Re: [OSPF] Stephen Farrell's No Objection on draft-ietf-ospf-te-metric-extensions-09: (with COMMENT)

Stephen Farrell <> Sun, 04 January 2015 13:56 UTC

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Date: Sun, 04 Jan 2015 13:55:58 +0000
From: Stephen Farrell <>
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Subject: Re: [OSPF] Stephen Farrell's No Objection on draft-ietf-ospf-te-metric-extensions-09: (with COMMENT)
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Thanks - fine answer to my not-quite-discuss.


On 04/01/15 09:39, Adrian Farrel wrote:
> Hi Stephen,
> I'd like the authors and shepherd to pitch in, but...
>> - I'd have thought that these TLVs would be sent more often than
>> others, and that (if enormous amounts of money are in play) then
>> use of OSPF authentication might be more likely needed (or some
>> equivalent security mechanisms). I'd even speculate that if
>> enormous amounts of money are in play, then confidentiality may
>> become a requirement (since if I can observe say A bit settings 
>> then that might give me insight into traffic levels - sort of a
>> lights burning at night in central bank implies interest-rate
>> change attack). Can you say why none of that needs to be mentioned
>> at all? Was any of that considered by the WG? (Can you send a
>> relevant link to the archive?)
> I think you are raising two points: 1. Are the TLVs sent more often
> than others and what are the implications? 2. What can be learned
> from sniffing these TLVs?
> To the first point, I don't think they are sent more often than other
> TE TLVs. Indeed metrics for loss and delay may be more stable than
> others, and Section 5 addresses measurement intervals and projects
> that on to announcement thresholds.
> So the risk is that changes in bandwidth availability will cause
> rapid or frequent announcement of those metrics.  However, just like
> the original bandwidth metrics, implementations apply thresholds so
> that small changes don't trigger re-announcement in order to avoid
> stressing the network. Section 6 discusses this.
> Thus, I think we can discard 1.
> The second point is important: you can find out a lot about a network
> by sniffing the IGP, and if your plan is to understand the state of
> your competitor's network or to find the week spots to attack, then
> this is a powerful tool. But in this matter I would argue that these
> no TLVs are no more sensitive than other, pre-existing TLVs, although
> (of course) the more TLVs, the more information is available to be
> sniffed.
> So, the question is how do we protect IGP information as it is
> advertised within a network. There are four elements: - IGP
> information is retained within an administrative domain. - If a
> router is compromised it has access to all of the information and
> there is nothing we can do. - If a node attempts to join a network to
> access the information it will be unknown and will not be able to
> peer. - If a link is sniffed (which is a somewhat more sophisticated
> attack) protection relies on encryption of the messages most probably
> at layer 2, but potentially at IP (which is an option for OSPF) or
> within the OSPF messages themselves.
> I think all of this is just "IGP security as normal", was discussed
> by KARP, and is everyday business for network operators.
> [snip]
>> - The security considerations of RFC 3630, from 2003, is 11 lines
>> long. Has nothing affected OSPF security in the last decade+ that
>> would be worth noting here?
> That is a good point. There is plenty of newer security work.
> Adrian