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Versions: (draft-papadimitriou-ccamp-gmpls-ason-reqts) 00 01 02 03 04 05 06 07 RFC 4139

CCAMP Working Group                          D. Papadimitriou (Alcatel)
Internet Draft                           Z. Lin (New York City Transit)
Category: Informational                              J. Drake (Calient)
                                                           J. Ash (ATT)
Expiration Date: December 2003                        A. Farrel (Movaz)
                                                         L. Ong (Ciena)

                                                              June 2003

     Requirements for Generalized MPLS (GMPLS) Usage and Extensions
           for Automatically Switched Optical Network (ASON)


Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC-2026.

   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 at any time. It is inappropriate to use Internet- Drafts
   as reference material or to cite them other than as "work in

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

1. Abstract

   The Generalized MPLS (GMPLS) suite of protocol has been defined to
   control different switching technologies as well as different
   applications. These include support for requesting TDM connections
   including SONET/SDH and Optical Transport Networks (OTNs).

   This document concentrates on the signaling aspects of the GMPLS
   suite of protocols. It identifies the features to be covered by the
   signalling protocol to support the capabilities of an Automatically
   Switched Optical Network (ASON). This document provides a problem
   statement and additional requirements on the GMPLS signaling
   protocol to support the ASON functionality.

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2. Conventions used in this document

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

3. Introduction

   The GMPLS suite of protocol specifications provides support for
   controlling different switching technologies as well as different
   applications. These include support for requesting TDM connections
   including SONET/SDH (see ANSI T1.105 and ITU-T G.707, respectively)
   as well as Optical Transport Networks (see ITU-T G.709). In
   addition, there are certain capabilities that are needed to support
   Automatically Switched Optical Networks control planes (their
   architecture is defined in [ITU-T G.8080]). These include generic
   capabilities such as call and connection separation and more
   specific capabilities such as support of soft permanent connections.

   This document concentrates on the signaling aspects of the GMPLS
   suite of protocols (see [RFC 3471]). It discusses functional
   requirements that lead to additional extensions to GMPLS to support
   the capabilities as specified in the above referenced document. A
   terminology section is provided in Appendix.

   Problem Statement:

   The Automatic Switched Optical Network (ASON) architecture describes
   the application of an automated control plane for supporting both
   call and connection management services (for a detailed description
   see [ITU-T G.8080]).

   The ASON control plane specification is meant to be applicable to
   different transport technologies (e.g., SDH/SONET, OTN) in various
   networking environments (e.g., inter-carrier, intra-carrier). Also,
   ASON model distinguishes reference points (representing points of
   protocol information exchange) defined (1) between an administrative
   domain and a user (2) between administrative domains and (3) between
   areas of the same administrative domain and when needed between
   control components (or simply controllers) within areas. A full
   description of the ASON terms and relationship between ASON model
   and GMPLS protocol suite may be found in [IPO-ASON].

   This document describes the use of GMPLS signalling (and in
   particular, [RFC 3471]) to provide call and connection management
   (see [ITU-T G.7713]). The following functionality are expected from
   the GMPLS protocol suite: (a) support for soft permanent connection
   capability (b) support for call and connection separation (c)
   support for extended restart capabilities during control plane
   failures (d) support for extended label usage (e) support for
   crankback capability (f) support for additional error cases.

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4. Requirements for Extending Applicability of GMPLS to ASON

   The applicability statements regarding how the GMPLS suite of
   protocols may be applied to the ASON architecture can be found in
   [IPO-ASON] and [IPO-REQS]. The former includes a summary of the ASON
   functions as well as a detailed discussion of the applicability of
   the GMPLS protocol suite.

   The next sections detail the requirements concerning the functions

      - Support for soft permanent connection capability
      - Support for call and connection separation
      - Support for extended restart capabilities during control plane
      - Support for extended label usage
      - Support for crankback capability
      - Support for additional error cases

   Note: support of the above functions is independent of any user-to-
   network interface and therefore not constrained or restricted by its
   implementation specifics (see [ITU-T G.8080] and [ITU-T G.7713]).

4.1 Support for Soft Permanent Connection (SPC) Capability

   An SPC is a combination of a permanent connection at the source
   user-to-network side, a permanent connection at the destination
   user-to-network side, and a switched connection within the network.
   An Element Management System (EMS) or a Network Management System
   (NMS) typically initiates the establishment of the switched
   connection by communicating with the ingress node. The latter then
   sets the connection using the distributed GMPLS signaling protocol.
   For the SPC, the communication method between the EMS/NMS and the
   ingress node is beyond the scope of this document (so it is for any
   other function described in this document).

