GMPLS PC/SPC conversion: Requirements for the Conversion between Permanent Connections and Switched Connections in a Generalized Multiprotocol Label Switching (GMPLS) Network

Network Working Group                                        D. Caviglia
Request for Comments: 5493                                   D. Bramanti
Category: Informational                                         Ericsson
                                                                   D. Li
                                           Huawei Technologies Co., Ltd.
                                                              D. McDysan
                                                                 Verizon
                                                              April 2009


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

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.

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Abstract

   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.

Table of Contents

   1. Introduction ....................................................3
      1.1. Conventions Used in This Document ..........................3
   2. Label Switched Path Terminology .................................3
   3. LSP within GMPLS Control Plane ..................................4
      3.1. Resource Ownership .........................................4
      3.2. Setting Up a GMPLS-Controlled Network ......................5
   4. Typical Use Cases ...............................................6
      4.1. PC-to-SC/SPC Conversion ....................................6
      4.2. SC-to-PC Conversion ........................................6
   5. Requirements ....................................................7
      5.1. Data Plane LSP Consistency .................................7
      5.2. No Disruption of User Traffic ..............................7
      5.3. Transfer from Management Plane to Control Plane ............7
      5.4. Transfer from Control Plane to Management Plane ............7
      5.5. Synchronization of State among Nodes during Conversion .....7
      5.6. Support of Soft Permanent Connections ......................8
      5.7. Failure of Transfer ........................................8
   6. Security Considerations .........................................8
   7. Contributors ....................................................9
   8. Acknowledgments .................................................9
   9. References ......................................................9
      9.1. Normative References .......................................9
      9.2. Informational References ..................................10

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 type, 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 (CP),
   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].

   Note, some aspects of a control-plane-initiated connection must be
   capable of being queried/controlled by the management plane.  These
   aspects should be independent of how the connection was established.

1.1.  Conventions Used in This Document

   Although this requirements document is an informational document, not
   a protocol specification, the key words "MUST", "MUST NOT",
   "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT",
   "RECOMMENDED",  "MAY", and "OPTIONAL" in this document are to be
   interpreted as described in RFC 2119 [RFC2119] for clarity of
   requirement specification.

2.  Label Switched Path Terminology

   A Label Switched Path (LSP) has different semantics depending on the
   plane in which 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 plane state
   information (such as the connection attributes and path information)
   associated with and necessary for the creation and maintenance of a
   data plane connection.

   In the control plane, an LSP is the control plane state information
   (such as the RSVP-TE [RFC3473] Path and Resv state) associated with
   and necessary for the creation and maintenance of a data plane
   connection.

   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 an LSP presence in the
   data plane for its entire length, but has a management plane presence
   for part of its length and a control plane presence for part of its
   length.

   In this document, when we discuss the LSP conversion between
   management plane and control plane, we mainly focus on the conversion
   of control plane state information and management plane state
   information.

3.  LSP within GMPLS Control Plane

   GMPLS ([RFC3471], [RFC3473], and [RFC3945]) defines a control plane
   architecture for transport networks.  This includes both routing and
   signaling protocols for the creation and maintenance of LSPs in
   networks whose data plane is based on different technologies, such as
   Time Division Multiplexing (SDH/SONET, G.709 at ODUk level) and
   Wavelength Division Multiplexing (G.709 at OCh level).

3.1.  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
   control plane (for the resources used by the switched connection
   segments 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
   established.

   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.  For example,
   consider the basic safety requirements that management commands must
   be able to put a laser out of service.

3.2.  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
   control.

   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 an LSP under GMPLS control might fail due to a
   number of reasons outside the scope of this document, it is also
   highly desirable to have a mechanism to convert the control of an LSP
   back to the management plane.

   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 also be needed (SC to PC, SPC to PC, and SC to
   SPC).

   Conversion to/from control/management will occur in MIBs or in
   information stored on the device (e.g., cross-connect, label
   assignment, label stacking, etc.) and is identified as either
   initiated by a specific control protocol or by manual operation
   (i.e., via an 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,
   the state of the hop-level information must be restored to that
   before the conversion was attempted, and an error condition must be
   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 indicate to each hop that a control protocol is now to be used,
   and then configure the data needed by the control protocol at the
   connection endpoints.  When converting from an SC to a PC, the
   management plane must change the owner of each hop.  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 to 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.

