BFD Extensions for PW Exchange

1
BFD Extensions for PW Exchange of Fault
Notifications draft-radoaca-l2vpn-bfd-inband-oam-
00.txt
Vasile Radoaca, Dave Allan Nortel Networks Ron
Insler RAD Communications Simon Delord France
Telecom
2
Background

• General agreement on need to relay fault
  notifications (down/AIS/RDI) when interworking
  PWs
• Alarm suppression/management
• Allows higher layers to react promptly

3
Motivations

• Current LDP Status TLV mechanism is useful (and
  viewed as minimal default implementation for
  interoperability), BUT it loads the control
  plane.
• Network may perform better if control plane is
  free to do other things
• Notifications will flow faster if not serialized
  through the control plane
• Data plane notifications delegates implementation
  to PW IWF
• Direct association of BFD PDU with incoming PW or
  use of discriminator means simpler protocol,
  simpler implementation
• Control plane optimizations (e.g. Group ID) have
  limited applicability
• Provides inter-domain mechanism
• There may not always be a control plane, or may
  be multiple/different control plane protocols

4
Approach

• If you got em, use em
• If support for BFD notifications agreed between
  PEs, then it is the preferred mechanism for
  relaying fault status
• Additional TLV exchanged during negotiation
  establishes mutual level of support
• BFD is extended to include diagnostic codes
• Draft currently suggests
• AC-AIS or down, AC-RDI
• PW-AIS or down, PW-RDI

5
Detail

• For BFD in on demand mode, a poll sequence is
  initiated to convey fault information
• If BFD already used in async mode, then this is
  simply additional information piggy-backed on the
  existing flows
• Reliability achieved through repetition

6
Discussion Points

• Do diagnostic codes need concept of fault
  location?
• Draft currently distinguishes between PW and AC
  failures
• Simple AIS/RDI with no specified location may be
  sufficient
• Do diagnostic codes need concept of direction
• down vs. AIS/RDI
• Overlap of current BFD functionality and PW fault
  notifications
• E.g. I cannot hear you direct analogy to PW-RDI

7
What do we want?

• 1) Agreement that data plane relay of PW fault
  notifications is useful
• 2) Adopt the draft as a L2VPN WG starting point
  for specifying procedures