Network Working Group                                     Diego Caviglia
Internet Draft                                             Dino Bramanti
                                                                  Dan Li
                                                            Dave McDysan

Intended Status: Informational
Expires: November, 19 2008                                  May 19, 2008

     Requirements for the Conversion Between Permanent Connections and
    Switched Connections in a Generalized Multiprotocol Label Switching
                              (GMPLS) Network


Status of this Memo

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   From a Carrier perspective, the possibility of turning a Permanent
   Connection (PC) into a Soft Permanent Connection (SPC) and vice
   versa, without actually affecting Data Plane traffic being carried
   over it, is a valuable option. In other terms, such operation can
   be seen as a way of transferring the ownership and control of an
   existing and in-use Data Plane connection between the Management
   Plane and the Control Plane, leaving its Data Plane state untouched.

   This memo sets out the requirements for such procedures within a
   Generalized Multiprotocol Label Switching (GMPLS) network.

Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC-2119 [RFC2119].

Table of Contents

   1. Introduction..................................................3
   2. Motivation....................................................3
   3. Label Switched Path Terminology...............................4
   4. LSP within GMPLS Control Plane................................4
      4.1. Resource Ownership.......................................4
      4.2. Setting Up a GMPLS Controlled Network....................5
   5. Typical Use Cases.............................................6
      5.1. PC to SC/SPC Conversion..................................6
      5.2. SC to PC Conversion......................................7
   6. Requirements..................................................7
      6.1. Data Plane LSP Consistency...............................7
      6.2. No Disruption of User Traffic............................7
      6.3. Transfer from Management Plane to Control Plane..........7
      6.4. Transfer from Control Plane to Management Plane..........7
      6.5. Synchronization of state among nodes during conversion...8
      6.6. Support of Soft Permanent Connections....................8
      6.7. Failure of Transfer......................................8
   7. Security Considerations.......................................8
   8. IANA Considerations...........................................9
   9. References....................................................9
      9.1. Normative References.....................................9
      9.2. Informative References...................................9
   10. Acknowledgments..............................................9
   11. Authors' Addresses...........................................9
   12. Full Copyright Statement....................................10
   13. Intellectual Property Statement.............................11

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1. Introduction

   In a typical, traditional transport network scenario, Data Plane
   connections between two end-points are controlled by means of a
   Network Management System (NMS) operating within the Management Plane
   (MP). The NMS/MP is the owner of such transport connections, being
   responsible of their setup, teardown, and maintenance. Provisioned
   connections of this kind, initiated and managed by the Management
   Plane, are known as Permanent Connections (PCs) [G.8081].

   When the setup, teardown, and maintenance of connections are achieved
   by means of a signaling protocol owned by the Control Plane such
   connections are known as Switched Connections (SCs) [G.8081].

   In many deployments a hybrid connection type will be used. A Soft
   Permanent Connection (SPC) is a combination of a permanent connection
   segment at the source user-to-network side, a permanent connection
   segment at the destination user-to-network side, and a switched
   connection segment within the core network. The permanent parts of
   the SPC are owned by the Management Plane, and the switched parts are
   owned by the Control Plane [G.8081].

   At least some aspects of a control plane initiated connection must be
   capable of being queried by the Management Plane. These aspects
   should be independent of how the connection was established.

2. Motivation

   The main motivation for this work is the LSP conversion from
   Management Plane PC to Control Plane SC. The objective is to be able
   to introduce a control plane into an existing network without
   disrupting user traffic.  An example of this is an operator
   establishing PCs before the SC technology is mature, or before SC
   interoperation is achieved between multiple implementations.

   Conversion from the Management Plane to Control Plane is stated as
   a mandatory requirement while the conversion from the Control Plane
   to Management is a desirable feature, or desirable, feature. The
   requirement for LSP conversion from Control Plane to Management Plane
   is scoped as a back-out procedure.

