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SPRING                                                  R. Nakamura, Ed.
Internet-Draft                                   The University of Tokyo
Intended status: Informational                                   Y. Ueno
Expires: May 2, 2020                      NTT Communications Corporation
                                                               T. Kamata
                                                     Cisco Systems, Inc.
                                                        October 30, 2019

  An Experiment of SRv6 Service Chaining at Interop Tokyo 2019 ShowNet


   This document reports lessons learned from an experimental deployment
   of service chaining with Segment Routing over the IPv6 data plane
   (SRv6) at an event network.  The service chaining part of the network
   was comprised of four SRv6-capable nodes (three products from
   different vendors), five SRv6 proxy nodes (two products from
   different vendors and three open source software), and six services.
   This network was deployed at Interop Tokyo 2019, and it successfully
   provided network connectivity and services to all the exhibitors and
   visitors on the event.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   This Internet-Draft will expire on May 2, 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

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   (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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SRv6 service chaining at Interop Tokyo 2019 ShowNet . . . . .   3
   4.  Lessons Learned . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  Transparency of SRv6 header . . . . . . . . . . . . . . .   5
     4.2.  Services that cannot co-exist with End.AM . . . . . . . .   6
     4.3.  Service liveness detection and conditional advertisement
           of service segments . . . . . . . . . . . . . . . . . . .   6
     4.4.  TTL Decrement on SRv6 Proxies . . . . . . . . . . . . . .   6
     4.5.  Control Plane Capabilities  . . . . . . . . . . . . . . .   7
     4.6.  Match Condition for Applying SRv6 Functions . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   7.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Standardizing functionalities for SRv6 service programming is still
   an ongoing agenda.  Meanwhile, some fundamental parts have begun to
   be implemented: basic transit behaviors, endpoint functions at
   ingress and egress nodes
   [I-D.filsfils-spring-srv6-network-programming], and SR proxies for
   SR-unaware services [I-D.ietf-spring-sr-service-programming].  Trying
   out such running codes and devices would clarify statuses of recent
   implementations and provide feedback to current and future
   standardization processes.

   To clarify the current status, we conducted an experiment of SRv6
   service chaining at Interop Tokyo.  Interop Tokyo is a large
   exhibition of networking technologies, and ShowNet is the event
   network built at Interop Tokyo while demonstrating new technologies
   and conducting interoperability tests.  In 2019, we deployed SRv6
   service chaining with the latest implementations at ShowNet and
   provided Internet connectivity for over 200 exhibitors and over
   155,000 visitors.  Through the experiment, we made several

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   observations from both implementation and specification perspectives:
   transparency of SRv6 header (SRH), services that cannot co-exist with
   the original masquerading proxy, how to integrate service liveness
   into advertisement of service segments, behaviors of TTL decrement on
   the masquerading proxy, necessity of control planes, and behavior of
   the longest prefix match and SRv6 functions.  This document reports
   and discusses these lessons learned from the experiment of SRv6
   service chaining.

2.  Terminology

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

3.  SRv6 service chaining at Interop Tokyo 2019 ShowNet

   The experiment was conducted on Interop Tokyo, from June 12 to June
   14, 2019.  This section describes the overview of SRv6 service
   chaining at ShowNet 2019.

   The devices contributed to the experiment are listed below:

    FUNCTION            NAME       CONTRIBUTOR
    T.Insert            FX201      Furukawa Electric
    T.Encaps            FX201      Furukawa Electric
    End.DT4             NCS55A1    Cisco Systems
                        NE40E-F1A  Huawei
    End                 FX201      Furukawa Electric
    End.AM              FX201      Furukawa Electric
                        Kamuee     NTT Communications
                        VPP        FD.io
    End.AN              TM VNFS    Trend Micro
    Variant of End.AD   Two open source software on Linux

   The variant of End.AD was the SRv6 tagging proxy designed for IPv4
   traffic encapsulated in SRv6 and implemented for ShowNet.  The detail
   is described in [I-D.eden-srv6-tagging-proxy].  In addition to the
   SRv6-capable devices, we deployed six SR-unaware services into the
   service chaining.  These services were applied to user traffic in
   accordance with service menus.

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    SERVICE         NAME                   CONTRIBUTOR
    Security        FortiGate 3601E        Fortinet
                    Lastline Defender      Lastline
                    PA-5280                Palo Alto Networks
                    Thunder 3230S CFW      A10 Networks
    CGN             Thunder 7440-11 CFW    A10 Networks

   Note that the detailed security services were different depending on
   each device (e.g., DPI, URL filtering, etc).

