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Versions: (draft-otani-pce-gmpls-aps-req) 00 01 02 03 04 05 06 07 08 09 RFC 7025

Network Working Group                                     Tomohiro Otani
Internet Draft                                                      KDDI
Intended status: Informational                             Kenichi Ogaki
                                                           KDDI R&D Labs
                                                          Diego Caviglia
                                                             Fatai Zhang

Expires: November 30, 2011                                   May 30,2011

               Requirements for GMPLS applications of PCE

               Document: draft-ietf-pce-gmpls-aps-req-04.txt

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with
   the provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   The list of current Internet-Drafts can be accessed at

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   This Internet-Draft will expire on November 30, 2011.


   The initial effort of PCE WG is specifically focused on MPLS (Multi-
   protocol label switching). As a next step, this draft describes

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   functional requirements for GMPLS (Generalized MPLS) application of
   PCE (Path computation element).

Conventions used in this document

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

Table of Contents

   1. Introduction ................................................ 2
   2. Terminology ................................................. 3
   3. GMPLS applications of PCE.................................... 3
      3.1. GMPLS network model..................................... 3
      3.2. Path computation in GMPLS network .......................4
      3.3. Unnumbered Interface.................................... 6
      3.4. Asymmetric Bandwidth Path Computation ...................6
   4. Requirements for GMPLS applications of PCE ...................6
      4.1. Requirements of Path Computation Request ................6
      4.2. Requirements of Path Computation Reply ..................7
      4.3. GMPLS PCE Management.................................... 8
   5. Security consideration....................................... 8
   6. IANA Considerations ......................................... 9
   7. Acknowledgement ............................................. 9
   8. References .................................................. 9
   9. Authors' Addresses ......................................... 11

1. Introduction

   The initial effort of PCE WG is focused on solving the path
   computation problem 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 networks such as photonics,
   TDM-based or Ethernet-based networks as well.

   [PCE-ARCH] and [PCECP-REQ] discuss the framework and requirements for
   PCE on both packet MPLS networks and (non-packet switch capable)
   GMPLS networks. This document complements these documents 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 series of PCE related

   Note that the requirements for inter-layer traffic engineering
   described in [PCE-INTER LAYER-REQ] are outside of the scope of this

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   Constraint based shortest path first (CSPF) computation within a
   domain or over domains for signaling GMPLS Label Switched Paths (LSPs)
   is more stringent than that of MPLS LSPs [MPLS-AS], because the
   additional constraints, e.g., interface switching capability, link
   encoding, link protection capability and so forth need to be
   considered to establish GMPLS LSPs [CSPF]. GMPLS signaling protocol
   [RFC3471, RFC3473] is designed taking into account bi-directionality,
   switching type, encoding type, SRLG, and protection attributes of the
   TE links spanned by the path, as well as LSP encoding and switching
   type for the end points, appropriately.

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

2. Terminology

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

3. GMPLS applications of PCE

3.1. GMPLS network model

   Figure 1 depicts a typical network, consisting of several
   GMPLSdomains, assumed in this document. D1, D2, D3 and D4 have
   multiple GMPLS inter-domain connections, while D5 has only one GMPLS
   inter-domain connection. These domains follow the definition in

            +---------|GMPLS  D2|----------+
            |         +----+----+          |
       +----+----+         |          +----+----+   +---------+
       |GMPLS  D1|         |          |GMPLS  D4|---|GMPLS  D5|
       +----+----+         |          +----+----+   +---------+
            |         +----+----+          |
            +---------|GMPLS  D3|----------+

                Figure 1: GMPLS Inter-domain network model.

   Each domain is configured using various switching and link
   technologies defined in [Arch] and an end-to-end route needs to
   respect TE link attributes like switching capability, encoding type,
   etc., making the problem a bit different from the case of classical

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   (packet) MPLS. In order to route from one GMPLS domain to another
   GMPLS domain appropriately, each domain manages traffic engineering
   database (TED) by PCE, and exchanges or provides route information of
   paths, while concealing its internal topology information.

3.2. Path computation in GMPLS network

   [CSPF] describes consideration of GMPLS TE attributes during path
   computation. Figure 2 depicts a typical GMPLS network, consisting of
   an ingress link, a transit link as well as an egress link, to
   investigate a consistent guideline 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 2: 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 2) must be 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) should be
   consistent with switching type of a LSP to be created.

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

   [CSPF] indicates the possible tables of switching capability,
   encoding type and bandwidth at the ingress link, transiting links and
   the egress link which need to be satisfied with GMPLS path
   computation of the created LSP.

   The non-packet GMPLS networks (e.g., TDM networks) are usually
   responsible for transmitting data for the client layer. These GMPLS
   networks can provide different types of connections for customer
   services based on different service bandwidth requests.

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   The applications and the corresponding additional requirements for
   applying PCE in non-packet networks, for example, GMPLS-based TDM
   networks, are described in Figure 3. 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 are similar.

