Subject: RE: [DNA] IMPORTANT: Combined DNA Solution draft

From: [email-masked]
Date: Tue, 08 Nov 2005 10:47:48 -0800

> >>>6.1.1 Data structures
> >>>
> >>>	The list will be referred to in this
> >>>     document as "DNARouterPrefixList".  Prefixes are
> >>
> >>learned by their
> >>
> >>>     reception within Prefix Information Options [3] in Router
> >>>     Advertisements.  Prefixes in Learned Prefix Options 
>(see Section
> >>>5.3)
> >>>     MUST NOT update the contents of DNARouterPrefixList
> >>>
> >>>  Why is there a "MUST NOT" ? I understand that the LPO 
>itself may  >>>  contain the prefixes of the router processing 
>the RA from  >>  >>a different  >>  >>>  router. But so does 
>the PIO. As DNARouterPrefixList contains just  >>>  the 
>prefixes not configured on this router, you need to filter 
>both  >>>  from PIO and LPO, right ?
> >>
> >>This is to make sure that when an administrator pulls a 
>prefix  >>out, that it will in fact go away, and not just kept 
>being  >>readvertised by the other routers on the link.  
>Basically we  >>only want prefixes to be learned by routers 
>from routers where  >>the prefix has been explicitly configured.
> >>
> >
> > I don't understand. Complete RA has both the configured and 
>learned  > prefixes. If an admin pulls a prefix out, it will 
>stop appearing  > in the RA from other routers, and eventually 
>all routers will  > converge with the prefixes that are 
>configured across all routers.
> > Routers that learnt the prefix would stop putting it in the 
>LPO  > eventually. Are you concerned that it might take longer 
>for this  > to happen ? The motivation for "MUST NOT" is not obvious.
>
>Say a prefix is explicitly configured on only one out of three 
>routers on a link.  That prefix will be learned by both of the 
>other routers on the link and included in LPOs in RAs from 
>those routers.  If the administrator withdraws the prefix from 
>the router on which it was configured, the other two routers 
>would continue to see the prefix in each other's LPOs and in 
>fact the original router would "learn" of the prefix from the 
>LPOs, and the prefix would never go away.  Does that explain 
>it adequately?
>
Yes, i can see the problem now. 
But section 6.1.10 says something about graceful removal
of the prefix where it adds to the DNARouterPrefixList and
sets it to expire in 1.5 hours. So, i would assume that
it would hear the same in the LPO from the other routers
(which should stop as per 6.1.4 as there is lifetime for
the learned prefixes also). I have to read a bit more
carefully...

-mohan

-mohan

>Brett.