Network Working Group                                           T. Otani
Internet-Draft                                                  K. Ogaki
Intended status: Informational                                      KDDI
Expires: December 12, 2013 January 22, 2014                                    D. Caviglia
                                                                F. Zhang
                                                     Huawei Technologies
                                                             C. Margaria
                                                        Coriant R&D GmbH
                                                           June 10,
                                                           July 21, 2013

               Requirements for GMPLS applications of PCE


   The initial effort of the PCE (Path computation element) WG is
   specifically was
   mainly focused on MPLS.  As a next step, this draft describes
   functional requirements for GMPLS application of PCE.

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   This Internet-Draft will expire on December 12, 2013. January 22, 2014.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  GMPLS applications of PCE . . . . . . . . . . . . . . . . . .   3
     2.1.  Path computation in GMPLS network . . . . . . . . . . . .   3
     2.2.  Unnumbered Interface  . . . . . . . . . . . . . . . . . .   5
     2.3.  Asymmetric Bandwidth Path Computation . . . . . . . . . .   5
   3.  Requirements for GMPLS application of PCE . . . . . . . . . .   5
     3.1.  Requirements on Path Computation Request  . . . . . . . .   5
     3.2.  Requirements on Path Computation Reply  . . . . . . . . .   6
     3.3.  GMPLS PCE Management  . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   The initial effort of the PCE (Path computation element) WG is was
   mainly focused on solving the path computation problem within a
   domain or over different domains in MPLS networks.  As the same case
   with MPLS, service providers (SPs) have also come up with
   requirements for path computation in GMPLS-controlled networks
   [RFC3945] such as wavelength, TDM-based or Ethernet-based networks as

   [RFC4655] and [RFC4657] discuss the framework and requirements for
   PCE on both packet MPLS networks and GMPLS-controlled networks.  This
   document complements these RFCs by providing some considerations of
   GMPLS applications in the intra-domain and inter-domain networking
   environments and indicating a set of requirements for the extended
   definition of PCE-related protocols.

   Note that the requirements for inter-layer and inter-area traffic
   engineering described in [RFC6457] and [RFC4927] are outside of the
   scope of this document.

   Constraint-based shortest path first (CSPF) computation within a
   domain or over domains for signaling GMPLS Label Switched Paths
   (LSPs) is usually more stringent than that of MPLS TE LSPs [RFC4216],
   because the additional constraints, e.g., interface switching
   capability, link encoding, link protection capability, SRLG (Shared
   risk link group) [RFC4202] and so forth need to be considered to
   establish GMPLS LSPs.  GMPLS signaling protocol [RFC3473] is designed
   taking into account bi-directionality, switching type, encoding type
   and protection attributes of the TE links spanned by the path, as
   well as LSP encoding and switching type of the end points,

   This document provides the investigated results of requirements for GMPLS applications of PCE for the in
   support of GMPLS path computation.  This document also
   provides computation, included are requirements for GMPLS applications of PCE in GMPLS intra-
   domain both
   intra-domain and inter-domain environments.

2.  GMPLS applications of PCE

2.1.  Path computation in GMPLS network

   Figure 1 depicts a typical model GMPLS network, consisting of an ingress
   link, a transit link as well as an egress link, link.  We will use this
   model to investigate a consistent guideline guidelines for GMPLS path
   computation.  Each link at each interface has its own switching
   capability, encoding type and bandwidth.

             Ingress             Transit             Egress
   +-----+   link1-2   +-----+   link2-3   +-----+   link3-4   +-----+
   |     |<------------|     |<------------|     |<------------|     |
   +-----+   link2-1   +-----+   link3-2   +-----+   link4-3   +-----+

   Figure 1: Path computation in GMPLS networks

   For the simplicity in consideration, the below basic assumptions are
   made when the LSP is created.

   (1) Switching capabilities of outgoing links from the ingress and
   egress nodes (link1-2 and link4-3 in Figure 1) are consistent with
   each other.