   The end-to-end connection is thus created by associating the
   incoming interface of the switched connection initiating network
   node (also referred to as ingress node) with the switched connection
   within the network and the outgoing interface of the switched
   connection terminating network node (also referred to as egress
   node). An SPC connection is illustrated in the following Figure,
   which shows user's node A connected to a provider's node B via link
   #1, user's node Z connected to a provider's node Y via link #3, and
   an abstract link #2 connecting provider's node B and node Y.

    ---       ---                 ---       ---
   | A |--1--| B |-----2-//------| Y |--3--| Z |
    ---       ---                 ---       ---

   In this instance, the connection on link #1 and link #3 are both
   provisioned (permanent connections that may be simple links). In
   contrast, the connection over link #2 is set up using the

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   distributed control plane. Thus the SPC is composed of the splicing
   of link #1, #2 and #3.

   Thus, to support the capability to request a SPC connection:

   - The GMPLS signaling protocol must be capable of supporting the
     ability to indicate the outgoing link and label information used
     when setting up the destination provisioned connection.

   - In addition, due to the inter-domain applicability of ASON
     networks, the GMPLS signaling protocol should also support the
     indication of the service level requested for the SPC. In the case
     where an SPC spans multiple domains, indication of both source and
     destination endpoints controlling the SPC request may be needed.
     These may be done via the source and destination signalling
     controller addresses.

4.2 Support for Call and Connection Separation

   A call may be simply described as "An association between endpoints
   that supports an instance of a service" [ITU-T G.8080]. Thus, it can
   be considered as a service provided between two end-points, where
   several calls may exist between them. To each call multiple
   connections may be associated. The call concept provides an abstract
   relationship between two users, where this relationship describes
   (or verifies) at which extent the users are willing to offer (or
   accept) service to each other. Therefore, a call does not provide
   the actual connectivity for transmitting user traffic, but only
   builds a relationship by which subsequent connections may be made.

   A property of a call is to contain zero, one or multiple
   connections. Within the same call, connections may be of different
   type and each connection may exist independently of other
   connections, i.e., each connection is setup and released with
   separate Path/Resv messages. For example, a call may contain a set
   of basic connection and virtually concatenated connections (see
   [GMPLS-SONET] for corresponding connection signaling extensions).

   The concept of the call allows for a better flexibility in how end-
   points set up connections and how network offers services to users.
   In essence, a call allows:

   - Support for virtual concatenation where each connection can travel
     on different diverse paths

   - Facilitate upgrading strategy of the control plane operations,
     where a call control (service provisioning) may be separate from
     actual nodes hosting the connections (where the connection control
     may reside)

   - Identification of the call initiator (with both network call
     controller as well as destination user) prior to connection, which
     may result in decreasing contention during resource reservation

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   - General treatment of multiple connections which may be associated
     for several purposes; for example a pair of working and recovery
     connections may belong to the same call.

   To support the introduction of the call concept, GMPLS signaling
   should include a call identification mechanism and allow for end-to-
   end call capability exchange.

   For instance, a feasible structure for the call identifier (to
   guarantee global uniqueness) may concatenate a globally unique fixed
   ID (e.g., may be composed of country code, carrier code) with an
   operator specific ID (where the operator specific ID may be composed
   of a unique access point code - such as source LSR address - and a
   local identifier). Other formats shall also be possible depending on
   the call identification conventions between parties involved in the
   call setup process.

4.3 Support for Extended Restart Capabilities

   Various types of failures may occur affecting the ASON control
   plane. Requirements placed on the control plane failure recovery by
   [ITU-T G.8080] include:

   - Any control plane failure must not result in releasing established

   - Upon recovery from a control plane failure, the recovered node
     must have the ability to recover the status of the connections
     established before failure occurrence.

   - Upon recovery from a control plane failure, the recovered node
     must have the ability to recover the connectivity information of
     its neighbors.

   - Upon recovery from a control plane failure, connections in the
     process of being established (i.e. pending connection setup
     requests) should be released or continued (with setup).

   - Upon recovery from a control plane failure, connections in the
     process of being released must be released.