                     N1                    N2

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

                      Figure 3: A simple SDH network

   Figure 3 shows a simple 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 from N1 to N4,
   and it could also be provided by three concatenated VC3 connections
   (Contiguous or Virtual concatenation) from N1 to N4.

   The type of connection(s) (one VC4 or three concatenated VC3) that is
   required needs to be specified by PCC (e.g., N1 or NMS), but could
   also be determined by PCE automatically based on policy [RFC5394].

   Therefore, the signal type, the type of the concatenation and the
   number of the concatenation should also be considered during path
   computation for PCE.

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3.3. Unnumbered Interfaces

   GMPLS support unnumbered interface ID that is defined in [RFC 3477],
   which means that the endpoints of the path may be unnumbered. It
   should also be possible to request a path between a numbered link and
   an unnumbered link, or a P2MP path between different types of
   endpoints. Therefore, the PCC should be capable of indicating the
   unnumbered interface ID of the endpoints in the PCReq message.

3.4. Asymmetric Bandwidth Path Computation

   As per [RFC 5467], 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.

4. Requirements for GMPLS application of PCE

   In this section, we describe requirements for GMPLS applications of
   PCE in order to establish GMPLS LSP.

4.1. Requirements of Path Computation Request

   As for path computation in GMPLS networks as discussed in section 3,
   the PCE needs to consider the GMPLS TE attributes appropriately
   according to tables in [CSPF] once a PCC or another PCE requests a
   path computation. Indeed, the path calculation request message from
   the PCC or the PCE needs to contain the information specifying
   appropriate attributes. According to [RFC5440],[PCEP-EXT],[ PCE-WSON-
   REQ] and to RSVP procedures like explicit label control(ELC),the
   additional attributes introduced are as follows: [RFC5440]

   (1) Switching capability: PSC1-4, L2SC, DCSC [DCSC-Ext], 802_1 PBB-TE

   (2) Encoding type: as defined in [RFC4202], [RFC4203], e.g., Ethernet,
   SONET/SDH, Lambda, etc.

   (3) Signal Type: Indicates the type of elementary signal that
   constitutes the requested LSP. A lot of signal types with
   different granularity have been defined in SONET/SDH and G.709 ODUk,
   such as VC11, VC12, VC2, VC3 and VC4 in SDH, and ODU1, ODU2 and ODU3
   in G.709 ODUk. See[RFC4606] , [RFC4328]and [OSPF-G709] or [RSVP-TE-

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   (4) Concatenation Type: In SDH/SONET and G.709 ODUk networks, 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 wavelength label as defined
   in [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 [RFC

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

4.2. Requirements of Path Computation Reply

   As described above, a PCC needs to support to initiate a PCReq
   message specifying above mentioned attributes. The PCE needs to
   compute the path that satisfies the constraints which are specified
   in the PCReq message. Then the PCE needs to 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 PCRep message needs to be extended to meet the
   following requirements.

   (1) Concatenation path computation

   In the case of concatenation path computation, when a PCE receives
   the PCReq message specifying the concatenation constraints described

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   in section 4.1, the PCE should compute the path which satisfies the
   specified concatenation constraints.

   For contiguous concatenation path computation, the routes of each
   member signal must be co-routed and all the interfaces along the
   route should support contiguous concatenation capability. Therefore,
   the PCE needs to compute a path based on the contiguous concatenation
   capability of each interface and only one ERO which carries the route
   information is needed for the response.

   For virtual concatenation path computation, only the ingress/egress
   interfaces need to support virtual concatenation capability and maybe
   there are 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 that one ERO
   represents several member signals among the total member signals, the
   number of member signals along the route of the ERO needs to be

   (2) Wavelength label

   In the case that a PCC doesn't specify the wavelength when requesting
   a wavelength path and the PCE is capable of performing the route and
   wavelength computation procedure, the PCE needs to be able to specify
   the wavelength of the path in a PCRep message.

   (3) Roles of the routes

   When a PCC specifies the protection type of the LSPs, the PCE needs
   to compute the working route and the corresponding protection
   route(s). Therefore, the PCRep should be capable of indicate which
   one is working or protection route.

4.3. GMPLS PCE Management

   PCE related Management Information Bases need to consider extensions
   to be satisfied with requirements for GMPLS applications. For
   extensions, [GMPLS-TEMIB] are defined to manage TE database and may
   be referred to accommodate GMPLS TE attributes in the PCE.

5. Security consideration

   PCE extensions to support GMPLS should be considered under the same
   security as current work. This extension will not change the
   underlying security issues.

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6. IANA Considerations

   This document has no actions for IANA.

7. Acknowledgement

   The author would like to express the thanks to Shuichi Okamoto for
   his comments.

8. References

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

   [PCE-ARCH] A. Farrel, et al, "A Path Computation Element (PCE)-Based
               Architecture", RFC4655, Aug., 2006.

   [PCECP-REQ] J. Ash, et al, "Path computation element (PCE)
               communication protocol generic requirements", RFC4657,
               Sept., 2007.

   [PCE-INTER LAYER-REQ] T.Takeda,et al,"PCC-PCE Communication and PCE
               Discovery Requirements for Inter-Layer
               Engineering",December 2010.

