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Versions: 00

PCE Working Group                                         Xiaoping Zheng
Internet-Draft                                                   Nan Hua
Intended status: Standards Track                            Wangyang Liu
Expires: April 27, 2015                                     Bingkun Zhou
                                                     Tsinghua University
                                                           Guoying Zhang
                                      China Academy of Telecom. Research
                                                        October 27, 2014


               Cooperative Stateful Path Computation Element (PCE)
              for Inter-Domain Inter-Vendor PCE-initiated LSP Setup
               draft-ietf-pce-stateful-pce-inter-domain-lsp-00.txt

Abstract

   A stateful Path Computation Element (PCE) maintains the information
   of Label Switched Path (LSP) and resource availability within a
   domain, so multiple stateful PCEs are able to provide traffic
   engineering inter-domain routing through cooperating with each other.
   This document introduces the applicability of cooperative stateful
   PCE for establishing inter-domain inter-vendor LSP which is initiated
   by PCE.

Requirements Language

   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 [RFC2119].

Status of This Memo

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

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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 progress."

   This Internet-Draft will expire on April 27, 2015.





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Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview of the Stateful PCE  . . . . . . . . . . . . . . . .   3
   4.  Multiple Stateful PCEs Deployment and Operation   . . . . . .   4
     4.1.  Traffic Engineering Database  . . . . . . . . . . . . . .   5
     4.2.  Cooperative Inter-domain Path Computation  . .. . . . . .   5
     4.3.  Cooperative Inter-domain LSP Setup  . . . . . . . . . . .   6
     4.4.  Vendor-specific Message Conversion  . . . . . . . . . . .   6
   5.  Applicability of Cooperative Stateful PCE   . . . . . . . . .   6
     5.1.  TED initialization  . . . . . . . . . . . . . . . . . . .   6
     5.2.  PCE-initiated LSP Setup . . . . . . . . . . . . . . . . .   7
       5.2.1.  Inter-domain Inter-vendor LSP Setup Request . . . . .   7
       5.2.2.  Inter-domain Path Computation . . . . . . . . . . . .   7
       5.2.3.  Inter-domain Path Segmentation . . . . . . . . .  . .   8
       5.2.4.  Intra-domain LSP Setup Procedure . . . . . .. . . . .   8
       5.2.5.  Inter-domain Inter-vendor LSP Setup Response .  . . .   9
     5.3.  TED Synchronization . . . . . . . . . . . . . . . . . . .   9
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  11
   10. Authors' Addresses  . . . . . . . . . . . . . . . . . . . . .  11



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1.  Introduction

   This document describes the setup of PCE-initiated inter-domain
   inter-vendor LSPs under the cooperative stateful PCE model, which is
   distributed controlled and deployed.

2.  Terminology

   This document uses the following terms defined in [RFC5440]: PCE.

   This document uses the following terms defined in [RFC4655]: TED.

   This document uses the following terms defined in [I-D.ietf-pce-
   stateful-pce-09]: Stateful PCE.

   This document uses the following terms defined in [I-D.ietf-pce-pce-
   initiated-lsp-02]: PCE-initiated LSP.

   The following terms are defined in this document:

   Source-PCE:  PCE that covers the source node of LSP request.

   Destination-PCE: PCE that covers the destination node of LSP request.

   Upstream-PCE:  The previous PCE that along the reversed direction of
   domain sequence.

   Downstream-PCE:  The next PCE that along the positive direction of
   domain sequence.

3.  Overview of the Stateful PCE

   [RFC4655] defines a stateful PCE to be one in which the PCE maintains
   "strict synchronization between the PCE and not only the network
   states (in term of topology and resource information), but also the
   set of computed paths and reserved resources in use in the network."

   Stateful pce [I-D.ietf-pce-stateful-pce-09] specifies a set of
   extensions to PCEP to enable stateful control of TE LSPs between and
   across PCEP sessions in compliance with [RFC4657]. It includes
   mechanisms to effect LSP state synchronization between PCCs and PCEs,
   delegation of control of LSPs to PCEs, and PCE control of timing and
   sequence of path computations within and across PCEP sessions and
   focuses on a model where LSPs are configured on the PCC and control
   over them is delegated to the PCE.



