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Re: [sfc] Mirja Kühlewind's Discuss on draft-farrel-sfc-convent-05: (with DISCUSS and COMMENT)

"Adrian Farrel" <adrian@olddog.co.uk> Thu, 08 February 2018 20:47 UTC

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Reply-To: adrian@olddog.co.uk
From: Adrian Farrel <adrian@olddog.co.uk>
To: 'Martin Stiemerling' <mls.ietf@gmail.com>, "'Mirja Kuehlewind (IETF)'" <ietf@kuehlewind.net>
Cc: draft-farrel-sfc-convent@ietf.org, tal.mizrahi.phd@gmail.com, sfc-chairs@ietf.org, iesg@ietf.org, sfc@ietf.org
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Date: Thu, 08 Feb 2018 20:46:57 -0000
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Subject: Re: [sfc] Mirja Kühlewind's Discuss on draft-farrel-sfc-convent-05: (with DISCUSS and COMMENT)
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Thanks Martin and Mirja,

> and it is probably explicitly noteworthy that one incoming packet can
> trigger one (or even multiple ?) new packet which may increase the
> number of packets related to the incoming flow by a factor of 2.

Well, it might be possible to create a use case that does that. OAM, for example, might cause a one-for-one copy. But one might as well say that this is a concern with IP because the payload protocol might result in one packet creating multiple replies.

But since this document is somewhat open-ended about how the is used, we should certainly flag up the concern with two mitigations:
1. Applications using this mechanism should be careful about this issue
2. Implementations should rate limit to:
  a. Protect against simple volume attacks (and accidents)
  b. Protect against amplification

I'll send some text SOON.

Cheers,
Adrian

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