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RE: BFD WG adoption for draft-haas-bfd-large-packets

"Les Ginsberg (ginsberg)" <ginsberg@cisco.com> Tue, 23 October 2018 23:52 UTC

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From: "Les Ginsberg (ginsberg)" <ginsberg@cisco.com>
To: Albert Fu <afu14@bloomberg.net>, "rtg-bfd@ietf.org" <rtg-bfd@ietf.org>
Subject: RE: BFD WG adoption for draft-haas-bfd-large-packets
Thread-Topic: BFD WG adoption for draft-haas-bfd-large-packets
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Date: Tue, 23 Oct 2018 23:52:50 +0000
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Albert -

From: Albert Fu (BLOOMBERG/ 120 PARK) <afu14@bloomberg.net>
Sent: Tuesday, October 23, 2018 8:45 AM
To: rtg-bfd@ietf.org; Les Ginsberg (ginsberg) <ginsberg@cisco.com>
Subject: RE: BFD WG adoption for draft-haas-bfd-large-packets

Hi Les,

Given that it takes relative lengthy time to troubleshoot the MTU issue, and the associated impact on customer traffic, it is important to have a reliable and fast mechanism to detect the issue.

[Les:] This is  one of the points where we are not in full agreement. I agree you need an easy and reliable way to detect the problem when it occurs.
However, I disagree that you need to do this “fast” – when fast is defined as sub-second.

You have something that we know only occurs during some maintenance event – which is planned and only occurs “once/day,week”.
Checking for this even once/second is overly aggressive.
If it came for free, then no reason not to do so.
But as this discussion has shown, there are costs/risks.

For example, if you were using IS-IS and you detected this within the default adjacency hold time (30 seconds on p2p circuits) – would that be too slow for you? If so, please explain why this is too slow.

I think the primary issue here is ease of use and reliability. Whether detection time is one second or one minute seems relatively unimportant.

Do you disagree?

   Les

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