Subject: Re: Fwd: Re: I-D ACTION:draft-ietf-manet-lanmar-00.txt (fwd)

From: Richard <[email-masked]>
Date: Tue, 05 Dec 2000 22:51:11 -0800

Mario and Xiaoyan:

In my earlier message, I mentioned that LANMAR may have
a problem with triangle routing, i.e., to route a packet
to a drifter, the packet must first be routed on the shortest
path from the source to the landmark associated with the drifter, 
and then on the shortest path from the landmark to the drifter.
Another potential problem is traffic concentration at the
landmarks, since unless the drifter is drifting toward the
source of the packet, the packet to a drifter will have to 
be routed through the landmark.  (If the number of drifters
is small then this is not a significant problem.)

I think that both of these potential problems can be alleviated 
using the approach I mentioned in my earlier message, i.e., 
applying the concept of mobile IPv6 to landmark routing.
In this approach, the drifter reports its new "foreign" landmark 
(or care-of address) to its "home" landmark (analogous to a home 
agent in mobile IP). The first packet to the drifter is then 
rerouted by the "home" landmark toward the "foreign" landmark.  
Then the drifter can inform the source (correspondent node) of 
its new "foreign" landmark so that subsequent packets can be 
routed directly toward the new landmark (thus alleviating
triangle routing and traffic concentration).

I am probably not the first person to think of this, since
it seems to be a straightforward application of mobile IP to 
landmark routing. Have you or anyone considered this approach?   

Richard

-----------------------
Richard Ogier
Sr. Research Engineer
SRI International
333 Ravenswood Ave.
Menlo Park, CA 94025
Tel: 650-859-4216
Fax: 650-859-4812
Email: [email-masked]
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From: Cesar Santivanez <[email-masked]>
Date: Wed, 6 Dec 2000 13:45:23 -0500 (EST)

Richard, Mario, and Xiaoyan:

I have been working in a protocol named SOAP which shares 
LANMAR's main concepts. In SOAP I considered the triangulation problem 
that Richard  mentioned in his previous e-mail, and apply
a dynamic binding (as in mobile IPv6) to solve it.

You can take a look to the protocol specification and some discussion on:

http://www.cdsp.neu.edu/info/students/cesar/SOAP.ps 

Unfortunately, I do not have simulation results yet ...

BTW, I read in LANMAR I-D that it supports unidirectional links?
It seems that it will only be true for the `last mile',
i.e. for those unidirectional link closer to the destination 
(`in scope'). For those unidirectional link far away from the
destination, the DSDV or some protocol is engaged in order to track
the landmark node. These protocols (DSDV, TORA, etc.) tends to rely
on bidirectional links (i.e. the availability of a reverse path). 
Thus, they will not take advantage of unidirectional links. 
I guess they could be extended for supporting unidirectional
links, but it will increase the complexity of the protocol 
and the amount of overhead the protocol induces. 
Am I wrong?? If so, please let me know ...

Cesar Santivanez
CDSP Center
ECE Department
Northeastern University