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PCE                                                              S. Peng
Internet-Draft                                                  Q. Xiong
Intended status: Standards Track                         ZTE Corporation
Expires: January 30, 2020                                  July 29, 2019


                   PCEP Extension for TE Constraints
                    draft-peng-pce-te-constraints-00

Abstract

   This document proposes a set of constraints for PCEP to configure PCE
   to use specific virtual network topology or application attributes
   during path computation.  A simple COLOR parameter is also introduced
   to simplify network operations.

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
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   This Internet-Draft will expire on January 30, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   3.  PCEP Extensions for Constraints . . . . . . . . . . . . . . .   3
     3.1.  Source Protocol Object  . . . . . . . . . . . . . . . . .   3
     3.2.  Multi-topology Object . . . . . . . . . . . . . . . . . .   4
     3.3.  The AII Object  . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Application Specific Object . . . . . . . . . . . . . . .   6
     3.5.  The Color Object  . . . . . . . . . . . . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   [RFC5440] describes the Path Computation Element Protocol (PCEP)
   which is used between a Path Computation Element (PCE) and a Path
   Computation Client (PCC) (or other PCE) to enable computation of
   Multi-protocol Label Switching (MPLS) for Traffic Engineering Label
   Switched Path (TE LSP).  PCEP Extensions for the Stateful PCE Model
   [RFC8231] describes a set of extensions to PCEP to enable active
   control of MPLS-TE and Generalized MPLS (GMPLS) tunnels.  [RFC8281]
   describes the setup and teardown of PCE-initiated LSPs under the
   active stateful PCE model, without the need for local configuration
   on the PCC, thus allowing for dynamic centralized control of a
   network.

   Till now there are known path computation constraint parameters such
   as metric, bandwidth, delay, affinity, etc.  However all these
   parameters can't meet increasing service requirements.  A PCE always
   perform path computation based on the network topology information
   collected through BGP-LS [RFC7752].  BGP-LS can get multiple link-
   state database from multiple IGP instance, or multiple virtual
   topology from a single IGP instance.  It is necessary to limit PCE to
   a small topology scope during path computation for some special
   purpose.  BGP-LS can also get application specific TE attributes for
   a link, it is also necessary to limit PCE to use TE attributes of
   specific application during path computation.

   This document will extend PCEP to support some new constraint
   parameters during path computation, e.g, IGP instance, virtual
   network, specific application, as well as a simple COLOR parameter.




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2.  Conventions used in this document

2.1.  Terminology

   The terminology is defined as [RFC5440] and [RFC7752].

2.2.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  PCEP Extensions for Constraints

3.1.  Source Protocol Object

   The Source Protocol object is optional and can be used for several
   purposes.

   In a PCReq message, a PCC MAY insert one Source Protocol object to
   indicate the source protocol that MUST be considered by the PCE, The
   later will perform path computation based on the sub-topology
   identified by the specific source protocol.  The absence of the
   Source Protocol object MUST be interpreted by the PCE as a path
   computation request for which no constraints need be applied to any
   of the source protocols.

   In a PCRep/PCInit/PCUpd message, the Source Protocol object MAY be
   inserted so as to provide the source protocol information for the
   computed path.

   Only one Source Protocol Object could be inserted in the above
   messages, otherwise the first one MUST be considered and others MUST
   be ignored.

   Source Protocol Object-Class is TBA.

   Source Protocol Object-Type is 1.

   The format of the Source Protocol object is shown as Figure 1:









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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  Protocol-ID  |                  Reserved                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                          Identifier                           |
      |                           (64 bits)                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                     Figure 1: Source Protocol Object

   The Source Protocol object body has a fixed length of 12 bytes.

   Protocol-ID (8 bits): defined in [RFC7752] section 3.2.

   Reserved (24 bits): This field MUST be set to zero on transmission
   and MUST be ignored on receipt.

   Identifier (64 bits): defined in [RFC7752] section 3.2.

3.2.  Multi-topology Object

   The Multi-topology object is optional and can be used for several
   purposes.

   In a PCReq message, a PCC MAY insert one Multi-topology object to
   indicate the sub-topology of an IGP instance that MUST be considered
   by the PCE, The later will perform path computation based on the sub-
   topology identified by the specific Multi-Topology ID within a source
   protocol.  The absence of the Multi-topology object MUST be
   interpreted by the PCE as a path computation request for which no
   constraints need be applied to any of the multi-topologies.

