IETF 74th meeting, San Francisco

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IETF 74th meeting, San Francisco L3VPN WG

• Multicast VPN fast fail-overdraft-morin-l3vpn-mvp
  n-fast-failover-00
• Wim Henderickx, Praveen Muley Alcatel Lucent
• Thomas Morin FT Orange
• Yakov Rekhter, Rahul Aggarwal Juniper

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Introduction

• Goal
• Minimize connectivity restoration time for
  multicast VPN services in the presence of
  failures
• Relying on rerouting for multicast connectivity
  restorationtypically involves
• Waiting for unicast routing to converge
• Additional signaling to restore multicast
  forwarding state (join)
• That may not be fast enough for certain multicast
  applications...
• Certain multicast applications often have high
  availability expectations
• This work proposes tools to provide fast
  connectivity restoration for multicast VPN
  traffic
• Two complementary mechanisms providing different
  levels of failure coverage and restoration
  performance
• Focus on upstream failures in the provider scope
• Upstream PE failures
• Core node/link failures
• (other failures too, depending on the strategy
  implemented)

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UMH selection based on tunnel status

• UMH selection taking into account tunnel status
• Reminder
• UMH Selection specifies procedures by which a
  downstream PE determines the PE from which it
  will receive a said multicast flow (C-S, C-G)
• In the current spec, UMH Selection is done
  solely based on the VPN unicast routing
  information
• Does not take into account the state of the
  P-tunnel that the selected UMH uses to send (C-S,
  C-G) to the local PE
• Idea let UMH procedures take into account the
  state of the P-tunnel from the selected/primary
  UMH to the PE
• Make UMH Selection on a (downstream) PE switch
  to a backup (upstream) PE as soon as the
  (downstream) PE determines that the P-tunnel from
  the selected/primary (upstream) PE is down,
  without waiting for unicast VPN convergence
• Different possible ways for a PE to detect that a
  P-tunnel from the selected/primary UMH to the PE
  is down
• P2MP OAM (Multipoint BFD)
• Traffic counters
• P-Tunnel signaling (RSVP-TE PathTear)
• IGP tunnel root tracking
• Key avoid waiting for unicast convergence

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Standby BGP C-Multicast route

• Standby BGP C-Multicast route
• Idea prepare the backup PE so that it is ready
  to become UMH when the primary PE fails
• How ?
• Besides advertising a normal (C-S,C-G)
  C-multicast Tree Join route to the nominal
  upstream PE, downstream PEs advertise a Standby
  C-multicast Tree Join route to the backup
  upstream PE
• The backup upstream PE prepares for a possible
  failure (e.g. by joining the source)
• The backup upstream PE monitors the reachability
  of C-S through the nominal/primary PE
• On failure, traffic is forwarded by backup PE
• Failure detection can be done, for instance
• based on P2MP OAM
• based on unicast VPN reachability to C-S
• Key avoid additional signaling at failure time

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Standby C-multicast route - Example
Standby BGP C-multicast route
Secondaryupstream PE
receivers
?
source
downstreamCE
upstreamCE
PrimaryupstreamPE
downstreamPE
receivers
"normal" BGP C-multicast route
Warm standby Example
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Different protection levels

• Cold standby
• Backup PE joins towards the CE only after it
  detects failure of the primary PE
• Warm standby
• Backup PE is ready to send traffic when it
  detects the failure of the primary PE (backup PE
  is pre-joined toward the CE)
• Hot standby
• Backup PE sends the traffic before the failure
  occurs
• Downstream PE switch to backup tunnel based on
  VPN unicast routes
• Hot leaf standby
• Backup PE sends the traffic before the failure
  occurs
• Downstream PE switch to backup tunnel based on
  tunnel status

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Conclusion

• Wrap up two simple mechanisms to reduce
  connectivity restoration time for multicast
  traffic in a VPN context, for upstream failures
  in the provider scope (upstream PE core
  failures)
• UMH Selection based on P-tunnel status avoid
  waiting for unicast convergence
• Standby C-multicast route avoid signaling at
  failure-time by preparing the backup upstream PE
• These mechanisms can be used, each one alone or
  together, depending on the failure coverage and
  level of protection wanted
• Different levels of protection cold, warm, hot,
  leaf hot
• Working group feedback ?