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Versions: 00 01 02 03 04                                                
LSR Working Group                                               Yao. Liu
Internet-Draft                                              Zheng. Zhang
Intended status: Standards Track                         ZTE Corporation
Expires: August 27, 2020                               February 24, 2020


           IGP Extensions for Segment Routing Service Segment
                draft-lz-lsr-igp-sr-service-segments-01

Abstract

   This document defines extensions to the link-state routing protocols
   (IS-IS and OSPF) in order to carry service segment information via
   IGP.

Status of This Memo

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

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   This Internet-Draft will expire on August 27, 2020.

Copyright Notice

   Copyright (c) 2020 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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   described in the Simplified BSD License.





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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  IGP Extensions for Service Segments . . . . . . . . . . . . .   3
     2.1.  IS-IS Extensions  . . . . . . . . . . . . . . . . . . . .   3
     2.2.  OSPF Extensions . . . . . . . . . . . . . . . . . . . . .   5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   5.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     5.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Segments are introduced in the SR architecture [RFC8402].  Segment
   Routing (SR) allows for a flexible definition of end-to-end paths by
   encoding paths as sequences of topological sub-paths, called
   "segments".

   Service Function Chaining (SFC) [RFC7665] provides support for the
   creation of composite services that consist of an ordered set of
   Service Functions (SF) that are to be applied to packets and/or
   frames selected as a result of classification.

   [I-D.ietf-spring-sr-service-programming] describes how a service can
   be associated with a SID and how to achieve service funtion chaining
   in SR-enabled MPLS and IPv6 networks.  It also defines SR-aware and
   SR-unaware services.  For a SR-unaware service ,there has to be a SR
   proxy handling the SR processing on behalf of the service .

   [I-D.dawra-idr-bgp-ls-sr-service-segments] propose extensions to BGP-
   LS for Service Chaining to distribute the service segment information
   to SR Controller.

   The network topology is shown in figure 1.

                  SR-C
                    |
                    |
               A----1----2----3----4----5----B
                         |         |
                         |         |
                         S1        S2 proxy----S2



                 Figure 1: Figure 1:Network with Services



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   Node 1-5 are nodes capital of segment routing.  A and B are two end
   hosts.  S1 is an SR-aware Service.  S2 is an SR-unaware Service.

   SR Controller (SR-C) is connected to node 1, but may be attached to
   any node 1-5 in the network.

   SR-C is capable of receiving BGP-LS updates to discover topology, and
   calculating constrained paths between 1 and 5.

   If node 1 gets the service segment information, it can use the BGP-LS
   extensions [I-D.ietf-spring-sr-service-programming] to advertise it
   to the SR-C, but how can node 1 get it is a question.but node 1 must
   get the service segment information from other nodes at first.

   This document proposes extensions for IGP to advertise service
   segment information so that there is only one SR node needed per
   Autonomous System to be connected with the SR-C through BGP-LS to
   advertise the information to it.

   This extension works for both SR-MPLS and SRv6.

2.  IGP Extensions for Service Segments

   After an SFF like node 2 or node 4 get the service segment
   information, it needs to advertise the information to other SR nodes
   in the domain through IGP.

   How can SFFs like node 2 and node 4 get the service segment
   information from S1 and S2 proxy will be discussed further.

   There may be other alternate mechanisms and are outside of scope of
   this document.

2.1.  IS-IS Extensions

   This document introduces new TLVs for SRv6 End SID sub-TLV
   [I-D.ietf-lsr-isis-srv6-extensions] and SID/Label sub-TLV [RFC8666]
   for SR-MPLS to associate the Service SID Value with Service-related
   Information.

   One of the new TLVs is Service Chaining (SC) TLV, the TLV is defined
   as follows :









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             +---------------------------------------+
             |         Type (1 octet)                |
             +---------------------------------------+
             |        Length (1 octet)               |
             +---------------------------------------+
             |        Service Type(ST) (2 octet)     |
             +---------------------------------------+
             |        Flags (1 octet)                |
             +---------------------------------------+
             |        Traffic Type(1 octet)          |
             +---------------------------------------+
             |        RESERVED (2 octet)             |
             +---------------------------------------+

                    Figure 2:Service Chaining (SC) TLV

   where:

   Type,Length,Flags,Traffic Type and RESERVED are the same as the SC
   TLV defined in [I-D.dawra-idr-bgp-ls-sr-service-segments] chapter 2.

   Service Type: 16-bits field.The right most 12 bits categorize the
   Service: (such as "Firewall", "Classifier" etc.).

   0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | P FLAG|    Service info       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 3:Service Type(ST) Field

   The first 4 bits are P FLAG which is used to indicate the SR proxy
   type with the following values:

   0000:SR-aware function.

   0001:Static proxy.

   0010:Dynamic proxy.

   0011:Masquerading proxy.

   0100:Shared memory proxy.

   Other values are reserved for new types of proxy.

   The P FLAG is mainly defined for SR-MPLS.




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   In SRv6,although most proxy types can be represented by the END
   functions[I-D.ietf-spring-sr-service-programming], there may be
   situations that the new type of proxy cannot be associated with the
   network programming function, or the SR proxy node does not support
   standard network programming, so the P flag is still useful.