                           |The Internet|
             +--------+    +-----+------+    +--------+
             |Services|          |           |Services|
             +-+----+-+          |           +-+----+-+
               |    |            |             |    |
           +---+----+---+   /----+-----\   +---+----+---+
           |SRv6 Proxies+---+          +---+SRv6 Proxies|
           +------------+   |          |   +------------+
                            | Backbone |
                            |          |
                  +---------+          +--------+
                  |         \----------/        |
                  |                             |
              +---+---+   +-----+  +-----+   +--+-----+
              |NCS55A1+---+FX201|  |FX201+---+N40E-F1A|
              +---+---+   +-----+  +-----+   +--+-----+
                  |                             |
               +--+---+                      +--+---+
               |Router|                      |Router|
               +--+---+                      +--+---+
                  |                             |
               +               End users            +

          Figure 1: Overview of SRv6 Service Chaining at ShowNet

   Figure 1 illustrates an overview of the experimental topology.  End
   users, i.e., exhibitors and visitors, were accommodated by two non-
   SR-capable routers.  The two FX201 had default routes for users, and
   the FX201 applied T.Insert and T.Encaps to received IPv6 and IPv4
   packets from the users, respectively.  The packets with the SRH were
   delivered to the SRv6 proxies by the active service segments.  The
   SRv6 proxies connected to the backbone received the packets and

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   performed the proxy behaviors to take the packets through the
   services.  Lastly, Segment List[0] representing endpoint functions
   took the packets to FX201 again for End and popping the SRH, or
   NCS55A1 or NE40E-F1A for End.DT4.

   From the Internet to users, packets followed a similar path: FX201
   inserted SRH to the packets, services were applied to the packets in
   the reverse order, and FX201 removed the SRH from IPv6 packets, or
   NCS55A1 or NE40E-F1A decapsulated IPv4 packets in the SRH and outer
   IPv6 headers.

   The reason why we chose T.Insert instead of T.Encaps for IPv6 packets
   is to use the masquerading proxy (End.AM).  SR proxies excluding
   End.AM require a proxy instance or an interface for receiving traffic
   returning from the service (IFACE-IN) for each SR service policy.  In
   the ShowNet, there were over 200 individual users (exhibitors);
   therefore, there was the possibility that we needed to prepare over
   200 proxy instances or interfaces for each service.  It was possible,
   however, not reasonable for the temporal network for the three-days
   event.  Therefore, we used T.Insert and End.AM for IPv6 packets to
   multiplex service chains on a proxy instance for a service.

   End.AM is applicable to only SRv6 insertion; thus, IPv4 traffic still
   has the same issue.  To address this issue, we designed the SRv6
   tagging proxy, which is a new variant of End.AD, for IPv4 packets
   encapsulated in SRv6 [I-D.eden-srv6-tagging-proxy].  An XDP-based
   implementation was used for delivering all user traffic, and a Linux
   kernel-based implementation was also tested at ShowNet.

   Although we faced some challenges described in the next section, this
   SRv6 service chaining finally fulfilled the role.  It delivered all
   user traffic and applied the services during the period of Interop
   Tokyo 2019.

4.  Lessons Learned

   This section shares lessons learned from the experimental deployment.

4.1.  Transparency of SRv6 header

   First, we report that all the services contributed to ShowNet
   transparently delivered IPv6 packets under the End.AM proxies,
   although SRH is a new IPv6 extension header.  There were no devices
   that dropped packets due to the unrecognized extension header.

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4.2.  Services that cannot co-exist with End.AM

   When we designed the ShowNet, we intended to deploy a captive portal
   at service chaining.  However, we could not accomplish that.  The
   masquerading proxy assumes that the service under the proxy can only
   inspect, drop, or perform limited changes to the packets as noted in
   [I-D.ietf-spring-sr-service-programming].  Besides, it assumes that
   the packets returning from IFACE-IN have masqueraded SRH.  This means
   that packets originated by SR-unaware services do not have SRH;
   therefore, the packets cannot be de-masqueraded.  A captive portal is
   one of the examples that originate packets.  These SR-unaware
   services cannot be integrated with the original masquerading proxy.

   Instead, the variant 2 of masquerading proxy (Caching) defined in
   Section 6.4.3 of [I-D.ietf-spring-sr-service-programming] would be
   capable of handling such services.

4.3.  Service liveness detection and conditional advertisement of
      service segments

   Advertising service segments should be stopped when corresponding
   services are down to achieve redundancy of services in SRv6 service
   chaining.  It is also expected that SR proxies are capable of
   stopping service segment advertisements.  Meanwhile, the proxies
   contributed to ShowNet had not implemented such functionality yet
   because they were focusing on data plane functionalities at that

   Link downs do not always represent service downs; services might be
   physical appliances behind switches or virtual machines on
   hypervisors.  To detect failures on the services, we suggest that SR
   proxies should have some probing mechanisms for determining the
   statuses of services under the proxies and integrate the statuses
   with the advertisement process of the service segments.  For example,
   Bidirectional Forwarding Detection (BFD) [RFC8562] between IFACE-IN
   and IFACE-OUT would determine the liveness of the services, and the
   liveness property could be integrated into triggers for advertising
   corresponding service segments.

