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

[Greg Mirsky <[e-mail]>]

Hi Manav,
the update could be in addition of either broadcast or link local multicast
or both with appropriate normative language. But I would not agree that
these wouldn't work.
Regards, Greg
On Apr 8, 2016 12:34 PM, "Manav Bhatia" <[e-mail]> wrote:

> 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
>>
>>
>>
>>
>>
>
>
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