   In a PCRep/PCInit/PCUpd message, the Multi-topology object MAY be
   inserted so as to provide the Multi-topology information for the
   computed path.

   Only one Multi-topology Object could be inserted in the above
   messages, otherwise the first one MUST be considered and others MUST
   be ignored.  It MUST be inserted with a Source Protocol Object, if
   not it MUST be ignored.

   Multi-topology Object-Class is TBA.

   Multi-topology Object-Type is 1.

   The format of the Multi-topology object is shown as Figure 2:



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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |R R R R|   Multi-Topology ID   |          Reserved             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                      Figure 2: Multi-topology Object

   The Multi-topology object body has a fixed length of 4 bytes.

   Multi-Topology ID (16 bits): Semantics of the IS-IS MT-ID are defined
   in Section 7.2 of [RFC5120].  Semantics of the OSPF MT-ID are defined
   in Section 3.7 of [RFC4915].  If the value is derived from OSPF, then
   the upper 9 bits MUST be set to 0.  Bits R are reserved and SHOULD be
   set to 0 when originated and ignored on receipt.

   Reserved (16 bits): This field MUST be set to zero on transmission
   and MUST be ignored on receipt.

3.3.  The AII Object

   The AII object is optional and can be used for several purposes.

   In a PCReq message, a PCC MAY insert one AII object to indicate the
   global virtual network that MUST be considered by the PCE, The later
   will perform path computation based on the intra or inter-domain sub-
   topology identified by the specific AII, which is independent of
   routing protocols such as IGP/BGP.  The absence of the AII object
   MUST be interpreted by the PCE as a path computation request for
   which no constraints need be applied to any of the virtual network,
   i.e, a default AII (0) will be applied.

   In a PCRep/PCInit/PCUpd message, the AII object MAY be inserted so as
   to provide the network slicing information for the computed path.

   Only one AII Object could be inserted in the above messages,
   otherwise the first one MUST be considered and others MUST be
   ignored.

   AII Object-Class is TBA.

   AII Object-Type is 1.

   The format of the AII object is shown as 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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           AII                                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                           Figure 3: AII Object

   The AII object body has a fixed length of 4 bytes.

   AII (32 bits): Administrative Instance Identifier defined in
   [I-D.peng-lsr-network-slicing].

3.4.  Application Specific Object

   The Application Specific object is optional and can be used for
   several purposes.

   In a PCReq message, a PCC MAY insert one Application Specific object
   to indicate the appliaction that MUST be considered by the PCE, The
   later will perform path computation using the specific application
   attributes.  The absence of the Application Specific object MUST be
   interpreted by the PCE as a path computation request for which no
   constraints need be applied to any of the Application Specific
   attributes.

   In a PCRep/PCInit/PCUpd message, the Application Specific object MAY
   be inserted so as to provide the Application Specific information for
   the computed path.

   Only one Application Specific Object could be inserted in the above
   messages, otherwise the first one MUST be considered and others MUST
   be ignored.

   Application Specific Object-Class is TBA.

   Application Specific Object-Type is 1.

   The format of the Application Specific object is shown as Figure 4:











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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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Standard Application ID                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               User Defined Application ID                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                   Figure 4: Application Specific Object

   The Application Specific object body has a fixed length of 8 bytes.

   Standard Application ID : Represents a bit-position value for a
   single STANDARD application that is defined in the IANA "IGP
   Parameters" registries under the "Link Attribute Applications"
   registry [I-D.ietf-isis-te-app].

   User Defined Application ID : Represents a single user defined
   application that is implementation specific.

3.5.  The Color Object

   The Color object is optional and can be used for several purposes.

   In a PCReq message, a PCC MAY insert one Color object to indicate the
   traffic engineering purpose that is recognized by the both PCE and
   PCC with no conflict meaning.  The later will perform path
   computation based on the color template defined in local and extract
   the detailed constraints from the color template.  Note the same
   color template is also defined in PCC side.  At this time, any other
   traditional constraints (i.e, metric, bandwidth, dealy, etc) that is
   directly contained in the message MUST be ignored.  The absence of
   the Color object MUST be interpreted by the PCE as a path computation
   request for which traditional constraints that are contained in
   message need be applied.

