PCE Working Group                                                  Q. Wu
Internet-Draft                                                  D. Dhody
Intended status: Standards Track                                  Huawei
Expires: March 18, 2015                                     M. Boucadair
                                                            C. Jacquenet
                                                          France Telecom
                                                             J. Tantsura
                                                                Ericsson
                                                      September 14, 2014


    PCEP Extensions for traffic steering support in Service Function
                                Chaining
                  draft-wu-pce-traffic-steering-sfc-05

Abstract

   This document provides an overview of the usage of Path Computation
   Element (PCE) with Service Function Chaining (SFC); which is
   described as the definition and instantiation of an ordered set of
   such service functions (such as firewalls, load balancers), and the
   subsequent "steering" of traffic flows through those service
   functions.

   This document specifies extensions to the Path Computation Element
   Protocol (PCEP) that allow a stateful PCE to compute and instantiate
   Service Function Paths (SFP).

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 March 18, 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
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   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Service Function Paths and PCE  . . . . . . . . . . . . . . .   3
   4.   Overview of PCEP Operation in SFC-enabled Networks . . . . .   5
     4.1.  SFP Instantiation . . . . . . . . . . . . . . . . . . . .   5
     4.2.  SFP Withdrawal  . . . . . . . . . . . . . . . . . . . . .   5
     4.3.  SFP Delegation and Cleanup  . . . . . . . . . . . . . . .   5
     4.4.  SFP State Synchronization . . . . . . . . . . . . . . . .   5
     4.5.  SFP Update and Report . . . . . . . . . . . . . . . . . .   6
   5.  Object Formats  . . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  The OPEN Object . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  The LSP Object  . . . . . . . . . . . . . . . . . . . . .   6
       5.2.1.  SFP Identifiers TLV . . . . . . . . . . . . . . . . .   7
   6.  Backward Compatibility  . . . . . . . . . . . . . . . . . . .   7
   7.  Relationship to SR  . . . . . . . . . . . . . . . . . . . . .   7
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Service chaining enables the creation of composite services that
   consist of an ordered set of Service Functions (SF) that must be
   applied to packets and/or frames selected as a result of
   classification as described in [I-D.ietf-sfc-architecture] and
   referred to as Service Function Chain (SFC).  A Service Function Path
   (SFP) is the instantiation of a SFC in the network.  Packets follow a
   Service Function Path from a classifier through the requisite Service
   Functions (SF).



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   [RFC5440] describes the Path Computation Element Protocol (PCEP) as
   the communication between a Path Computation Client (PCC) and a Path
   Control Element (PCE), or between PCE and PCE, enabling computation
   of Multiprotocol Label Switching (MPLS) for Traffic Engineering Label
   Switched Path (TE LSP).

   [I-D.ietf-pce-stateful-pce] specifies extensions to PCEP to enable
   stateful control of MPLS TE LSPs.  [I-D.ietf-pce-pce-initiated-lsp]
   provides the fundamental extensions needed for stateful PCE-initiated
   LSP instantiation.

   This document specifies extensions to the PCEP that allow a stateful
   PCE to compute and instantiate Service Function Paths (SFP).

2.  Conventions used in this document

   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 [RFC2119].

   The following terminologies are used in this document:

   PCC:  Path Computation Client.

   PCE:  Path Computation Element.

   PCEP:  Path Computation Element Protocol.

   PDP:  Policy Decision Point.

   SF:  Service Function.

   SFC:  Service Function Chain.

   SFP:  Service Function Path.

   SFF:  Service Forwarder Function.

   UNI:  User-Network Interface.

3.  Service Function Paths and PCE

   Services are constructed as a sequence of SFs that represent an SFC,
   where a SF can be a virtual instance or be embedded in a physical
   network element, and one or more SFs may be supported by the same
   physical network element.  A SFC creates an abstracted view of a
   service and specifies the set of required SFs as well as the order in
   which they must be executed.



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   When an SFC is instantiated into the network it is necessary to
   select the specific instances of SFs that will be used, and to create
   the service topology for that SFC using SF network locators.  Thus,
   instantiation of the SFC results in the creation of a Service
   Function Path (SFP) and is used for forwarding packets through the
   SFC.  In other words, an SFP is the instantiation of the defined SFC
   as described in [I-D.ietf-sfc-architecture].

   The selection of SFP can be based on a set of policy attributes
   (forwarding and routing, QoS, security, etc., or a combination
   thereof), ranging from simple to more elaborate selection criteria
   and the use of stateful PCE with extensions to PCEP are one such way
   to achieve this.

