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Advertising per-node administrative tags in OSPF
draft-hegde-ospf-node-admin-tag-01

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This is an older version of an Internet-Draft whose latest revision state is "Replaced".
Authors Shraddha Hegde , Harish Raghuveer , Hannes Gredler , Rob Shakir , Anton Smirnov
Last updated 2014-02-14
Replaced by draft-ietf-ospf-node-admin-tag, RFC 7777
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draft-hegde-ospf-node-admin-tag-01
Open Shortest Path First IGP                                    S. Hegde
Internet-Draft                                              H. Raghuveer
Intended status: Standards Track                              H. Gredler
Expires: August 18, 2014                          Juniper Networks, Inc.
                                                               R. Shakir
                                                         British Telecom
                                                              A. Smirnov
                                                     Cisco Systems, Inc.
                                                       February 14, 2014

            Advertising per-node administrative tags in OSPF
                   draft-hegde-ospf-node-admin-tag-01

Abstract

   This document describes an extension to OSPF protocol [RFC2328] to
   add an optional operational capability, that allows tagging and
   grouping of the nodes in an OSPF domain.  This allows
   simplification,ease of management and control over route and path
   selection based on configured policies.

   This document describes the protocol extensions to disseminate per-
   node admin-tags to the OSPFv2 and OSPFv3 protocol.

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 http://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 August 18, 2014.

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Copyright Notice

   Copyright (c) 2014 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
   (http://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  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Administrative Tag TLV  . . . . . . . . . . . . . . . . . . . . 3
   4.  OSPF per-node administrative tag TLV  . . . . . . . . . . . . . 3
     4.1.  TLV format  . . . . . . . . . . . . . . . . . . . . . . . . 3
     4.2.  Elements of procedure . . . . . . . . . . . . . . . . . . . 4
   5.  Applications  . . . . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . . . 7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   8.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     9.2.  Informative References  . . . . . . . . . . . . . . . . . . 8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 8

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1.  Introduction

   This document provides mechanisms to advertise per-node
   administrative tags in the OSPF Router Information LSA [RFC4970].  In
   certain path-selection applications like for example in traffic-
   engineering or LFA backup selection there is a need to tag the nodes
   based on their roles in the network and have policies to prefer or
   prune a certain group of nodes.

2.  Applicability

   For the purpose of advertising per-node administrative tags within
   OSPF a new TLV is proposed.  Because path selection is a functional
   set which applies both to TE and non-TE applications, this new TLV is
   carried in the Router Information LSA (RI LSA) [RFC4970]

3.  Administrative Tag TLV

   An administrative Tag is a 32-bit integer value that can be used to
   identify a group of nodes in the OSPF domain.

   The new TLV defined will be carried within an RI LSA for OSPFV2 and
   OSPFV3.  Router information LSA [RFC4970] can have link,area or AS
   level flooding scope.  Choosing the flooding scope to flood the group
   tags are defined by the policies and is a local matter.

   The TLV specifies one or more administrative tag values.  An OSPF
   node advertises the set of groups it is part of in the OSPF domain.
   (for example, all PE-nodes are configured with certain tag value, all
   P-nodes are configured with a different tag value in a domain).

4.  OSPF per-node administrative tag TLV

4.1.  TLV format

   The format of the TLVs within the body of an RI LSA is the same as
   the format used by the Traffic Engineering Extensions to OSPF
   [RFC3630].

   The LSA payload consists of one or more nested Type/Length/Value
   (TLV) triplets.  The format of each TLV is:

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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Administrative Tag #1                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Administrative Tag #2                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                                                             //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Administrative Tag #N                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 1: OSPF per-node Administrative Tag TLV

   Type : TBA

   Length: A 16-bit field that indicates the length of the value portion
   in octets and will be a multiple of 4 octets dependent on the number
   of tags advertised.

   Value: A sequence of multiple 4 octets defining the administrative
   tags.  The number of tags carried in this TLV is restricted to 64.

