On Tue, Nov 17, 2020 at 4:01 AM Gyan Mishra <hayabusa...@gmail.com> wrote:
> > > 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. > Gyan>. We could use Aijun’s passive interface new top level TLV to link the next hop rewrite loopback to the PE-CE links all being set to passive. So if any PE-CE link goes down a PUA is sent and the next hop converges PIC core PE-CE link which is now associated with the Loopback. This would be a major benefit of PUA for PIC core convergence when next-hop-self is used which applies to MPLS and SR and IP based core. https://datatracker.ietf.org/doc/draft-wang-lsr-passive-interface-attribute/ So the two main critical use cases where this solution solves a problem is partitioned area scenario and nest hop convergence when next-hop-self is used scenario. I will update the presentation deck and share. >> Thx, >> R. >> >> >> -- > > <http://www.verizon.com/> > > *Gyan Mishra* > > *Network Solutions A**rchitect * > > > > *M 301 502-134713101 Columbia Pike *Silver Spring, MD > > -- <http://www.verizon.com/> *Gyan Mishra* *Network Solutions A**rchitect * *M 301 502-134713101 Columbia Pike *Silver Spring, MD
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