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SPRING                                                      Y. Ueno, Ed.
Internet-Draft                            NTT Communications Corporation
Intended status: Standards Track                             R. Nakamura
Expires: April 29, 2020                          The University of Tokyo
                                                               T. Kamata
                                                     Cisco Systems, Inc.
                                                        October 27, 2019


                           SRv6 Tagging proxy
                    draft-eden-srv6-tagging-proxy-00

Abstract

   This document describes the tagging method of SRv6 proxy.  SRv6 proxy
   is an SR endpoint behavior for processing SRv6 traffic on behalf of
   an SR-unaware service.

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 https://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 29, 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
   Provisions Relating to IETF Documents
   (https://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




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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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SRv6 Tagging proxy  . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  SRv6 pseudocode . . . . . . . . . . . . . . . . . . . . .   4
       3.1.1.  Tagging proxy for inner type IPv4 . . . . . . . . . .   4
       3.1.2.  Tagging proxy for inner type IPv6 . . . . . . . . . .   5
   4.  Implementation status . . . . . . . . . . . . . . . . . . . .   5
   5.  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  SRv6 Endpoint Behaviors . . . . . . . . . . . . . . . . .   6
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Segment Routing (SR) is a source routing architecture defined in
   [RFC8402].  SR uses segment identifiers (SIDs) to identify each
   entity in an SR network.  SR can be applied two types of data plane,
   MPLS and IPv6.  IPv6 based SR is called Segment Routing IPv6 (SRv6)
   and its header format is defined in
   [I-D.ietf-6man-segment-routing-header].  As for the SRv6 packets, the
   SIDs are embedded in packets in the form of a list with the current
   index of the list, called SegmentsLeft (SL).  Packets with Segment
   Routing Headers (SRHs) are steered through the ordered list of SIDs.
   Note that the proxy behavior defined in this document can only be
   applied for SRv6 packets.

   Because SR can steer packets through arbitrary SR nodes, SR can be
   applied to Service Function Chaining (SFC).  SFC, defined in
   [RFC7665], is an architecture that realizes the on-demand
   instantiation of an ordered set of service functions.  Although there
   are differences in the specific packet steering method, SR defined in
   [RFC8402] can realize SFC and
   [I-D.xuclad-spring-sr-service-programming] describes SR proxy
   behaviors to integrate SR-unaware services to it.

   This document describes a new SRv6 proxy, called tagging proxy.  The
   tagging proxy, which is a variant of the dynamic SR proxy, supports




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   both IPv4 and IPv6 and multiple service chains by one proxy instance
   without state management.

2.  Terminology

   This document leverages the terminology proposed in [RFC8402],
   [I-D.ietf-spring-segment-routing-policy], and
   [I-D.xuclad-spring-sr-service-programming].

3.  SRv6 Tagging proxy

   The proxy is a variant of the dynamic proxy defined in
   [I-D.xuclad-spring-sr-service-programming].  The dynamic proxy caches
   the outer IPv6 header and SRH before removing it from the incoming
   traffic.  After removal of the outer IPv6 and SRH headers, the
   dynamic proxy sends the traffic to an associating service and the
   same headers are re-attached to the traffic returning from the
   service.

   For caching outer headers, the tagging proxy uses arguments of SRv6
   SIDs as indexes for cache entires.  The arguments are determined by
   the operator to correspond one-to-one with the service chains, and
   the process could be automated by the network controllers.  Upon
   receiving a packet whose active segment matches a tagging SR proxy
   function, the proxy node caches the IPv6 header and SRH.
   Corresponding cache entry for a packet is indicated by an argument
   part of the SRv6 SID.  Every time a packet arrives, a corresponding
   cache entry is updated.

   The tagging proxy removes the IPv6 header and SRH for sending the
   inner packet to the SR-unaware service.  At that time the tagging
   proxy treats the index as a "tag", that is embedded into the inner
   packet.  As a field to embed the tag, Type of Service (ToS) is used
   for IPv4 packets and Traffic Class (TC) is used for IPv6 packets.
   Note that the argument length of the SID for tagging proxy cannot be
   greater than 8-bit because of the length of ToS and TC fields.

   When the proxy node receives the packet returning from the SR-unawre
   service, the proxy node pushes the IPv6 header and SRH onto the
   packet.  The headers are retrieved from the cache entry that
   corresponds to the tag extracted from the ToS or TC field of the
   packet.

   A tagging SR proxy segment is associated with the following mandatory
   parameters:

   o  NH-ADDR: Next hop Ethernet address (only for inner type IPv4 and
      IPv6)



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   o  IFACE-OUT: Local interface for sending traffic towards the service

   o  IFACE-IN: Local interface receiving the traffic coming back from
      the service

   A tagging SR proxy segment is thus defined for a specific service.
   It is also bound to a pair of directed interfaces on the proxy.
   These may be both directions of a single interface, or opposite
   directions of two different interfaces.  The latter is recommended in
   case the service is to be used as part of a bi-directional SR SC
   policy.  If the proxy and the service both support 802.1Q, IFACE-OUT
   and IFACE-IN can also represent sub-interfaces.