   In the IS-IS notification message, when both SR proxy END function
   and P FLAG exist, the proxy type represented by END function shall
   prevail.

   Another Optional Opaque Metadata(OM) TLV is defined in figure 4.  The
   definition and structure are the same as the OM TLV defined in
   [I-D.dawra-idr-bgp-ls-sr-service-segments] chapter 2.

              +---------------------------------------+
              |         Type (1 octet)                |
              +---------------------------------------+
              |        Length (1 octet)               |
              +---------------------------------------+
              |        Opaque  Type (2 octet)         |
              +---------------------------------------+
              |        Flags (1 octet)                |
              +---------------------------------------+
              |        Value (variable)               |
              +---------------------------------------+

                     Figure 4:Opaque Metadata(OM) TLV

2.2.  OSPF Extensions

   This document introduces new TLVs for SRv6 End SID sub-TLV
   [I-D.li-ospf-ospfv3-srv6-extensions] and SID/Label sub-TLV
   [RFC8665]for SR-MPLS to associate the Service SID Value with Service-
   related Information.

   One of the new TLVs is Service Chaining (SC) TLV,















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              +---------------------------------------+
              |         Type (2 octet)                |
              +---------------------------------------+
              |        Length (2 octet)               |
              +---------------------------------------+
              |        Service Type(ST) (2 octet)     |
              +---------------------------------------+
              |        Flags (1 octet)                |
              +---------------------------------------+
              |        Traffic Type(1 octet)          |
              +---------------------------------------+
              |        RESERVED (2 octet)             |
              +---------------------------------------+

                    Figure 5:Service Chaining (SC) TLV

   where:

   Type,Length,Flags,Traffic Type and RESERVED are the same as the SC
   TLV defined in [I-D.dawra-idr-bgp-ls-sr-service-segments] chapter 2.

   The definition and use principle of the Service Type field is the
   same as that defined in the IS-IS extension above.

   Another Optional Opaque Metadata(OM) TLV is defined in figure 6.  The
   definition and structure are the same as the OM TLV defined in
   [I-D.dawra-idr-bgp-ls-sr-service-segments] chapter 2.

              +---------------------------------------+
              |         Type (2 octet)                |
              +---------------------------------------+
              |        Length (2 octet)               |
              +---------------------------------------+
              |        Opaque  Type (2 octet)         |
              +---------------------------------------+
              |        Flags (1 octet)                |
              +---------------------------------------+
              |        Value (variable)               |
              +---------------------------------------+

                     Figure 6:Opaque Metadata(OM) TLV

3.  Security Considerations

   Procedures and protocol extensions defined in this document do not
   affect the IS-IS and OSPF security model





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4.  IANA Considerations

   TBD

5.  References

5.1.  Normative References

   [I-D.dawra-idr-bgp-ls-sr-service-segments]
              Dawra, G., Filsfils, C., Talaulikar, K., Clad, F.,
              daniel.bernier@bell.ca, d., Uttaro, J., Decraene, B.,
              Elmalky, H., Xu, X., Guichard, J., and C. Li, "BGP-LS
              Advertisement of Segment Routing Service Segments", draft-
              dawra-idr-bgp-ls-sr-service-segments-03 (work in
              progress), January 2020.

   [I-D.ietf-lsr-isis-srv6-extensions]
              Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
              Z. Hu, "IS-IS Extension to Support Segment Routing over
              IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-05
              (work in progress), February 2020.

   [I-D.ietf-spring-sr-service-programming]
              Clad, F., Xu, X., Filsfils, C., daniel.bernier@bell.ca,
              d., Li, C., Decraene, B., Ma, S., Yadlapalli, C.,
              Henderickx, W., and S. Salsano, "Service Programming with
              Segment Routing", draft-ietf-spring-sr-service-
              programming-01 (work in progress), November 2019.

   [I-D.li-ospf-ospfv3-srv6-extensions]
              Li, Z., Hu, Z., Cheng, D., Talaulikar, K., and P. Psenak,
              "OSPFv3 Extensions for SRv6", draft-li-ospf-
              ospfv3-srv6-extensions-07 (work in progress), November
              2019.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <https://www.rfc-editor.org/info/rfc7665>.

   [RFC8665]  Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler,
              H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", RFC 8665,
              DOI 10.17487/RFC8665, December 2019,
              <https://www.rfc-editor.org/info/rfc8665>.






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   [RFC8666]  Psenak, P., Ed. and S. Previdi, Ed., "OSPFv3 Extensions
              for Segment Routing", RFC 8666, DOI 10.17487/RFC8666,
              December 2019, <https://www.rfc-editor.org/info/rfc8666>.

5.2.  Informative References

   [RFC8402]  Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
              Decraene, B., Litkowski, S., and R. Shakir, "Segment
              Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
              July 2018, <https://www.rfc-editor.org/info/rfc8402>.

Authors' Addresses

   Liu Yao
   ZTE Corporation
   No. 50 Software Ave, Yuhuatai Distinct
   Nanjing
   China

   Email: liu.yao71@zte.com.cn


   Zhang Zheng
   ZTE Corporation
   No. 50 Software Ave, Yuhuatai Distinct
   Nanjing
   China

   Email: zzhang_ietf@hotmail.com






















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