Subject: [DNA] Possible way forward: combining Link ID and Landmark?

From: Pekka Nikander <[email-masked]>
Date: Mon, 08 Aug 2005 14:11:59 +0200

[As I wrote earlier, I haven't been able to follow the ML discussion,  
and won't.  My sincere apologies.]

Based on what I heard during the WG meeting on Thursday and in some  
discussions afterwards, the following proposal occurred to me.  It  
may be completely off the mark.  If so, please ignore it.  I am  
offering this just in the case it might be useful and let the WG to  
move forward.

Would the following work?

   1. Define a new Link ID RA option, as in the Link ID draft.

   2. Define new Landmark RS and RA options, as in the landmark draft.

   3. Routers in a link are encouraged to create a Link ID and  
announce it, but not required.  [Details need to be filled in, e.g.,  
if all routers need to agree etc.]

   4a. A host that arrives on a link *with* a Link ID picks the Link  
ID as its landmark.

   4b. A host that arrives on a link *without* a Link ID picks one of  
the prefixes as a landmark, just as in the current landmark draft.

   5. When a host detects that it may have changed links, it looks  
for a landmark (as in the landmark draft) unless it gets a Link ID  
(as the landmark) very quickly (as in the case of FastRA-like  
optimisation).

Based on my very partial understanding, the above outline might  
work.  However, it may also be more expensive (in term of bytes or  
packets) than the current proposals.  On the other hand, it might  
also be more flexible or robust.

Maybe someone could do further thinking and analysis.

--Pekka

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From: Syam Madanapalli <[email-masked]>
Date: Mon, 08 Aug 2005 21:48:27 +0530

Hi Pekka,

We need to use linkid for its robustness against 
changes in linkid due to prefix addition/deletion,
landmark to benifit for nodes moving from non-DNA
to DNA link, complete RA to build the CPL fast for
fast moving nodes. And also it may be good to use
Landmark YES answer and to avoid the periodic
complete RA to save the bandwidth (use linkid).

So I am thinking about the following solution.

1. On DNA links routers advertise linkid in RAs.

2. A node with Link_Up sends an RS with landmark,
   if the landmark presents, the router sends an 
   RA with linkid.

   The other alternative is to send YES answer.

3. If the Landmark does not present, it sends a
   complete RA with linkid (i.e. I bit set for one
   of the prefixes)

4. If no linkid present (moving from non-DNA to DNA link)
   the node picks one of the prefixes as the landmark.

The complete RA is sent only when there is a link change.

-Syam

PS: are we over engineering?

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From: Greg Daley <[email-masked]>
Date: Tue, 09 Aug 2005 15:20:06 +1000

Hi Pekka and Syam,

I agree that these are potential mechanisms for combining
the systems for link identification.   At this stage,
but without necessarily preempting the consensus call,
the chairs will soon approach people to help move toward
having a single solution, so that if the consensus
is confirmed, we're in a good position to move forward.

Syam's question at the end: are we over engineering?
is probably a relevant one, though.

At this stage there seems to be an agreement that the
actual solution's form isn't as important as the fact
that it does the job well most of the time, and we
move forward with it.

Greg

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From: JinHyeock Choi <[email-masked]>
Date: Fri, 12 Aug 2005 14:10:02 +0900

Dear Pekka 

> Maybe someone could do further thinking and analysis.

It may be better for us to combine proposed schemes. In brief, 
LinkID is useful for link identification under prefix change and 
unsolicted RAs, CompleteRA for CPL generation and Landmark for 
interoperability with non-supporting links and bandwidth saving.

We may put those features together to produce a robust and flexible 
solution. I need to do further thinking and analysis for the efficient 
way to merge them. (I am still in After-Meeting-Slumber. :-))

Thanks for your kind consideration.

Best Regards

JinHyeock