RFC3294: General Switch Management Protocol (GSMP) Applicability

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Network Working Group                                           A. Doria
Request for Comments: 3294                Lulea University of Technology
Category: Informational                                       K. Sundell
                                                         Nortel Networks
                                                               June 2002

        General Switch Management Protocol (GSMP) Applicability

Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (2002).  All Rights Reserved.


   This memo provides an overview of the GSMP (General Switch Management
   Protocol) and includes information relating to its deployment in a IP
   network in an MPLS environment.  It does not discuss deployment in an
   ATM (Asynchronous Transfer Mode) network or in a raw ethernet

1. Overview

   The General Switch Management Protocol (GSMP) has been available to
   the IETF community for several years now as informational RFCs.  Both
   GSMPv1.1 (released in March 1996 as RFC 1987 [2]) and GSMPv2.0
   (released in August 1998 as RFC 2297 [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 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 and sections needed to be 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.

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   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 the control plane and the 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 scenario.

   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

2. GSMP V3 Document Set

   The current version of GSMP is documented in 3 documents:

   -  GSMP: General Switch Management protocol V3 [5]

   -  GSMP-ENCAPS: General Switch Management Protocol (GSMP) Packet
      Encapsulations for Asynchronous Transfer Mode (ATM), Ethernet and
      Transmission Control Protocol (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

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      controller of asynchronous events such as a link going down.  The
      GSMPv3 protocol is asymmetric, the controller being the master and
      the switch being the slave.

   A physical switch can be partitioned 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:

      -  GSMPv3 operation across an IP network is specified.

      -  GSMPv3 operation across an ATM virtual channel is specified.

      -  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.  GSMPv3
      supports TLV labels similar to those defined in MPLS.  Examples of
      labels which are defined include ATM, Frame Relay, DS1, DS3, E1,
      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 connections
      each of which specifies a different input label with the same
      output labels.

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   In general a connection is established with a certain quality of
      service (QoS).  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.  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 states 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 changes.

3.1 Switch Partitioning

   In GSMPv3 switch partitioning is static and occurs prior to running
   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 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 of resources.

   GSMPv3 controls a partitioned switch through the use of a partition
   identifier that is carried in every 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 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

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   of the controllers, and will execute all commands as they are
   received.  It is the controller 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
   GSMPv3's scope.

3.3 Service support

   All GSMPv3 switches 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, a 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.

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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

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      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].  For all uses of GSMP over an IP network, it is REQUIRED that
   GSMP be run over TCP/IP using the security considerations discussed
   in [4].


   [1] Sjostrand, H., Buerkle, J. and B. Srinivasan, "Definitions of
       Managed Objects for the General Switch Management Protocol
       (GSMP)", RFC 3295, June 2002.

   [2] 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 1996.

   [3] Newman, P., Edwards, W., Hinden, R., Hoffman, E., Ching Liaw, F.,
       Lyon, T. and G. Minshall, "Ipsilon's General Switch Management
       Protocol Specification Version 2.0", RFC 2297, March 1998.

   [4] Worster, T., Doria, A. and J. Buerkle, "General Switch Management
       Protocol (GSMP) Packet Encapsulations for Asynchronous Transfer
       Mode (ATM), Ethernet and Transmission Control Protocol (TCP)",
       RFC 3293, June 2002.

   [5] Doria, A., Sundell, K., Hellstrand, F. and T. Worster, "General
       Switch Management Protocol (GSMP) V3", RFC 3292, June 2002.

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Authors' Addresses

   Avri Doria
   Div. of Computer Communications
   Lulea University of Technology
   S-971 87 Lulea

   Phone: +1 401 663 5024
   EMail: avri@acm.org

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

   EMail: sundell@nortelnetworks.com

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