INTERNET DRAFT                                               Avri Doria
GSMP Working Group                                      Kenneth Sundell
Informational Track                                     Nortel Networks
                                                             July 2000
                                                            August 2001

                 General Switch Management Protocol Applicability



     This document is an Internet-Draft and is in full conformance with
     all provisions of Section 10 of RFC2026.

     Internet-Drafts are working documents of the Internet Engineering
     Task Force (IETF), its areas, and its working groups.  Note that
     other groups may also distribute working documents as Internet-

     Internet-Drafts are draft documents valid for a maximum of six
     months and may be updated, replaced, or obsoleted by other
     documents at any time.  It is inappropriate to use Internet-
     Drafts as reference material or to cite them other than as "work
     in progress."

     The list of current Internet-Drafts can be accessed at

     The list of Internet-Draft Shadow Directories can be accessed at


     This memo provides an overview of the GSMP protocol and includes
     information relating to its deployment in a IP network in an MPLS
     environment.  It does not discuss deployment in an ATM nework or
     in a raw ethernet configuration.

1. Overview

     The General Switch Management Protocol (GSMP) has been available
     to the IETF community for several years now as informational
     RFC's. Both GSMPv1.1 released in March 1996 as RFC1987 [2], and
     GSMPv2.0 released in August 1998 as RFC2297 [3] are available.
     Several vendors have implemented GSMPv1.1.

     In V1.1 and V2 GSMP was intended only for use with ATM switches.
     During the course of the last year, two years, the GSMP working group
     has decided to expand the purview of GSMP to the point where it
     can be used to control a number of different kinds of switch and
     can thus live up to what its name indicates; a general switch
     management protocol. To do this, commands and arguments needed to
     be generalised, with sections added discussing the manner in which
     the generalised protocol could be applied to specific kinds of
     switches and port types. In short the protocol has gone through
     major changes in the last 24 months.

     GSMP provides an interface that can be used to separate the data
     forwarder from the routing and other control plane protocols such
     as LDP. As such it allows service providers to move away from
     monolithic systems that bundle control plane and data plane into a
     single tightly coupled system - usually in a single chassis.
     Separating the control components from the forwarding components
     and using GSMP for switch management, enables service providers to
     create multi-service systems composed of various vendors
     equipment.  It also allows for a more dynamic means of adding
     services to their networks.

     The IETF GSMP working group was established in the routing area
     because GSMP was being seen as an optional part of the MPLS
     solution. In a MPLS system, it is possible to run the routing
     protocols and label distribution protocols on one system while
     passing data across a generic switch, e.g. an ATM switch.  GSMP
     provides the switch resource management mechanism needed in such a

     GSMP has also been selected by the Multiservice Switching
     Forum(MSF) as its protocol of choice for the Switch Control
     Interface identified in their architecture.  The MSF is an
     industry forum, which among its activities establishes their
     member's requirements and then works with the appropriate
     standards bodies to foster their goals.  In the case of GSMP, the
     MSF presented the IETF GSMP Working Group with a set of
     requirements for GSMP. The working group has made a determined
     effort to comply with those requirements in its specifications.

2. GSMP V3 Document Set

  The current version of GSMP is documented in 3 documents:

       - GSMP: General Switch Management protocol V3 [5]

       - GSMP-ENCAPS: GSMP Packet Encapsulations for ATM, Ethernet
       and TCP[4]

       - GSMP-MIB: Definitions of Managed Objects for the General
       Switch Management Protocol [1]

3. General Description

   The General Switch Management Protocol V3 (GSMPv3) [5], is a
       general purpose protocol to control a label switch. GSMP allows
       a controller to establish and release connections across the
       switch; add and delete leaves on a multicast connection;
       reserve resources; manage switch ports; request configuration
       information; and request statistics. It also allows the switch
       to inform the controller of asynchronous events such as a link
       going down. The GSMP GSMPv3 protocol is asymmetric, the controller
       being the master and the switch being the slave.

   A physical switch can be partitioned in into many virtual switches.
       GSMPv3 does not provide support for defining switch partitions.
       GSMPv3 treats a virtual switch as if it were a physical switch.


  GSMPv3 may be transported in three ways:

       -  GSMP  GSMPv3 operation across an IP network is specified.

       -  GSMP  GSMPv3 operation across an ATM virtual channel is

       -  GSMP  GSMPv3 operation across an Ethernet link is specified.

