rfc3033.txt

最新的RFC

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



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RFC 3033             GIT and UUS Assignment for IP          January 2001


   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.















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RFC 3033             GIT and UUS Assignment for IP          January 2001


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.





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   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.




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   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.







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RFC 3033             GIT and UUS Assignment for IP          January 2001


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.

































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RFC 3033             GIT and UUS Assignment for IP          January 2001


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