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Versions: (draft-xu-isis-mpls-elc) 00 01 02 03 04 05 06 07

Network Working Group                                              X. Xu
Internet-Draft                                               Alibaba Inc
Intended status: Standards Track                                 S. Kini
Expires: January 30, 2019
                                                            S. Sivabalan
                                                             C. Filsfils
                                                                   Cisco
                                                            S. Litkowski
                                                                  Orange
                                                           July 29, 2018


  Signaling Entropy Label Capability and Entropy Readable Label Depth
                              Using IS-IS
                      draft-ietf-isis-mpls-elc-05

Abstract

   Multiprotocol Label Switching (MPLS) has defined a mechanism to load
   balance traffic flows using Entropy Labels (EL).  An ingress Label
   Switching Router (LSR) cannot insert ELs for packets going into a
   given tunnel unless an egress LSR has indicated via signaling that it
   has the capability of processing ELs, referred to as Entropy Label
   Capability (ELC), on that tunnel.  In addition, it would be useful
   for ingress LSRs to know each LSR's capability of reading the maximum
   label stack depth and performing EL-based load-balancing, referred to
   as Entropy Readable Label Depth (ERLD), in the cases where stacked
   LSPs are used for whatever reasons.  This document defines mechanisms
   to signal these two capabilities using IS-IS.  These mechanisms are
   useful when the label advertisement is also done via IS-IS.  In
   addition, this document introduces the Non-IGP Functional
   Capabilities Sub-TLV for advertising IS-IS router's actual non-IGP
   functional capabilities.  ELC is one of such non-IGP functional
   capabilities.

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




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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 January 30, 2019.

Copyright Notice

   Copyright (c) 2018 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
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   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 . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Non-IGP Functional Capabilities Sub-TLV . . . . . . . . . . .   3
   4.  Advertising ELC Using IS-IS . . . . . . . . . . . . . . . . .   4
   5.  Advertising ERLD Using IS-IS  . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   [RFC6790] describes a method to load balance Multiprotocol Label
   Switching (MPLS) traffic flows using Entropy Labels (EL).  [RFC6790]
   introduces the concept of Entropy Label Capability (ELC) and defines
   the signalings of this capability via MPLS signaling protocols.
   Recently, mechanisms are being defined to signal labels via link-
   state Interior Gateway Protocols (IGP) such as IS-IS
   [I-D.ietf-isis-segment-routing-extensions].  In such scenario, the
   signaling mechanisms defined in [RFC6790] are inadequate.  This draft
   defines a mechanism to signal the ELC [RFC6790] using IS-IS.  This
   mechanism is useful when the label advertisement is also done via IS-
   IS.



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   In addition, in the cases where stacked LSPs are used for whatever
   reasons (e.g., SR-MPLS [I-D.ietf-spring-segment-routing-mpls]), it
   would be useful for ingress LSRs to know each intermediate LSR's
   capability of reading the maximum label stack depth and performing
   EL-based load-balancing.  This capability, referred to as Entropy
   Readable Label Depth (ERLD) as defined in
   [I-D.ietf-mpls-spring-entropy-label] may be used by ingress LSRs to
   determine whether it's necessary to insert an EL for a given LSP of
   the stacked LSP tunnel in the case where there has already been at
   least one EL in the label stack [I-D.ietf-mpls-spring-entropy-label].

2.  Terminology

   This memo makes use of the terms defined in [RFC6790] and [RFC4971].

   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].

3.  Non-IGP Functional Capabilities Sub-TLV

   This document defines the Non-IGP Functional Capabilities Sub-TLV
   with Sub-TLV type of TBD1 within the body of the IS-IS Router
   Capability TLV.  An IS-IS router advertising an IS-IS Router
   Capability TLV MAY include the Non-IGP Functional Capabilities Sub-
   TLV.  The Sub-TLV MUST reflect the advertising IS-IS router's actual
   non-IGP functional capabilities in the flooding scope of the
   containing Router Capability TLV.

   The format of the Router Non-IGP Functional Capabilities Sub-TLV is
   as follows:

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Type=TBD1  |    Length=4   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |               Non-IGP Functional Capabilities                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             Figure 1: Non-IGP Functional Capabilities Sub-TLV Format

      Type: TBD1.

      Length: Indicates the length of the value portion in octets and
      will be a multiple of 4 octets dependent on the number of
      capabilities advertised.  Initially, the length will be 4,
      denoting 4 octets of non-IGP functional capability bits.




