the setup protocol and new setup
   protocols are likely to be developed in the future.  Therefore, to
   generalize the discussion, the procedure for the setup protocol in
   this example is the general connection setup procedure using
   confirmed service.

   To implement this signaling procedure, the B-ISDN signaling must
   include the User-user information element that the capacity is
   sufficient to forward the setup protocol.

3. Overview of the Generic Identifier and User-to-user Signaling

3.1 Overview of the Generic Identifier

   The Generic Identifier enables the transfer of identifiers between
   end-to-end users in the ATM network, and it is defined in the Q.2941
   Part 1 (Q.2941.1) [3] and Part 2 (Q.2941.2) [4] as an optional
   information element for the Q.2931 [1] and Q.2971 [2] UNI signaling
   protocol.  The SETUP, ALERTING, CONNECT, RELEASE, RELEASE COMPLETE,
   ADD PARTY, PARTY ALERTING, ADD PARTY ACK, ADD PARTY REJECT, DROP
   PARTY, and DROP PARTY ACK messages that are transferred between end-
   to-end users in the ATM network may contain up to three Generic
   Identifier information elements.  The ATM network transfers the
   Generic Identifier information element transparently if it contains
   no coding rule errors.

   The format of the Generic Identifier information element specified in
   the Q.2941 is shown in Fig. 3.1.

                              Bits
           8     7     6     5     4     3     2     1    Octets
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |        Information element identifier         |
        |    = Generic identifier transport IE (0x7F)   |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |  1  |   Coding  |    IE instruction field     |
        | Ext |  standard |Flag |Res. |  IE action ind. |  2
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |   Length of contents of information element   |  3-4
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |    Identifier related standard/application    |  5
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier type                |  6
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               Identifier length               |  7
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier value               |  8-
        =                                               =
        +-----+-----+-----+-----+-----+-----+-----+-----+
        =                                               =
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier type                |
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               Identifier length               |
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier value               |
        =                                               =
        +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 3.1: Format of the Generic Identifier information element.

   The usage of the first 4 octets of fields is specified in section 4
   of the Q.2931.

   The Identifier related standard/application field identifies the
   standard or application that uses the identifier.  Assignment of the
   Identifier related standard/application field for the Internet
   protocol is as follows.  A leading 0x means hexadecimal.

     0x03: IPv4.

     0x04: ST2+.

     0x05: IPv6.

     0x06: MPLS.

   Note: DSM-CC, H.310/H.321, MPOA, ATM VCC Trunking, AAL2, and
   H.323/H.245 are also supported.

   A transferred identifier is given by the combination of the
   Identifier type, length and value fields, and a Generic Identifier
   information element may contain multiple identifiers.

   Assignment of the Identifier type field for the Internet protocol is
   as follows.  A leading 0x means hexadecimal.

     0x01: Session.

     0x02: Resource.

     0x10-0xFD: Reserved for IANA assignment.

     0xFE: Experiment/Organization specific.

   The maximum length of the Generic Identifier information element is
   63 octets.

   See the Q.2941.1 and Draft Q.2941.2 for detailed protocol
   specifications of the Generic Identifier.

3.2 Overview of the User-to-user Signaling

   The User-to-user Signaling enables the transfer of information
   between end-to-end users in the ATM network, and it is defined in
   Q.2957 [5, 6] and in Q.2971 annex D [2] as an optional information
   element for the Q.2931 [1] and Q.2971 [2] UNI signaling protocol.
   The SETUP, ALERTING, CONNECT, RELEASE, RELEASE COMPLETE, PROGRESS,
   ADD PARTY, PARTY ALERTING, ADD PARTY ACK, ADD PARTY REJECT, DROP
   PARTY, and DROP PARTY ACK messages that are transferred between end-
   to-end users in the ATM network may contain a User-user information
   element.  The ATM network transfers the User-user information element
   transparently if it contains no coding rule errors.

   From the viewpoint of B-ISDN signaling applications, it seems the
   Generic Identifier and User-to-user Signaling are similar functions.
   But their rules for processing exceptions are not completely the
   same, because their purposes are different.  The Generic Identifier
   is designed for the transfer of identifiers between the c-planes,
   while the User-to-user Signaling is designed for the transfer of user
   data via the c-planes.  Another difference is that the latter
   supports interworking with the user-user information element in the

   Q.931 N-ISDN signaling, but the Generic Identifier does not.  Note
   that the ATM network may check the contents of the Generic Identifier
   information element, but does not check the contents of the User-to-
   user information element.

