Re: [trill] Alvaro Retana's Discuss on draft-ietf-trill-directory-assisted-encap-10: (with DISCUSS)

"Susan Hares" <> Wed, 07 March 2018 18:48 UTC

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From: Susan Hares <>
To: 'Donald Eastlake' <>, 'Alvaro Retana' <>
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Date: Wed, 07 Mar 2018 13:48:05 -0500
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Subject: Re: [trill] Alvaro Retana's Discuss on draft-ietf-trill-directory-assisted-encap-10: (with DISCUSS)
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Donald and Alvaro: 

Do we have an agreed upon text changes?   If so, can we send a proposed change to Alvaro for review prior to Thursday's meeting? 

Sue Hares

-----Original Message-----
From: Donald Eastlake [] 
Sent: Monday, March 5, 2018 3:27 PM
To: Alvaro Retana
Cc: The IESG;;; Susan Hares; trill IETF mailing list
Subject: Re: Alvaro Retana's Discuss on draft-ietf-trill-directory-assisted-encap-10: (with DISCUSS)

Hi Alvaro,

On Mon, Mar 5, 2018 at 2:32 PM, Alvaro Retana <> wrote:
> Alvaro Retana has entered the following ballot position for
> draft-ietf-trill-directory-assisted-encap-10: Discuss
> ...
> ----------------------------------------------------------------------
> ----------------------------------------------------------------------
> I have significant concerns about this document; as currently written, 
> I believe the technology is underspecified and can cause significant 
> damage to a DC network where it might be deployed.  I am then balloting a DISCUSS.
> The document (including the security considerations) is written 
> assuming that the TRILL-ENs can be trusted (and are not compromised), 
> and that the directory information is accurate.  However, I believe 
> there are several cases that have been overlooked.
> (1) There aren't any basic safeguards specified to at least make sure 
> that a TRILL-EN is doing the right thing (or something sensible).  For 
> example, what if the Ingress RBridge Nickname field in the TRILL 
> header doesn't correspond to the first rBridge at the domain boundary?  Should that frame be accepted?

This concern doesn't seem very different from the general insecurity of Layer 2.

If a link has no TRILL router adjacencies, then I guess it it reasonable to check that the ingress nickname is that of the receiving RBridge but it gets harder if you have a mixed link with both end stations and TRILL routers (probably rare in deployments but, on the other hand, in TRILL a "link" can be a bridged LAN...).

> (2) rfc8171 talks about issues with incorrect directory mappings.  
> Consider the case where a TRILL-EN uses (on purpose!) an incorrect 
> mapping.  That "can result in data being delivered to the wrong end 
> stations, or set of end stations in the case of multi-destination packets, violating security policy."
> [rfc8171]  How can this risk be mitigated?

I'm not sure how using "an incorrect mapping" is that different from just using whatever nicknames it feels like...

> I don't think that there are easy mitigations for these issues, but at 
> least mentioning them so that operators are aware of the risk would be 
> enough to clear this DISCUSS.

It is certainly reasonable to mention these. One possible mitigation is the use of end-to-end encryption.

 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA