Subject: Re: [savi] RFC6620 Page 15 - Data Trigger

From: Joel Halpern Direct <[email-masked]>
Date: Wed, 07 May 2014 14:30:55 -0000

With regard to protecting hosts from "on-link" attackers, there are two 
different cases.
If the SAVI function is on the device with a dedicated port to the end 
device (or an authenticated port) then there is no value in sending the 
NS back to the entity which sent it.  (Some of this is conceptually 
buried in the definition of binding scopes in SAVI, and can be hard to 
realize.)

In the case where the SAVI function is upstream of the usage port (for 
example, it is on the router port, with bridges / switches between the 
prot and the users) there are many weaknesses in SAVI efficacy.  That is 
clearly stated in the documents.  Sending the NS back on that port will 
not as far as I can tell help resolve much, if any, of those weaknesses. 
  We did discuss this extensively in the working group.

Yours,
Joel

On 5/6/14, 11:21 PM, Leaf Yeh wrote:
> Joel - The goal of SAVI is very specific. it is to prevent one node from
> claiming an address that is belongs to (by assignment or proper
> claiming) another node.  Can you please restate your concern with the data
> trigger in terms of how it fails to meet that goal?....
> Sending solicitations back onto that LAN (which seems to be what you are
> asking for) does not actually help with that problem.
>
> I guess your logic sounds right. DAD_NS should sent through the TP, which
> may connect to other SAVI device (and more hosts) within the same scope,
> i.e. the same link, or the same broadcast domain. But the above logic sounds
> not cover my concern on the host to abuse the source address within the
> on-link prefix.
>
> Sending DAD_NS back to the VP receiving the data trigger, sounds useful for
> a check. Wrong or harmful?
>
>
> Best Regards,
> Leaf
>
>