   The format of the User-user information element is shown in Fig. 3.2.

                              Bits
           8     7     6     5     4     3     2     1    Octets
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |        Information element identifier         |
        |    = User-user information element (0x7E)     |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |  1  |   Coding  |    IE instruction field     |
        | Ext |  standard |Flag |Res. |  IE action ind. |  2
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |   Length of contents of information element   |  3-4
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |             Protocol discriminator            |  5
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               User information                |  6-
        =                                               =
        |                                               |
        +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 3.2: Format of the User-user information element.

   The usage of the first 4 octets of fields is specified in section 4
   of the Q.2931.

   The Protocol discriminator field identifies the upper layer protocol
   that uses the user-user information.

   The User information field contains the user-user information to be
   transferred.

   The maximum length of the User-user information element is 133
   octets.

   See Q.2957, Draft Q.2957 amendment 1, and Q.2971 annex D for detailed
   protocol specifications of the User-to-user Signaling.

4. Information Field and Protocol Identifier Assignment

4.1 Assignment in the Generic Identifier Information Element

4.1.1 Use of Generic Identifier

   The information field and protocol identifier assignment principle
   for the Internet protocol in the Generic Identifier information
   element is shown in Fig. 4.1.

                              Bits
           8     7     6     5     4     3     2     1    Octets
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |        Information element identifier         |
        |    = Generic identifier transport IE (0x7F)   |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |  1  |   Coding  |    IE instruction field     |
        | Ext |  standard |Flag |Res. |  IE action ind. |  2
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |   Length of contents of information element   |  3-4
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |    Identifier related standard/application    |
        |          = IPv4, ST2+, IPv6, or MPLS          |  5
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier type                |
        |       = Session, Resource, or Experiment   |  6
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               Identifier length               |  7
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier value               |  8-
        =                                               =
        +-----+-----+-----+-----+-----+-----+-----+-----+
        =                                               =
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier type                |
        |       = Session, Resource, or Experiment   |
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               Identifier length               |
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier value               |
        =                                               =
        +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 4.1: Principle of assignment in the Generic Identifier
                information element.

   The Identifier related standard/application field is the IPv4, ST2+,
   IPv6, or MPLS.

   The Identifier type field is the Session, Resource, or
   Experiment/Organization specific.

   The Identifier value field is assigned to Internet protocol related
   information which is identified by the Identifier related
   standard/application field and Identifier type field.  The following
   identifiers are specified.

                                     Std./app.               Id type

     IPv4 session identifier         IPv4                    Session

     IPv6 session identifier         IPv6                    Session

     MPLS VCID                       MPLS                    Resource

     Exp./Org. specific              IPv4/ST2+/IPv6/MPLS     Experiment

   As described in section 3.1, the B-ISDN signaling message transferred
   between end-to-end users may contain up to three Generic Identifier
   information elements.  These elements may contain multiple
   identifiers.  This document does not specify the order of identifiers
   when multiple identifiers appear in a signaling message.

   This document also does not specify the semantics when multiple
   identifiers having the same Identifier type appear in a signaling
   message, or when a signaling message contains a Generic Identifier
   information element that does not contain identifiers.

   When a B-ISDN signaling message containing a Generic Identifier
   information element enters an ATM network that does not support the
   Generic Identifier, the network clears the call, discards the
   information element, or discards the signaling message.  (See
   sections 4.5.1 and 5.6.8.1 of Q.2931 and section 9.3 of Q.2941.1 for
   details.)

   To enable reliable Generic Identifier information element transfer,
   when the calling party sends a SETUP or ADD PARTY message with up to
   three Generic Identifier information elements, the CONNECT or ADD
   PARTY ACK message returned by the called party must contain at least
   one Generic Identifier information element.  The called party may not
   respond with the same identifiers received from the calling party.
   The calling party should confirm that the response message contains
   at least one Generic Identifier information element.  This rule
   enables identifier negotiation; this document does not specify the
   detailed procedure of this negotiation.

4.1.2 IPv4 session identifier

   If the Identifier related standard/application field in the Generic
   Identifier information element is the IPv4, and the Identifier type
   field in the identifier is the Session, the identifier is the IPv4
   session identifier.  The format of the IPv4 session identifier is
   shown in Fig. 4.2.