   Stateful pce [I-D.ietf-pce-stateful-pce] specifies a set of
   extensions to PCEP to enable stateful control of TE LSPs.
   [I-D.ietf-pce-pce-initiated-lsp] provides the fundamental motivations
   and extensions needed for stateful PCE-initiated LSP instantiation.
   This document specifies extensions that allow a stateful PCE to
   compute and instantiate Service Function Paths (SFP) via PCEP.

                 +------------------------+
                 |           stateful PCE |
                 |  +-------+  +-------+  |
                 |  |Policy |  | TE-DB |  |    +-------+
                 |  +-------+  +-------+  |    |  SFC  |
      +----------|      +-------------+   |<---|control|
      |SFP       |      |LSP-DB/SFP-DB|   |    | plane |
      |Instan-   |      +-------------+   |    +-------+
      |tiation   +------------------------+
      |            +-----+ +-----+          +-----+
      |            |SF-1 | |SF-2 |          |SF-3 |
      |            |     | |     |          |     |
      |            +---+-+ +-+---+          +--+--+
      |                |     |                 |
      |               ++-----++           +----+--+
      V               |       |           |       |
   +-----+  Signaling |       | Signaling |       | Signaling
   | SF  |----------->| SFF-1 | --------->| SFF-2 |----------->
   Classifier         |       |           |       |
   |Node |            |       |           |       |
   +-----+            +-------+           +-------+

                   Figure 1: PCE based SFP instantiation

   SFC Control plane components are responsible for maintaining SFC
   Policy Tables and enforcing appropriate policies in SF Classifier and
   SFF Nodes as described in



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   [I-D.ietf-sfc-architecture][I-D.ww-sfc-control-plane].  The SFC
   Control plane component can be seen as a policy Decision point
   (PDP,[RFC5394]).  Such PDP can then operates a stateful PCE and its
   instantiation mechanism to compute and instantiate Service Function
   Paths (SFP).  The PCE maybe co-located with the SFC Control plane
   component or an external entity.

4.  Overview of PCEP Operation in SFC-enabled Networks

   A PCEP speaker indicates its ability to support PCE provisioned
   dynamic SFP paths during the PCEP Initialization phase via a
   mechanism described in Section 5.1.  A PCE can initiate SFPs only for
   PCCs that advertised this capability and a PCC will follow the
   procedures described in this document only on sessions where the PCE
   advertised this capability. .

   As per section 5.1 of [I-D.ietf-pce-pce-initiated-lsp], the PCE sends
   a Path Computation LSP Initiate Request (PCInitiate) message to the
   PCC to instantiate or delete a LSP.  This document makes no change to
   the PCInitiate message format but extends LSP objects described in
   Section 5.2.

4.1.  SFP Instantiation

   The Instantiation operation of a SFP is the same as defined in
   section 5.3[I-D.ietf-pce-pce-initiated-lsp].  Rules of processing and
   error codes remain unchanged.

4.2.  SFP Withdrawal

   The withdrawal operation of a SFP is the same as defined in section
   5.4 of [I-D.ietf-pce-pce-initiated-lsp] : the PCE sends an LSP
   Initiate Message with an LSP object carrying the PLSP-ID of the SFP
   to be removed and an SRP object with the R flag set (LSP-REMOVE as
   per section 5.2 of [I-D.ietf-pce-pce-initiated-lsp]).  Rules of
   processing and error codes remain unchanged.

4.3.  SFP Delegation and Cleanup

   SFP delegation and cleanup operations are similar to those defined in
   section 6 of [I-D.ietf-pce-pce-initiated-lsp].  Rules of processing
   and error codes remains unchanged.

4.4.  SFP State Synchronization

   State Synchronization operations described in Section 5.4 of
   [I-D.ietf-pce-stateful-pce]can be applied for SFP state maintenance
   as well.



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4.5.  SFP Update and Report

   A PCE can send an SFP Update request to a PCC to update one or more
   attributes of an SFP and to re-signal the SFP with the updated
   attributes.  A PCC can send an SFP state report to a PCE, and which
   contains the SFP State information.  The mechanism is described in
   [I-D.ietf-pce-stateful-pce] and can be applied for SFPs as well.

5.  Object Formats

5.1.  The OPEN Object

   This document defines a new optional TLV for use in the OPEN Object
   to indicate the PCEP speaker's Service function Chaining capability.

   The SFC-PCE-CAPABILITY TLV is an optional TLV for use in the OPEN
   Object to advertise the SFC capability during the PCEP session.  The
   format of the SFC-PCE-CAPABILITY TLV is shown in the
   followingFigure 2 :

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Type=TBD           |            length=4           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            Reserved           |             Flags             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       SFC-PCE-CAPABILITY TLV Format

   The code point for the TLV type is to be defined by IANA.  The TLV
   length is 4 octets.

   The value is TBD.

