Hi James, > James Bensley > Sent: Wednesday, December 21, 2016 10:06 AM > To: cisco-nsp@puck.nether.net > Subject: Re: [c-nsp] Incremental SFP (ISPF) - Provide any benefits "now"? > > On 16 December 2016 at 14:01, CiscoNSP List <cisconsp_l...@hotmail.com> > wrote: > > Hey Adam - Have a TAC case open atm on ASR920 rLFA FRR (Tunnels being > created, when they shouldnt, and not used)...anyway, from this case, MPLS, > OSPF + ASR920 Dev teams have been working on it, and they have stated > that "ISPF conf under router ospf is not recommended anymore. The > command will soon be deprecated." - Its not related to the tac case, its was > just a recommendation from them....I asked why is it being deprecated, and > the reason they gave is that was introduced to improve convergence on > slower processors, processors are fast now, so it is no longer > needed.....somewhat strange, but I pressed them for more info, and that is > all that they have provided so far... > > > > In the case of IP FRR (r)LFA, iSPF is not a recommended setting under OSPF. > When there is a failure with FRR LFA enabled, my understanding is that traffic > will re-route via the backup LSP however the entire OSPF DB needs to be > crawled as a new backup tunnel(s) needs to be calculated now, iSPF could > hinder this process because not all possible paths would be explored in the > OSPF DB, instead the first "suitable" match would be used. That is what Cisco > had lead me to believe although it was unclear at the time so happy to be > corrected here. > Hmmm, I'm not entirely convinced, as the LFA/rLFA is not a matter of a simple iSPF calculation but rather: P-space; SPF rooted at S. Extended P-space; SPF rooted at neighbours of S. Q-space, rSPF rooted at E (for each protected prefix).
So I'd assume that iSPF is used solely in case of primary path computation not for LFA/rLFA selection. But who knows... adam netconsultings.com ::carrier-class solutions for the telecommunications industry:: _______________________________________________ cisco-nsp mailing list cisco-nsp@puck.nether.net https://puck.nether.net/mailman/listinfo/cisco-nsp archive at http://puck.nether.net/pipermail/cisco-nsp/