   (2) Switching capabilities of all transit links including incoming
   links to the ingress and egress nodes (link2-1 and link3-4) are
   consistent with switching type of a LSP to be created.

   (3) Encoding-types of all transit links are consistent with encoding
   type of a LSP to be created.

   GMPLS-controlled networks (e.g., GMPLS-based TDM networks) are
   usually responsible for transmitting data for the client layer.

   These GMPLS-controlled networks can provide different types of
   connections for customer services based on different service
   bandwidth requests.

   The applications and the corresponding additional requirements for
   applying PCE to, for example, GMPLS-based TDM networks, are described
   in Figure 2.  In order to simplify the description, this document
   just discusses the scenario in SDH networks as an example.  The
   scenarios in SONET or G.709 ODUk layer networks OTN are similar to this scenario.

                     N1                    N2
    +-----+       +------+              +------+
    |     |-------|      |--------------|      |       +-------+
    +-----+       |      |---|          |      |       |       |
       A1         +------+   |          +------+       |       |
                     |       |             |           +-------+
                     |       |             |              PCE
                     |       |             |
                     |      +------+       |
                     |      |      |       |
                     |      |      |-----| |
                     |      +------+     | |
                     |         N5        | |
                     |                   | |
                  +------+              +------+
                  |      |              |      |        +-----+
                  |      |--------------|      |--------|     |
                  +------+              +------+        +-----+
                     N3                    N4              A2

   Figure 2: A simple TDM (SDH) network

   Figure 2 shows a simple TDM (SDH) network topology, where N1, N2, N3,
   N4 and N5 are all SDH switches.  Assume that one Ethernet service
   with 100M bandwidth is required from A1 to A2 over this network.  The
   client Ethernet service could be provided by a VC4 connection container from N1
   to N4, and it could also be provided by three concatenated VC3
   containers (Contiguous or Virtual concatenation) from N1 to N4.

   In this scenario, when the ingress node (e.g., N1) receives a client
   service transmitting request, the type of connections containers (one VC4 or
   three concatenated VC3) could be determined by PCC (Path computation
   client) (e.g., N1 or NMS), but could also be determined by PCE
   automatically based on policy [RFC5394].  If it is determined by PCC,
   PCC should be capable of specifying the ingress node and egress node,
   signal type, the type of the concatenation and the number of the
   concatenation in a PCReq (Path computation request) message.  PCE
   should consider those parameters during path computation.  The route
   information (co-route or separated-route) should be specified in a
   PCRep (Path computation reply) message if path computation is
   performed successfully.

   As described above, PCC should be capable of specifying TE attributes
   defined in the next section and PCE should compute a path

   Where a GMPLS network is consisting of inter-domain (e.g., inter-AS
   or inter-area) GMPLS-controlled networks, requirements on the path
   computation follows [RFC5376] and [RFC4726].

2.2.  Unnumbered Interface

   GMPLS supports unnumbered interface ID that is defined in [RFC3477],
   which means that the endpoints of the path may be unnumbered.  It
   should also be possible to request a path consisting of the mixture
   of numbered links and unnumbered links, or a P2MP (Point-to-
   multipoint) path with different types of endpoints.  Therefore, the
   PCC should be capable of indicating the unnumbered interface ID of
   the endpoints in the PCReq message.

2.3.  Asymmetric Bandwidth Path Computation

   As per [RFC6387], GMPLS signaling can be used for setting up an
   asymmetric bandwidth bidirectional LSP.  If a PCE is responsible for
   the path computation, the PCE should be capable of computing a path
   for the bidirectional LSP with asymmetric bandwidth.  It means that
   the PCC should be able to indicate the asymmetric bandwidth
   requirements in forward and reverse directions in the PCReq message.

