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PCE                                                              S. Peng
Internet-Draft                                                  Q. Xiong
Intended status: Standards Track                         ZTE Corporation
Expires: June 1, 2020                                             F. Qin
                                                            China Mobile
                                                       November 29, 2019


                 PCE TE Constraints for Network Slicing
                    draft-peng-pce-te-constraints-02

Abstract

   This document proposes a set of extensions for PCEP to support the
   constraints for network slicing during path computation, e.g, IGP
   instance, virtual network, specific application, color template and
   FA-id etc.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 June 1, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   include Simplified BSD License text as described in Section 4.e of




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   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
     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
     3.6.  The FA-id Object  . . . . . . . . . . . . . . . . . . . .   8
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

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.  As depicted
   in [RFC4655], a PCE MUST be able to compute the path of a TE LSP by
   operating on the TED and considering bandwidth and other constraints
   applicable to the TE LSP service request.  The constraint parameters
   are provided such as metric, bandwidth, delay, affinity, etc.
   However these parameters can't meet the network slicing requirements.

   According to 5G context, network slicing is the collection of a set
   of technologies to support network service differentiation and
   meeting the diversified requirements from vertical industries.  The
   slices may be seen as virtual networks and partition the network
   resources into sub-topologies in transport network.  Multiple
   existing identifiers could be used to identify the virtual network
   resource and viewed as constraints of network slicing when PCE is
   deployed.

   A PCE always perform path computation based on the network topology
   information collected through BGP-LS [RFC7752].  BGP-LS can get



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   multiple link-state data from multiple IGP instance, or multiple
   virtual topologies from a single IGP instance.  It is necessary to
   restrict the 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 restrict PCE to use
   TE attributes of specific application The PCE MUST take the
   identifier of slicing into consideration during path computation.

   This document proposes a set of extensions for PCEP to support the
   constraints for network slicing during path computation, e.g, IGP
   instance, virtual network, specific application, color template and
   FA-id etc.

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
   PCE 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.






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   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:


       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 PCE 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.



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   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:


       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 (12 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 PCE
   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.




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   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:


       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
   PCE 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.




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   Application Specific Object-Type is 1.

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

       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 which is a specific implementation.

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 PCE will perform path computation
   based on the color template.  The same color template may be also
   defined at PCC and the exsiting constraints (i.e, metric, bandwidth,
   dealy, etc) carried 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.



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   Color Object-Type is 1.

   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): indicate a TE template, 0 is invalid value.  It is
   consistent with the Color Extended Community defined in
   [I-D.ietf-idr-tunnel-encaps], and color of SR policy defined in
   [I-D.ietf-spring-segment-routing-policy].

   Note that Color Object defined in this document is used to represent
   a TE template, 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
   proposed the 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 exsiting constraints such as
   metric, bandwidth, dealy, affinity parameters, and the sub-topology
   constraints above defined in this document.

3.6.  The FA-id Object

   FA-id defined in [I-D.ietf-lsr-flex-algo] is a short mapping of SR
   policy color to optimaze segment stack depth for the IGP area partial
   of the entire SR policy.  The overlay service that want to be carried
   over a particual SR-FA path must firstly let the SR policy supplier
   know that requirement.  There are two possible ways to map a color to
   an FA-id.  One is explicit mapping configuration within color
   template, the other is dynamic to replace a long segment list to
   short FA segment by headend or controller once the creterias
   contained in the color-template equal to that contained in FAD.

   In a PCReq message, a PCC MAY insert one FA-id object to indicate the
   above explicit FA-id mapping.  The PCE will perform path computation
   based on the FA-id.  In detailed, The PCE will check if there are



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   connectivity within the corresponding Flex-algo plane to the
   destination.  If yes, the path computation result will be represented
   as segment list with a single prefix-SID@FA for intra-domain case, or
   serveral prefix-SID@FA for inter-domain case.

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

   In general, the FA-id object is only meaningful for the domain that
   headend node belongs to.  For inter-domain case, operator MUST ensure
   the FA-id configuration of different domain are same for an E2E
   slice, when he want to explicitly indicate FA-id in PCEP message.

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

   FA-id Object-Class is TBA.

   FA-id Object-Type is 1.

   The format of the FA-id object is shown as Figure 6:


       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   FA-id       |                   Unused                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                          Figure 6: FA-id Object

   The FA-id object body has a fixed length of 4 bytes.

   FA-id (8 bits): indicate an explicit FA-id mapping.

4.  Security Considerations

   TBA

5.  Acknowledgements

   TBA







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6.  IANA Considerations

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

      +---------+-------------------------------+------------------+
      |  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]  |
      |  TBA6   |  FA-id Object                 | [this document]  |
      +---------+-------------------------------+------------------+

                                  Table 1

7.  Normative References

   [I-D.barth-pce-segment-routing-policy-cp]
              Koldychev, M., Sivabalan, S., Barth, C., Li, C., and H.
              Bidgoli, "PCEP extension to support Segment Routing Policy
              Candidate Paths", draft-barth-pce-segment-routing-policy-
              cp-04 (work in progress), October 2019.

   [I-D.ietf-idr-tunnel-encaps]
              Patel, K., Velde, G., and S. Ramachandra, "The BGP Tunnel
              Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-14
              (work in progress), September 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-09 (work in progress), October 2019.

   [I-D.ietf-lsr-flex-algo]
              Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
              A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
              algo-05 (work in progress), November 2019.

   [I-D.ietf-spring-segment-routing-policy]
              Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and
              P. Mattes, "Segment Routing Policy Architecture", draft-
              ietf-spring-segment-routing-policy-03 (work in progress),
              May 2019.






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   [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>.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [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>.





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Authors' Addresses

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

   Email: peng.shaofu@zte.com.cn


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

   Email: xiong.quan@zte.com.cn


   Fengwei Qin
   China Mobile
   Beijing
   China

   Email: qinfengwei@chinamobile.com

























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