Internet DRAFT - draft-anderson-req-dyn-part


Internet Draft                                T. Anderson 
Expiration: August 2001                          Intel 
File: draft-anderson-req-dyn-part-00.txt      A. Doria 
                                                 Nortel Networks 
                                                  February 2001 
      Requirements for the Dynamic Partitioning of Network Elements 
Status of this Memo 
   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-Drafts. 
   Internet-Drafts are draft documents valid for a maximum of six 
   months and may be updated, replaced, or obsoleted by other documents 
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   reference material or to cite them other than as ``work in 
   To view the current status of any Internet-Draft, please check the  
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Conventions used in this document 
   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   
   this document are to be interpreted as described in [RFC2119]. 
   This document identifies a set of requirements for the mechanisms 
   used to dynamically reallocate the resources of a partitionable 
   network element (NE).  These requirements are particularly critical 
   in the case of an operator creating a virtual NE (by partitioning a 
   physical NE) and then leasing control of that virtual NE to a third 
1.   Definitions 
   In this document, the following definitions will be used. 

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   Partition - A partition is a defined set of a physical network 
   element (NE) resources that can be used to create a virtual NE. 
   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 partitionĘs resources without requiring a restart of 
   that partition.  Instances of repartitioning in which connections to 
   controllers are disconnected before resources are reallocated 
   therefore fall into this category.  
   Dynamic Partitioning - In dynamic partitioning, an active 
   partitionĘs resources can be reapportioned without requiring a 
   restart of the partition. 
   Frozen Partition - A frozen partition is an active partition which 
   is in the process of 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 NE. 
   Deterministic Partitioning - In deterministic partitioning, each 
   active partition is given an allotted quantity of each resource.  
   The usage of resources in one active partition do 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. 
   Proactive Notification - A proactive notification is a message sent 
   from a NE to its controller at the time an event occurs.  
   Specifically, if a NE asynchronously sends the controller a message 
   when it is dynamically partitioned, we say that the NE has 
   proactively notified its controller of the resource reapportionment. 
   Explicit Reactive Notification - In explicit reactive notification, 
   the NE does not asynchronously send a message when dynamic 
   partitioning occurs.  Instead, the NE includes a "resource changed" 
   error code in the response to a subsequent request by the 
   Implicit Reactive Notification - This is similar to an Explicit 
   Reactive Notification except that the protocol does not contain an 
   explicit "resource changed" error.  In this case, all that the NE 

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   can do is to indicate that some unspecified error has occurred when 
   the controller attempts to use non-allocated resources. 
2.   Introduction 
   Several logical entities are involved in the partitioning and 
   control of a NE.  First, there is the physical NE itself that is 
   capable of having its resources partitioned.  (This also implies the 
   ability to enforce this division of resources between competing 
   partitions).  The partition manager (PM) is the management entity 
   that specifies the number of virtual NEs, partitions, in which the 
   physical NE should be partitioned.  The PM then allocates the 
   resources of the physical NE to those virtual NEs.  Subsequently, 
   one or more controllers would direct the use of the resources of 
   that now active partition.   
   In many cases, the physical realm reflects this logical division of 
   functionality.  For example, MEGACO [RFC3015] and GSMP [GSMPv3] are 
   examples of protocols that allow control functionality to be 
   physically separated from switching/forwarding 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 physical NE to partition the NE into several virtual NEs, 
   partitions, and then to lease these to third parties.  In this case, 
   the PM must be physically separate from all of the controllers.  
   Since the physical NE must also be remotely configurable, the PM 
   will also be physically separate from the physical NE.  The 
   following illustration depicts this arrangement.  The dashed lines 
   indicate potential interactions. 
   ------------------             ------------------- 
   |                |      3      |                 | 
   |    Partition   |-------------|   Controller    | 
   |     Manager    |             |                 | 
   ------------------             ------------------- 
                   \               /  
                    \             /   
                     \ 1       2 /    
                      \         /         
                    |               | 
                    |    Network    | 
                    |    Element    | 
   The interaction labeled "1" is one in which the PM partitions the NE 
   and allocates resources to the partitions.  In order to support 
   dynamic partitioning, this document will place certain requirements 
   on proposed (or new) solutions in this space such as [MSF-SPMIB]. 
   The interaction labeled "2" is one by which the controller 
   configures and manages an active partition of the physical NE.  

