Network Working Group                                            W. Zhou
Internet-Draft                                             cisco Systems
Intended status: Informational                          October 15, 2012
Expires: April 18, 2013


                       VRRP PIM Interoperability
                       draft-zhou-pim-vrrp-00.txt

Abstract

   This document introduces VRRP Aware PIM, a redundancy mechanism for
   the Protocol Independent Multicast (PIM) to interoperate with Virtual
   Router Redundancy Protocol (VRRP).  It allows PIM to track VRRP state
   and to preserve multicast traffic upon failover in a redundant
   network with virtual routing groups enabled.

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 April 18, 2013.

Copyright Notice

   Copyright (c) 2012 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.



Zhou                     Expires April 18, 2013                 [Page 1]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Tracking and Failover  . . . . . . . . . . . . . . . . . . . .  4
   3.  PIM Assert Metric Auto-Adjustment  . . . . . . . . . . . . . .  5
   4.  DF Election for BiDir Group  . . . . . . . . . . . . . . . . .  6
   5.  Tracking Multiple VRRP Groups on an Interface  . . . . . . . .  7
   6.  Support of HSRP  . . . . . . . . . . . . . . . . . . . . . . .  8
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  Informative References . . . . . . . . . . . . . . . . . . . . 11
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 12







































Zhou                     Expires April 18, 2013                 [Page 2]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  Introduction

   Virtual Router Redundancy Protocol (VRRP) [RFC5798] is a redundancy
   protocol for establishing a fault-tolerant default gateway.  The
   protocol establishes a framework between network devices in order to
   achieve default gateway failover if the primary gateway becomes
   inaccessible .

   PIM has no inherent redundancy capabilities and its operation is
   completely independent of VRRP group states.  As a result, IP
   multicast traffic is forwarded not necessarily by the same device as
   is elected by VRRP.  The VRRP Aware PIM feature provides consistent
   IP multicast forwarding in a redundant network with virtual routing
   groups enabled.

   In a multi-access segment (such as LAN), PIM designated router (DR)
   election is unaware of the redundancy configuration, and the elected
   DR and VRRP master router (MR) may not be the same router.  In order
   to ensure that the PIM DR is always able to forward PIM Join/Prune
   message towards RP or FHR, the VRRP MR becomes the PIM DR (if there
   is only one VRRP group).  PIM is responsible for adjusting DR
   priority based on the group state.  When a failover occurs, multicast
   states are created on the new MR elected by the VRRP group and the MR
   assumes responsibility for the routing and forwarding of all the
   traffic addressed to the VRRP virtual IP address.  This ensures the
   PIM DR runs on the same gateway as the VRRP MR and maintains mroute
   states.  It enables multicast traffic to be forwarded through the
   VRRP MR, allowing PIM to leverage VRRP redundancy, avoid potential
   duplicate traffic, and enable failover, depending on the VRRP states
   in the device.





















Zhou                     Expires April 18, 2013                 [Page 3]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  Tracking and Failover

   With VRRP Aware PIM enabled, PIM listens to the state change
   notifications from VRRP and automatically adjusts the priority of the
   PIM DR based on the VRRP state, and ensures VRRP MR (if there is only
   one VRRP group) becomes the DR of the LAN.  If there are multiple
   VRRP groups, the DR is determined by user-configured priority.

   PIM triggers communication between upstream and downstream devices
   upon failover in order to create mroute states on the new MR.  PIM
   sends additional PIM Hello message using the VRRP virtual IP
   addresses as the source address for each active VRRP group when a
   device becomes VRRP Active.  The PIM Hello will carry a new GenID in
   order to trigger other routers to respond to the failover.  When a
   downstream device receives this PIM Hello, it will add the virtual
   address to its PIM neighbor list.  The new GenID carried in the PIM
   Hello will trigger downstream routers to resend PIM Join messages
   towards the virtual address.  Upstream routers will process PIM Join/
   Prunes (J/P) based on VRRP group state.

