[Off topic warning...] > we did a measurement study to understand the causes of such excessive > duplicate announcements, the results are reported in the following > paper: > "Investigating Occurrence of Duplicate Updates in BGP Announcements" > http://www.cs.ucla.edu/~jpark/dupbgp.pdf > to be presented at PAM conference next month
Interestingly, I'm not sure that this is worth fixing. Most BGP implementations store a copy of all of the best paths that they've received from neighbors. They then compute the 'best path' amongst this set and advertise it appropriately. Truly fixing this problem would require that an implementation retain state on a per-neighbor basis about which attributes were advertised (and in some cases, what changes to what attributes were performed). Further, the implementation would still have to effectively compute the update because output policy could have a substantial impact on the result. Thus, the question really becomes whether transmitting the update and receiving it is more expensive than additional filtering in the sender. Given that bandwidth is 'free', the tradeoff is now between the sender with additional state and processing, or the processing in the receiver. Note that the receivers task is to parse the update, realize that there is, in fact, no change, and not do anything. Tony _______________________________________________ rrg mailing list rrg@irtf.org http://www.irtf.org/mailman/listinfo/rrg