3.  Requirements for GMPLS application of PCE

3.1.  Requirements on Path Computation Request

   As for path computation in GMPLS-controlled networks as discussed in
   section 2, the PCE should appropriately consider the GMPLS TE
   appropriately listed below once a PCC or another PCE requests a path
   Indeed, the  The path calculation request message from the PCC or
   the PCE must contain the information specifying appropriate
   attributes.  According to [RFC5440], [PCE-WSON-REQ] and to RSVP
   procedures like explicit label control(ELC),the additional attributes
   introduced are as follows:

   (1) Switching capability/type: as defined in [RFC3471], [RFC4203]
   and, all current and future values.

   (2) Encoding type: as defined in [RFC3471], [RFC4203] and, all
   current and future values.

   (3) Signal Type: as defined in [RFC4606] and, all current and future

   (4) Concatenation Type: In SDH/SONET and G.709 ODUk networks, OTN, two kinds of
   concatenation modes are defined: contiguous concatenation which
   requires co-route for each member signal and requires all the
   interfaces along the path to support this capability, and virtual
   concatenation which allows diverse routes for the member signals and
   only requires the ingress and egress interfaces to support this
   capability.  Note that for the virtual concatenation, it also may
   specify co-routed or separated-routed.  See [RFC4606] and [RFC4328]
   about concatenation information.

   (5) Concatenation Number: Indicates the number of signals that are
   requested to be contiguously or virtually concatenated.  Also see
   [RFC4606] and [RFC4328].

   (6) Technology-specific label(s) such as defined in [RFC4606],
   [RFC6060], [RFC6002] or [RFC6205].

   (7) e2e Path protection type: as defined in [RFC4872], e.g., 1+1
   protection, 1:1 protection, (pre-planned) rerouting, etc.

   (8) Administrative group: as defined in [RFC3630]

   (9) Link Protection type: as defined in [RFC4203]

   (10)Support for unnumbered interfaces: as defined in [RFC3477]

   (11)Support for asymmetric bandwidth request: as defined in [RFC6387]

   (12)Support for explicit label control during the path computation.

   (13)Support of label restrictions in the requests/responses,
   similarly to RSVP-TE ERO (Explicit route object) and XRO (Exclude
   route object) as defined in [RFC3473] and [RFC4874].

3.2.  Requirements on Path Computation Reply
   As described above, a PCE should compute the path that satisfies the
   constraints which are specified in the PCReq message.  Then the PCE
   should send a PCRep message including the computation result to the
   PCC.  For Path Computation Reply message (PCRep) in GMPLS networks,
   there are some additional requirements.  The PCEP (PCE communication
   protocol) PCRep message must be extended to meet the following

   (1) Path computation with concatenation

   In the case of path computation involving concatenation, when a PCE
   receives the PCReq message specifying the concatenation constraints
   described in section 3.1, the PCE should compute a path accordingly.

   For path computation involving contiguous concatenation, a single
   route is required and all the interfaces along the route should
   support contiguous concatenation capability.  Therefore, the PCE
   should compute a path based on the contiguous concatenation
   capability of each interface and only one ERO which should carry the
   route information for the response.

   For path computation involving virtual concatenation, only the
   ingress/egress interfaces need to support virtual concatenation
   capability and there may be diverse routes for the different member
   signals.  Therefore, multiple EROs may be needed for the response.
   Each ERO may represent the route of one or multiple member signals.
   In the case where one ERO represents several member signals among the
   total member signals, the number of member signals along the route of
   the ERO must be specified.

   (2) Label constraint

   In the case that a PCC does not specify the exact label(s) when
   requesting a label-restricted path and the PCE is capable of
   performing the route computation and label assignment computation
   procedure, the PCE needs to be able to specify the label of the path
   in a PCRep message.

   Wavelength restriction is a typical case of label restriction.  More
   generally in GMPLS-controlled networks label switching and selection
   constraints may apply and a PCC may request a PCE to take label
   constraint into account and return an ERO containing the label or set
   of label that fulfil the PCC request.

