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:[email protected]]
Sent: Tuesday, March 15, 2022 11:12 PM
To: Wanghaibo (Rainsword) <[email protected]>
Cc: [email protected]; BESS <[email protected]>; rtg-bfd
WG <[email protected]>
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)
<[email protected]<mailto:[email protected]>> 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:[email protected]<mailto:[email protected]>]
Sent: Tuesday, March 15, 2022 12:44 AM
To: Wanghaibo (Rainsword)
<[email protected]<mailto:[email protected]>>;
[email protected]<mailto:[email protected]>;
BESS <[email protected]<mailto:[email protected]>>; rtg-bfd WG
<[email protected]<mailto:[email protected]>>
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
