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## Re: Comparison of symmetric and asymmetric PLSN algorithms

 Subject: Re: Comparison of symmetric and asymmetric PLSN algorithms mike shand Wed, 08 Jun 2005 13:24:31 +0100
 ```At 22:29 07/06/2005, mike shand wrote: ``````At 21:56 07/06/2005, Alia Atlas wrote: ``````Mike, ```Do you have any info on the length of the multi-hop loops? I.e., one loop that is 5 links long might want to count more... ```The numbers are very interesting. Alia ``````Alia, ``` No. At the moment I don't even know how many multihop loops there are (if any). Of course I could record both of those statistics... I'll see what I can do tomorrow. Well, it turns out that it is rather more difficult than I thought to get this information owing to the recursive way I explore for loops. However, it seems this was a bad choice of network, since despite the presence of asymmetric costs there are no multi-hop loops caused by them. So it is not surprising that we get the result we did! Going back to the original asymmetric cost diagram that Pierre used, we get the following results ```asym sym 0 0 0 0 0 0 4 5 3 of which are 3 hop loops 0 0 0 0 0 0 8 6 all 6 of which are 3 hop loops So this is more of a swings and roundabouts case. ```I'm beginning to think that we can ignore the asymmetric cost case unless we have evidence that doing so would make things dramatically worse. My only caveat would be that if we want to combine PLSN with some other loop prevention technique to get 100% coverage (e.g. using tunnels only for the cases not dealt with by PLSN), then we should probably use the asymmetric cost algorithm even though it might result in using more tunnels than necessary. The reason is that the multi-hop loops which occur while using the symmetric cost algorithm are (currently) unpredictable, and hence it is difficult to know when to use a tunnel to avoid them. Whereas the extra single link loops which occur by using the asymmetric algorithm are at least predictable (they can only occur over type C pairs). Of course if we could figure out how to predict the multi-hop loops, then this wouldn't matter. Hmmm. Is it true that using the asymmetric algorithm prevents ALL multi-hop links, or can we still get multi-hop loops around cycles which are all type C. ```The more I think about this the more my brain hurts. Mike `````` Mike _______________________________________________ Rtgwg mailing list [email protected] https://www1.ietf.org/mailman/listinfo/rtgwg ``````_______________________________________________ Rtgwg mailing list [email protected] https://www1.ietf.org/mailman/listinfo/rtgwg ```
 Current Thread Comparison of symmetric and asymmetric PLSN algorithms, mike shand Re: Comparison of symmetric and asymmetric PLSN algorithms, Alia Atlas Re: Comparison of symmetric and asymmetric PLSN algorithms, mike shand Re: Comparison of symmetric and asymmetric PLSN algorithms, mike shand <= Message not available