  Other encapsulations are possible, but have not been defined.
  Encapsulations are defined in [4].

   A label switch is a frame or cell switch that supports connection
       oriented switching using the exact match forwarding algorithm
       based on labels attached to incoming cells or frames.

   A label switch may support multiple label types, however, each
       switch port can support only one label type. The label type
       supported by a given port is indicated in a port configuration
      message. Connections may be established between ports
      supporting different label types using the adaptation methods.
     There are two forms of labels support; short 28 bit labels
     which are sufficient for many purposes and
      GSMPv3 supports TLV labels which are similar to those defined for labels that do not fit in 28 bits. Examples of the
     label types that can use the short form include ATM, Frame
     Relay, and MPLS Generic Labels. MPLS.
      Examples of labels which are defined to use the TLV form include ATM, Frame Relay,
      DS1, DS3, E1, E3 E3, MPLS Generic Labels and MPLS FECs.

   A connection across a switch is formed by connecting an incoming
      labelled channel to one or more outgoing labelled channels.
      Connections are generally referenced by the input port on which
      they arrive and the label values of their incoming labelled
      channel. In some messages connections are referenced by the
      output port.


   GSMPv3 supports point-to-point and point-to-multipoint
      connections. A multipoint-to-point connection is specified by
      establishing multiple point-to-point connections each of which
      specifies the same output label. A multipoint-to-multipoint
      connection is specified by establishing multiple point-to-multipoint point-to-
      multipoint connections each of which specifies a different
      input label with the same output labels.

   In general a connection is established with a certain quality of
      service (QoS). This version of GSMP GSMPv3 includes a default QoS Configuration and
      additionally allows the negotiation of alternative, optional
      QoS configurations. The default QoS Configuration includes
      three QoS Models: a default service model, a simple priority
      model and a QoS profile model. This
     version of GSMP GSMPv3 also supports the
      reservation of resources when the labels are not yet known.
      This ability can be used in support of MPLS.

   GSMP contains an adjacency protocol. The adjacency protocol is
      used to synchronise state across the link, to negotiate which
      version of the GSMP protocol to use, to discover the identity
      of the entity at the other end of a link, and to detect when it

3.1 Switch Partitioning

  In this version of GSMP GSMPv3 switch partitioning is static and occurs prior to
  running GSMP. the protocol. The partitions of a physical switch are
  isolated from each other by the implementation and the controller
  assumes that the resources allocated to a partition are at all
  times available to that partition and only to that partition. A
  partition appears to its controller as a physical label switch.
  The resources allocated to a partition appear to the controller as
  if they were the actual physical resources of a physical switch.
  For example if the bandwidth of a port is divided among several
  partitions, each partition would appear to the controller to have
  its own independent port with its fixed set or resources.


     GSMPv3 controls a partitioned switch through the use of a
     partition identifier that is carried in every GSMP GSMPv3 message. Each
     partition has a one-to-one control relationship with its own
     logical controller entity (which in the remainder of the document
     is referred to simply as a controller) and GSMP GSMPv3 independently
     maintains adjacency between each controller-partition pair.

3.2 Switch and controller interactions

     Multiple switches may be controlled by a single controller using
     multiple instantiations of the protocol over separate control

     Alternatively, multiple controllers can control a single switch.
     Each controller would establish a control connection to the switch
     using the adjacency protocol.  The adjacency mechanism maintains a
     state table indicating the control connections that are being
     maintained by the same partition.  The switch provides information
     to the controller group about the number and identity of the
     attached controllers.  It does nothing, however, to co-ordinate
     the activities of the controllers, and will execute all commands
     as they are received.  It is the controller group group's responsibility
     to co-ordinate its use of the switch.  This mechanism is most
     commonly used for controller redundancy and load sharing.
     Definition of the mechanism by which controllers use to co-
     ordinate their control is not within GSMP's GSMPv3's scope.

3.3 Service support

     All GSMP GSMPv3 switches must support the default QoS Configuration. A
     GSMPv3 switch may additionally support one or more alternative QoS
     Configurations. GSMP includes a negotiation mechanism that allows
     a controller to select from the QoS configurations that a switch

     The default QoS Configuration includes three models:

        The Service Model is based on service definitions found
           external to GSMP such as in CR-LDP, Integrated Services or
           ATM Service Categories. Each connection is assigned a
           specific service that defines the handling of the
           connection by the switch. Additionally, traffic parameters
           and traffic controls may be assigned to the connection
           depending on the assigned service.

