Re: [tcpm] DISCUSS: draft-ietf-tcpm-tcp-soft-errors

Fernando Gont <> Fri, 18 July 2008 17:36 UTC

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Date: Fri, 18 Jul 2008 14:33:07 -0300
To: Jari Arkko <>,,
From: Fernando Gont <>
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Subject: Re: [tcpm] DISCUSS: draft-ietf-tcpm-tcp-soft-errors
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At 07:22 a.m. 17/07/2008, Jari Arkko wrote:

>First, I was unable to find any evidence of review from the 6MAN or V6OPS
>communities. No request for review has been posted to the lists, at least.
>Has there been such review, and if not, can we ensure it happens now?
>Normally, in general and in particularly for Informational documents IETF
>Last Call suffices, but as I outlined above, this specification is
>important enough to warrant that we get it right.

Actually, the document took off from an initial ID from v6ops. e.g., 
the "Contributors" section in the draft acknowledges this (also it 
does not explicitly reference the v6ops wg).

>Section 2.1 says:
>    When receiving an ICMP error message that indicates a hard error
>    condition, TCP will simply abort the corresponding connection,
>    regardless of the connection state.
>Question. I was under the impression that recent specifications have
>started to say to not blindly believe ICMP errors due to denial-
>of-service concerns? If this is not the case, then no problem.

I'm the author of the TCPM WG's "ICMP attacks against TCP draft". 
While that draft was initially meant for the informational track, it 
is now aims at "Informational". So, even when virtually all current 
implementations behave as you describe, the IETF specifications 
remain unchanged.

>Section 3.2 says:
>    In scenarios where a node has no default routers and Neighbor
>    Unreachability Detection (NUD) [RFC4861] fails for destinations
>    assumed to be on-link, or where firewalls or other systems that
>    enforce scope boundaries send ICMPv6 errors, the sending node will be
>    signaled of the unreachability problem.  However, as discussed in
>    Section 2.2, standard TCP implementations will not abort connections
>    when receiving ICMP error messages that indicate soft errors.
>Clarity. This is somewhat misleading. When the node has no default
>routers it also has no prefixes, no global addresses and it will not
>even try to use IPv6 towards other global addresses.

Why not? What if a Router Advertisement has a "Router Lifetime" of 0? 
Am I missing something?


Kind regards,

Fernando Gont
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