Agreed. Robert
Can you explain the BGP scenario you had in mind that you have mentioned a number of times that you think this PUA feature would pertain? I will respond to your other email separately. I was trying to guess as to the BGP next hop use case you were referring to but apparently was way off. Thank you Gyan On Tue, Nov 17, 2020 at 9:43 AM Acee Lindem (acee) <a...@cisco.com> wrote: > Speaking as WG member: > > > > I think it would be good to hone in on the BGP PE failure convergence use > case as suggested by Robert. It seems there is some interest here although > I’m not convinced the IGP is the right place to solve this problem. > > > > Thanks, > > Acee > > > > *From: *Lsr <lsr-boun...@ietf.org> on behalf of Gyan Mishra < > hayabusa...@gmail.com> > *Date: *Tuesday, November 17, 2020 at 4:02 AM > *To: *Robert Raszuk <rob...@raszuk.net> > *Cc: *lsr <lsr@ietf.org>, Jeff Tantsura <jefftant.i...@gmail.com>, Aijun > Wang <wangai...@tsinghua.org.cn>, "Acee Lindem (acee)" <acee= > 40cisco....@dmarc.ietf.org> > *Subject: *Re: [Lsr] Prefix Unreachable Announcement Use Cases > > > > > > > > On Tue, Nov 17, 2020 at 3:36 AM Robert Raszuk <rob...@raszuk.net> wrote: > > > > > > Robert, I believe the original intention was related to having the data > plane converge quickly when summarization is used and flip so traffic > converges from the Active ABR to the Backup ABR. > > > > I do not buy this use case. Flooding within the area is fast such that > both ABRs will get the same info. As mentioned before there is no practical > use of PUA for making any routing or fwd decision on which ABR to use. If > your ABRs are not connected with min redundancy this draft is a worst patch > ever to work around such a design. > > > > Gyan> Agreed. The point of PUA in ABR use case is the ability to track > the component prefixes and in case where component is down and traffic is > still forwarded to the ABR and dropped. The other more important use case > is when links are down within the area and the area is partitioned and so > one ABR has all component prefixes however other ABR is missing half the > component prefixes. So since the ABR will by default advertise the summary > as long as their is one component UP the summary is still advertised. So > this use case is severely impacting as now you have an ECMP path to the > other area for the summary via the two ABRs and you drop half your > traffic. So now with PUA the problem is fixed and the PUA is sent and now > traffic is only sent to the ABR that has the component prefixes. > > > > Please present us a picture indicating before and after ABRs behaviour. > > > > Gyan> will do > > > > However PUA can be used in the absence of area segmentation within a > single area when a link or node fails to converge the data plane quickly by > sending PUA for the backup path so the active path. > > > > If there is no area segmentation then there is no summaries. So what are > we missing in the first place ? > > > > Gyan> Sorry I am stating that PUA feature can also be used intra area > where if a link or node goes down to improve data plane convergence. > > > > > > With the IGP tuned with BFD fast detection on ISIS or OSPF links and LFA & > RLFA for MPLS or TI-LFA for SR local protection - with those tweaks the > convergence is well into sub second. So for Intra area convergence with > all the optimizations mentioned I am not sure how much faster the data > plane will converge with PUA. > > > > Even without any of the above listed chain of acronymous things will > generally work well intra-area without PUAs. > > > > Gyan> Agreed which is why I mentioned the BGP next hop self use case > if I could figure out how PUA could help there that would be a major > benefit of PUA. > > > > Thx, > R. > > > > > > -- > > [image: Image removed by sender.] <http://www.verizon.com/> > > <https://www.google.com/maps/search/13101+Columbia+Pike+%0D%0A+Silver+Spring,+MD?entry=gmail&source=g> > > *Gyan Mishra* > > *Network Solutions Architect * > > > > *M 301 502-1347 13101 Columbia Pike > <https://www.google.com/maps/search/13101+Columbia+Pike+%0D%0A+Silver+Spring,+MD?entry=gmail&source=g> > *Silver Spring, MD > <https://www.google.com/maps/search/13101+Columbia+Pike+%0D%0A+Silver+Spring,+MD?entry=gmail&source=g> > > > -- <http://www.verizon.com/> *Gyan Mishra* *Network Solutions A**rchitect * *M 301 502-134713101 Columbia Pike *Silver Spring, MD
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