Subject: [DNA] Proposed resolution to issue 9 for draft-pentland-dna-protocol-01.txt

From: Brett Pentland <[email-masked]>
Date: Thu, 04 Aug 2005 02:26:08 +1000

Hi DNA WG,

All of the recent discussion on the issue of RAs that include
a "no" answer in a Landmark Option but also include prefixes
that have been seen on the link, has been in favour of
treating this as an indication that link change has not
taken place.  Here is some proposed text to reflect this:

Old text:

       Instead if the 'N' bit is set in the received Landmark Option, a
       change of link is indicated and the host SHOULD initiate
       reconfiguration using the information in the Router Advertisement.

New text:

       Instead if the 'N' bit is set in the received Landmark Option, AND
       there is no overlap between the list of prefixes in the Router
       Advertisement and the list of prefixes that the host has stored
       for CPL [14], a change of link is indicated and the host SHOULD
       initiate reconfiguration using the information in the Router
       Advertisement.

       If the 'N' bit is set in the received Landmark Option, but there
       is one or more prefixes in the Router Advertisement that are also
       in the list of prefixes the host has stored for CPL, this is an
       indication that no link change has occured but there is prefix
       change underway on the link.  The host MUST NOT invalidate its
       current configuration.

Any comments?
Brett.

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From: Syam Madanapalli <[email-masked]>
Date: Wed, 03 Aug 2005 19:00:25 +0200

Hi Brett,

I think we may need to check for the prefixes that the other routers
on the link advertising. That is we need to build CPL on the new
link.

-Syam

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From: Syam Madanapalli <[email-masked]>
Date: Wed, 03 Aug 2005 19:22:36 +0200

I was thinking that the completeRA may not be complete all the time.
If the 'complete RA' is assumed then it is ok to check the prefixes in
the RA received.

-Syam

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From: Greg Daley <[email-masked]>
Date: Thu, 04 Aug 2005 17:12:53 +1000

> on the link advertising. That is we need to build CPL on the new

Hi Syam,

I think that as each RA arrives, it can be compared to the
CPL, following this rule.

Greg

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From: Greg Daley <[email-masked]>
Date: Thu, 04 Aug 2005 17:18:53 +1000

Hi Syam,

> If the 'complete RA' is assumed then it is ok to check the prefixes in

If an RA doesn't contain all prefixes on link, it doesn't
have the completeness flag set, and is not a CompleteRA.

Even if the prefixes aren't complete, then the RA can still be
compared with the CPL.  This may still have problems with false
changes if prefixes have been added or retracted very recently.

The function therefore doesn't change, and it sometimes benefits
from the existing prefixes in the RA.

Greg

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From: Syam Madanapalli <[email-masked]>
Date: Thu, 04 Aug 2005 09:46:10 +0200

Hi Greg,

> CPL, following this rule.

Yes I got it.  Now the question is how long the MN should wait
for receiving all RAs from the routers? In between if an RA comes
with YES answer then we can assume link change otherwise, the
MN needs to wait for all RAs.

---

From: Brett Pentland <[email-masked]>
Date: Thu, 04 Aug 2005 18:09:21 +1000

Hi Syam,

> MN needs to wait for all RAs.

Why would it wait.  If the host has the CPL on the old link, then it
can make the decision immediately on recption of the first RA.  If we
specify that the NO answer include a DNAO, then the host doesn't even
need to have the CPL on the previous link to make an immediate
decision.

Brett.

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From: Syam Madanapalli <[email-masked]>
Date: Thu, 04 Aug 2005 10:57:07 +0200

Hi Brett,

The CPL requires to build complete prefix list on both the previous 
link as well as on the new link. Is this correct? 

Also Greg said the MN checks all RAs as they arrive. This means
MN cannot make decision based on single RA with NO answer, unless
the RA is a 'Complete RA'.

Also I am wondering how would CPL works without building complete
prefix list on previous link? Are you assuming 'Complete RA'? 

I am sorry, I am getting confused.

-Syam

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From: "Tero Kauppinen (JO/LMF)" <[email-masked]>
Date: Thu, 04 Aug 2005 11:55:24 +0200

Hi Syam,

> link as well as on the new link. Is this correct?

Let's assume that the node has built a complete prefix for the old link. 
It then moves to a new link, and gets a "NO" answer. It's not required 
the node to receive all prefixes on the "new" link in order to detect 
that it's actually on the same link. The node can conclude this from a 
single joint prefix, or have I misunderstood the question?

Tero

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From: Syam Madanapalli <[email-masked]>
Date: Thu, 04 Aug 2005 12:02:17 +0200

Hi Tero,

> single joint prefix, or have I misunderstood the question?

Yes, it can detect if there is a single joint prefix. The node should 
check all the prefixes on the link or until it finds  a joint prefix.
(I think :-))

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From: Brett Pentland <[email-masked]>
Date: Thu, 04 Aug 2005 20:12:51 +1000

> check all the prefixes on the link or until it finds  a joint prefix.

I don't think so.  If the CPL has been generated, and then the host
gets a L2 indication that movement may have happened, and the next RA
has no prefixes in common with the CPL, then the host can take this
to indicate link change.

Brett.