OSPF Working Group                                                 X. Xu
Internet-Draft                                                    Huawei
Intended status: Standards Track                                 S. Kini
Expires: July 7, 2018
                                                            S. Sivabalan
                                                             C. Filsfils
                                                                   Cisco
                                                            S. Litkowski
                                                                  Orange
                                                         January 3, 2018


Signaling Entropy Label Capability and Readable Label-stack Depth Using
                                  OSPF
                      draft-ietf-ospf-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, referred to as Readable Label-stack Depth (RLD),
   in the cases where stacked LSPs are used for whatever reasons.  This
   document defines mechanisms to signal these two capabilities using
   OSPF.  These mechanisms are useful when the label advertisement is
   also done via OSPF.  In addition, this document introduces the Router
   Non-OSPF Functional Capabilities TLV for advertising OSPF router's
   actual non-OSPF functional capabilities.  ELC is one of such non-OSPF
   functional capabilities.

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




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   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 July 7, 2018.

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
   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 . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Non-OSPF Functional Capabilities TLV  . . . . . . . . . . . .   3
   4.  Advertising ELC Using OSPF  . . . . . . . . . . . . . . . . .   4
   5.  Advertising RLD Using OSPF  . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

.  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 OSPF



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   [I-D.ietf-ospf-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 OSPF.  This
   mechanism is useful when the label advertisement is also done via
   OSPF.  In addition, in the cases where stacked LSPs are used for
   whatever reasons (e.g., SPRING-MPLS
   [I-D.ietf-spring-segment-routing-mpls]), it would be useful for
   ingress LSRs to know each LSR's capability of reading the maximum
   label stack depth.  This capability, referred to as Readable Label-
   stack Depth (RLD) 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].

.  Terminology

   This memo makes use of the terms defined in [RFC6790] and [RFC7770].

.  Non-OSPF Functional Capabilities TLV

   This document defines the Router Non-OSPF Functional Capabilities TLV
   for advertisement in the OSPF Router Information LSA.  An OSPF router
   advertising an OSPF RI LSA MAY include the Router Non-OSPF Functional
   Capabilities TLV.  If included, it MUST be included in the first
   instance of the LSA.  Additionally, the TLV MUST reflect the
   advertising OSPF router's actual non-OSPF functional capabilities in
   the flooding scope of the containing OSPF RI LSA.

   The format of the Router Non-OSPF Functional Capabilities 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             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                 Non-OSPF Functional Capabilities              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
             Figure 1: Non-OSPF Functional Capabilities 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-OSPF 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-OSPF Functional Capabilities TLV MAY be followed by optional
   TLVs that further specify a non-OSPF functional capability.  In
   contrast to the OSPF Router Functional Capabilities TLV, the non-OSPF
   functional capabilities advertised in this TLV have no impact on the
   OSPF protocol operation.  The specifications for non-OSPF functional
   capabilities advertised in this TLV MUST describe protocol behavior
   and address backwards compatibility.

.  Advertising ELC Using OSPF

   One bit of the Non-OSPF Functional Capability Bits 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.

.  Advertising RLD Using OSPF

   A new TLV within the body of the OSPF RI LSA, called RLD TLV is
   defined to advertise the capability of the router to read the maximum
   label stack depth.  As showed in Figure 2, it is formatted as
   described in Section 2.3 of [RFC7770] with a Type code to be assigned
   by IANA and a Length of one.  The Value field is set to the maximum
   readable label stack depth in the range between 1 to 255.  The scope
   of the advertisement depends on the application but it is RECOMMENDED
   that it SHOULD be domain-wide.  If a router has multiple line cards
   with different capabilities of reading the maximum label stack depth,
   the router MUST advertise the smallest one in the RLD TLV.  This TLV
   is applicable to both OSPFv2 and OSPFv3.

        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=TBD2           |            Length             |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |     RLD       |
       +-+-+-+-+-+-+-+-+
                          Figure 2: RLD TLV Format

.  Acknowledgements

   The authors would like to thank Yimin Shen, George Swallow, Acee
   Lindem, Carlos Pignataro and Bruno Decraene for their valuable
   comments and suggestions.



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.  IANA Considerations

   This document requests IANA to allocate one TLV type from the OSPF RI
   TLVs registry for the Non-OSPF Functional Capabilities TLV.
   Futhermore, this document requests IANA to creat a subregistry for
   "Non-OSPF Functional Capability Bits" within the "Open Shortest Path
   First v2 (OSPFv2) 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.  All Non-
   OSPF Functional Capability TLV additions are to be assigned through
   IETF Review [RFC5226].

   This document also requests IANA to allocate one TLV type from the
   OSPF RI TLVs registry for the RLDC TLV.

.  Security Considerations

   The security considerations as described in [RFC7770] is applicable
   to this document.  This document does not introduce any new security
   risk.

.  References

9.1.  Normative 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-07 (work in
              progress), October 2017.

   [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>.

   [RFC7770]  Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
              S. Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
              February 2016, <https://www.rfc-editor.org/info/rfc7770>.

9.2.  Informative References

   [I-D.ietf-ospf-segment-routing-extensions]
              Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", draft-ietf-ospf-segment-
              routing-extensions-24 (work in progress), December 2017.



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   [I-D.ietf-spring-segment-routing-mpls]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-11
              (work in progress), October 2017.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <https://www.rfc-editor.org/info/rfc5226>.

   [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>.

Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxh.mail@gmail.com


   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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