RE: BFD stability follow-up from IETF-91

["Fan, Peng" <[e-mail]>]

Hi Gregory,

 

I was just giving an example :) Application traffic usually cannot stand
small packet loss, not to say 30% loss.

 

I am actually asking for a debug function that could give us some useful
hints of poor connection with small protocol change, besides the basic
connectivity information. If it measures something, it measures packets of
BFD itself. So I don't expect it to be considered as a performance
measurement tool.

 

Best regards,

Peng

 

From: Gregory Mirsky [mailto:[e-mail]] 
Sent: Saturday, November 29, 2014 3:37 AM
To: Fan, Peng; 'MALLIK MUDIGONDA (mmudigon)'; [e-mail]
Subject: RE: BFD stability follow-up from IETF-91

 

Hi Peng,

this is very interesting scenario. I think that if BFD experiences ~30%
packet loss, then highly likely so are affected other applications. Then it
is not just BFD issue but condition that should be detected  by performance
measurement method, whether active or passive packet loss measurement.

I'm convinced that overloading BFD with performance measurement provisions
is counter-productive and is inappropriate. 

 

                Regards,

                                Greg

 

From: Rtg-bfd [mailto:[e-mail]] On Behalf Of Fan, Peng
Sent: Friday, November 28, 2014 4:34 AM
To: 'MALLIK MUDIGONDA (mmudigon)'; [e-mail]
Subject: RE: BFD stability follow-up from IETF-91

 

Hi Mallik,

 

Exactly. Packets may be experiencing slight loss, but the link can hardly be
regarded as connected. More importantly, the experience of upper-level
applications can be degraded severely (e.g. TCP traffic is not able to go
fast in face of even small continuous loss). But what if one BFD frame is
lost every three frames? Then the loss rate is 30% on average, which is
already a very severe value.

 

Best regards,

Peng

 

From: MALLIK MUDIGONDA (mmudigon) [mailto:[e-mail]] 
Sent: Friday, November 28, 2014 7:53 PM
To: Fan, Peng; [e-mail]
Subject: Re: BFD stability follow-up from IETF-91

 

Hi Peng,

 

If the BFD packets are lost, doesn't the BFD session go DOWN? Are you saying
that packet loss is not big enough to make BFD session go DOWN?

 

Thanks

 

Regards

Mallik

 

From: <Fan>, Peng <[e-mail]>
Date: Friday, 28 November 2014 4:20 pm
To: "[e-mail]" <[e-mail]>
Subject: RE: BFD stability follow-up from IETF-91

 

Hi Jeff, all,

 

I have been following this stability extension from the beginning, and as an

operator I would like to express that this draft enables the "advanced

feature" we desire for BFD to provide additional useful information that

helps operators understand network issues. A relevant use case is detecting

lossy or "quasi-disconnected" links or member LAG links. An example of such

situation we experienced was a loosely connected fiber link resulting in

continuous, small amount of packet loss. BFD could get the information of

lost BFD frames on such unstable link, and probably report when a target

level is reached, say a certain number of frames are lost over a period or

among a total number of frames.

 

Best regards,

Peng