   If the J/P destination matches the VRRP group virtual address and if
   the destination device is in VRRP active state, the new MR processes
   the PIM Join because it is now the acting PIM DR.  This allows all
   PIM Join/Prunes to reach the VRRP group virtual address and minimizes
   changes and configurations at the downstream routers side.


























Zhou                     Expires April 18, 2013                 [Page 4]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  PIM Assert Metric Auto-Adjustment

   It is possible that, after VRRP active switched from A to B; A is
   still forwarding multicast traffic which will result in duplicate
   traffic and PIM Assert mechanism will kick in.  PIM Assert with
   redundancy is enabled.

   o  If only one VRRP group, passive routers will send a large penalty
      metric preference (PIM_ASSERT_INFINITY - 1) and make MR the Assert
      winner.

   o  If there are multiples VRRP groups configured on an interface,
      Assert metric preference will be (PIM_ASSERT_INFINITY - 1) if and
      only if all VRRP groups are in passive.

   o  If there is at least one VRRP group is in Active, then original
      Assert metric preference will be used.  That is, winner will be
      selected between routers using their real Assert metric preference
      with at least one active VRRP Group, just like no VRRP is
      involved.































Zhou                     Expires April 18, 2013                 [Page 5]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  DF Election for BiDir Group

   Change to DF offer/winner metric is handled similarly to PIM Assert
   handling with VRRP.

   o  If only one VRRP group, passive routers will send a large penalty
      metric preference in Offer (PIM_BIDIR_INFINITY_PREF- 1) and make
      MR the DF winner.

   o  If there are multiples VRRP groups configured on an interface,
      Offer metric preference will be (PIM_BIDIR_INFINITY_PREF- 1) if
      and only if all VRRP groups are in passive.

   o  If there is at least one VRRP group is in Active, then original
      Offer metric preference to RP will be used.  That is, winner will
      be selected between routers using their real Offer metric with at
      least one active VRRP Group, just like no VRRP is involved.


































Zhou                     Expires April 18, 2013                 [Page 6]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  Tracking Multiple VRRP Groups on an Interface

   User can configure PIM to track more than one VRRP groups on an
   interface.  This allows other applications to exploit the PIM/VRRP
   interoperability to achieve various goals (e.g., load balancing).
   Since each VRRP groups configured on an interface could be in
   different states at any moment, the DR priority is adjusted.  PIM
   Assert metric and PIM Bidir DF metric if and only if all VRRP groups
   configured on an interface are in passive (non-Active) states to
   ensure that interfaces with all-passive VRRP groups will not win in
   DR, Assert and DF election.  In other words, DR, Assert, DF winner
   will be elected among the interfaces with at least one Active VRRP
   group.






































Zhou                     Expires April 18, 2013                 [Page 7]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  Support of HSRP

   Although there are differences between VRRP and Hot Standby Router
   Protocol (HSRP) [RFC2281] including number of backup (standby)
   routers, virtual IP address and timer intervals, the proposed scheme
   can also enable HSRP aware PIM with similar switchover and tracking
   mechanism described in this draft.












































Zhou                     Expires April 18, 2013                 [Page 8]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  Security Considerations

   The proposed tracking mechanism has no negative impact on security.
















































Zhou                     Expires April 18, 2013                 [Page 9]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  Acknowledgments

   I would like to give a special thank you and appreciation to Stig
   Venaas for his ideas and comments in this draft.















































Zhou                     Expires April 18, 2013                [Page 10]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


.  Informative References

   [RFC2281]  Li, T., Cole, B., Morton, P., and D. Li, "Cisco Hot
              Standby Router Protocol (HSRP)", RFC 2281, March 1998.

   [RFC5798]  Nadas, S., "Virtual Router Redundancy Protocol (VRRP)
              Version 3 for IPv4 and IPv6", RFC 5798, March 2010.












































Zhou                     Expires April 18, 2013                [Page 11]

 
Internet-Draft          VRRP PIM Interoperability           October 2012


Author's Address

   Wei Zhou
   cisco Systems
   Tasman Drive
   San Jose, CA  95134
   USA

   Email: weizho2@cisco.com










































Zhou                     Expires April 18, 2013                [Page 12]