INTERNET DRAFT                                      Avri Doria, Nokia
GSMP Working Group                   Kenneth Sundell, Nortel Networks
Standards Track                                        10 March, 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 V1.1  released in March 1996 as RFC1987 [2], and V2.0
   released in August 1998 as RFC2297 [3] are available. V1.1 has
   been implemented by several vendors.

   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 18 months.

   GSMP provides an interface which 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 which 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

   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 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 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

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2.  GSMP V3 Document Set

   The current version of GSMP is documented in 3 documents:

       - General Switch Management protocol V3 [5]

       - GSMP Packet Encapsulations for ATM, Ethernet and TCP

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

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3.  Description of protocol

   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 may run across an ATM link connecting the controller
          to the switch, on a control connection (virtual channel)
          established at initialisation.

       - GSMP operation across an Ethernet link is specified.

       - GSMP operation across an IP network is specified.

   Other encapsulation are possible, but have not been defined.
   Encapsulation are defined in a separate standards track document.

   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 by the switch to the
      controller in a port configuration message. Connections may be
      established between ports supporting different label types.
      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 which use the short form include ATM, Frame Relay,
      and MPLS Generic Labels. Examples of labels which use the TLV
      form include DS1, DS3, E1, E3 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 Labels values of their incoming labelled

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      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 them specifying the
      same output branch. A multipoint-to-multipoint connection is
      specified by establishing multiple point-to-multipoint trees
      each of them specifying the same output branches.

   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.

   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
   if they were the actual physical resources of the partition. 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.

   GSMP controls a partitioned switch through the use of a partition
   identifier which 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.

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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 which the control connections that are
   being maintained to the same partition.  The switch provides
   minimal 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 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
          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.

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      The QoS Profile Model provides a simple mechanism that allows
         connection to be assigned QoS semantics defined external to
         GSMP.  Each profile is an opaque indicator which 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.  V1.1 or V2 commands which 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 Specifc  - 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]  Sjostrand, H., "Definitions of Managed Objects for the
              General Switch Management Protocol (GSMP)," Internet-Draft
              draft-ietf-gsmp-mib-01, March 2000.

     [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 Minshall, G., "Ipsilon's General
              Switch Management Protocol Specification," Version 2.0,
              RFC 2397, March 1998.

     [4]  T. Worster, "GSMP Packet Encapsulations for ATM, Ethernet
              and TCP," Internet-Draft draft-ietf-gsmp-encaps-00, Jan

     [5]  Doria, A, Sundell, K, Hellstrand, F, Worster, T, "General
              switch Management Protocol V3," Internet Draft draft-ietf-
              gsmp-04.txt, March 2000

     [6]  Worster, T,. " GSMP Packet Encapsulations for ATM,
              Ethernet and TCP," Internet Draft draft-ietf-gsmp-encaps-
              00.txt, October 1999

Authors' Addresses

   Avri Doria
   5 Wayside Road
   Burlington MA 01803
   Phone: +1 781 993 4656

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

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