   (3) Roles of the routes

   When a PCC specifies the protection type of an LSP, the PCE should
   compute the working route and the corresponding protection route(s).

   Therefore, the PCRep should allow to distinguish the working
   (nominal) and the protection routes.  According to these routes,
   RSVP-TE procedure appropriately creates both the working and the
   protection LSPs for example with ASSOCIATION object [RFC6689].

3.3.  GMPLS PCE Management

   PCE-related Management Information Bases must consider extensions

   This document does not change any of the management or operational
   details for networks that utilise PCE.  Please refer to
   be satisfied with requirements [RFC4655] for
   an overview of this scenery.  However, this document proposes the
   introduction of several PCEP objects and data for the better
   integration of PCE with GMPLS applications.  For
   extensions, [RFC4802] are defined networks.  Those protocol elements will
   need to manage TE database and may be
   referred visible in any management tools that apply to so as the PCE,
   PCC, and PCEP.  That includes, but is not limited to, adding
   appropriate objects to accommodate existing PCE MIB modules that are used for
   modelling and monitoring PCEP deployments [PCEP-MIB].  Ideas for what
   objects are needed may be guided by the relevant GMPLS TE attributes extensions in the PCE.

4.  Security Considerations

   PCEP extensions to support GMPLS should be considered under the same
   security as current PCE work.  This work and this extension will not change the
   underlying security issues.  Sec. 10 of [RFC5440] describes the list
   of security considerations in PCEP.  At the time [RFC5440] was
   published, TCP Authentication Option (TCP-AO) had not been fully
   specified for securing the TCP connections that underlie PCEP
   sessions.  TCP-AO [RFC5925] has now been published and PCEP
   implementations should fully support TCP-AO according to [RFC6952].

5.  IANA Considerations

   This document has no actions for IANA.

6.  Acknowledgement

   The author would like to express the thanks to Ramon Casellas, Julien
   Meuric, Adrian Farrel Farrel, Yaron Sheffer and Shuichi Okamoto for their

7.  References

7.1.  Normative References

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

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

   [RFC3477]  Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links
              in Resource ReSerVation Protocol - Traffic Engineering
              (RSVP-TE)", RFC 3477, January 2003.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630, September

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

   [RFC4202]  Kompella, K. and Y. Rekhter, "Routing Extensions in
              Support of Generalized Multi-Protocol Label Switching
              (GMPLS)", RFC 4202, October 2005.

   [RFC4203]  Kompella, K. and Y. Rekhter, "OSPF Extensions in Support
              of Generalized Multi-Protocol Label Switching (GMPLS)",
              RFC 4203, October 2005.

   [RFC4328]  Papadimitriou, D., "Generalized Multi-Protocol Label
              Switching (GMPLS) Signaling Extensions for G.709 Optical
              Transport Networks Control", RFC 4328, January 2006.

   [RFC4606]  Mannie, E. and D. Papadimitriou, "Generalized Multi-
              Protocol Label Switching (GMPLS) Extensions for
              Synchronous Optical Network (SONET) and Synchronous
              Digital Hierarchy (SDH) Control", RFC 4606, August 2006.

   [RFC4802]  Nadeau, T. and A. Farrel, "Generalized Multiprotocol Label
              Switching (GMPLS) Traffic Engineering Management
              Information Base", RFC 4802, February 2007.

   [RFC4872]  Lang, J., Rekhter, Y., and D. Papadimitriou, "RSVP-TE
              Extensions in Support of End-to-End Generalized Multi-
              Protocol Label Switching (GMPLS) Recovery", RFC 4872, May

   [RFC4927]  Le Roux, J., "Path Computation Element Communication
              Protocol (PCECP) Specific Requirements for Inter-Area MPLS
              and GMPLS Traffic Engineering", RFC 4927, June 2007.

   [RFC5376]  Bitar, N., Zhang, R., and K. Kumaki, "Inter-AS
              Requirements for the Path Computation Element
              Communication Protocol (PCECP)", RFC 5376, November 2008.

