Mike Takefman7/16/2007IEEE RPRWG PIRC Architecture July 2007 Plenary Session San Francisco Mike Takefman Cisco Systems

Mike Takefman7/16/2007IEEE RPRWG My PIRC High Level Goals Built on top of b MAC Assumption is an L2 switched network PIRC has to provide loop-free dual connectivity Multiple Load-Balancing methods Compatible with non-PIRC stations ideally no MAC or operational changes needed for other nodes usable with existing standard product chips

Mike Takefman7/16/2007IEEE RPRWG Where To Put Filtering PIRC is essentially adding new filtering rules to the system assumption is that ingress and egress filter rules exist Our scope requires that these filtering rules exist in the MAC level, but the actual position is implementation dependant side effect on whether b learning occurs no easy way to arbitrarily allow or not allow learning question is one of compliance Tributary support requires egress filtering rules in addition to ingress rules

Mike Takefman7/16/2007IEEE RPRWG Hash Filtering Previous presentations have pointed out that certain constraints must be followed in order to insure connectivity net result is that the basic hash function is based on outer VLAN hence this form of hash filtering is essentially VLAN filtering and any other hashing function is by definition proprietary

Mike Takefman7/16/2007IEEE RPRWG 2 Span Failure Scenarios It has been suggested that PIRC support both 1 and 2 span failures it must be assumed that the network is otherwise loop free 2 cuts on a leaf ring is trivial as a loop cannot be created 2 cuts on an intermediate ring is more interesting and has a few cases D C B A

Mike Takefman7/16/2007IEEE RPRWG 2 Span Failure Scenarios D C B A Isolated Node no connectivity to that node no loops created Nothing can be done, and there are no PIRC issues

Mike Takefman7/16/2007IEEE RPRWG 2 Span Failure Scenarios D C B A Isolated Neighbour Ring no connectivity to that sub-tree no loop created Nothing can be done, and there are no PIRC issues

Mike Takefman7/16/2007IEEE RPRWG 2 Span Failure Scenarios D C B A Isolated Partial Ring full connectivity possible no loop created PIRC could restore connectivity A&B operated normally D&C both do full forwarding

Mike Takefman7/16/2007IEEE RPRWG 2 Span Failure Scenarios D C B A Split Ring full connectivity possible BUT loop created with current suggested PIRC filtering PIRC could restore connectivity A&B, C&D forward everything from neighbour ring to “broken ring” one of A|B, C|D forward to neighbour ring never forward back from mate done with egress filtering if tribs are needed else ingress

Mike Takefman7/16/2007IEEE RPRWG 2 Span Failure Scenarios D C B A How to recognize split ring? Nodes on affected ring observe mate has disappeared on one ring but not the other

Mike Takefman7/16/2007IEEE RPRWG 2 Span Failure Scenarios D C A B Does the split ring scenario scale to 3 PIRC pairs? A&B,C&D are partially isolated from B&E A&B is split from C&D the problem is that the split rules are different from the partially isolated rules implies you need to apply rules based on ringSA -> YUCK E F

Mike Takefman7/16/2007IEEE RPRWG Conclusions Dual Failure scenario can only be handled for limited cases likely not worth doing