   In a PCRep/PCInit/PCUpd message, the Color object MAY be inserted so
   as to provide the TE purpose information for the computed path, the
   PCC recognize the color value that match a local color-template.

   Only one Color Object could be inserted in the above messages,
   otherwise the first one MUST be considered and others MUST be
   ignored.

   Color Object-Class is TBA.

   Color Object-Type is 1.



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   The format of the Color object is shown as Figure 5:


       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                           Color                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                          Figure 5: Color Object

   The Color object body has a fixed length of 4 bytes.

   Color (32 bits): Represent a TE purpose, 0 is invalid value.  It is
   consistent with the meaning of Color Extended Community that is
   defined in [I-D.ietf-idr-tunnel-encaps], and color of SR policy that
   is also defined in [I-D.ietf-spring-segment-routing-policy].

   Note that Color Object defined in this document is used to represent
   a TE purpose, it can be suitable for any TE instance such as RSVP-TE,
   SR-TE, SR-policy.  [I-D.barth-pce-segment-routing-policy-cp] has
   already been using SR policy KEY (that also includes a color
   information) as an association group KEY to associate many candidate
   paths, however it is only for association purpose but not constraint
   purpose for path computation.

   A color tempate can be defined to use any constraints such as
   traditional metric, bandwidth, dealy, affinity parameters, but also
   any sub-topology parameters above defined in this document.  Both PCE
   and PCC MUST have the same understanding for a same color value.

4.  Security Considerations

   TBA

5.  Acknowledgements

   TBA

6.  IANA Considerations

   IANA is requested to make allocations from the registry, as follows:








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       +--------+------------------------------+------------------+
       | Value  |            Object            |    Reference     |
       +--------+------------------------------+------------------+
       |  TBA1  |    Source Protocol Object    | [this document]  |
       |  TBA2  |    Multi-topology Object     | [this document]  |
       |  TBA3  |          AII Object          | [this document]  |
       |  TBA4  | Application Specific Object  | [this document]  |
       |  TBA5  |         Color Object         | [this document]  |
       +--------+------------------------------+------------------+

                                  Table 1

7.  Normative References

   [I-D.barth-pce-segment-routing-policy-cp]
              Koldychev, M., Sivabalan, S., Barth, C., and C. Li, "PCEP
              extension to support Segment Routing Policy Candidate
              Paths", draft-barth-pce-segment-routing-policy-cp-03 (work
              in progress), July 2019.

   [I-D.ietf-idr-tunnel-encaps]
              Patel, K., Velde, G., Ramachandra, S., and E. Rosen, "The
              BGP Tunnel Encapsulation Attribute", draft-ietf-idr-
              tunnel-encaps-13 (work in progress), July 2019.

   [I-D.ietf-isis-te-app]
              Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
              J. Drake, "IS-IS TE Attributes per application", draft-
              ietf-isis-te-app-06 (work in progress), April 2019.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Sivabalan, S., daniel.voyer@bell.ca, d.,
              bogdanov@google.com, b., and P. Mattes, "Segment Routing
              Policy Architecture", draft-ietf-spring-segment-routing-
              policy-03 (work in progress), May 2019.

   [I-D.peng-lsr-network-slicing]
              Peng, S., Chen, R., and G. Mirsky, "Packet Network Slicing
              using Segment Routing", draft-peng-lsr-network-slicing-00
              (work in progress), February 2019.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.






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   [RFC4915]  Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
              Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
              RFC 4915, DOI 10.17487/RFC4915, June 2007,
              <https://www.rfc-editor.org/info/rfc4915>.

   [RFC5120]  Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
              Topology (MT) Routing in Intermediate System to
              Intermediate Systems (IS-ISs)", RFC 5120,
              DOI 10.17487/RFC5120, February 2008,
              <https://www.rfc-editor.org/info/rfc5120>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

Authors' Addresses

   Shaofu Peng
   ZTE Corporation
   No.50 Software Avenue
   Nanjing, Jiangsu  210012
   China

   Email: peng.shaofu@zte.com.cn




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   Quan Xiong
   ZTE Corporation
   No.6 Huashi Park Rd
   Wuhan, Hubei  430223
   China

   Email: xiong.quan@zte.com.cn












































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