                              Bits                         Octet
           8     7     6     5     4     3     2     1     length
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier type                |
        |                = Session (0x01)               |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               Identifier length               |
        |               = 13 octets (0x0D)              |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |              Source IPv4 address              |  4
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |           Destination IPv4 address            |  4
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                   Protocol                    |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                  Source Port                  |  2
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Destination Port               |  2
        +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 4.2: IPv4 session identifier.

   The Identifier type field is the Session (0x01).

   The Identifier length is 13 octets.

   The Source IPv4 address, Destination IPv4 address, Protocol, Source
   Port, and Destination Port [7, 9, 10] are assigned in that order to
   the Identifier value field.

   Note: This specific session identifier is intended for use only with
   the explicit reservation.  If wild card associations are needed at a
   later date, another identifier type will be used.

4.1.3 IPv6 session identifier

   If the Identifier related standard/application field in the Generic
   Identifier information element is the IPv6, and the Identifier type
   field in the identifier is the Session, the identifier is the IPv6
   session identifier.  The format of the IPv6 session identifier is

   shown in Fig. 4.3.

                              Bits                         Octet
           8     7     6     5     4     3     2     1     length
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier type                |
        |                = Session (0x01)               |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               Identifier length               |
        |               = 37 octets (0x25)              |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |              Source IPv6 address              |  16
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |           Destination IPv6 address            |  16
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                   Protocol                    |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                  Source Port                  |  2
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Destination Port               |  2
        +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 4.3: IPv6 session identifier.

   The Identifier type field is the Session (0x01).

   The Identifier length is 37 octets.

   The Source IPv6 address, Destination IPv6 address, Protocol, Source
   Port, and Destination Port [8, 9, 10] are assigned in that order to
   the Identifier value field.

   Note: This specific session identifier is intended for use only with
   the explicit reservation.  If wild card associations are needed at a
   later date, another identifier type will be used.

4.1.4 MPLS VCID

   If the Identifier related standard/application field in the Generic
   Identifier information element is the MPLS, and the Identifier type
   field in the identifier is the Resource, the identifier is the MPLS
   VCID.  The format of the MPLS VCID is shown in Fig. 4.4.

                                 Bits                         Octet
              8     7     6     5     4     3     2     1     length
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |                Identifier type                |
           |               = Resource (0x02)               |  1
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |               Identifier length               |
           |               = 4 octets (0x04)               |  1
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |                   MPLS VCID                   |  4
           +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 4.4: MPLS VCID.

   The Identifier type field is the Resource (0x02).

   The Identifier length is 4 octets.

   The MPLS VCID [13] is assigned to the Identifier value field.

4.1.5 Experiment/Organization specific

   If the Identifier related standard/application field in the Generic
   Identifier information element is the IPv4, ST2+, IPv6, or MPLS, and
   the Identifier type field in the identifier is the
   Experiment/Organization specific, the identifier is the
   Experiment/Organization specific.  The format of the
   Experiment/Organization specific is shown in Fig. 4.5.

                              Bits                         Octet
           8     7     6     5     4     3     2     1     length
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier type                |
        |   =  Experiment/Organization specific (0xFE)  |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               Identifier length               |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |    Organizationally unique identifier (OUI)   |  3
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |     Experiment/Organization specific info.    |
        =                                               =
        |                                               |
        +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 4.5: Experiment/Organization specific.

   The Identifier type field is the Experiment/Organization specific
   (0xFE).

   The first 3 octets in the Identifier value field must contain the
   Organizationally unique identifier (OUI) (as specified in IEEE 802-
   1990; section 5.1).

4.2 Assignment in the User-user Information Element

4.2.1 Use of User-to-user Signaling

   The information field and protocol identifier assignment principle
   for the Internet protocol in the User-user information element is
   shown in Fig. 4.6.

                              Bits
           8     7     6     5     4     3     2     1    Octets
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |        Information element identifier         |
        |    = User-user information element (0x7E)     |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |  1  |   Coding  |    IE instruction field     |
        | Ext |  standard |Flag |Res. |  IE action ind. |  2
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |   Length of contents of information element   |  3-4
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |             Protocol discriminator            |
        |     = Internet protocol/application (0x06)    |  5
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |    Internet protocol/application identifier   |  6
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |   Internet protocol/application related info. |  7-
        =                                               =
        |                                               |
        +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 4.6: Principle of assignment in the User-user information
                element.

