Re: [mpls] Two new drafts on (micro-)BFD over MC-LAG interfaces

[Manav Bhatia <[e-mail]>]

Hi Greg,

Not sure i understand how it can "update RFC 7130". Is that by using a link
local mcast IP instead of a Unicast IP?

We know that, that wouldnt work.

Cheers, Manav

On Fri, Apr 8, 2016 at 9:44 PM, Gregory Mirsky <[e-mail]>
wrote:

> Hi Reshad,
>
> thank you for your comments. Indeed, RFC 7130 is restricted and thus
> hardly applicable to MC-LAG case. We realize that if this proposal is
> adopted it not only enhance applicability on u-BFD but will update RFC 7130.
>
>
>
> Regards,
>
>                                 Greg
>
>
>
> *From:* Reshad Rahman (rrahman) [mailto:[e-mail]]
> *Sent:* Friday, April 08, 2016 8:51 AM
> *To:* Manav Bhatia; Gregory Mirsky
> *Cc:* [e-mail]; [e-mail];
> [e-mail]; Alia Atlas ([e-mail]); [e-mail];
> [e-mail]
>
> *Subject:* Re: Two new drafts on (micro-)BFD over MC-LAG interfaces
>
>
>
> I agree with Manav, and nothing in RFC7130 seems to preclude using
> different unicast IP address as destination on different member links.
>
>
>
> Regards,
>
> Reshad (as individual contributor).
>
>
>
> *From: *Rtg-bfd <[e-mail]> on behalf of Manav Bhatia <
> [e-mail]>
> *Date: *Friday, April 8, 2016 at 11:04 AM
> *To: *Gregory Mirsky <[e-mail]>
> *Cc: *"[e-mail]" <
> [e-mail]>, "[e-mail]" <
> [e-mail]>, "[e-mail]" <[e-mail]>, "Alia
> Atlas ([e-mail])" <[e-mail]>, "[e-mail]" <
> [e-mail]>, "[e-mail]" <[e-mail]>
> *Subject: *Re: Two new drafts on (micro-)BFD over MC-LAG interfaces
>
>
>
> Hi Greg,
>
>
>
> Why cant different micro-BFD packets use the IP address of the MC-LAG end
> points? Ones going to router 1 will all carry the same unicast IP address.
> The ones going towards the other router will all carry some other IP
> address, which would be configured along with the MC-LAG configs.
>
>
>
> In fact i would argue that the u-bfd packets going to different routers
> must use different IP addresses so that you can actually verify the data
> plane liveliness. Whats the point in sending a contrived IP address if the
> path that it takes is different from the other regular packets?
>
>
>
> Cheers, Manav
>
>
>
> On Fri, Apr 8, 2016 at 6:09 PM, Gregory Mirsky <
> [e-mail]> wrote:
>
> Hi Manav,
>
> thank you for sharing insight view of discussions around RFC 7130,
> extremely helpful.
>
> We believe, and Jeff is co-author of RFC 7130 too, that MC-LAG presents
> different case and the compromise that you’ve pointed too is justified. We
> will add more details on the potential differences between unicast and
> multicast fast paths in the next update.
>
> We are open to the discussion and always welcome comments and alternative
> proposals.
>
>
>
>                 Regards,
>
>                                 Greg
>
>
>
> *From:* Manav Bhatia [mailto:[e-mail]]
> *Sent:* Thursday, April 07, 2016 7:39 PM
> *To:* Mach Chen
> *Cc:* Gregory Mirsky; [e-mail]; [e-mail];
> [e-mail]; [e-mail];
> [e-mail]; Alia Atlas ([e-mail])
> *Subject:* Re: Two new drafts on (micro-)BFD over MC-LAG interfaces
>
>
>
> I believe it had to do with multicast datapath (especially link local)
> being different from the unicast datapath in most routers. Using link local
> multicast IP addresses may not necessarily guarantee Unicast IP
> reachability.
>
>
>
> When writing 7130 we spent quite a bit of time ensuring that we dont carve
> out a special data path for the micro-BFD packets. Using link local would
> have made it a lot simpler.
>
>
>
> And this is where i think the current proposal is flawed -- they use link
> local multicast to ensure IP unicast reachability which is incorrect.
>
>
>
> Cheers, Manav
>
>
>
> On Thu, Apr 7, 2016 at 11:16 PM, Mach Chen <[e-mail]> wrote:
>
> Hi Greg and all,
>
>
>
> I just have quick review on the drafts. If my understanding is correct,
> the idea is to use multicast destination address other than unicast address
> when  sending BFD packets over LAG links. And actually this idea has been
> proposed in https://tools.ietf.org/html/draft-chen-bfd-interface-00 (the
> predecessor of RFC 7130). And at that time, the co-authors of RFC 7130 did
> discuss the idea of using multicast destination address, but for some
> reason I forget now(I may need to reiterate the discussions on the
> archive), the idea was abandoned, although I still think multicast
> destination address is a smart idea.
>
>
>
> Best regards,
>
> Mach
> ------------------------------
>
> *From:* Rtg-bfd [[e-mail]] on behalf of Gregory Mirsky [
> [e-mail]]
> *Sent:* Tuesday, April 05, 2016 6:16
> *To:* [e-mail]; [e-mail]
> *Cc:* [e-mail];
> [e-mail]; [e-mail]; Alia Atlas (
> [e-mail])
> *Subject:* Two new drafts on (micro-)BFD over MC-LAG interfaces
>
> Dear All,
>
> two new drafts, related to RFC 7130, were published before the meeting:
>
> ·         BFD on MC-LAG interfaces in IP network
> <https://tools.ietf.org/html/draft-tanmir-rtgwg-bfd-mc-lag-ip-00>
>
> ·         BFD on MC-LAG interfaces in IP/MPLS network
> <https://tools.ietf.org/html/draft-tanmir-rtgwg-bfd-mc-lag-mpls-00>
>
>
>
> Greatly appreciate your reviews, comments, questions and suggestions.
>
>
>
> Regards,
>
>         Greg
>
>
>
>
>