        In the Simple Abstract Model a connection is assigned a
           priority when it is established. It may be assumed that for
              connections that share the same output port, an cell or
              frame on a connection with a higher priority is much more
              likely to exit the switch before a cell or frame on a
              connection with a lower priority if they are both in the
              switch at the same time.

           The QoS Profile Model provides a simple mechanism that allows
           QoS semantics defined externally to GSMP to be assigned to
           connections.  Each profile is an opaque indicator that has
           been predefined in the controller and in the switch.

4. Summary of Message Set

  The following table gives a summary of the messages defined in
  this version of the specification. It also makes a recommendation
  of the minimal set of messages that should be supported in an MPLS
  environment.  These messages will be labelled as "Required",
  though the service provided by the other messages are essential
  for the operation of carrier quality controller/ switch
  operations.  GSMPv1.1 or GSMPv2 commands that are no longer
  support are marked as "Obsolete" and should no longer be used.

4.1 Messages Table

  Message Name                      Message Number  Status

  Connection Management Messages
       Add Branch .......................16          Required
           ATM Specific - VPC............26
       Delete Tree.......................18
       Verify Tree.......................19          Obsoleted
       Delete All Input..................20
       Delete All Output.................21
       Delete Branches...................17          Required
       Move Output Branch............... 22
           ATM Specific - VPC............27
       Move Input Branch.................23
           ATM Specific  - VPC............28

  Port Management Messages
       Port Management...................32          Required
       Label Range.......................33

  State and Statistics Messages
       Connection Activity...............48
       Port Statistics...................49          Required
       Connection Statistics.............50
       QoS Class Statistics..............51          Reserved
       Report Connection State...........52

  Configuration Messages
       Switch Configuration..............64          Required
       Port Configuration................65          Required
       All Ports Configuration...........66          Required
       Service Configuration.............67
     Reservation Messages
       Reservation Request.............. 70          Required
       Delete Reservation................71          Required
       Delete All Reservations...........72

     Event Messages
       Port Up...........................80
       Port Down.........................81
       Invalid Label.....................82
       New Port..........................83
       Dead Port.........................84

     Abstract and Resource Model Extension Messages
         Reserved.Message Range.............200-249

     Adjacency Protocol....................10         Required

5. Security Considerations

     The security of GSMP's TCP/IP control channel has been addressed
     in [4]. Any potential remaining For all uses of GSMP over an IP network it is REQUIRED
     that GSMP be run over TCP/IP using the security considerations are not
     addressed considertaions
     discussed in the current revision of this draft. [4].


       [1]  [GSMP-MIB] Sjostrand, H., "Definitions of Managed Objects
                        for the General Switch Management Protocol
                          (GSMP),"Internet-Draft draft-ietf-gsmp-mib-
                        (GSMP)," Internet-Draft draft-ietf-gsmp-mib-02,
                        July 2000. work in progress

       [2]  [GSMPv1.1] Newman, P, Edwards, W., Hinden, R., Hoffman, E.
                         Ching Liaw, F., Lyon, T. and Minshall, G.,
                         "Ipsilon's General Switch Management Protocol
                         Specification," Version 1.1, RFC 1987, August

       [3]  [GSMPv2]   Newman, P, Edwards, W., Hinden, R., Hoffman,
                         E., Ching Liaw, F., Lyon, T. and Minshall, G.,
                         "Ipsilon's General Switch Management Protocol
                         Specification," Version 2.0, RFC 2397, March

       [4]  [GSMP-ENCAPS] T. Worster, "GSMP Packet Encapsulations for
                         ATM, Ethernet and TCP," Internet-Draft draft-
                         ietf-gsmp-encaps-02, July 2000. work in

       [5]  [GSMP]     Doria, A, Sundell, K, Hellstrand, F, Worster,
                         T, "General switch Management Protocol V3,"
                         Internet Draft draft-ietf-gsmp-06.txt, July
                         2000. work in progress

Authors' Addresses

     Avri Doria
     Nortel Networks
     600 Technology Park Drive
     Billerica, MA
     Phone: +1 401 663 5024

     Kenneth Sundell
     Nortel Networks AB
     S:t Eriksgatan 115 A
     P.O. Box 6701
     SE-113 85 Stockholm Sweden