   The Protocol discriminator field is the Internet protocol/application
   (0x06).  In this case, the first 1 octet in the User information
   field is the Internet protocol/application identifier field.

   Assignment of the Internet protocol/application identifier field is
   as follows.  A leading 0x means hexadecimal.

     0x00: Reserved.

     0x01: Reserved for ST2+.

     0x02: RSVP message.

     0x03-0xFD: Reserved for IANA assignment.

     0xFE: Experiment/Organization specific.

     0xFF: Reserved.

   The field that follows the Internet protocol/application identifier
   field is assigned to Internet protocol/application related
   information that is identified by the Internet protocol/application
   identifier field.

   When a B-ISDN signaling message containing a User-user information
   element enters an ATM network that does not support the User-to-user
   Signaling, the network clears the call, discards the information
   element, or discards the signaling message.  (See sections 4.5.1 and
   5.6.8.1 of Q.2931, section 1.9 of Q.2957, and Q.2971 annex D for
   details.)

   To enable reliable User-user information element transfer, when the
   calling party sends a SETUP or ADD PARTY message with a User-user
   information element, the CONNECT or ADD PARTY ACK message returned by
   the called party must contain a User-user information element.  The
   called party may not respond with the same user information received
   from the calling party.  The calling party should confirm that the
   response message contains a User-user information element.  This rule
   enables negotiation; this document does not specify the detailed
   procedure of this negotiation.

4.2.2 RSVP message

   The format of the RSVP message is shown in Fig. 4.7.

                                 Bits
              8     7     6     5     4     3     2     1    Octets
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |        Information element identifier         |
           |    = User-user information element (0x7E)     |  1
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |  1  |   Coding  |    IE instruction field     |
           | Ext |  standard |Flag |Res. |  IE action ind. |  2
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |   Length of contents of information element   |  3-4
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |             Protocol discriminator            |
           |     = Internet protocol/application (0x06)    |  5
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |    Internet protocol/application identifier   |
           |              = RSVP message (0x02)            |  6
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |                  RSVP message                 |  7-
           =                                               =
           |                                               |
           +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 4.7: RSVP message.

   The Internet protocol/application identifier field is the RSVP
   message (0x02).

   The RSVP message [12] is assigned to the Internet
   protocol/application related information field.  The SETUP message
   may contain the RSVP Resv message.  The CONNECT message may contain
   the RSVP ResvConf message.  The RELEASE message may contain the RSVP
   ResvErr or ResvTear message.

4.2.3 Experiment/Organization specific

   The format of the Experiment/Organization specific is shown in Fig.
   4.8.

                                 Bits
              8     7     6     5     4     3     2     1    Octets
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |        Information element identifier         |
           |    = User-user information element (0x7E)     |  1
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |  1  |   Coding  |    IE instruction field     |
           | Ext |  standard |Flag |Res. |  IE action ind. |  2
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |   Length of contents of information element   |  3-4
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |             Protocol discriminator            |
           |     = Internet protocol/application (0x06)    |  5
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |    Internet protocol/application identifier   |
           |  =  Experiment/Organization specific (0xFE)   |  6
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |    Organizationally unique identifier (OUI)   |  7-9
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |     Experiment/Organization specific info.    |  10-
           =                                               =
           |                                               |
           +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. 4.8: Experiment/Organization specific.

   The Internet protocol/application identifier field is the
   Experiment/Organization specific (0xFE).

   The first 3 octets in the Internet protocol/application related
   information field must contain the Organizationally unique identifier
   (OUI) (as specified in IEEE 802-1990; section 5.1).

5. Open Issues

   The following issues are still remain in this document.

   o Generic Identifier support for session aggregation.

      Session aggregation support may be needed in a backbone
      environment.  Wild card style aggregated session identifier may be
      feasible.  However, before specifying Generic Identifier support
      for it, session aggregation model in ATM VCs should be clarified.

   o Generic Identifier support for the IPv6 flow label and traffic
      classes.

      The IPv6 flow label and traffic classes support may be needed in
      future.  However, currently their semantics are not clear.

6. IANA Considerations

   When the Identifier related standard/application field in the
   Q.2941.2 Generic Identifier information element is the IPv4, ST2+,
   IPv6, or MPLS, numbers between 0x10-0xFD in the Identifier type field
   are reserved for IANA assignment.  (See section 3.1.)  Following the
   policies outlined in [14], these numbers are allocated through an
   IETF Consensus action.