   A significant benefit of GMPLS in networks is discovering and
   validating the current state of the network. For example, an operator
   could invoke an SC, determine that the automatically discovered path
   is good and then "pin" a connection to this specific path using the
   SC to PC conversion procedures.  This is attractive to network
   operators who prefer the static nature of the path for a PC as
   compared with the potentially dynamic path of an SC.

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3. Label Switched Path Terminology

   A Label Switched Path (LSP) has different semantics depending on the
   plane in which it the term is used.

   In the Data Plane, an LSP indicates the Data Plane forwarding path.
   It defines the forwarding or switching operations at each network
   entity. It is the sequence of Data Plane resources (links, labels,
   cross-connects) that achieves end-to-end data transport.

   In the Management Plane, an LSP is the management state information
   (such as the connection attributes and path information) associated
   with and necessary for the creation and maintenance of a Data Plane

   In the Control Plane, an LSP is the Control Plane state information
   (such as RSVP-TE [RFC3473] Path and Resv state) associated with and
   necessary for the creation and maintenance of a Data Plane

   A Permanent Connection has an LSP presence in the Data Plane and the
   Management Plane. A Switched Connection has an LSP presence in the
   Data Plane and the Control Plane. An SPC has LSP presence in the Data
   Plane for its entire length, but has Management Plane presence for
   part of its length and Control Plane presence for part of its length.

   In this document, when we talk about the LSP conversion between
   Management Plane and Control Plane, we mainly focus on the conversion
   of Control Plane state information and Management Plane state

4. LSP within GMPLS Control Plane

   Generalized Multiprotocol Label Switching (GMPLS) [RFC3471],
   [RFC3473], [RFC3945] defines a powerful Control Plane architecture
   for transport networks. This includes both routing and signaling
   protocols for the creation and maintenance of Label Switched Paths
   (LSPs) in networks whose Data Plane is based on different
   technologies such as TDM (SDH/SONET G.709 at ODUk level) transport
   and WDM (G.709 OCh level).

4.1. Resource Ownership

   A resource used by an LSP is said to be 'owned' by the plane that was
   used to set up the LSP through that part of the network. Thus, all
   the resources used by a Permanent Connection are owned by the
   Management Plane, and all the resources used by a Switched Connection
   are owned by the Control Plane. The resources used by an SPC are
   divided between the Management Plane (for the resources used by the
   permanent connection segments at the edge of the network) and the

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   Control Plane (for the resources used by the switched segment in the
   middle of the network).

   The division of resources available for ownership by the Management
   and Control Planes is an architectural issue. A carrier may decide to
   pre-partition the resources at a network entity so that LSPs under
   Management Plane control use one set of resources and LSPs under
   Control Plane control use another set of resources. Other carriers
   may choose to make this distinction resource-by-resource as LSPs are

   It should be noted, however, that even when a resource is owned by
   the Control Plane it will usually be the case that the Management
   Plane has a controlling interest in the resource. Consider e.g. the
   basic safety requirements that imply that management commands must be
   available to set laser out of service.

4.2. Setting Up a GMPLS Controlled Network

   The implementation of a new network using a Generalized Multiprotocol
   Label Switching (GMPLS) Control Plane may be considered as a green
   field deployment. But in many cases it is desirable to introduce a
   GMPLS Control Plane into an existing transport network that is
   already populated with permanent connections under Management Plane

   In a mixed scenario, Permanent Connections owned by the Management
   Plane and Switched Connections owned by the Control Plane have to
   coexist within the network.

   It is also desirable to transfer the control of connections from the
   Management Plane to the Control Plane so that connections that were
   originally under the control of an NMS are now under the control of
   the GMPLS protocols. In case such connections are in service, such
   conversion must be performed in a way that does not affect traffic.

   Since attempts to move a LSP under GMPLS control might fail due to a
   number of reasons outside the scope of this draft, it is also highly
   desirable to have a mechanism to convert the control of an LSP back
   to the Management Plane, in fact undoing the whole process for
   reasons summarized in the motivation section.

