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Versions: 00 01 draft-ietf-ospf-link-overload

Open Shortest Path First IGP                                    S. Hegde
Internet-Draft                                                 P. Sarkar
Intended status: Standards Track                              H. Gredler
Expires: January 17, 2016                         Juniper Networks, Inc.
                                                              M. Nanduri
                                                   Microsoft Corporation
                                                                L. Jalil
                                                                 Verizon
                                                           July 16, 2015


                           OSPF Link Overload
                   draft-hegde-ospf-link-overload-01

Abstract

   Many OSPFv2 or OSPFv3 deployments run on overlay networks provisioned
   by means of pseudo-wires or L2-circuits.  when the devices in the
   underlying network go for maintenance, it is useful to divert the
   traffic away from the node before the maintenance is actually
   scheduled.  Since the nodes in the underlying network are not visible
   to OSPF, existing stub router mechanism described in [RFC3137] cannot
   be used.  It is useful for routers in OSPFv2 or OSPFv3 routing domain
   to be able to advertise a link being in overload state to indicate
   impending maintenance activity in the underlying network devices.

   This document describes the protocol extensions to disseminate link
   overload information in 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




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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 17, 2016.

Copyright Notice

   Copyright (c) 2015 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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Link overload sub TLV . . . . . . . . . . . . . . . . . . . .   3
     2.1.  OSPFv2 Link overload sub TLV  . . . . . . . . . . . . . .   3
     2.2.  OSPFv3 Link overload sub TLV  . . . . . . . . . . . . . .   3
   3.  Elements of procedure . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Point-to-point links  . . . . . . . . . . . . . . . . . .   4
     3.2.  Broadcast/NBMA links  . . . . . . . . . . . . . . . . . .   4
     3.3.  Point-to-multipoint links . . . . . . . . . . . . . . . .   5
   4.  Backward compatibility  . . . . . . . . . . . . . . . . . . .   5
   5.  Applications  . . . . . . . . . . . . . . . . . . . . . . . .   5
     5.1.  Pseudowire Services . . . . . . . . . . . . . . . . . . .   5
     5.2.  Controller based Traffic Engineering Deployments  . . . .   6
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   It is useful for routers in OSPFv2 or OSPFv3 routing domain to be
   able to advertise a link being in overload state to indicate
   impending maintenance activity on the link.  This document provides
   mechanisms to advertise link overload state in the flexible encodings



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   provided by OSPFv2 Prefix/Link Attribute Advertisement(
   [I-D.ietf-ospf-prefix-link-attr]) and OSPFv3 Extended LSA
   ([I-D.ietf-ospf-ospfv3-lsa-extend]).  Throughout this document, OSPF
   is used when the text applies to both OSPFv2 and OSPFv3.  OSPFv2 or
   OSPFv3 is used when the text is specific to one version of the OSPF
   protocol.

2.  Link overload sub TLV

2.1.  OSPFv2 Link overload sub TLV

   Link overload sub TLV is carried as part of the Extended link TLV as
   defined in [I-D.ietf-ospf-prefix-link-attr] for OSPFv2.



        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            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                     Remote IP address                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                Figure 1: Link overload sub TLV for OSPFv2

   Type : TBA

   Length: 4

   Value: Remote IPv4 address.  The remote IP4 address is used to
   identify the particular link that is in overload state when there are
   multiple parallel links between two nodes.


2.2.  OSPFv3 Link overload sub TLV

   Link overload sub TLV is carried in the Router-link TLV as defined in
   the [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3.  The Router-Link
   TLV contains the neighbor interface-id and can uniquely identify the
   link on the remote node.









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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            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                Figure 2: Link overload sub TLV for OSPFv3

   Type : TBA

   Length: 0

3.  Elements of procedure

   The Link Overload sub TLV indicates that the Link which carries the
   sub TLV is overloaded.  The node that has the link going for
   maintenance, sets metric of the link to MAX-METRIC and re-originates
   the router LSA.  The metric in the reverse direction also need to
   change to divert the traffic from reverse direction.  The node SHOULD
   originate Link overload sub TLV and include it in Extended link TLV
   and originate the Extended Link Opaque LSA as defined in
   [I-D.ietf-ospf-prefix-link-attr] for OSPFv2 and E-Router-LSA as
   defined in [I-D.ietf-ospf-ospfv3-lsa-extend] for OSPFv3 and flood in
   the OSPF area.

   when the originator of the Link Overload sub TLV, purges the extended
   link opaque LSA or re-originates without the Link Overload sub TLV,
   the metric on the remote node SHOULD be changed back to the original
   value.

   Based on the link type of the overloaded link below actions MAY be
   taken by the receiver.

3.1.  Point-to-point links

   When a link overload TLV is received for a point-to-point link the
   receiver SHOULD identify the local link which corresponds to the
   overloaded link and set the metric to MAX-METRIC (0xffff).  Receiver
   node MUST re-originate the router-LSA with the changed metric and
   flood into the OSPF area.