4.2.  Elements of procedure

   Meaning of the Node administrative tags is generally opaque to OSPF.
   Router advertising the Node administrative tag (or tags) may be
   configured to do so without knowing (or even explicitly supporting)
   functionality implied by the tag.

   Interpretation of the tag values is implementation-specific.  The
   meaning of a Node administrative tag is defined by the network local
   policy and is controlled via the configuration.  There are no tag
   values defined by this specification.

   The semantics of the tag order are implementation-dependent.  That
   is, there is no implied meaning to the ordering of the tags that
   indicates a certain operation or set of operations that need to be
   performed based on the ordering.

   Each tag SHOULD be treated as an independent identifier that MAY be
   used in policy to perform a policy action.  Whether or not tag A
   precedes or succeeds tag B SHOULD not change the meaning of the tag
   set.

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   To avoid incomplete or inconsistent interpretations of the Node
   administrative tags the same tag value MUST NOT be advertised by a
   router in RI LSAs of different scopes.  The same tag MAY be
   advertised in multiple RI LSAs of the same scope, for example, OSPF
   Area Border Router (ABR) may advertise the same tag in area-scope RI
   LSAs in multiple areas connected to the ABR.

   The Node administrative tags are not meant to be extended by the
   future OSPF standards.  The new OSPF extensions MUST NOT require use
   of Node administrative tags or define well-known tag values.
   Instead, the future OSPF extensions must define their own data
   signaling tailored to the needs of the feature.

   Being part of the RI LSA, the Node administrative tag TLV must be
   reasonably small and stable.  In particular, but not limited to,
   implementations supporting the Node administrative tags MUST NOT tie
   advertised tags to changes in the network topology (both within and
   outside the OSPF domain) or reachability of routes.

5.  Applications

   This section lists several examples of how implementations might use
   the Node administrative tags.  These examples are given only to
   demonstrate generic usefulness of the router tagging mechanism.
   Implementation supporting this specification is not required to
   implement any of the use cases.  It is also worth noting that in some
   described use cases routers configured to advertise tags help other
   routers in their calculations but do not themselves implement the
   same functionality.

   1.  Service auto-discovery

       Router tagging may be used to automatically discover group of
       routers sharing a particular service.

       For example, service provider might desire to establish full mesh
       of MPLS TE tunnels between all PE routers in the area of MPLS VPN
       network.  Marking all PE routers with a tag and configuring
       devices with a policy to create MPLS TE tunnels to all other
       devices advertising this tag will automate maintenance of the
       full mesh.  When new PE router is added to the area, all other PE
       devices will open TE tunnels to it without the need of
       reconfiguring them.

   2.  Fast-Rerouting policy

       Increased deployment of Loop Free Alternates (LFA) as defined in

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       [RFC5286] poses operation and management challenges.
       [I-D.litkowski-rtgwg-lfa-manageability] proposes policies which,
       when implemented, will ease LFA operation concerns.

       One of the proposed refinements is to be able to group the nodes
       in IGP domain with administrative tags and engineer the LFA based
       on configured policies.

       (a)  Administrative limitation of LFA scope

            Service provider access infrastructure is frequently
            designed in layered approach with each layer of devices
            serving different purposes and thus having different
            hardware capabilities and configured software features.
            When LFA repair paths are being computed, it may be
            desirable to exclude devices from being considered as LFA
            candidates based on their layer.

            For example, if the access infrastructure is divided into
            the Access, Distribution and Core layers it may be desirable
            for a Distribution device to compute LFA only via
            Distribution or Core devices but not via Access devices.
            This may be due to features enabled on Access routers; due
            to capacity limitations or due to the security requirements.
            Managing such a policy via configuration of the router
            computing LFA is cumbersome and error prone.

