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rfc:rfc3532

Network Working Group T. Anderson Request for Comments: 3532 Intel Labs Category: Informational J. Buerkle

                                                       Nortel Networks
                                                              May 2003
  Requirements for the Dynamic Partitioning of Switching Elements

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 (2003).  All Rights Reserved.

Abstract

 This document identifies a set of requirements for the mechanisms
 used to dynamically reallocate the resources of a switching element
 (e.g., an ATM switch) to its partitions.  These requirements are
 particularly critical in the case of an operator creating a switch
 partition and then leasing control of that partition to a third
 party.

Table of Contents

 1.  Definitions ................................................  2
 2.  Introduction ...............................................  3
 3.  Dynamic Partitioning .......................................  6
 4.  Requirements ...............................................  7
 5.  Security Considerations ....................................  9
 6.  Intellectual Property Considerations .......................  9
 7.  Acknowledgements ...........................................  9
 8.  Normative References ....................................... 10
 9.  Informative References ..................................... 10
 10. Authors' Addresses ......................................... 10
 11. Full Copyright Statement ................................... 11

Anderson, et al. Informational [Page 1] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

1. Definitions

 In this document, the following definitions will be used.
 Switching Element - A device that switches packets (e.g., an ATM
    switch or MPLS LSR) and whose resources can be divided into
    partitions, each of which can be independently controlled by a
    different controller.
 Partition - A partition is a set of switching element (SE)
    resources.  Partitions are also referred to as virtual SEs.
 Active Partition - An active partition is a partition in which the
    resources are in use; either under the direct control of a
    separate controller or under internal policy-based control.
 Controller - The entity responsible for controlling the operations
    of an active partition.
 Static Partitioning - In static partitioning, no changes can be made
    to any active partition's resources without requiring a restart of
    that partition.  Instances of repartitioning in which connections
    to controllers are disconnected before resources can be
    reallocated therefore fall into this category.
 Dynamic Partitioning - In dynamic partitioning, an active
    partition's resources can be reapportioned without requiring a
    restart of the partition.
 Frozen Partition - A frozen partition is an active partition that is
    in the process of being shutdown.  A frozen partition's unused
    resources are relinquished, but all current connections are
    allowed to remain until removed by the controller.  As connections
    close, the resources are returned to the SE.
 Deterministic Partitioning - In deterministic partitioning, each
    active partition is given an allotted quantity of each resource.
    The usage of resources in one active partition does not influence
    the resources available to another active partition.  All
    discussions in these requirements presuppose the use of
    deterministic partitioning.
 Statistical Partitioning - In statistical partitioning, some or all
    resources are pooled among the active partitions, and allocations
    may be based on percentages or on some other metric.  Discussion
    of statistical partitions is outside the scope of these
    requirements.

Anderson, et al. Informational [Page 2] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

 Proactive Notification - A proactive notification is a message sent
    from a SE to its controller at the time an event occurs.
    Specifically, if a SE asynchronously sends the controller a
    message when it is dynamically partitioned, we say that the SE has
    proactively notified its controller of the resource
    reapportionment.
 Explicit Reactive Notification - In explicit reactive notification,
    the SE does not asynchronously send a message when dynamic
    partitioning occurs.  Instead, the SE includes an explicit,
    resources-reassigned error code in the response to a subsequent
    request by the controller for an unavailable resource.
 Implicit Reactive Notification - This is similar to an Explicit
    Reactive Notification except that the protocol does not contain
    any explicit resources-reassigned error codes.  In this case, all
    that the SE can do is to indicate that some general, unknown error
    or generic resource error (i.e., some resource error problem has
    occurred but the exact cause is not specified) has occurred when
    the controller attempts to use unavailable resources.  In such
    cases, the controller may attempt to determine whether a resource
    shortfall caused the error by using whatever messages are
    available through the control protocol to query available
    resources.

