a few comments/questions on draft-bryant-shand-ipfrr-notvia-addresses-03.txt
"Alia Atlas" <akatlas@gmail.com> Mon, 06 November 2006 07:39 UTC
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Date: Sun, 05 Nov 2006 23:39:14 -0800
From: Alia Atlas <akatlas@gmail.com>
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Subject: a few comments/questions on draft-bryant-shand-ipfrr-notvia-addresses-03.txt
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I have a few comments and a question on the draft. 1) In Section 4.3, the draft says: "It may be that the cost of reaching X using local delivery from the alternate router is greater than the cost of reaching X via P. Under those circumstances, the alternate router would normally forward to X via P, which would cause the IPFRR repair to loop. To prevent the repair from looping the alternate router must locally deliver a packet received via a repair encapsulation. This may be specified by using a special address with the above semantics. Note that only one such address is required per node." Could I suggest modifying the first sentence to be "...from the alternate router (i.e. Z)..." to clarify that this is a concern for avoiding loops for both? Otherwise, b/c of the previous paragraph, it sounds like this applies to only Y and not to Z... Am I correct that you mean this to apply to Z and not Y? If it were Y, the address used is a not-via address - which would imply that all not-via addresses would require local delivery. Could you better define local delivery in the draft? Is this a requirement for an additional, separate forwarding table that is populated only by prefixes advertised by the router and which is entered into on decapsulation based upon the outer address? 2) The semantics of the not-via address Ps changes from simply "P not-via the link S-P" to be "P not-via the link S-P or any other link with which S-P shares an SRLG" >From all earlier discussion, Ps means "P not-via the node S" and not "P not-via the link S-P". If S is sending the packet encapsulated to Ps, then this avoids it coming back to S, but it could still go through a broadcast link connecting P,S and another node X. 3) In Section 7, the draft suggests a router signal if it has an LFA-protected link. However. that is derived info that is dependent upon (potentially) the entire LSDB. The idea of the optimization is appealing, but have you thought about the ramifications of advertising this derived information? What happens if the info is old? What about issues from many routers reissuing their LSA/LSP on a single topology change? 4) The discussion of interactions with LANs is quite good and clear. It would be nice if the draft specifically stated the behavior to use - or at the very least specified in a clear section which not-via addresses a router should advertise and what elements should be pruned for each such case. 5) In the next version, a discussion of the routing extensions required would be very useful. Alia _______________________________________________ rtgwg mailing list rtgwg@ietf.org https://www1.ietf.org/mailman/listinfo/rtgwg