            With the Node administrative tags it is possible to assign a
            tag to each layer and implement LFA policy of computing LFA
            repair paths only via neighbors which advertise the Core or
            Distribution tag.  This requires minimal per-node
            configuration and network automatically adapts when new
            links or routers are added.

       (b)  LFA calculation optimization

            Calculation of LFA paths may require significant resources
            of the router.  One execution of Dijkstra algorithm is
            required for each neighbor eligible to become next hop of
            repair paths.  Thus a router with a few hundreds of
            neighbors may need to execute the algorithm hundreds of
            times before the best (or even valid) repair path is found.
            Manually excluding from the calculation neighbors which are
            known to provide no valid LFA (such as single-connected
            routers) may significantly reduce number of Dijkstra
            algorithm runs.

            LFA calculation policy may be configured so that routers

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            advertising certain tag value are excluded from LFA
            calculation even if they are otherwise suitable.

   3.  Controlling Remote LFA tunnel termination

       [I-D.ietf-rtgwg-remote-lfa] proposed method of tunneling traffic
       after connected link failure to extend the basic LFA coverage and
       algorithm to find tunnel tail-end routers fitting LFA
       requirement.  In most cases proposed algorithm finds more than
       one candidate tail-end router.  In real life network it may be
       desirable to exclude some nodes from the list of candidates based
       on the local policy.  This may be either due to known limitations
       of the node (the router does accept targeted LDP sessions
       required to implement Remote LFA tunneling) or due to
       administrative requirements (for example, it may be desirable to
       choose tail-end router among co-located devices).

       The Node administrative tag delivers simple and scalable
       solution.  Remote LFA can be configured with a policy to accept
       during the tail-end router calculation as candidates only routers
       advertising certain tag.  Tagging routers allows to both exclude
       nodes not capable of serving as Remote LFA tunnel tail-ends and
       to define a region from which tail-end router must be selected.

6.  Security Considerations

   This document does not introduce any further security issues other
   than those discussed in [RFC2328] and [RFC5340].

7.  IANA Considerations

   IANA maintains the registry for the TLVs.  OSPF Administrative Tags
   will require one new type code for the TLV defined in this document.

8.  Acknowledgments

   Thanks to Bharath R and Pushpasis Sarakar for useful inputs.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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   [RFC2328]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              September 2003.

   [RFC4970]  Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
              Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 4970, July 2007.

   [RFC5340]  Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
              for IPv6", RFC 5340, July 2008.

9.2.  Informative References

   [I-D.ietf-rtgwg-remote-lfa]
              Bryant, S., Filsfils, C., Previdi, S., Shand, M., and S.
              Ning, "Remote LFA FRR", draft-ietf-rtgwg-remote-lfa-02
              (work in progress), May 2013.

   [I-D.litkowski-rtgwg-lfa-manageability]
              Litkowski, S., Decraene, B., Filsfils, C., and K. Raza,
              "Operational management of Loop Free Alternates",
              draft-litkowski-rtgwg-lfa-manageability-01 (work in
              progress), February 2013.

   [RFC5286]  Atlas, A. and A. Zinin, "Basic Specification for IP Fast
              Reroute: Loop-Free Alternates", RFC 5286, September 2008.

Authors' Addresses

   Shraddha Hegde
   Juniper Networks, Inc.
   Embassy Business Park
   Bangalore, KA  560093
   India

   Email: shraddha@juniper.net

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   Harish Raghuveer
   Juniper Networks, Inc.
   Embassy Business Park
   Bangalore  560093
   India

   Email: hraghuveer@juniper.net

   Hannes Gredler
   Juniper Networks, Inc.
   1194 N. Mathilda Ave.
   Sunnyvale, CA  94089
   US

   Email: hannes@juniper.net

   Rob Shakir
   British Telecom

   Email: rob.shakir@bt.com

   Anton Smirnov
   Cisco Systems, Inc.
   De Kleetlaan 6a
   Diegem,   1831
   Belgium

   Email: as@cisco.com

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