2. Introduction

 This document identifies the logical entities involved in the
 partitioning of switching elements.  Furthermore, this document
 provides a set of requirements for the behavior of these logical
 entities as well as the protocols used by these logical entities to
 communicate with one another.  A primary goal of the requirements
 specified herein is to allow the resources allocated to a partition
 to be increased or decreased while the partition is currently active
 (i.e., it has an active connection with a controller).  This document
 is primarily intended to facilitate the partitioning of GSMP
 switches.  However, while we believe that the logical entities and
 requirements specified here are necessary for the partitioning of
 non-GSMP switches and (longest prefix match) forwarders (e.g.,
 routers), we do not believe that these requirements are necessarily
 sufficient for the partitioning of those devices.
 Three logical entities are involved in the partitioning and control
 of a SE.  First, a switching element (for the purposes of this
 document) is a device that "switches" packets, whose resources can be
 partitioned and whose partitions can each be controlled by a single
 controller.  This partitioning also implies the ability to enforce
 this division of resources between competing partitions.  Second, the

Anderson, et al. Informational [Page 3] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

 partition manager (PM) is a management entity that specifies the
 number of virtual SEs into which the SE should be partitioned and the
 resources to be allocated to each virtual SE.  Lastly, a controller
 directs the use of the resources of one or more partitions to provide
 a set of services.
 In the rest of this document, we will deal exclusively with logical
 entities although it is worth noting here that there are many
 possible mappings of logical entities to physical entities.  For
 example, there may be multiple logical controllers running on a
 single physical processor (and for convenience we may refer to this
 processor as a physical controller).  Conversely, a single logical
 controller could consist of processes running on multiple physical
 processors collaborating to provide proper control.  Likewise, there
 may be multiple partition managers running on a single management
 workstation.  A switching element may consist of one or more whole or
 fractional physical elements.  For example, a SE may be a single
 whole physical switch (e.g., blade in a chassis), multiple whole
 physical switches (e.g., two blades in a chassis made to appear as a
 single logical entity), a single fraction of a physical switch (which
 would enable nested partitions), or multiple fractions of either the
 same or different physical switches (e.g., ports 1-3 on blade 1 and
 ports 2-4 on blade 2).  Finally, any combination of these logical
 entities could theoretically be co-located on the same physical
 resources.
 However, for many reasons, the physical realm often reflects this
 logical division of functionality.  To facilitate this division,
 several protocols, such as MEGACO [RFC3015] and GSMP [RFC3292], exist
 that allow control functionality to be physically separated from
 switching functionality.  Recently, some regulatory environments have
 mandated multi-provider access to a single physical infrastructure.
 To satisfy these regulations, a common use of partitioning will be
 for the owner of the SE to partition the SE into several virtual SEs
 and then to lease these to third parties. In this case, the PM will
 likely be physically separate from all of the controllers.  For
 locality (and therefore ease) of management, SEs will be remotely
 configurable and thus the PM will be physically separated from the
 SE.  The following illustration depicts this arrangement.  The dashed
 lines indicate interactions between the entities and are labeled with
 the cardinality of the relationship between the entities.

Anderson, et al. Informational [Page 4] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

  1. —————– ——————-

| | * * | |

         |    Partition   |-------------|   Controller    |
         |     Manager    |      C      |                 |
         ------------------             -------------------
                       1 \                / *
                          \              /
                           \ A        B /
                            \          /
                           * \        / *
                         ------------/------
                         |  --------/---   |
                         |  |Partition |   |
                         |  |          |   |
                         |  ------------   |
                         |Switching element|
                         -------------------
 Interaction A is one in which the PM partitions the SE and allocates
 resources to the partitions it creates.  There is a one-to-many
 relationship between PMs and SEs.  In order to support dynamic
 partitioning, this document will place certain requirements on
 proposed (or new) solutions in this space.
 Interaction B is one in which the controller configures and manages
 an active partition.  Current protocols implementing this interaction
 include GSMP [RFC3292] and MEGACO [RFC3015].  These protocols allow a
 many-to-many relationship between controller and partition.
 Interaction C is one by which a PM and a controller could communicate
 to alter the nature of an active partition.  There is a many-to-many
 relationship between PMs and controllers.  For example, there are
 multiple PMs per controller in the case where a controller is
 managing two partitions from different SEs and there are multiple
 controllers per PM in the case where a SE has two partitions each
 managed by a different controller.  Possible types of interactions
 between PM and controller include:
  1. A controller could request that the resources of one of its active

partitions be altered; either increased or decreased.

  1. The PM could respond to a controller request for altered resource

levels.