3.2.  Broadcast/NBMA links

   Broadcast or NBMA networks in OSPF are represented by a star topology
   where the Designated Router (DR) is the central point to which all
   other routers on the broadcast or NBMA network connect.  As a result,
   routers on the broadcast or NBMA network advertise only their
   adjacency to the DR.  Routers that do not act as DR do not form or



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   advertise adjacencies with each other.  For the Broadcast links, the
   MAX-METRIC on the outgoing link cannot be changed since all the
   neighbors are on same link.  Setting the link cost to MAX-METRIC
   would impact paths going via all neighbors.

   When a link-overload TLV is received by the remote end for a
   broadcast/NBMA link

   - If it's DROther or BDR for that link, SHOULD not take any action.
   - If receiving node is DR for the link, it MUST remove the originator
   of the link overload TLV from the list of connected neighbors and
   MUST re-originate the network LSA and flood into the OSPF area.

3.3.  Point-to-multipoint links

   Operation for the point-to-multipoint links is similar to the point-
   to-point links.  When a link overload TLV is received for a point-to-
   multipoint link the receiver SHOULD identify the neighbor which
   corresponds to the overloaded link and set the metric to MAX-METRIC
   (0xffff).  Receiver node MUST re-originate the router-LSA with the
   changed metric and flood into the OSPF area.

4.  Backward compatibility

   The mechanism described in the document is fully backward
   compatible.It is required that the originator and receiver of link-
   overload sub TLV understand the extensions defined in this document
   and in case of broadcast links the originator and the DR need to
   understand the extensions.  Other nodes in the network compute based
   on increased metric and hence the feature is backward compatible.

5.  Applications

5.1.  Pseudowire Services


           ---------PE3----------------PE4----------
          |                                         |
          |                                         |
        CE1---------PE1----------------PE2---------CE2
          |                                         |
          |                                         |
           -----------------------------------------
                    Private VLAN


                       Figure 3: Pseudowire Services




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   Many service providers offer pseudo-wire services to customers using
   L2 circuits.  The IGP protocol that runs in the customer network
   would also to run over the pseudo-wire to get seamless private
   network for the customer.  Service providers want to offer overload
   kind of functionality when the PE device is taken-out for
   maintenance.The provider should guarantee that the PE is taken out
   for maintenance only after the service is successfully diverted on
   the alternate path.  Link overload feature provides facilities to
   achieve this service by increasing the metric on the link but still
   allowing the traffic to use the link when there is no alternate path
   available.

5.2.  Controller based Traffic Engineering Deployments

                         _____________
                        |             |
           -------------| Controller  |--------------
          |             |____________ |             |
          |                                         |
          |  ------- Primary Path ---------------    |
          PE1---------P1----------------P2---------PE2
                      |                  |
                      |                  |
                      |________P3________|

                         Alternate Path


              Figure 4: Controller based Traffic Engineering

   Controller based deployments where the controller participates in the
   IGP protocol gets the link-overload information when the link
   maintenance is impending.  Using this information controller finds an
   alternate path.  If there are no alternate paths satisfying the
   traffic engineering constraints, controller might temporarily relax
   the constraints and put the service on different path.  In the above
   example when P1->P2 link goes for maintenance, controller gets the
   link-overload information and sets up an alternate path via
   P1->P3->P2.  Once the traffic is diverted, P1->P2 link can be taken
   out for maintenance/upgrade.

6.  Security Considerations

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






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7.  IANA Considerations

   This specification updates one OSPF registry:

   OSPF Extended Link TLVs Registry

   i) TBD - Link Overload TLV OSPFV3 Router Link TLV Registry

   i) TBD - Link Overload TLV

8.  Acknowledgements

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.

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

   [RFC3137]  Retana, A., Nguyen, L., White, R., Zinin, A., and D.
              McPherson, "OSPF Stub Router Advertisement", RFC 3137,
              June 2001.

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

9.2.  Informative References

   [I-D.ietf-ospf-ospfv3-lsa-extend]
              Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
              LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-06
              (work in progress), February 2015.

   [I-D.ietf-ospf-prefix-link-attr]
              Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", draft-ietf-ospf-prefix-link-attr-03 (work
              in progress), February 2015.

Authors' Addresses









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

   Email: shraddha@juniper.net


   Pushpasis Sarkar
   Juniper Networks, Inc.
   Embassy Business Park
   Bangalore, KA  560093
   India

   Email: psarkar@juniper.net


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

   Email: hannes@juniper.net


   Mohan Nanduri
   Microsoft Corporation
   One Microsoft Way
   Redmond, WA  98052
   US

   Email: mnanduri@microsoft.com


   Luay Jalil
   Verizon

   Email: luay.jalil@verizon.com











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