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

                 General Switch Management Protocol Applicability


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

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     This memo provides an overview of the GSMP protocol and includes
     information relating to its deployment in a MPLS environment.

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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, 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.

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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 protocol is asymmetric, the controller
       being the master and the switch being the slave.

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

  GSMP may be transported in three ways:

       -  GSMP operation across an IP network is specified.

       -  GSMP operation across an ATM virtual channel is specified.

       -  GSMP 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

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     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 TLV labels which are
     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. Examples of labels which are
     defined to use the TLV form include DS1, DS3, E1, E3 and MPLS

   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.

   GSMP 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.

   In general a connection is established with a certain quality of
     service (QoS). This version of GSMP 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 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 switch partitioning is static and occurs
  prior to running GSMP. 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

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     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.

     GSMP controls a partitioned switch through the use of a partition
     identifier that is carried in every GSMP 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 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 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 scope.

3.3 Service support

     All GSMP switches must support the default QoS Configuration. A
     GSMP 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

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            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.

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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

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     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 security considerations are not
     addressed in the current revision of this draft.

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       [1]  [GSMP-MIB] Sjostrand, H., "Definitions of Managed Objects
                          for the General Switch Management Protocol
                          (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

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