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4.  Multiple Stateful PCEs Deployment and Operation

   Multiple stateful PCEs can be deployed in a distributed architecture,
   shown in Figure 1. Each domain contains a single stateful PCE, which
   is responsible for maintaining intra-domain resource information and
   controlling intra-domain LSP setup. All the PCEs are mesh-connected
   and they may communicate with each other in a Virtual Local Area
   Network (VLAN).

   The transport devices located in different domains may be supplied by
   various vendors and probably own private configuration parameters,
   such as IP address, port attribute, signaling protocol, etc.
   Therefore, each domain is equipped with a dedicated Interface Adapter
   (IA), which can convert different vendor-specific messages into
   unified interface messages.

   Network Management System (NMS) is a centralized management entity,
   which is aware of entire network resources and connected with all the
   PCEs. NMS can initiate inter-domain LSP setup request that will be
   sent to the source-PCE.

   The inter-domain path is computed by a set of distributed PCEs that
   collaborate during path computation. The source PCE initiates inter-
   domain inter-vendor LSP setup, which is completed through cooperation
   between multiple PCEs.









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                            +-------+
           +----------------+  NMS  +------------------+
           |                +----+--+                  |
           |                     |                     |
      +----+---+                 |                +----+---+
      |        |                 |                |        |
      | PCE #1 +----------------------------------+ PCE #3 |
      |        |                 |                |        |
      +----+---+            +----+---+            +----+---+
           |   |            |        |            |    |
           |   +------------+ PCE #2 +------------+    |
           |                |        |                 |
           |                +----+---+                 |
           |                     |                     |
       +---+---+             +---+---+             +---+---+
       | IA #1 |             | IA #2 |             | IA #3 |
       +---+---+             +---+---+             +---+---+
           |                     |                     |
           |                     |                     |
   +-------+--------+    +-------+--------+    +-------+--------+
   |                |    |                |    |                |
   |   Domain #1    |    |   Domain #2    |    |   Domain #3    |
   |   (Vendor A)   +----+   (Vendor B)   +----+   (Vendor C)   |
   |                |    |                |    |                |
   +----------------+    +----------------+    +----------------+

                   Figure 1  Cooperative PCEs Deployment

4.1.  Traffic Engineering Database

   Each PCE may collect local topology and TE information from transport
   plane. Besides, in order to complete inter-domain path computation,
   each PCE may collect all the inter-domain links and domains
   information from a specific management entity, such as Network
   Management System (NMS), which has the global visibility of network.

4.2.  Cooperative Inter-domain Path Computation

   When source-PCE receives an inter-domain path computation request
   from NMS, the source-PCE will first determine an optimal domain
   sequence and then cooperate with other PCEs to compute an optimal
   inter-domain path based on the required constraints. The source-PCE
   will generate the full set of strict hops from source node to
   destination node.



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4.3.  Cooperative Inter-domain LSP Setup

   After inter-domain path computation, source-PCE splits the inter-
   domain path into multiple independent sub-paths according to domain
   ID. Then, the source-PCE simultaneously sends all the sub-paths to
   the relevant PCEs. Each PCE is responsible for its corresponding
   intra-domain LSP setup.

   The source-PCE asynchronously receives the intra-domain LSP setup
   response from all the relevant PCEs. If all the intra-domain LSPs are
   successfully established and there are sufficient resources in the
   relevant inter-domain links, the inter-domain inter-vendor LSP is
   successfully established. Otherwise, the inter-domain inter-vendor
   LSP fails to be established.

4.4.  Vendor-specific Message Conversion

   In order to eliminate the differences in vendor-specific message
   formats of various vendors' domains, each domain is equipped with a
   dedicated Interface Adapter (IA), which can convert different vendor-
   specific messages into unified interface messages.

5.  Applicability of Cooperative Stateful PCE

5.1.  TED initialization

   The Traffic Engineering Database (TED) of PCE includes intra-domain
   information and inter-domain information, shown in Figure 2.

   In the process of TED initialization, every PCE sends TED request to
   the corresponding transport plane, which contains physical nodes and
   physical links. Every PCE receives TED response from the transport
   plane and stores the intra-domain resource information into its TED.

   Meanwhile, every PCE sends TED request to Network Management System
   (NMS), which is responsible for maintaining inter-domain links and
   all the PCEs in the entire network. Every PCE receives TED response
   from NMS and generates a global domain topology for subsequent inter-
   domain path computation. The domain topology stored in every PCE
   should be the same.



