Hi Haibo, thank you for the clarification. I may suggest a text for Section 3:
In some EVPN deployments, for example, when it spans over multiple domains, only one of a pair of interconnected PEs benefits from monitoring the status of the connection. In such a case, using S-BFD [RFC7880] is advantageous as it reduces the load on one of the PEs while providing the benefit of faster convergence. The following sections provide examples of EVPNs that would benefit from using S-BFD. What are your thoughts? Regards, Greg On Tue, Mar 15, 2022 at 7:18 PM Wanghaibo (Rainsword) < rainsword.w...@huawei.com> wrote: > Hi Greg, > > Thanks for you comments. > > Yes, the resources will save at PE1 and PE2 as figure 1. This is a typical > 3PE scenario. > > The service is like this: > > +-----+ +-----+ +-----+ > > | UCE1|----| APE1|--------|SPE1 |, > > +-----+ +-----+` /+-----+ `. > > `, .' `.+-----+ > > ...... \/ | SCE1| > > /\ `+-----+ > > ` `. ,' > > +-----+ +-----+,' .+-----+ ` > > | uCEn|----| APEn|--------|SPE2 |` > > +-----+ +-----+ +-----+ > > There may be many Access PEs，used to access User CE. And they all > multi-homed to a couple Servicc PE, SPE1 and SPE2. > > (shown as the PE1 and PE2 as figure 1) > > Access PE needs to detect Service PE’s reachability. Access PE > creates SBFD session as an initiator, SPE as the reflector. This will save > Service PEs’ resources. > > > > Regards, > > Haibo > > > > *From:* Greg Mirsky [mailto:gregimir...@gmail.com] > *Sent:* Tuesday, March 15, 2022 11:12 PM > *To:* Wanghaibo (Rainsword) <rainsword.w...@huawei.com> > *Cc:* draft-wang-bess-sbfd-discrimina...@ietf.org; BESS <b...@ietf.org>; > rtg-bfd WG <rtg-bfd@ietf.org> > *Subject:* Re: A question about the draft-wang-bess-sbfd-discriminator > > > > Hi Haibo, > > thank you for your expedient response. If I understand the scenario you're > addressing, it is where a single PE with moderate resources is connected to > a PE that acts as the edge device for the access network. To improve the > quality of user experience, customer's PE is connected to a secondary PE > that is used as a backup. You are concerned that maintaining two BFD > sessions on the customer's PE might overload the resource-limited PE. But > isn't that the PE that initiates S-BFD sessions toward two access > network edge PEs in your draft? I think that the savings are on the side of > these two PEs, not the subscriber's PE. Would you agree? > > > > Regards, > > Greg > > > > On Tue, Mar 15, 2022 at 7:20 AM Wanghaibo (Rainsword) < > rainsword.w...@huawei.com> wrote: > > Hi Greg, > > Thanks for your comments. > > The scenario you pointed out is a 4PE scenario, but in our > solution, a large number of scenarios are based on 3PE. > > In a 3PE scenario, deploying BFD wastes resources. A large number of > single-homed PEs may be connected to the dual-homed PEs. The dual-homed PEs > may not have enough resources to create BFD sessions. > > > > Regards, > > Haibo > > > > *From:* Greg Mirsky [mailto:gregimir...@gmail.com] > *Sent:* Tuesday, March 15, 2022 12:44 AM > *To:* Wanghaibo (Rainsword) <rainsword.w...@huawei.com>; > draft-wang-bess-sbfd-discrimina...@ietf.org; BESS <b...@ietf.org>; > rtg-bfd WG <rtg-bfd@ietf.org> > *Subject:* A question about the draft-wang-bess-sbfd-discriminator > > > > Hi Haibo and the Authors, > > thank you for updating the draft. I've read the new version and have a > question about the use case presented in the document. There are three PEs > with two of them providing redundant access to a CE. It appears that a more > general case would be if both CEs use redundant connections to the EVPN. > Asume, PE4 is added and connected to CE2. In that case, it seems reasonable > that each PE is monitoring remote PEs, i.e., PE1 monitors PE3 and PE4, PE2 > - PE3 and PE4, PE3 - PE1 and PE2, and PE4 - PE1 and PE2. So, now there are > pairs of S-BFD sessions between PEs connected to CE1 and CE2 respectively. > That seems like too many sessions and that number can be reduced if one > uses BFD instead of S-BFD. Would you agree? To simplify operations, it > might be helpful to use the technique described in > draft-ietf-bfd-unsolicited > <https://datatracker.ietf.org/doc/html/draft-ietf-bfd-unsolicited-09>. In > the recent discussion of the draft on the BFD WG ML, the authors noted that > they are working on extending the scope to include the multi-hop BFD. > > Greatly appreciate your thoughts about the number of S-BFD sessions. > > > > Regards, > > Greg > >