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      Value: A variable-length sequence of capability bits rounded to a
      multiple of 4 octets padded with undefined bits.  Initially, there
      are 4 octets of capability bits.  Bits are numbered left to right
      starting with the most significant bit being bit 0.

   The Non-IGP Functional Capabilities Sub-TLV MAY be followed by
   optional Sub-TLVs that further specify a non-IGP functional
   capability.  The specifications for non-IGP functional capabilities
   advertised in this Sub-TLV MUST describe protocol behavior and
   address backwards compatibility.

4.  Advertising ELC Using IS-IS

   One bit of the Non-IGP Functional Capability Bits (Bit 0 is desired)
   is to be assigned by the IANA for the ELC [RFC6790].  If a router has
   multiple line cards, the router MUST NOT announce the ELC [RFC6790]
   unless all of its linecards are capable of processing ELs.

5.  Advertising ERLD Using IS-IS

   A new MSD-type of the Node MSD sub-TLV
   [I-D.ietf-isis-segment-routing-msd], called ERLD is defined to
   advertise the ERLD of a given router.  As shown in Figure 2, it is
   formatted as described in [I-D.ietf-isis-segment-routing-msd] with a
   new MSD-Type code to be assigned by IANA (the type code of 2 is
   desired) and the Value field is set to the ERLD in the range between
   0 to 255.  The scope of the advertisement depends on the application.
   If a router has multiple linecards with different capabilities of
   reading the maximum label stack deepth, the router MUST advertise the
   smallest one.

         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
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        | MSD-Type=TBD2 |     ERLD      |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 2: ERLD MSD-Type Format

6.  Acknowledgements

   The authors would like to thank Yimin Shen, George Swallow, Acee
   Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura and Carlos
   Pignataro for their valuable comments.








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7.  IANA Considerations

   This document requests IANA to allocate one sub-TLV type of the
   Router Capability TLV registry for the Non-IGP Functional
   Capabilities Sub-TLV.  Futhermore, this document requests IANA to
   creat a subregistry for "Non-IGP Functional Capability Bits" within
   the "Interior Gateway Protocol (IGP) Parameters" registry.  This
   subregistry is comprised of the fields Bit Number, Capability Name,
   and Reference.  Initially, one bit is reqested to be assigned for the
   ELC.  The registration procedure is "Expert Review" as defined in
   [RFC8126].  The following values are defined by this document:

         Bit No.     Capability Name                  Reference
         -----       ---------------------            -------------
         0           ELC                              This document
         1-31        Unassigned                       This document

              Figure 3: Non-IGP Functional Capability Bits Registry

   IANA is requested to allocate a MSD type (the type code of 2 is
   desired) from the "IGP MSD Types" registry for ERLD.

8.  Security Considerations

   The security considerations as described in [RFC4971] is applicable
   to this document.  This document does not introduce any new security
   risk.

9.  References

9.1.  Normative References

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
              Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
              "IS-IS Extensions for Segment Routing", draft-ietf-isis-
              segment-routing-extensions-19 (work in progress), July
              2018.

   [I-D.ietf-isis-segment-routing-msd]
              Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
              "Signaling MSD (Maximum SID Depth) using IS-IS", draft-
              ietf-isis-segment-routing-msd-13 (work in progress), July
              2018.







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   [I-D.ietf-spring-segment-routing-mpls]
              Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-14
              (work in progress), June 2018.

   [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>.

   [RFC4971]  Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
              "Intermediate System to Intermediate System (IS-IS)
              Extensions for Advertising Router Information", RFC 4971,
              DOI 10.17487/RFC4971, July 2007,
              <https://www.rfc-editor.org/info/rfc4971>.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, DOI 10.17487/RFC6790, November 2012,
              <https://www.rfc-editor.org/info/rfc6790>.

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/info/rfc8126>.

9.2.  Informative References

   [I-D.ietf-mpls-spring-entropy-label]
              Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
              Shakir, R., and J. Tantsura, "Entropy label for SPRING
              tunnels", draft-ietf-mpls-spring-entropy-label-12 (work in
              progress), July 2018.

Authors' Addresses

   Xiaohu Xu
   Alibaba Inc

   Email: xiaohu.xxh@alibaba-inc.com






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   Sriganesh Kini

   Email: sriganeshkini@gmail.com


   Siva Sivabalan
   Cisco

   Email: msiva@cisco.com


   Clarence Filsfils
   Cisco

   Email: cfilsfil@cisco.com


   Stephane Litkowski
   Orange

   Email: stephane.litkowski@orange.com






























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