   When the Protocol discriminator field in the Q.2957 User-user
   information element is the Internet protocol/application, numbers
   between 0x03-0xFD in the Internet protocol/application identifier
   field are reserved for IANA assignment.  (See section 4.2.1.)
   Following the policies outlined in [14], these numbers are allocated
   through an IETF Consensus action.

7. Security Considerations

   This document specifies the information field and protocol identifier
   assignment in the Q.2941 Generic Identifier and Q.2957 User-to-user
   Signaling for the Internet protocol, so these do not weaken the
   security of the B-ISDN signaling.

   In a called party of the B-ISDN signaling, if the incoming SETUP
   message contains the calling party number and if it is verified and
   passed by the ATM network or it is provided by the network, then it
   is feasible to use the calling party number for part of the calling
   party authentication to strengthen security.

Appendix. Information Field and Protocol Identifier Assignment for ST2+

   This appendix specifies information field and protocol identifier
   assignment in the Generic Identifier and User-to-user Signaling for
   ST2+.  Note that this appendix is NOT part of the standard.

A.1 ST2+ session identifier

   If the Identifier related standard/application field in the Generic
   Identifier information element is the ST2+, and the Identifier type
   field in the identifier is the Session, the identifier is the ST2+
   session identifier.  The format of the ST2+ session identifier is
   shown in Fig. A.1.

                              Bits                         Octet
           8     7     6     5     4     3     2     1     length
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Identifier type                |
        |                = Session (0x01)               |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |               Identifier length               |
        |               = 6 octets (0x06)               |  1
        +-----+-----+-----+-----+-----+-----+-----+-----+
        |                Stream ID (SID)                |  6
        +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. A.1: ST2+ session identifier.

   The Identifier type field is the Session (0x01).

   The Identifier length is 6 octets.

   The Stream ID (SID) [11] is assigned to the Identifier value field.

A.2 ST2+ SCMP

   The format of the User-user information element for the ST2+ SCMP is
   shown in Fig. A.2.

                                 Bits
              8     7     6     5     4     3     2     1    Octets
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |        Information element identifier         |
           |    = User-user information element (0x7E)     |  1
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |  1  |   Coding  |    IE instruction field     |
           | Ext |  standard |Flag |Res. |  IE action ind. |  2
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |   Length of contents of information element   |  3-4
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |             Protocol discriminator            |
           |     = Internet protocol/application (0x06)    |  5
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |    Internet protocol/application identifier   |
           |               = ST2+ SCMP (0x01)              |  6
           +-----+-----+-----+-----+-----+-----+-----+-----+
           |                   ST2+ SCMP                   |  7-
           =                                               =
           |                                               |
           +-----+-----+-----+-----+-----+-----+-----+-----+

      Fig. A.2: ST2+ SCMP.

   The Internet protocol/application identifier field is the ST2+ SCMP
   (0x01).

   The ST2+ SCMP [11] is assigned to the Internet protocol/application
   related information field.  The SETUP and ADD PARTY messages may
   contain the ST2+ SCMP CONNECT message.  The CONNECT and ADD PARTY ACK
   messages may contain the ST2+ SCMP ACCEPT message.  The RELEASE and
   DROP PARTY messages may contain the ST2+ SCMP DISCONNECT message.
   The RELEASE, RELEASE COMPLETE, ADD PARTY REJECT, and DROP PARTY
   messages may contain the ST2+ SCMP REFUSE message.

References

   [1]  ITU-T, "Broadband Integrated Services Digital Network (B-
        ISDN)-Digital Subscriber Signaling System No. 2 (DSS 2)-User-
        Network Interface (UNI) Layer 3 Specification for Basic
        Call/Connection Control," ITU-T Recommendation Q.2931, September
        1995.

   [2]  ITU-T, "Broadband Integrated Services Digital Network (B-ISDN)-
        Digital Subscriber Signaling System No. 2 (DSS 2)-User-Network
        Interface Layer 3 Specification for Point-to-Multipoint
        Call/Connection Control," ITU-T Recommendation Q.2971, October
        1995.

   [3]  ITU-T, "Broadband Integrated Services Digital Network (B-ISDN)
        Digital Subscriber Signaling System No. 2 (DSS 2): Generic
        Identifier Transport," ITU-T New Recommendation Q.2941.1,
        September 1997.