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            Intra-domain TED              Inter-domain TED
            +------------>    +---------+   <------------+
            +------------+----+   PCE   +---+------------+
            |                 +---------+                |
        +---+--+                                         |
        |  IA  |                                         |
        +---+--+                                         |
            |                                            |
            |                                            |
   +--------+--------+                             +-----+----+
   | Transport Plane |                             |    NMS   |
   +-----------------+                             +----------+

                   Figure 2  TED Initialization Procedure

5.2.  PCE-initiated LSP Setup

5.2.1.  Inter-domain Inter-vendor LSP Setup Request

   The inter-domain inter-vendor LSP setup request is initiated through
   NMS. The request contains source node information (IP address,
   interface ID, timeslot), destination node information (IP address,
   interface ID, timeslot), required bandwidth, granularity type,
   protection type, and domain sequence. The request is sent to source-
   PCE.

5.2.2.  Inter-domain Path Computation

    +-------------------+
    |  Domain Topology  |
    |  #1----#2----#3   |
    |                   |
    +------X------------+
          X
         X
   +-----X----+  Request   +--------------+  Request   +-------------+
   |  PCE #1  | |--------> |    PCE #2    | +--------> |   PCE #3    |
   | (Source) +------------+(Intermediate)+------------+(Destination)|
   |          | <--------+ |              | <--------| |             |
   +----------+  Response  +--------------+  Response  +-------------+

              Figure 3  Inter-domain Path Computation Procedure

   In the inter-domain path computation procedure (shown in Figure 3),
   source-PCE computes an optimal domain sequence according to global
   domain topology. The domain sequence is an ordered list which
   contains domain IDs from source-domain to destination-domain.


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   Source-PCE forwards the path computation request to downstream-PCE
   according to the domain sequence. The downstream-PCE keeps on
   forwarding the path computation request to its downstream-PCE until
   the request is arrived at destination-PCE.

   Considering both the constraint requirements of request and local TED
   information, destination-PCE computes many candidate paths from local
   ingress border nodes to destination node. The path computation
   response (including the candidate paths) are sent to upstream-PCE
   according to the reversed domain sequence. The upstream-PCE generates
   an integrated topology including local physical topology, inter-
   domain links and the candidate paths derived from the downstream-PCE.
   The upstream-PCE computes many candidate paths from local ingress
   border nodes to destination node in the new integrated topology. The
   path computation response (including the candidate paths) are sent to
   its upstream-PCE. The above process is recursive until the path
   computation response is arrived at source-PCE. Finally, the source
   PCE selects an optimal inter-domain path.

5.2.3.  Inter-domain Path Segmentation

   The source-PCE splits the inter-domain path into multiple independent
   sub-paths according to domain ID. Different sub-path belongs to
   different domain.

5.2.4.  Intra-domain LSP Setup Procedure

   In Figure 4, the source-PCE simultaneously sends all the sub-paths to
   the relevant PCEs. Each PCE is responsible for its corresponding
   intra-domain LSP setup. In the intra-domain LSP setup procedure, PCE
   sends intra-domain LSP setup request to local Interface Adapter (IA).
   IA converts the LSP setup request into vendor-specific message and
   then sends the message to transport plane. IA receives LSP setup
   response from transport plane and converts it into a unified message.
   PCE receives intra-domain LSP setup response from IA and the intra-
   domain LSP setup procedure is finished.



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               Response
              +-------->    +-------+
           +--+--------+----+  NMS  +------------------+
           |                +----+--+                  |
           |                     |                     |
      +----+---+  Request        |                +----+---+
      |        | +-------->      |                |        |
      | PCE #1 +----------------------------------+ PCE #3 |
      |        | <--------+      |                |        |
      +----+---+  Response       |                +----+---+
           |   |  Request   +----+---+            |    |    ?
        +^ |   | +--------> |        |            |    | +^
        || |   +------------+ PCE #2 +------------+    | ||
        || |     <--------+ |        |                 | ||
        v+ |      Response  +----+---+ +^              | v+
           |                     |     ||              |
       +---+---+             +---+---+ ||          +---+---+
       | IA #1 |             | IA #2 | v+          | IA #3 |
       +---+---+             +---+---+             +---+---+
           |                     |                     |
   +-------+--------+    +-------+--------+    +-------+--------+
   |                |    |                |    |                |
   |   Domain #1    |    |   Domain #2    |    |   Domain #3    |
   |   (Vendor A)   +----+   (Vendor B)   +----+   (Vendor C)   |
   |                |    |                |    |                |
   +----------------+    +----------------+    +----------------+

         Figure 4  Inter-domain Inter-vendor LSP Setup Procedure

5.2.5.  Inter-domain Inter-vendor LSP Setup Response

   The source-PCE asynchronously receives the intra-domain LSP setup
   response from all the relevant PCEs. If all the intra-domain LSPs are
   successfully established and there are sufficient resources in the
   relevant inter-domain links, the inter-domain inter-vendor LSP is
   successfully established. Otherwise, the inter-domain inter-vendor
   LSP fails to be established.