   Note that a Permanent Connection may be converted to a Switched
   Connection or to an SPC, and an SPC may be converted to a Switched
   Connection as well (PC to SC, PC to SPC, and SPC to SC). So the
   reverse mappings may be also needed (SC to PC, SC to SPC, and SPC to

   Conversion to/from control/management will occur in many MIBs or
   network management data structures where the owner of the hop level

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   information (e.g., cross-connect, label assignment, label stacking,
   etc.) is identified as either a specific control protocol, or manual
   (i.e., NMS). When converting, this hop-level owner information needs
   to be completed for all hops. If conversion cannot be done for all
   hops, then the conversion must be done for no hops and the state of
   the hop level information restored to that before the conversion was
   attempted, and an error condition reported to the management system.

   In either case of conversion, the Management Plane shall initiate the
   change. When converting from a PC to an SC, the management system
   must somehow indicate to each hop that a control protocol is now to
   be used, and then configure the data needed by control protocol at
   the connection endpoints. When converting from an SC to a PC, the
   Management Plane must change the owner of each hop. Somehow, then the
   instance in the Control Plane must be removed without affecting the
   Data Plane.

   The case where the CP and/or MP fail at one or more nodes during the
   conversion procedure must be handled in the solution. If the network
   is viewed as the database of record (including data, control and
   Management Plane elements), then a solution that has procedures
   similar to those of a two-phase database commit process may be needed
   to ensure integrity and support the need to revert to the state prior
   to the conversion attempt if there is a CP and/or MP failure during
   the attempted conversion.

5. Typical Use Cases

5.1. PC to SC/SPC Conversion

   A typical scenario where a PC to SC (or SPC) procedure can be a
   useful option is at the initial stage of Control Plane deployment in
   an existing network. In such a case all the network connections,
   possibly carrying traffic, are already set up as PCs and are owned by
   the Management Plane.

   The next step in this conversion process presents a similar scenario
   where the network is partially controlled by the Management Plane and
   partially controlled by the Control Plane (PCs and SCs/SPCs coexist).

   In this case an upgrade of the Control Plane functionalities, such as
   new signaling extensions, may be required.

   In both cases the point is that a connection, set up and owned by
   the Management Plane, may need to be transferred to Control Plane
   control. If a connection is carrying traffic, its transfer has to be
   done without any disruption to the Data Plane traffic.

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5.2. SC to PC Conversion

   The main reason making a SC to PC conversion interesting is to give
   an operator the chance of undoing somehow the action represented by
   the above introduced PC to SC conversion.

   In other words the SC to PC conversion is a back-out procedure and as
   such is not specified as mandatory in this document, but is still a
   highly desirable function.

   Again it is worth stressing the requirement that such 'SPC to PC'
   conversion is achieved without any effect on the associated Data
   Plane state so that the connection continues to be operational and to
   carry traffic during the transition.

6. Requirements

   This section sets out the basic requirements for procedures and
   processes that are used to perform the functions this document is
   about. Notation form [RFC2119] is used to clarify the level of each

6.1. Data Plane LSP Consistency

   The Data Plane LSP, staying in place throughout the whole transfer
   process, MUST follow the same path through the network and MUST use
   the same network resources.

6.2. No Disruption of User Traffic

   The transfer process MUST NOT cause any disruption of user traffic
   flowing over the LSP whose control is being transferred or any other
   LSP in the network.

   SC to PC conversion and vice-versa SHALL occur without generating
   Management Plane alarms toward the end users at neither the UNI
   endpoints nor the NMS.

6.3. Transfer from Management Plane to Control Plane

   It MUST be possible to transfer the ownership of an LSP from the
   Management Plane to the Control Plane

6.4. Transfer from Control Plane to Management Plane

   It SHOULD be possible to transfer the ownership of an LSP from the
   Control Plane to the Management Plane.

