Pseudo-Wire Protection

1
Pseudo-Wire Protection

• Ping Pan
• ppan_at_hammerheadsystems.com
• IETF 65

2
Why?
PW (Important traffic)
Tunnel-1 (BW1)
Node 2
Node1
PW (Best effort)
Tunnel-2 (BW2), backup Tunnel-1
Switch-over

• Conventional mechanism (e.g. MPLS FRR) would
  work, if
• Tunnel-1 and Tunnel-2 have the same bandwidth
  (i.e.,BW1 BW2)
• All PWs are equally important
• Otherwise, if BW2 lt BW1,
• Important traffic may get dropped/delayed during
  network failure
• PW protection
• Each PW needs to have its own importance and
  QoS level
• During switch-over, preempt others if necessary

3
Design Considerations (1)

• Need to work in single and multi-segement
  environment
• Work with Generic ID FEC only
• Working and protection PWs must be uniquely
  identified
• But make the use of AII/AGI may not be a good idea

working
protection
Need to know what to process
4
Design Considerations (2)

• On Backup Path Determination
• Carrying ERO should be optional
• Use hop-by-hop forwarding for the working PW
• Get RRO information from PW Switching Point
  TLV (SP-TLV)
• Build the protection PW base on SP-TLV
• May use SP-TLV for loop-detection
• On CAC at each hop
• Should be optional depending the traffic types
• Other relevant protection information
• 11 or 1N need to validate the need of 1N
• Fate-sharing useful in multi-hop applications
• Hot-standby vs. cold-standby

5
Protocol Extension

• Protection-TLV
• Setup and Holding Preference Levels
• Protection Type hot or cold standby
• Schemes 11 or 1N
• Flags
• Fate-sharing allowed
• Per-hop BW CAC required
• Reference ID unique identify working and
  protecting PWs
• PW Status
• Bad message, no bandwidth etc.
• Everything else
• Keep as it is
• AII/AGI must be the same on all working and
  protecting PWs

6
How does it work?
Working PW
Protecting PW
Node 3
Node 2
Node1

1. Run the Generic FEC procedure to setup the
   working PW
2. Run the Generic FEC procedure to setup the
   protection PW
3. When working, pointing user traffic to the
   protecting PW
4. During failure (learned from BFD etc.), switch
   over
5. Preempt traffic when needed

1. Run MHOP PW for working and protection PW setup
2. Use SP-TLV for loop detection
3. Use Protection-TLV and SP-TLV to forward working
   and protection PWs
4. Forward failure status if not working

1. Send out Label Mapping and setup the working PW
2. When working, setup the protecting PW (base on
   SP-TLV)
3. When working, pointing user traffic to the
   protecting PW
4. During failure (learned from BFD etc.), switch
   over
5. Preempt traffic when needed

7
Next Step

• This proposal works in both single-segment and
  multi-segment cases
• Like to
• Continue to gather feedback
• Iron out the details with others
• Make this into a WG Working Document
• THANK YOU ALL