4.  Typical Use Cases

4.1.  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.

   At a latter stage, when the network is partially controlled by the
   management plane and partially controlled by the control plane (PCs
   and SCs/SPCs coexist) and it is desired to extend the control plane,
   a PC-to-SC procedure can be used to transfer a PC or SPC to a SC.

   In both cases, a connection, set up and owned by the management
   plane, needs to be transferred to control plane control.  If a
   connection is carrying traffic, its control transfer has to be done
   without any disruption to the data plane traffic.

4.2.  SC-to-PC Conversion

   The main need for an SC-to-PC conversion is to give an operator the
   capability of undoing the action of 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 it is
   still a highly desirable function.

   Again, it is worth stressing the requirement that such an SPC-to-PC
   conversion needs to be 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.

5.  Requirements

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

5.1.  Data Plane LSP Consistency

   The data plane LSP MUST stay in place throughout the whole control
   transfer process.  It MUST follow the same path through the network
   and MUST use the same network resources.

5.2.  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 over any
   other LSP in the network.

   SC-to-PC conversion and vice-versa SHALL occur without generating
   alarms towards the end users or the NMS.

5.3.  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.

5.4.  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.

5.5.  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 is considered
   complete.

5.6.  Support of Soft Permanent Connections

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

5.7.  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 issues arise causing an unsuccessful
   or unexpected result, it MUST be assured that:

   1.  Traffic over the data plane is not affected.

   2.  The LSP status is consistent in all the network nodes 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 is fully under the control of the owning entity.

6.  Security Considerations

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

   A solution to the requirements in this document will utilize the
   security mechanisms supported by the management plane and GMPLS
   control plane protocols, and no new security requirements over the
   general requirements described in [RFC3945] are introduced.  It is
   expected that solution documents will include an analysis of the
   security issues introduced by any new protocol extensions.

   The management plane interactions MUST be supported through protocols
   that can offer adequate security mechanisms to secure the
   configuration and protect the operation of the devices that are
   managed.  These mechanisms MUST include at least cryptographic
   security and the ability to ensure that the entity giving access to
   configuration parameters is properly configured to give access only
   to those principals (users) that have legitimate rights to
   read/create/change/delete the parameters.  IETF standard management
   protocols (Netconf [RFC4741] and SNMPv3 [RFC3410]) offer these
   mechanisms.

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

7.  Contributors

   Nicola Ciulli
   NextWorks
   Corso Italia 116
   56125 Pisa, Italy
   EMail: n.ciulli@nextworks.it


   Han Li
   China Mobile Communications Co.
   53 A Xibianmennei Ave. Xuanwu District
   Deijing 100053 P.R. China
   Phone: 10-66006688 ext.3092
   EMail: lihan@chinamobile.com


   Daniele Ceccarelli
   Ericsson
   Via A. Negrone 1/A
   Genova-Sestri Ponente, Italy
   Phone: +390106002515
   EMail: daniele.ceccarelli@ericsson.com

8.  Acknowledgments

   We wish to thank the following people (listed randomly): Adrian
   Farrel for his editorial assistance to prepare this document for
   publication; Dean Cheng, 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.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3410]  Case, J., Mundy, R., Partain, D., and B.
              Stewart,"Introduction and Applicability Statements for
              Internet-Standard Management Framework", RFC 3410,
              December 2002.

9.2.  Informative References

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

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

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

   [RFC4741]  Enns, R., Ed., "NETCONF Configuration Protocol", RFC 4741,
              December 2006.

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

Authors' Addresses

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

   EMail: diego.caviglia@ericsson.com


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

   EMail: dino.bramanti@ericsson.com


   Dan Li
   Huawei Technologies Co., Ltd.
   Shenzhen 518129
   Huawei Base, Bantian, Longgang
   China

   EMail: danli@huawei.com


   Dave McDysan
   Verizon
   Ashburn, VA
   USA

   EMail: dave.mcdysan@verizon.com