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6.5. Synchronization of State Among Nodes During Conversion

   It MUST be assured that the state of the LSP is synchronized among
   all nodes traversed by it before the conversion in considered

6.6. Support of Soft Permanent Connections

   It MUST be possible to segment an LSP such that it is converted to or
   from an SPC.

6.7. Failure of Transfer

   It MUST be possible for a transfer from one plane to the other to
   fail in a non-destructive way leaving the ownership unchanged and
   without impacting traffic.

   If during the transfer procedure some issues arise causing an
   unsuccessful or incomplete, unexpected result it MUST be assured that
   at the end:

   1. Traffic over Data Plane is not affected

   2. The LSP status is consistent in all the Transport Network Elements
      (TNEs) involved in the procedure

   Point 2 above assures that, even in case of some failure during the
   transfer, the state of the affected LSP is brought back to the
   initial one and it is fully under control of the owning entity.

7. Security Considerations

   Allowing control of an LSP to be taken away from a plane introduces
   another way in which services may be disrupted by malicious

   It is expected that any solution to the requirements in this document
   will utilize the security mechanisms inherent in the Management Plane
   and Control Plane protocols, and no new security mechanisms are
   needed if these tools are correctly used.

   If SNMP MIBs are used for configuration, then the Management Plane
   should support at least authentication for PC<>SC configuration
   changes as specified in [RFC3414].

   Note also that implementations may enable policy components to help
   determine whether individual LSPs may be transferred between planes.

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8. IANA Considerations

   This requirement document makes no requests for IANA action.

9. References

9.1. Normative References

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC2119, March 1997

   [G.8081]  ITU-T, "Terms and definitions for Automatically Switched
             Optical Networks (ASON)," Recommendation G.8081/Y.1353,
             June 2004

   [RFC3414] U. Blumenthal, B. Wijnen, "User-based Security Model(USM)
             for version 3 of the Simple Network Management Protocol
             (SNMPv3)," RFC 3414, December 2002

9.2. Informative References

   [RFC3471] L. Berger (Ed.) "Generalized Multi-Protocol Label
             Switching (GMPLS) Signaling Functional Description", RFC
             3471, January 2003

   [RFC3473] L. Berger (Ed.) "Generalized Multi-Protocol Label
             Switching (GMPLS) Signaling Resource ReserVation
             Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC
             3473, January 2003

   [RFC3945] E. Mannie (Ed.) "Generalized Multi-Protocol Label
             Switching (GMPLS) Architecture", RFC 3945, October 2004

10. Acknowledgments

   We whish to thank the following people (listed randomly) Adrian
   Farrel for his editorial assistance to prepare this draft for
   publication, Dean Cheng and Julien Meuric, Dimitri Papadimitriou,
   Deborah Brungard, Igor Bryskin, Lou Berger, Don Fedyk, John Drake and
   Vijay Pandian for their suggestions and comments on the CCAMP list.

11. Authors' Addresses

   Diego Caviglia
   Via A. Negrone 1/A
   Genova-Sestri Ponente, Italy

   Phone: +390106003738

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   Dino Bramanti
   Via Moruzzi 1
   C/O Area Ricerca CNR
   Pisa, Italy


   Nicola Ciulli
   Corso Italia 116
   56125 Pisa, Italy


   Dan Li
   Huawei Technologies Co., LTD.
   Huawei Base, Bantian, Longgang,
   Shenzhen 518129 P.R.Chin

   Phone: +86-755-28972910

   Han Li
   China Mobile Communications Co.
   53A Xibianmennei Ave. Xuanwu District
   Beijing 100053 P.R. China

   Phone: +86-10-66006688 ext.3092

   Dave McDysan
   Ashburn, VA, USA


12. Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
   contained in BCP 78, and except as set forth therein, the authors
   retain all their rights.

   This document and the information contained herein are provided on

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