1. PW MUX
PWE – 71st IETF
10 March 2008
Yaakov (J) Stein

2. ACs and PWs ACs PWs RFC 3985 states that PWs connect forwarders
PSN
RFC 3985 states that PWs connect forwarders
The ingress forwarder selects into which PW to inject traffic based on
the AC
payload content
configured forwarding information
Thus the forwarder function can be used for
PW protection
AC protection
PW load balancing and inverse mux
When the mapping of PW to AC is not one-to-one
we will call the forwarder function - a PW MUX

3. Are there enough labels?
There are only 220 unique PW labels
If we assign multiple PW labels for each AC
won't we run out of labels ?
This question is ill-posed
When using multiple PWs for protection or load balancing
these PWs will not be in the same tunnel
RFC3985 mentions that the PW label MAY be unique per PE
but it only MUST be unique per tunnel
In theory, we could even use the same PW label
for all the PWs associated with the same AC
So using multiple PWs does not lead to label space exhaustion

4. 1+1 PW Protection AC PSN PW MUX
active PW AC
PSN
PW MUX
PW MUX needs to map the AC to the appropriate PWs
PW set up protocol associates multiple PW labels with the single AC
Ingress forwarder needs to replicate packets
Egress forwarder needs to detect and reject duplicate packets

5. 1:1 PW Protection AC PSN PW MUX
active PW
backup PW AC
PSN
PW MUX
PW MUX needs to map the AC to the appropriate PW(s)
PW set up protocol associates multiple PW labels with the single AC
Ingress forwarder labels traffic with label of the active PW
Egress forwarder extracts traffic from active PW
Use VCCV to monitor continuity of active PW
Use LDP status message to trigger switch from active to backup PW
May revert to original PW when fault is rectified

6. 1+1 AC Protection PSN ACs native service MUX PW MUX
PW MUX needs to map one PW to multiple ACs
PW setup protocol associates multiple ACs with a single PW label
Ingress forwarder needs to select highest quality AC and encapsulate
Egress forwarder needs to map PW label to both ACs

7. 1:1 AC Protection PSN ACs native service MUX PW MUX
PW MUX needs to map one PW to multiple ACs
PW setup protocol associates multiple ACs with a single PW label
Ingress forwarder needs to extract traffic from active AC
and encapsulate with the PW label
Egress forwarder needs to copy PW traffic to active AC
Native OAM needs to monitor active AC
Native protection mechanisms used to switch between ACs

8. PW load-balancing and inverse mux
balancing PW AC AC
PSN
PW MUX
PW MUX
PW MUX needs to map the AC to the appropriate PW(s)
PW set up protocol needs to associate multiple PWs with the single AC
Ingress forwarder makes a per-packet decision as to which PW to use
Egress forwarder needs to collect packets from all PWs in use

9. Proposal PWE3 should select a single method for handling PW protection
AC protection
Load balancing and inverse mux
This means a unified mechanism should be used for
associating PW labels to AC identifiers
designating PW status (active, backup, balancing)
signaling between forwarders (when needed)