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					                     PW
                     MUX
                   PWE – 70th IETF

                   4 December 2007

Yaakov (J) Stein
                                     PWE-70   Slide 1
                                ACs and PWs
                                   PSN


               forwarder                            forwarder


        ACs                                                     ACs
                                   PWs
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

When the mapping of PW to AC is not one-to-one
   we will call the forwarder function - a PW MUX
                                                                         PWE-70   Slide 2
                    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


                                                                PWE-70   Slide 3
                            1+1 PW Protection

    active PW



                    AC                                                    AC
                                           PSN




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



                                                                      PWE-70   Slide 4
                            1:1 PW Protection
   active PW
   backup PW



           AC                                                   AC
                                     PSN



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 to switch from active to backup PW
May revert to original PW when fault is rectified                  PWE-70   Slide 5
                           1+1 AC Protection


                                PSN


            ACs                                        ACs
native service    PW MUX                      PW MUX         native service
     MUX                                                          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
                                                                  PWE-70   Slide 6
                           1:1 AC Protection
                                PSN


            ACs                                        ACs
native service    PW MUX                      PW MUX         native service
     MUX                                                          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
                                                                   PWE-70   Slide 7
                         PW load-balancing

 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
Forwarder needs to make a per-packet decision as to which PW to use

                                                                 PWE-70   Slide 8
                               Proposal


PWE3 should select a single method for handling
 PW protection
 AC protection
 Load balancing

This means a unified mechanism should be used for
   associating PW labels to AC identifiers
   designating PW status (active, backup, balancing)




                                                        PWE-70   Slide 9

				
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