   - Upon recovery from a control plane failure, a call must have
     the ability to re-synchronize with its associated connections.

4.4 Support for Extended Label Usage

   Labels are defined in GMPLS (see [RFC 3471]) to provide information
   on the resources used on link local basis for a particular
   connection. The labels may range from specifying a particular
   timeslot, a particular wavelength to a particular port/fiber.

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   In the ASON context, the value of a label MAY not be consistently
   the same across a link. For example, the figure below illustrates
   the case where two GMPLS capable nodes (A and Z) are interconnected
   across two non-GMPLS capable nodes (B and C), where these nodes are
   all SONET/SDH nodes providing, e.g., a VC-4 service.

    -----                     -----
   |     |    ---     ---    |     |
   |  A  |---| B |---| C |---|  Z  |
   |     |    ---     ---    |     |
    -----                     -----

   Labels have an associated implicit imposed structure based on
   [GMPLS-SONET] and [GMPLS-OTN]. Thus, once the local label is
   exchanged with its neighboring control plane node, the structure of
   the local label MAY not be significant to the neighbor node since
   the association between the local and the remote label may not
   necessarily be the same. This issue does not present a problem in a
   simple point-to-point connections between two control plane-enabled
   nodes where the timeslots are mapped 1:1 across the interface.
   However, once a non-GMPLS capable sub-network is introduced between
   these nodes (as in the above figure, where the sub-network provides
   re-arrangement capability for the timeslots) label scoping MAY
   become an issue.

   In this context, there is an implicit assumption that the data plane
   connections between the GMPLS capable edges already exist prior to
   any connection request. For instance, node A's outgoing VC-4's
   timeslot #1 (with SUKLM label=[1,0,0,0,0]) as defined in [GMPLS-
   SONET]) may be mapped onto node B's outgoing VC-4's timeslot #6
   (label=[6,0,0,0,0]) may be mapped onto node C's outgoing VC-4's
   timeslot #4 (label=[4,0,0,0,0]). Thus by the time node Z receives
   the request from node A with label=[1,0,0,0,0], the node Z's local
   label and the timeslot no longer corresponds to the received label
   and timeslot information.

   As such to support this capability, a label association mechanism
   has to be used by the control plane node to map the received
   (remote) label into a locally significant label. The information
   necessary to allow mapping from received label value to a locally
   significant label value may be derived in several ways including:

   - Manual provisioning of the label association
   - Discovery of the label association

   Either method may be used. In case of dynamic association, this
   implies that the discovery mechanism operates at the timeslot/label
   level before the connection request is processed at the ingress
   node. Note that in the case where two nodes are directly connected,
   no association is required. In particular, for directly connected
   TDM interfaces no mapping function (at all) is required due to the
   implicit label structure (see [GMPLS-SONET] and [GMPLS-OTN]). In

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   such instances, the label association function provides a one-to-one
   mapping of the received to local label values.

4.5 Support for Crankback

   Crankback has been identified as a requirement for ASON networks. It
   allows an LSP setup request to be retried on an alternate path that
   detours around a blocked link or node upon a setup failure.

   Crankback mechanisms can also be applied to LSP restoration by
   indicating the location of the failure link or node. This would
   significantly improve the successful recovery ratio for failed LSPs,
   especially in situations where a large number of setup requests are
   simultaneously triggered. [GMPLS-CRANK] specifies crankback GMPLS-
   based signalling mechanisms.

4.6 Support for Additional Error Cases

   To support the ASON network, the following additional category of
   error cases are defined:

   - Errors associated with basic call and soft permanent connection
     support. For example, these may include incorrect assignment of
     IDs for the call or an invalid interface ID for the soft permanent

   - Errors associated with policy failure during processing of the new
     call and soft permanent connection capabilities. These may include
     unauthorized request for the particular capability.

   - Errors associated with incorrect specification of the service

5. Security Considerations

   Per [ITU-T G.8080], a connection cannot be established until the
   associated call has been set up. Also, policy and authentication
   procedures are applied prior to the establishment of the call (and
   can then also be restricted to connection establishment in the
   context of this call).

   This document introduces no new security requirements to GMPLS
   signalling (see [RFC3471]).

6. Acknowledgements

   The authors would like to thank Nic Larkin, Osama Aboul-Magd and
   Dimitrios Pendarakis for their comments and contributions to the
   previous version of this document.