   [RFC5440]  Vasseur, JP. and JL. Le Roux, "Path Computation Element
              (PCE) Communication Protocol (PCEP)", RFC 5440, March

   [RFC6002]  Berger, L. and D. Fedyk, "Generalized MPLS (GMPLS) Data
              Channel Switching Capable (DCSC) and Channel Set Label
              Extensions", RFC 6002, October 2010.

   [RFC6060]  Fedyk, D., Shah, H., Bitar, N., and A. Takacs,
              "Generalized Multiprotocol Label Switching (GMPLS) Control
              of Ethernet Provider Backbone Traffic Engineering (PBB-
              TE)", RFC 6060, March 2011.

   [RFC6205]  Otani, T. and D. Li, "Generalized Labels for Lambda-
              Switch-Capable (LSC) Label Switching Routers", RFC 6205,
              March 2011.

   [RFC6387]  Takacs, A., Berger, L., Caviglia, D., Fedyk, D., and J.
              Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
              Switched Paths (LSPs)", RFC 6387, September 2011.

   [RFC6689]  Berger, L., "Usage of the RSVP ASSOCIATION Object", RFC
              6689, July 2012.

7.2.  Informative References

              Lee, Y., Bernstein, G., Martensson, J., Takeda, T.,
              Tsuritani, T., and O. de Dios, "PCEP Requirements for WSON
              Routing and Wavelength Assignment", draft-ietf-pce-wson-
              routing-wavelength-09 (work in progress), October 2012. June 2013.

              Koushik, A., Emile, S., Zhao, Q., King, D., and J.
              Hardwick, "PCE communication protocol (PCEP) Management
              Information Base", draft-ietf-pce-pcep-mib-05 (work in
              progress), July 2013.

   [RFC4216]  Zhang, R. and J. Vasseur, "MPLS Inter-Autonomous System
              (AS) Traffic Engineering (TE) Requirements", RFC 4216,
              November 2005.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655, August 2006.

   [RFC4657]  Ash, J. and J. Le Roux, "Path Computation Element (PCE)
              Communication Protocol Generic Requirements", RFC 4657,
              September 2006.

   [RFC4726]  Farrel, A., Vasseur, J., and A. Ayyangar, "A Framework for
              Inter-Domain Multiprotocol Label Switching Traffic
              Engineering", RFC 4726, November 2006.

   [RFC4874]  Lee, CY., Farrel, A., and S. De Cnodder, "Exclude Routes -
              Extension to Resource ReserVation Protocol-Traffic
              Engineering (RSVP-TE)", RFC 4874, April 2007.

   [RFC5394]  Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash,
              "Policy-Enabled Path Computation Framework", RFC 5394,
              December 2008.

   [RFC5925]  Touch, J., Mankin, A., and R. Bonica, "The TCP
              Authentication Option", RFC 5925, June 2010.

   [RFC6457]  Takeda, T. and A. Farrel, "PCC-PCE Communication and PCE
              Discovery Requirements for Inter-Layer Traffic
              Engineering", RFC 6457, December 2011.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, May 2013.

Authors' Addresses

   Tomohiro Otani
   KDDI Corporation
   2-3-2 Nishi-shinjuku
   Shinjuku-ku, Tokyo

   Phone: +81-(3) 3347-6006

   Kenichi Ogaki
   KDDI Corporation
   3-10-10 Iidabashi
   Chiyoda-ku, Tokyo

   Phone: +81-(3) 6678-0284
   Diego Caviglia
   16153 Genova Cornigliano

   Phone: +390106003736

   Fatai Zhang
   Huawei Technologies Co., Ltd.
   F3-5-B R&D Center, Huawei Base
   Bantian, Longgang District, Shenzhen 518129

   Phone: +86-755-28972912

   Cyril Margaria
   Coriant R&D GmbH
   St Martin Strasse 76
   Munich, 81541

   Phone: +49 89 5159 16934