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Versions: 00

Network Working Group                                            X. Geng
Internet-Draft                                                   M. Mach
Intended status: Experimental                                     Huawei
Expires: November 8, 2019                                    May 7, 2019


                       SRv6 Based Bounded Latency
            draft-geng-detnet-srv6-based-bounded-latency-00

Abstract

   One of the goals of DetNet is to provide bounded end-to-end latency
   for critical flows.  This document defines how to leverage Segment
   Routing over IPv6 (SRv6) to implement bounded latency.  Specifically,
   new SRv6 SID function is used to specify transmission time (cycles)
   of a packet.  When forwarding devices along the path follow the
   instructions carried in the packet, the bounded latency is achieved.
   This mechanism of latency guarantee is called Cycle Specified Queuing
   and Forwarding (CSQF) which is defined in
   [I-D.chen-detnet-sr-based-bounded-latency].

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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 November 8, 2019.








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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
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology and Conventions . . . . . . . . . . . . . . . . .   3
     2.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Conventions . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  SRv6 DetNet Data Plane Overview . . . . . . . . . . . . . . .   4
     3.1.  Encapsulation . . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Functions . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Normative References  . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   Deterministic Networking(DetNet) provides a capability to carry
   specified data flows with extremely low data loss rates and bounded
   latency within a network domain.  DetNet is enabled by a group of
   technologies, such as resource allocation, service protection and
   explicit routes.([I-D.ietf-detnet-architecture])

   Segment Routing(SR) leverages the source routing paradigm.  A ingress
   node steers a packet through an ordered list of instructions, called
   "segments".  SR can be applied over IPv6 data plane using Routing
   Extension Header(SRH).  Besides routing, the segment of SRv6 can
   indicate functions which are executed locally in the node where they
   are defined.  SRv6 network programming makes it convenient to add
   sophisticated operations in the network.  ([RFC8402])

   This document describes how to implement DetNet with SRv6.  It can
   provide : 1.  Source routing, which can steer the DetNet flows go



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   through the network according to an explicit route with allocated
   resource by segment list in SRH; 2.  Network programming, which can
   give packet instructions in every node along the path to guarantee
   bounded latency.  DetNet SRv6 encapsulation and new SRv6 functions
   for DetNet are defined in this document.

   Control plane and OAM are not in the scope of this document.

2.  Terminology and Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.1.  Terminology

   Terminologies for DetNet go along with the definition in
   [I-D.ietf-detnet-architecture].  Other terminologies are defined as
   follows:

   o  NH: The IPv6 next-header field.

   o  SID: A Segment Identifier which represents a specific segment in a
      segment routing domain([RFC8402]).

   o  SRH: The Segment Routing Header
      ([I-D.ietf-6man-segment-routing-header]).

2.2.  Conventions

   Conventions in the document are defined as follows:

   o  NH=SRH means that NH is 43 with routing type 4.

   o  A SID list is represented as <S1, S2, S3> where S1 is the first
      SID to visit, S2 is the second SID to visit and S3 is the last SID
      to visit along the SR path.

   o  SRH[SL] represents the SID pointed by the SL field in the first
      SRH.  In our example, SRH[2] represents S1, SRH[1] represents S2
      and SRH[0] represents S3.

   o  (SA,DA) (S3, S2, S1; SL) represents an IPv6 packet with:

         IPv6 header with source and destination addresses SA and DA
         respectively, and next-header SRH, with SID list <S1, S2, S3>
         with SegmentsLeft = SL




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         The payload of the packet is not represented

         (S3, S2, S1; SL) represents the same SID list as <S1, S2, S3>,
         but encoded in the SRH format where the rightmost SID in the
         SRH is the first SID and the leftmost SID in the SRH is the
         last SID

3.  SRv6 DetNet Data Plane Overview

   [I-D.chen-detnet-sr-based-bounded-latency] defines a new segment that
   is called a Cycle SID, which is used to identify a cycle. .

   A Cycle SID has two meanings: 1) identify an interface/link, just
   like the adjacency segment does; 2) identify a cycle of the
   interface/link.  To specify to which interface and in which cycle a
   packet should be transmitted.  By attaching a list of Cycle Segments
   to a packet in SRH, it can not only implement the explicit route of
   the packet that is required by DetNet [I-D.ietf-detnet-architecture],
   but also specify the sending cycle at each node along the path
   without maintaining per-flow states at the intermediate and egress
   nodes.

   SRv6 Cycle SID can be represented as LOC:FUNCT:ARG::, where LOC,
   abbreviated for "LOCATION", directs the explicit route, FUNCT,
   abbreviated for "FUNCTION", directs the packet processing in the
   local node, and ARG, abbreviated for "ARGUMENTS", provides the cycle
   information.  New SID functions for DetNet is defined in section 3.2.

3.1.  Encapsulation

   The SRH for DetNet in the outer IPv6 header is showed as follows:




















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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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |  Next Header  |   Hdr Ext Len |  Routing Type |  Segment Left |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |   Last Entry  |     Flags     |              Tag              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                  Location & Function                          |
    |       (Segment List[0] for transit node with CSQF Function)   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    Cycle Information                          |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                              ...                              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                                                               |
    |                      Segment List[n]                          |
    |                                                               |
    |                                                               |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                          Optional TLVS                        |
    |                              ...                              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   where:

   o  Location&Function: the 64 most significant bits that are used for
      routing and function indication;

   o  Cycle Information : 64 bits, which are used for indicate the cycle
      number in which the packet is supposed to transmit through the
      output port;

3.2.  Functions

   New SID functions are defined as follows:

   End.X.Cycle.Indication

   1.  IF NH=SRH and SL > 0

   2.  decrement SL

   3.  reserve the value of cycle information field

   4.  update the IPv6 DA with SRH[SL]

   5.  forward to layer-3 adjacency bound to the Location



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   6.  put the packet in the queue corresponding to the cycle
       information reserved

   7.  ELSE

   8.  drop the packet

4.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

5.  Security Considerations

   TBD

6.  Acknowledgements

7.  Normative References

   [I-D.chen-detnet-sr-based-bounded-latency]
              Chen, M., Geng, X., and Z. Li, "Segment Routing (SR) Based
              Bounded Latency", draft-chen-detnet-sr-based-bounded-
              latency-00 (work in progress), October 2018.

   [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.

   [I-D.ietf-6man-segment-routing-header]
              Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and
              d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
              (SRH)", draft-ietf-6man-segment-routing-header-18 (work in
              progress), April 2019.

   [I-D.ietf-detnet-architecture]
              Finn, N., Thubert, P., Varga, B., and J. Farkas,
              "Deterministic Networking Architecture", draft-ietf-
              detnet-architecture-12 (work in progress), March 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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   [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

   Xuesong Geng
   Huawei

   Email: gengxuesong@huawei.com


   Mach(Guoyi) Chen
   Huawei

   Email: mach.chen@huawei.com


































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