7. References

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7.1 Normative References

   [RFC-2026]     S.Bradner, "The Internet Standards Process --

                  Revision 3", BCP 9, RFC 2026, October 1996.

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

   [RFC-3209]     D.Awduche et al., "RSVP-TE: Extensions to RSVP for
                  LSP Tunnels," RFC 3209, December 2001.

   [RFC-3471]     L.Berger (Editor) et al., "Generalized MPLS -
                  Signaling Functional Description," RFC 3471, January

   [ITUT G.8080]  ITU-T Rec. G.8080/Y.1304, "Architecture for the
                  Automatically Switched Optical Network (ASON),"
                  November 2001 (and Revision, January 2003).

   [GMPLS-CRANK]  A.Farrel (Editor), "Crankback Routing Extensions for
                  MPLS Signaling," Work in Progress, draft-iwata-mpls-
                  crankback-06.txt, May 2003.

   [GMPLS-SONET]  E.Mannie and D.Papadimitriou (Editors), "GMPLS
                  Extensions for SONET and SDH Control, Work in
                  Progress," draft-ietf-ccamp-gmpls-sonet-sdh-08.txt,
                  February 2003.

   [GMPLS-OTN]    D.Papadimitriou (Editor), "GMPLS Signalling
                  Extensions for G.709 Optical Transport Networks
                  Control," Work in progress, draft-ietf-ccamp-gmpls-
                  g709-04.txt, May 2003.

7.2 Informative References

   [IPO-ASON]     Aboul-Magd (Editor) et al., "Automatic Switched
                  Optical Network (ASON) Architecture and Its Related
                  Protocols," Work in progress, draft-ietf-ipo-ason-
                  02.txt, March 2002.

   [IPO-REQS]     Y.Xue (Editor) et al., "Optical Network Service
                  Requirements," Work in progress, draft-ietf-ipo-

   [ITUT G.7713]  ITU-T Rec. G.7713/Y.1304, "Distributed Call and
                  Connection Management," November 2001.

8. Author's Addresses

   Dimitri Papadimitriou (Alcatel)
   Francis Wellesplein 1,
   B-2018 Antwerpen, Belgium

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   Email: dimitri.papadimitriou@alcatel.be

   Zhi-Wei Lin (New York City Transit)
   2 Broadway, Room C3.25
   New York, NY 10004
   Email: zhiwlin@nyct.com

   John Drake (Calient)
   5853 Rue Ferrari,
   San Jose, CA 95138, USA
   Email: jdrake@calient.net

   Adrian Farrel (Movaz Networks)
   7926 Jones Branch Drive,
   McLean, VA 22102, USA
   Email: afarrel@movaz.com

   Gerald R. Ash (ATT)
   AT&T Labs, Room MT D5-2A01
   200 Laurel Avenue
   Middletown, NJ 07748, USA
   Email: gash@att.com

   Lyndon Ong (Ciena)
   5965 Silver Creek Valley Road
   San Jose, CA 95138, USA
   Email: lyong@ciena.com

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Appendix - Terminology

   This draft defines the following terms:

   Administrative domain: See Recommendation G.805.

   Call: association between endpoints that supports an instance of a

   Connection: concatenation of link connections and sub-network
   connections that allows the transport of user information between
   the ingress and egress points of a sub-network.

   Control plane: performs the call control and connection control
   functions. Through signaling, the control plane sets up and releases
   connections, and may restore a connection in case of a failure.

   (Control) Domain: represents a collection of entities that are
   grouped for a particular purpose. G.8080 applies this G.805
   recommendation concept (that defines two particular forms, the
   administrative domain and the management domain) to the control
   plane in the form of a control domain. The entities that are grouped
   in a control domain are components of the control plane.

   External NNI: interfaces are located between protocol controllers
   between control domains.

   Internal NNI: interfaces are located between protocol controllers
   within control domains.

   Link: See Recommendation G.805.

   Management plane: performs management functions for the Transport
   Plane, the control plane and the system as a whole. It also provides
   coordination between all the planes. The following management
   functional areas are performed in the management plane: performance,
   fault, configuration, accounting and security management

   Management domain: See Recommendation G.805.

   Transport plane: provides bi-directional or unidirectional transfer
   of user information, from one location to another. It can also
   provide transfer of some control and network management information.
   The Transport Plane is layered; it is equivalent to the Transport
   Network defined in G.805.

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