   [MPLS-AS]  R. Zhan, et al, "MPLS Inter-Autonomous System (AS)
               Traffic Engineering (TE) Requirements", RFC4216, November

   [CSPF]     T. Otani, et al, "Considering Generalized Multiprotocol
               Label Switching Traffic Engineering Attributes During
               Path Computation", draft-otani-ccamp-gmpls-cspf-
               constraints-07.txt, Feb., 2008.

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

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

   [RFC4726]  A. Farrel, et al, "A framework for inter-domain MPLS
               traffic engineering", RFC4726, November 2006.

   [Arch]     E. Mannie, et al, "Generalized Multi-Protocol Label
               Switching Architecture", RFC3945, October, 2004.

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   [RFC5394]   I.Bryskin,et al,"Policy-Enabled Path Computation
               Framework",RFC5394,December 2008.

   [RFC3477]   K.Kompella,et al,"Signalling Unnumbered Links in Resource
               ReSerVation Protocol-Traffic Engineering(RSVP-
               TE)",January 2003.

   [RFC5476]   B.Claise,Ed,"Packet Sampling(PSAMP) Protocol
               Specifications",March 2009.

   [RFC5440]  J.P. Vasseur, et al, "Path Computation Element (PCE)
               Communication Protocol (PCEP)", RFC5440, March 2009.

   [PCEP-EXT]  C.Margaria,et al, "PCEP extensions for GMPLS",draft-
               ietf-pce-gmpls-PCEP-EXTs-02.txt,March 2011.

   [PCE-WSON-REQ] Y.Lee, et al,"PCEP Requirements for WSON Routing and
               Wavelength Assignment",draft-ietf-pce-wson-routing-
               wavelength-04.txt,March 2011.

   [RFC4202]  K. Kompella, and Y. Rekhter, "Routing Extensions in
               Support of Generalized Multi-Protocol Label Switching",
               RFC4202, Oct. 2005.

   [RFC4203]  K. Kompella, and Y. Rekhter, "OSPF Extensions in Support
               of Generalized Multi-Protocol Label Switching", RFC4203,
               Oct. 2005.

   [RFC4872]  J.P. Lang, Ed., "RSVP-TE Extensions in Support of End-to-
               End Generalized Multi-Protocol Label Switching (GMPLS)
               Recovery", RFC4872, May 2007.

   [GMPLS-TEMIB]   T. Nadeau and A. Farrel, Ed., "Generalized
               Multiprotocol Label Switching (GMPLS) Traffic Engineering
               Management Information Base", RFC4802, Feb. 2007.

   [RFC3630]  D. Katz et al., "Traffic Engineering (TE) Extensions to
               OSPF Version 2", RFC3630, September 2003.

   [Lambda-label] T. Otani, Ed., "Generalized Labels for G.694 Lambda-
               Switching Capable Label Switching Routers", draft-ietf-
               ccamp-gmpls-g-694-lambda-labels, in progress.

   [RFC5394]  I. Bryskin et al., " Policy-Enabled Path Computation
               Framework", RFC5394, December 2008.

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

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

   [RFC3477]   K.Kompella,"Signalling Unnumbered Links in Resource
               ReServation Protocol-Traffic Engineering(RSVP-
               TE)",January 2003.

   [OSPF-G709] D.Ceccarelli,et al,"Traffic Engineering Extensions to
               OSPF for Generalized MPLS(GMPLS) Control of Evolving
               G.709 OTN Networks",March 2011.

   [RSVP-TE-G709] Fatai Zhang,et al,"Generalized Multi-Protocol Label
               Switching(GMPLS) Signaling Extensions for the evolving
               G.709 Optical Transport Network Control",March 2011.

   [DCSC-Ext] Lou Berger, et al.,"Generalized MPLS (GMPLS) Data Channel
               Switching Capable (DCSC) and Channel Set Label
               Extensions", in progress.

   [GMPLS-PBB-TE] Don Fedyk, et al., "Generalized Multiprotocol Label
               Switching (GMPLS) control of Ethernet PBB-TE", in

9. Authors' Addresses

   Tomohiro Otani
   KDDI Corporation
   2-3-2 Nishi-shinjuku Shinjuku-ku, Tokyo 163-8003 Japan
   Phone:  +81-3-3347-6006
   Email:  tm-otani@kddi.com

   Kenichi Ogaki
   KDDI R&D Laboratories, Inc.
   2-1-15 Ohara Fujimino-shi, Saitama 356-8502 Japan
   Phone:  +81-49-278-7897
   Email:  ogaki@kddilabs.jp

   Diego Caviglia
   16153 Genova Cornigliano, ITALY

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   Phone: +390106003736
   Email: diego.caviglia@ericsson.com

   Fatai Zhang
   Huawei Technologies Co., Ltd.
   F3-5-B R&D Center, Huawei Base,
   Bantian, Longgang District
   Shenzhen 518129 P.R.China
   Phone: +86-755-28972912
   Email: zhangfatai@huawei.com

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