5.3.  TED Synchronization

   In order to avoid resource conflicts, the TED stored in every PCE
   must be updated in time. Once an inter-domain inter-vendor LSP is
   successfully established, the modification of network resources must
   be announced to all the relevant PCEs.

   TED synchronization process includes intra-domain TED synchronization
   process and inter-domain TED synchronization process. PCEs that are


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   involved to the inter-domain LSP should synchronize their intra-
   domain resources with underlying transport plane. And every PCE
   should synchronize inter-domain links to ensure that its global
   domain topology is identical to other PCEs.

   In the process of intra-domain TED synchronization, source-PCE sends
   intra-domain links synchronization requests to the relevant PCEs.
   Each relevant PCE synchronizes intra-domain links information with
   underlying transport plane through message conversion by local
   Interface Adapter (IA).

   In the process of inter-domain TED synchronization, source-PCE sends
   inter-domain links synchronization requests to all the PCEs. Every
   PCE should modifies the information of inter-domain links and updates
   its global domain topology for subsequent inter-domain path
   computation.

6.  Security Considerations

   PCEP security is defined [RFC5440]. Any multi-domain operation
   necessarily involves the exchange of information across domain
   boundaries. This does represent a significant security and
   confidentiality risk. PCEP allows individual PCEs to maintain
   confidentiality of their domain path information using path-keys
   [RFC5520].

   For further considerations of the security issues related to inter-
   domain path computation, see [RFC5376].

7.  IANA Considerations

   This document makes no requests for IANA action.

8.  Acknowledgements

   This document was prepared using 2-Word-v2.0.template.dot.

9.  References

9.1.  Normative References

   [I-D.ietf-pce-stateful-pce-09]
             E. Crabbe, I. Minei, J. Medved, and R. Varga, "PCEP
             Extensions for Stateful PCE", draft-ietf-pce-stateful-pce-
             09 (work in progress), June 2014.

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   [I-D.ietf-pce-pce-initiated-lsp-02]
             E. Crabbe, I. Minei, S. Sivabalan, and R. Varga, "PCEP
             Extensions for PCE-initiated LSP Setup in a Stateful PCE
             Model", draft-ietf-pce-pce-initiated-lsp-02 (work in
             progress), October 2014.

9.2.  Informative References

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

   [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.

   [RFC5376] Bitar, N., et al., "Inter-AS Requirements for the Path
             Computation Element Communication Protocol (PCECP)", RFC
             5376, November 2008.

   [RFC5440] Ayyangar, A., Farrel, A., Oki, E., Atlas, A., Dolganow, A.,
             Ikejiri, Y., Kumaki, K., Vasseur, J., and J. Roux, "Path
             Computation Element (PCE) Communication Protocol (PCEP)",
             RFC 5440, March 2009.

   [RFC5520] Bradford, R., Ed., Vasseur, JP., and A. Farrel, "Preserving
             Topology Confidentiality in Inter-Domain Path Computation
             Using a Path-Key-Based Mechanism", RFC 5520, April 2009.

10.  Authors' Addresses

   Xiaoping Zheng
   Tsinghua University
   Beijing 100084
   P.R.China

   Email: xpzheng@tsinghua.edu.cn


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   Nan Hua
   Tsinghua University
   Beijing 100084
   P.R.China

   Email: huan@mail.tsinghua.edu.cn

   Wangyang Liu
   Tsinghua University
   Beijing 100084
   P.R.China

   Email: liuwy06@mails.tsinghua.edu.cn

   Bingkun Zhou
   Tsinghua University
   Beijing 100084
   P.R.China

   Email: zbk-dee@tsinghua.edu.cn

   Guoying Zhang
   Research Institute of Telecommunications Transmission (RITT),
   China Academy of Telecom. Research (CATR), MIIT
   Beijing 100084
   P.R.China

   Email: zhangguoying@ritt.cn











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