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   Proposed solutions in this space include GSMP [GSMPv3] and MEGACO 
   The interaction labeled "3" is one by which a PM and a controller 
   could communicate to alter the nature of an active partition.  
   Possible interactions include:  
      - A controller could request that the resources of one  
        of its active partitions be altered; either increased  
        or decreased. 
      - The PM could respond to a controller request for 
        altered resource levels. 
      - The PM could request that a controller release  
        resources currently allocated to one of its active   
        partitions. This could involve the following types of  
        - A request to relinquish allocated but currently unused 
          resources.  That is to put a freeze on additional use  
          of the specified resources. 
        - A request to relinquish used resources. 
        - A request to relinquish an active partition.  That is  
          a request that a controller shut down an active  
      - The controllerĘs response to a PM request. 
   As far as the authors know, no proposed standard solutions currently 
   exist for type 3 interactions.   
3.   Dynamic Partitioning 
   Static repartitioning of a NE can be a costly and inefficient 
   process.  First, before static repartitioning can take place, all 
   existing connections with controllers must be severed.  When this 
   happens, the NE will typically release all the state configured by 
   the controller.  Then, the virtual NE 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 the active partition.  Thus, 
   static repartitioning results in a period of downtime and a period 
   in which the controllers are reestablishing state.  This is the case 
   even if resources that are not currently in use in one partition, 
   either and active or an inactive partition, are intended for a fully 
   loaded active partition. 
   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 exist for dynamic partitioning.  Some questions 
   to be answered include the following: 
      - Who initiates the repartitioning on the NE?   
      - How is the controller notified of an increase or  
        decrease in resources?   
      - What should happen when the PM would like to decrease  
        the resources allocated to a partition but those  

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        resources are in use? 
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. If a PM instructs a NE to release resources allocated to an 
      active partition and if any of those resources are currently in 
      use, the NE MUST deny the PMĘs request. 
   2. During dynamic repartitioning, a NE MUST maintain all existing 
      connection state. 
   3. If a NE denies a repartitioning request due to resources being in 
      use, the PM MAY contact the controller to ask it to reduce its 
      resource utilization. 
   4. If a PM has requested that a controller reduce resource 
      utilization so that a partition can be downsized and that 
      controller is not cooperating, the PM MUST be able to "down" the 
      virtual NE, thereby disconnecting the controller, and then reduce 
      the partitionĘs resources.  In other words, the PM must be able 
      to resort to static partitioning when a controller is 
   5. Control protocols SHOULD NOT include any mechanism by which a NE 
      can ask its controller to reduce its resource usage. 
   6. Because controllers cannot be trusted to use only those resources 
      allocated to their active partitions, the NE MUST reject all such 
      attempts.  Preferably, the control protocol would allow the NE to 
      do so with an explicit reactive notification although implicit 
      reactive notifications are also permitted. 
   7. Control protocols MAY contain proactive resource notification 
      messages by which a NE could instantaneously inform the 
      controller of an increase or decrease in resources.  When 
      present, dynamic partitioning solutions MAY make use of proactive 
      notifications.  However, 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 #6. 
   8. A PM MAY directly inform a controller of a change in virtual NE 
      resources rather than rely on the implicit resource exhaustion 
      mechanism of the control protocol. 
   9. NEs MAY inform the PM of resource exhaustion on a particular 
   10. A controller MAY ask the PM for further resources or a reduction 
      in existing resources. 
   11. To support the automation of interaction between the PM and 
      attached controllers, the PM MUST be able to determine from the 
      NE the addresses of the controllers that are currently attached 
      to a virtual NE. 
5.   Security Considerations 
   Only authorized PMs MUST be allowed to dynamically repartition a NE.  
   Similarly, only the PM (or an authorized agent of the PM) that is 

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   authorized to partition a NE 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 NE have come from a controller authorized to control 
   the specified virtual NE. 
6.   Intellectual Property Considerations 

   The IETF is being notified of intellectual property rights claimed 
   in regard to some or all of the specification contained in this 
   document.  For more information, consult the online list of claimed 
7.   References 
   [GSMPv3]     A. Doria, et. al, "Draft-ietf-gsmp-08.txt", work in 
   [SPMIB]  T. Anderson, et. al, "draft-anderson-partitioning-mib-
           00.txt", work in progress, February 2001. 
   [RFC2119]  S. Bradner, "Key words for use in RFCs to Indicate 
             Requirement Levels", RFC 2119, BCP 14, March 1997. 
   [RFC2297]  P. Newman, et. al., "IpsilonĘs General Switch Management 
             Protocol Version 2.0," RFC2297, March 1998. 
   [RFC3015]  F. Cuervo, et. al., "Megaco Protocol 1.0," RFC3015, 
             November 2000. 
8.   Author Information 
   Todd A. Anderson 
   2111 NE 25th Avenue 
   Hillsboro, OR 97124 USA 
   +1 503 712 1760 
   Avri Doria 
   Nortel Networks 
   600 Technology Park Drive 
   Billerica, MA 01821 
   Phone: +1 401 663 5024 

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