   As per [I-D.ietf-pce-stateful-pce], a PCEP speaker advertises the
   capability of instantiating PCE-initiated LSPs via the Stateful PCE
   Capability TLV (LSP-INSTANTIATION-CAPABILITY bit) conveyed in an Open
   message.  The inclusion of the SFC-PCE-CAPABILITY TLV in an OPEN
   object indicates that the sender is SFC-capable.  Both mechanisms
   indicate the SFP instantiation capability of the PCEP speaker.

5.2.  The LSP Object

   The LSP object is defined in [I-D.ietf-pce-pce-initiated-lsp] and
   included here for reference (Figure 3).





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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                PLSP-ID                | Flags |F|C|  O|A|R|S|D|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                        TLVs                                 //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                             LSP Object Format

   A new flag, called the SFC (F) flag, is introduced.  The F Flag set
   to 1 indicates that this LSP is actually an SFP.  The C flag will
   also be set to indicate it was created via a PCInitiate message.

5.2.1.  SFP Identifiers TLV

   The SFP Identifiers TLV MUST be included in the LSP object for
   Service Function Paths (SFP).

   The format and operations are TBD.

6.  Backward Compatibility

   The SFP instantiation capability PCEP protocol extensions described
   in this document MUST NOT be used if PCCs or the PCE did not
   advertise its SFP instantiation stateful capability, as per
   Section 5.1.  If this is not the case and stateful operations on SFPs
   are attempted, then a PCErr with error-type 19 (Invalid Operation)
   and error-value TBD needs to be generated.

   [Editor Note: more information on exact error value is needed]

7.  Relationship to SR

   Segment Routing (SR) technology leverages the source routing and
   tunneling paradigms where a source node can choose a path without
   relying on hop-by-hop signaling.  A stateful PCE can be used for
   computing one or more SR-TE paths taking into account various
   constraints and objective functions.  Once a path is chosen, the
   stateful PCE can instantiate an SR-TE path on a PCC using PCEP
   extensions specified in [I-D.sivabalan-pce-segment-routing].

   The SFP instantiation mechanism described in this document is not
   tightly coupled to any SFP signaling mechanism.  Thus, SR-based SFP
   can also utilize the mechanism described here and does not need any
   other specific protocol extensions.




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8.  Security Considerations

   The security considerations described in [RFC5440] and
   [I-D.ietf-pce-pce-initiated-lsp] are applicable to this
   specification.  No additional security measure is required.

9.  IANA Considerations

   TBD

10.  References

10.1.  Normative References

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

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

   [I-D.ietf-pce-pce-initiated-lsp]
              Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
              Extensions for PCE-initiated LSP Setup in a Stateful PCE
              Model", draft-ietf-pce-pce-initiated-lsp-01 (work in
              progress), June 2014.

10.2.  Informative References

   [RFC2753]  Yavatkar, R., Pendarakis, D., and R. Guerin, "A Framework
              for Policy-based Admission Control", RFC 2753, January
              2000.

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

   [RFC5440]  Vasseur, JP. and JL. Le Roux, "Path Computation Element
              (PCE) Communication Protocol (PCEP)", RFC 5440, March
              2009.

   [I-D.ietf-sfc-architecture]
              Halpern, J. and C. Pignataro, "Service Function Chaining
              (SFC) Architecture", draft-ietf-sfc-architecture-01 (work
              in progress), September 2014.





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   [I-D.ww-sfc-control-plane]
              Li, H., Wu, Q., Huang, O., Boucadair, M., Jacquenet, C.,
              and W. Haeffner, "Service Function Chain Control Plane
              Framework", draft-ww-sfc-control-plane-02 (work in
              progress), July 2014.

   [I-D.sivabalan-pce-segment-routing]
              Sivabalan, S., Medved, J., Filsfils, C., Crabbe, E.,
              Raszuk, R., Lopez, V., and J. Tantsura, "PCEP Extensions
              for Segment Routing", draft-sivabalan-pce-segment-
              routing-03 (work in progress), July 2014.

Authors' Addresses

   Qin Wu
   Huawei
   101 Software Avenue, Yuhua District
   Nanjing, Jiangsu  210012
   China

   EMail: sunseawq@huawei.com


   Dhruv Dhody
   Huawei
   Leela Palace
   Bangalore, Karnataka  560008
   INDIA

   EMail: dhruv.ietf@gmail.com


   Mohamed Boucadair
   France Telecom
   Rennes 35000
   France

   EMail: mohamed.boucadair@orange.com


   Christian Jacquenet
   France Telecom
   Rennes 35000
   France

   EMail: christian.jacquenet@orange.com





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   Jeff Tantsura
   Ericsson
   300 Holger Way
   San Jose, CA  95134
   US

   EMail: Jeff.Tantsura@ericsson.com












































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