  1. The PM could request that a controller release resources currently

allocated to one of its active partitions. This could involve the

    following types of request:

Anderson, et al. Informational [Page 5] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

  1. A request to relinquish allocated, but currently unused

resources. That is to put a freeze on additional use of the

       specified resources.
  1. A request to relinquish used resources.
  1. A request to relinquish an active partition. That is a request

that a controller release control of an active partition.

  1. The controller's response to a PM request.
 As far as the authors know, no proposed standard solutions currently
 exist for interactions of type C.

3. Dynamic Partitioning

 Static repartitioning of a SE can be a costly and inefficient
 process.  First, before static repartitioning can take place, all
 existing connections with controllers for the affected partitions
 must be severed.  (This severing must always occur even if the
 resources to be reapportioned are not currently in use.)  When this
 happens, the SE will typically release all the state configured by
 the controller.  Then, the virtual SE must be placed in the "down"
 state while the repartitioning takes place.  Once the repartitioning
 is completed, the partitions are placed in the "up" state and the
 controllers are allowed to reconnect to the partitions.  Then, the
 controllers can reestablish state in those partitions.  Thus, static
 repartitioning results in a period of downtime and a period in which
 the controllers are reestablishing state for affected partitions.
 Partitions of a SE that are not affected by a static resource
 reallocation need not be transitioned to the down state nor would
 controllers have to reestablish state with unaffected partitions.
 Therefore, dynamic partitioning is to be preferred to static
 partitioning since it avoids the downtime and loss of state
 associated with static partitioning.  However, a different set of
 potential problems exists for dynamic partitioning.  Some questions
 to be answered include the following:
  1. How is the controller notified of an increase or decrease in

resources?

  1. What should happen when the PM would like to decrease the

resources allocated to a partition but those resources are in use?

Anderson, et al. Informational [Page 6] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

4. Requirements

 This document does not attempt to answer the preceding questions but
 instead defines a set of requirements that any solution to these
 problems MUST satisfy.
 1.  There MUST be a mechanism by which a PM can create virtual SEs on
     the SE and allocate SE resources to those virtual SEs.
 2.  SEs MUST ensure that controllers do not use more resources than
     those currently allocated to each virtual SE.  Therefore, each
     control protocol MUST provide either an explicit reactive
     notification or an implicit reactive notification to indicate
     resource exhaustion.
 3.  Furthermore, there MUST be a mechanism by which a PM can
     partition all resources discoverable through GSMP (e.g., label
     tables). Partitioning of resources used by GSMP indirectly (e.g.,
     CPU), resources used by non-GSMP switches, or resources (e.g.,
     forwarding table entries) used by forwarding-based network
     elements MAY be supported.
 4.  If a PM instructs a SE to release resources allocated to an
     active partition and if any of those resources are currently in
     use, the SE MUST deny the PM's request.  (Requirement #8
     addresses the potential starvation issues raised by this
     requirement.)
 5.  Subsequent to a resource reallocation failure, the PM SHOULD make
     use of one or both of the capabilities described in requirements
     6 and 7.
 6.  A PM SHOULD be able to tell a SE to make an active partition into
     a frozen partition.
 7.  A PM SHOULD be able to contact the controller to ask it to reduce
     its resource utilization.
 8.  The PM MUST be able to exercise "power on/off" type control of
     the virtual SEs that it has created.  When the virtual power to
     an active partition is turned off, the partition becomes inactive
     and any controllers associated with that partition are
     disconnected. This capability allows a PM to resort to static
     partitioning when a controller is uncooperative about releasing
     resources.  This requirement allows permanent starvation as a
     result of requirement #4 to be avoided.