3.1.  SRv6 pseudocode

3.1.1.  Tagging proxy for inner type IPv4

   Upon receiving an IPv6 packet destined for S, where S is an IPv6
   tagging proxy segment for IPv4 traffic, a node N does:

   1.   IF NH=SRH & SL > 0 & ENH == 4 THEN
   2.       Cache IPv6 Header and SRH into CACHE[ARG]
   3.       Remove the (outer) IPv6 header and its extension headers
   4.       Embed ARG into the ToS field of the (inner) IPv4 header
   5.       Forward the exposed packet on IFACE-OUT towards NH-ADDR
   6.   ELSE
   7.       Drop the packet

   Upon receiving a non-link-local IPv4 packet on IFACE-IN, a node N
   does:

   1.   IF CACHE[ToS] THEN
   2.       Set ToS value to 0
   3.       Decrement TTL and update checksum of the inner IPv4 header
   4.       Push the IPv6 header and SRH in CACHE[ToS]
   5.       Set ENH value to 4
   6.       Update the payload length of the outer IPv6 header
   7.       Lookup outer DA in appropriate table and proceed accordingly
   8.   ELSE
   9.       Drop the packet

   Note that the proxy may cache and restore the ToS value of inner IPv4
   packet in addition to outer IPv6 header and SRH if the service chain
   uses single ToS value.







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3.1.2.  Tagging proxy for inner type IPv6

   Upon receiving an IPv6 packet destined for S, where S is an IPv6
   tagging proxy segment for IPv6 traffic, a node N does:

   1.   IF NH=SRH & SL > 0 & ENH == 41 THEN
   2.       Cache IPv6 Header and SRH into CACHE[ARG]
   3.       Remove the (outer) IPv6 header and its extension headers
   4.       Embed ARG into the TC field of the (inner) IPv6 header
   5.       Forward the exposed packet on IFACE-OUT towards NH-ADDR
   6.   ELSE
   7.       Drop the packet

   Upon receiving a non-link-local IPv6 packet on IFACE-IN, a node N
   does:

   1.   IF CACHE[TC] THEN
   2.       Set TC value to 0
   3.       Decrement Hop Limit of the inner IPv6 header
   4.       Push the IPv6 header and SRH in CACHE[TC]
   5.       Set ENH value to 41
   6.       Update the payload length of the outer IPv6 header
   7.       Lookup outer DA in appropriate table and proceed accordingly
   8.   ELSE
   9.       Drop the packet

   Note that the proxy may cache and restore the TC value of inner IPv6
   packet in addition to outer IPv6 header and SRH if the service chain
   uses single ToS value.

4.  Implementation status

   This section is to be removed before publishing as an RFC.

   The tagging SR proxy is available on the below open-source
   implementations.

   o  Linux XDP based implementation by Yukito Ueno

   o  Linux kernel based implementation (out-of-tree) by Ryo Nakamura

   Also, both implementations were operated for the traffic of
   exhibitors and visitors at Interop Tokyo 2019 ShowNet.








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5.  Discussion

   This tagging proxy uses ToS or Traffic Class field as a container of
   an index of a cache entry.  Upon receiving a packet returning from an
   SR-unaware service, the index is needed for the proxy node to decide
   which cache entry should be pushed to the packet.  On the other hand,
   the usage is different from the original purpose of ToS and TC
   fields.

6.  Acknowledgements

   The authors would like to thank all the members and contributors of
   Interop Tokyo 2019 ShowNet.  The authors are also thankful to
   Francois Clad for his comments.

7.  IANA Considerations

7.1.  SRv6 Endpoint Behaviors

   This I-D requests the IANA to allocate, within the "SRv6 Endpoint
   Behaviors" sub-registry belonging to the top-level "Segment-routing
   with IPv6 dataplane (SRv6) Parameters" registry, the following
   allocations:

   Value      Description                               Reference
   --------------------------------------------------------------
   TBA        End.AT - Tagging proxy                    [This.ID]

8.  Security Considerations

   The security requirements and mechanisms described in [RFC8402],
   [I-D.ietf-6man-segment-routing-header] and
   [I-D.filsfils-spring-srv6-network-programming] also apply to this
   document.  This document does not introduce any new security
   vulnerabilities.

9.  References

9.1.  Normative References

   [I-D.filsfils-spring-srv6-network-programming]
              Filsfils, C., Camarillo, P., Leddy, J.,
              daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6
              Network Programming", draft-filsfils-spring-srv6-network-
              programming-07 (work in progress), February 2019.






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   [I-D.ietf-6man-segment-routing-header]
              Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
              Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment
              Routing Header (SRH)", draft-ietf-6man-segment-routing-
              header-26 (work in progress), October 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.xuclad-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-xuclad-spring-sr-service-
              programming-02 (work in progress), April 2019.

   [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>.

9.2.  Informative References

   [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>.

Authors' Addresses

   Yukito Ueno (editor)
   NTT Communications Corporation
   Tokyo
   JP

   Phone: +80 90 3085 5274
   Email: yukito.ueno@ntt.com











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   Ryo Nakamura
   The University of Tokyo
   Tokyo
   JP

   Phone: +81 3 5841 2710
   Email: upa@haeena.net


   Teppei Kamata
   Cisco Systems, Inc.
   Tokyo
   JP

   Email: tkamata@cisco.comt




































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