   [4]  ITU-T, "Broadband Integrated Services Digital Network (B-ISDN)
        Digital Subscriber Signaling System No. 2 (DSS 2): Generic
        Identifier Transport Extensions," ITU-T New Recommendation
        Q.2941.2, December 1999.

   [5]  ITU-T, "Stage 3 Description for Additional Information Transfer
        Supplementary Service Using B-ISDN Digital Subscriber Signaling
        System No. 2 (DSS 2)-Basic Call Clause 1-User-to-User Signalling
        (UUS)," ITU-T Recommendation Q.2957, February 1995.

   [6]  ITU-T, "Stage 3 Description for Additional Information Transfer
        Supplementary Service Using B-ISDN Digital Subscriber Signaling
        System No. 2 (DSS 2)-Basic Call Clause 1-User-to-User Signalling
        (UUS)," ITU-T Recommendation Q.2957 Amendment 1, December 1999.

   [7]  Postel, J., Ed., "Internet Protocol", STD 5, RFC 791, September
        1981.

   [8]  Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
        Specification", RFC 2460, December 1998.

   [9]  Postel, J., "User Datagram Protocol", STD 6, RFC 768, August
        1980.

   [10] Postel, J., Ed., "Transmission Control Protocol", STD 7, RFC
        793, September 1981.

   [11] Delgrossi, L. and L. Berger, Ed., "Internet Stream Protocol
        Version 2 (ST2) Protocol Specification - Version ST2+", RFC
        1819, August 1995.

   [12] Braden, R., Ed., "Resource ReSerVation Protocol (RSVP) - Version
        1 Functional Specification", RFC 2205, September 1997.

   [13] Nagami, K., Demizu, N., Esaki, H., Katsube, Y. and P. Doolan,
        "VCID Notification over ATM link for LDP", RFC 3038, January
        2001.

   [14] Narten, T., and H. Alvestrand, "Guidelines for Writing an IANA
        Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

   [15] P. Newman, T. Lyon, and G. Minshall, "Flow Labelled IP: A
        Connectionless Approach to ATM," Proc. IEEE Infocom, March 1996.

   [16] S. Damaskos and A. Gavras, "Connection Oriented Protocols over
        ATM: A case study," Proc. SPIE, Vol. 2188, pp.226-278, February
        1994.

   [17] ITU-T, "Integrated Services Digital Network (ISDN) Overall
        Network Aspects and Functions ISDN Protocol Reference Model,"
        ITU-T Recommendation I.320, November 1993.

   [18] ITU-T, "Digital Subscriber Signaling System No. 1 (DSS 1)
        Specification of a Synchronization and Coordination Function for
        the Provision of the OSI Connection-mode Network Service in an
        ISDN Environment," ITU-T Recommendation Q.923, February 1995.

Acknowledgments

   I would like to thank Kenichi Kitami of the NTT Information Sharing
   Lab. Group, who is also the chair of ITU-T SG11 WP1, Shinichi
   Kuribayashi of the NTT Information Sharing Platform Labs., Hiroshi
   Yao and Takumi Ohba of the NTT Network Service Systems Labs., and
   Noriyuki Takahashi of the NTT Information Sharing Platform Labs., for
   their valuable comments and discussions.

   And I would also like to thank the active members of IETF, ITU-T, and
   ATM Forum, especially Joel Halpern of Newbridge Networks, Andrew
   Malis of Ascend Communications, George Swallow and Bruce Davie of
   Cisco Systems, Rao Cherukuri of IBM, Rajiv Kapoor of AT&T, Greg Ratta
   of Lucent, Kaoru Kenyoshi of NEC, Hiroto Uno of Hitachi, Hiroshi
   Esaki and Kenichi Nagami of Toshiba, and Noritoshi Demizu of NAIST
   for their valuable comments and suggestions.

   Also, this specification is based on various discussions during the
   ST2+ over ATM project at the NTT Multimedia Joint Project with
   NACSIS.  I would like to thank Professor Shoichiro Asano of the
   National Center for Science Information Systems for his invaluable
   advice in this area.

Author's Address

   Muneyoshi Suzuki
   NTT Information Sharing Platform Laboratories
   3-9-11, Midori-cho
   Musashino-shi, Tokyo 180-8585, Japan

   Phone: +81-422-59-2119
   Fax:   +81-422-37-7691
   EMail: suzuki.muneyoshi@lab.ntt.co.jp

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