4.4.  TTL Decrement on SRv6 Proxies

   We confirmed that there were variations on TTL decrement behaviors of
   the End.AM proxies.  An implementation decreases TTL of outer IPv6
   headers when sending packets to IFACE-OUT, and another implementation
   does not decrease TTL on IFACE-OUT.  TTL decrement also occurs for
   forwarding packets from IFACE-IN to the next segments.  As a result,
   TTL values of packets varied depending on the proxy implementations
   that the packets passed through.  The variation of TTL decrement is

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   not a significant matter for just forwarding traffic; however, it
   would complicate Operation, Administration, and Maintenance (OAM)
   because traceroute results would also vary depending on
   implementations.  Forwarding packets to IFACE-OUT is also layer-3
   processing based on IPv6 headers and SRH; therefore, we suggest that
   TTL should be decreased on IFACE-OUT.

4.5.  Control Plane Capabilities

   The SR node implementations in ShowNet were not capable of control
   planes; therefore, we configured all the SR policies in ShowNet
   manually.  Despite manually configuring SR nodes for service chaining
   is possible, it is hard to operate in realistic environments.
   Advertising SR policies via BGP
   [I-D.ietf-idr-segment-routing-te-policy] is also an essential
   capability for service chaining that is a work in progress

4.6.  Match Condition for Applying SRv6 Functions

   The SRv6 node implementations contributed to ShowNet applied SRv6
   functions by the longest prefix match: SRv6 functions are represented
   by pairs of destination prefixes for segments and functions.  Packets
   from users to the Internet would have arbitrary destinations;
   therefore, the transit behaviors must be associated with default
   routes.  On the other hand, SR service policies inserted to packets
   vary depending on users and their service menus.  To apply different
   SR service policies by the transit behaviors with default routes, we
   used VRFs on FX201 that performed T.Insert and T.Encaps.  An SR
   service policy was associated with a transit behavior for a default
   route on a VRF.  The user networks were attached to VRFs
   corresponding to their service menus.  By this technique, we
   accomplished per-user service chains at the transit nodes.

   Per-VRF transit behavior is a practical candidate for SRv6 service
   chaining.  On the other hand, users and their traffic can be
   distinguished by source addresses of packets.  Thus, applying SRv6
   functions in accordance with source addresses or other fields in
   packets can also be a candidate implementation.  For example,
   leveraging SRv6 functions as actions of BGP Flowspec [RFC5575] is a
   possible way for inserting SR policies into packets flexibly.  This
   is a different adaptation of BGP Flowspec to SRv6 in addition to

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5.  IANA Considerations

   This document has no IANA implications.

6.  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

   This document does not introduce any new security vulnerabilities.

7.  Contributors

   J.  Cao (Huawei), T.  Fujiwara (Furukawa Network Solution), M.  Udaka
   (Furukawa Network Solution), Y.  Oga (Furukawa Network Solution), Y.
   Ohara (NTT Communications), H.  Shirokura (NTT Communications), Y.
   Yamada (Keysight Technologies), K.  Noda (Keysight Technologies), L.
   Zhou (Spirent), T.  Kawada (TOYO Corporation), T.  Matsuba (TOYO
   Corporation), Y.  Matsubayashi (Trend Micro), and H.  Nishikawa
   (Trend Micro) substantially contributed to the content of this

8.  Acknowledgements

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

9.  Normative References

              Dawra, G., Filsfils, C., daniel.bernier@bell.ca, d.,
              Uttaro, J., Decraene, B., Elmalky, H., Xu, X., Clad, F.,
              and K. Talaulikar, "BGP-LS Advertisement of Segment
              Routing Service Segments", draft-dawra-idr-bgp-ls-sr-
              service-segments-02 (work in progress), July 2019.

              Ueno, Y., Nakamura, R., and T. Kamata, "SRv6 Tagging
              proxy", draft-eden-srv6-tagging-proxy-00 (work in
              progress), October 2019.

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              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.

              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.

              Previdi, S., Filsfils, C., Mattes, P., Rosen, E., Jain,
              D., and S. Lin, "Advertising Segment Routing Policies in
              BGP", draft-ietf-idr-segment-routing-te-policy-07 (work in
              progress), July 2019.

              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.

              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-00 (work in progress), October 2019.

              Velde, G., Patel, K., Li, Z., and H. Chen, "Flowspec
              Indirection-id Redirect for SRv6", draft-ietf0-idr-srv6-
              flowspec-path-redirect-02 (work in progress), July 2019.

   [RFC5575]  Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,

   [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>.

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   [RFC8562]  Katz, D., Ward, D., Pallagatti, S., Ed., and G. Mirsky,
              Ed., "Bidirectional Forwarding Detection (BFD) for
              Multipoint Networks", RFC 8562, DOI 10.17487/RFC8562,
              April 2019, <https://www.rfc-editor.org/info/rfc8562>.

Authors' Addresses

   Ryo Nakamura (editor)
   The University of Tokyo

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

   Yukito Ueno
   NTT Communications Corporation

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

   Teppei Kamata
   Cisco Systems, Inc.

   Email: tkamata@cisco.com

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