Re: [secdir] Secdir review of draft-ietf-isis-trill

Donald Eastlake <d3e3e3@gmail.com> Mon, 20 December 2010 21:57 UTC

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From: Donald Eastlake <d3e3e3@gmail.com>
Date: Mon, 20 Dec 2010 16:58:47 -0500
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Cc: ietf@ietf.org, secdir@ietf.org, Erik Nordmark <nordmark@acm.org>, draft-ietf-isis-trill@tools.ietf.org, Sam Hartman <hartmans-ietf@mit.edu>
Subject: Re: [secdir] Secdir review of draft-ietf-isis-trill
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Hi,

On Mon, Dec 20, 2010 at 2:05 PM, Stewart Bryant <stbryant@cisco.com> wrote:
> On 20/12/2010 18:43, Donald Eastlake wrote:
>>
>> Hi,
>>
>> On Mon, Dec 20, 2010 at 11:42 AM, Sam Hartman<hartmans-ietf@mit.edu>
>>  wrote:
>>>>>>>> "Radia" == Radia Perlman<radiaperlman@gmail.com>  writes:
>>>
>>>    Radia>  No objections.  Radia
>>>
>>> Can I get someone to confirm that the text in the proposed sentences is
>>> substantially true?
>>> I think so but I'm not an IS-IS expert.
>>
>> LSPs have sequences number, etc., and are idempotent. I think only
>> Hellos have the potential replay Denial of Service problem. So I would
>> suggest changing to:
>>
>> "Even when the IS-IS
>> authentication is used, replays of Hello packets can create
>> denial-of-service conditaions; see RFC 6039 for details. These issues
>> are similar in scope to those discussed in section 6.2 of
>> draft-ietf-trill-rbridge-protocol, and the same mitigations may apply."
>>
>> Thanks,
>> Donald
>
> ... as I recall from discussions with the ISIS WG the changes that were made
> to ISIS for TRILL make it more vulnerable to a hello attack than vanilla
> ISIS. This I understand is because there is more work to be done in
> processing a TRILL hello. Is that correct?

I think we are talking about Denial of Service due to replay of old
Hellos screwing up the state. This is unrelated to the work required
to process a Hello.

It is true that some processing is required for IS-IS LAN Hellos. One
reason for having a protocol like BFD is that you can send BFD
messages more frequently because they take less processing than
Hellos.  But I don't see why there would be that much difference
between the work involved in processing a TRILL LAN Hello and a Layer
3 IS-IS LAN Hello.

> - Stewart

Thanks,
Donald