RE: BFD stability follow-up from IETF-91

[Gregory Mirsky <[e-mail]>]

Hi Marc,
regarding your concern on ensuring that BFD Echo reply traverses the same constituent link as crossed by corresponding BFD Echo request , if it is indeed the requirement, I'll refer to revision of IEEE-802.1AX-REV in its part related to conversation-sensitive frame collection and distribution. Alternatively, we may realize the RFC 7130 needs an update that introduces or explains behavior of micro-BFD Echo over LAG.

	Regards,
		Greg

-----Original Message-----
From: Rtg-bfd [mailto:[e-mail]] On Behalf Of Marc Binderberger
Sent: Monday, December 08, 2014 1:21 PM
To: Manav Bhatia
Cc: [e-mail]
Subject: Re: BFD stability follow-up from IETF-91

Hello Manav,

> For the echo mechanism to work, do you agree that you would have to 
> continuously send Echos so that you can detect the issue?

that's what I had in mind, yes


> Or are you suggesting that once BFD flaps we will start sending Echoes 
> overloaded with debug information to detect the issue?

interesting idea - that would be an alternative use, collecting forensic data. Maybe we should support that too!


My biggest problem with the echo idea is so far BFD-over-LAG. But maybe it is 
not a real problem, any echo stamping/updating in the forwarding path would 
require an hardware update (or reprogramming, if your hardware allows) and in 
this case one could boldly state that the echo packet must leave via the 
ingress port :-)


Regards, Marc





On Mon, 8 Dec 2014 09:33:05 +0530, Manav Bhatia wrote:
> Hi Marc,
> 
>> 
>> 
>> * Greg's echo idea is of course do-able - when you think timestamping in
>> hardware can be done then it can be done in the forwarding path for echos 
>> as
>> well. Depends on your hardware :-) and on an agreed (minimal) format for
>> echo. As mentioned BFD echo is not defined/used for multiple BFD features,
>> which limits it's use though.
>> 
> 
> For the echo mechanism to work, do you agree that you would have to 
> continuously send Echos so that you can detect the issue?
> 
> Or are you suggesting that once BFD flaps we will start sending Echoes 
> overloaded with debug information to detect the issue?
> 
> I'd like to understand this before the mailing list sees a barrage of 
> emails. Alternatively, we can also take it offline and only report the 
> summary of our discussion to the list.
> 
> Cheers, Manav