Re: [secdir] review of draft-ietf-isis-bfd-tlv-02

Sam Hartman <> Sun, 25 July 2010 11:18 UTC

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From: Sam Hartman <>
To: Stephen Kent <>
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Date: Sun, 25 Jul 2010 07:18:39 -0400
In-Reply-To: <p06240803c870ffec1816@[]> (Stephen Kent's message of "Sat\, 24 Jul 2010 16\:44\:40 -0400")
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Subject: Re: [secdir] review of draft-ietf-isis-bfd-tlv-02
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>>>>> "Stephen" == Stephen Kent <> writes:

    Stephen> The Security Considerations section is just one paragraph,
    Stephen> which states that the addition of this feature does not
    Stephen> adversely affect the security mechanism (sic) of IS-IS. I'm
    Stephen> not questioning this assertion, based on reading this
    Stephen> document, but I think a couple of additional sentences are
    Stephen> needed here, to justify the assertion.

How about something like: This TLV does not adversely affect the
security of IS-Is. The primary consequence of using the BFD mechanism in
a case where it is not supported is incorrectly detecting a false
failure of bidirectional forwarding.  The primary consequence of not
using BFD when BFD is supported is failure to detect situations in which
bidirectional forwarding is not happening on a link. At worst, this
leads to a denial of service condition. However, a party who can
manipulate the contents of this TLV is already in a position to create
such a denial of service by disrupting IS-IS routing.

If the above paragraph is correct, I think it may go some distance to
addressing Stephen's concern.

However, I wonder how the authentication mechanisms of BFD interact with
the authentication mechanisms of IS-IS? Is it possible to get into a
situation where IS-IS is authenticated but BFD is not?  If so, that
should be discussed in the security considerations section.