Anderson, et al. Informational [Page 7] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

 9.  During dynamic repartitioning, a SE MUST maintain all existing
     state associated with the partitions being modified.
 10. Control protocols SHOULD NOT include any mechanism by which a SE
     can ask its controller to reduce its resource usage.
 11. Control protocols MAY contain proactive resource notification
     messages by which a SE could instantaneously inform the
     controller of an increase or decrease in resources.  (We do not
     specifically require control protocols to contain proactive
     notifications because all control protocols must already have
     explicit or implicit reactive notifications as mentioned in
     requirement #2).
 12. A PM MAY directly inform a controller of a change in virtual SE
     resources rather than rely on the implicit resource exhaustion
     mechanism of the control protocol.
 13. SEs MAY inform the PM of resource exhaustion on a particular
     partition.
 14. A controller MAY ask the PM for further resources or a reduction
     in existing resources.
 15. To support the automation of interaction between the PM and
     attached controllers, the PM MUST be able to determine from the
     SE the addresses of the controllers that are currently attached
     to a virtual SE.  Additionally, the SE MAY allow the PM to
     determine which control protocol (and version thereof) is
     currently managing each active partition.
 16. A SE MAY support the ability to have one virtual SE provide a
     service to another virtual SE within the same physical SE.  For
     example, a SE may be configured to provide a virtual link between
     two virtual SEs.  Furthermore:
    a. There MUST be a mechanism by which the SE can inform the PM
       which of these partition-to-partition services are provided by
       the SE.
    b. There MUST be a mechanism by which the PM can configure the
       available partition-to-partition services.
    c. If the configuration of a partition-to-partition service
       results in a virtual port being added/removed from a virtual
       SE, the SE MUST notify all controllers attached to that virtual
       SE (assuming that the corresponding control protocol supports
       such notifications).

Anderson, et al. Informational [Page 8] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

 17. There MUST be a mechanism by which a PM can query a SE to
     determine the resources of that SE, the partitions currently
     configured on that SE and the resources allocated to each
     partition.

5. Security Considerations

 Only authorized PMs MUST be allowed to dynamically repartition a SE.
 Therefore, SEs MUST use a secure process by which an authorized
 entity may instruct the SE as to which PM should control it.  This
 instruction MAY specify the PM explicitly or MAY specify the use of a
 (discovery) protocol to dynamically locate the PM.  Similarly, only
 the PM (or an authorized agent of the PM) that is authorized to
 partition a SE MUST be allowed to contact controllers to request that
 they decrease their resources or inform them that their resources
 have been increased.  Likewise, the PM MUST verify and authenticate
 that any requests for additional/fewer resources for a virtual SE
 have come from a controller authorized to control the specified
 virtual SE.

6. Intellectual Property Considerations

 The IETF takes no position regarding the validity or scope of any
 intellectual property or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; neither does it represent that it
 has made any effort to identify any such rights.  Information on the
 IETF's procedures with respect to rights in standards-track and
 standards-related documentation can be found in RFC 2026.  Copies of
 claims of rights made available for publication and any assurances of
 licenses to be made available, or the result of an attempt made to
 obtain a general license or permission for the use of such
 proprietary rights by implementors or users of this specification can
 be obtained from the IETF Secretariat.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights which may cover technology that may be required to practice
 this standard.  Please address the information to the IETF Executive
 Director.

7. Acknowledgements

 The authors would like to acknowledge the contributions of Avri Doria
 and Jonathan Sadler to this document.

Anderson, et al. Informational [Page 9] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

8. Normative References

 [RFC2119]  Bradner, S. "Key words for use in RFCs to Indicate
            Requirement Levels", BCP 14, RFC 2119, March 1997.
 [RFC3292]  Doria, A., Hellstrand, F., Sundell, K. and T. Worster,
            "General Switch Management Protocol (GSMP) V3", RFC 3292,
            June 2002.

9. Informative References

 [RFC3015]  Cuervo, F., Greene, N., Rayhan, A., Huitema, C., Rosem, B.
            and J. Segers, "Megaco Protocol 1.0," RFC 3015, November
            2000.

10. Authors' Addresses

 Todd A. Anderson
 Intel Labs
 JF2-60
 2111 NE 25th Avenue
 Hillsboro, OR 97124 USA
 Phone: +1 503 712 1760
 EMail: todd.a.anderson@intel.com
 Joachim Buerkle
 Nortel Networks Germany GmbH & Co. KG
 Hahnstrasse 37-39
 60528 Frankfurt
 Phone:  ++49 (0)69 6697 3281
 EMail: joachim.buerkle@nortelnetworks.com

Anderson, et al. Informational [Page 10] RFC 3532 Dynamic Partitioning of Switching Elements May 2003

11. Full Copyright Statement

 Copyright (C) The Internet Society (2003).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Anderson, et al. Informational [Page 11]

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