Subject: [manet] Interlayer Interactions

From: [email-masked]
Date: Mon, 31 Mar 2003 09:49:26 -0800

This is regarding the interlayer interactions in the case of ad hoc
networks. I think that if there is some mechanism that can give
bidirectional status messages between MAC layer-IP layer and IP
layer-Transport Layer, then we can take more intelligent (and faster)
routing decisions.

Moreover, congestion can be better signaled at Transport layer. In
wireless networks, there are more packet losses due to link failure than
the congestion in the network. So, we can send a signal from lower layer
about the status of link. So, TCP doesn't have to backup of thinking
that it's a packet loss. 

We can also add some mechanism on the lines of Snoop. That will give a
lot of flexibility and will help in making better decisions at all
layers.

I wanted to know if there is any active research going on in this field
(apart from the discussion on this mailing list in last few days). Can
anybody send me useful links about this.

Regards,
Ankur 

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From: Sukanta Kumar Hazra <[email-masked]>
Date: Mon, 31 Mar 2003 13:30:56 +0800

> layer-Transport Layer, then we can take more intelligent (and faster)

Goes back to question whether clear protocol layer seperation is
something that must guide our work in MANET, or should be take advantage
of the benefits provided by cross layer interactions to improve
performance. I support the latter, but I have heard many convincing
arguments of the former as well.

> about the status of link. So, TCP doesn't have to backup of thinking

In a multihop case, how does the TCP sender get the signal if the first
hop is good but the last hop is not. Do you mean the TCP sender will
know the link status of all the hops in the path?

If wireless is being used only in the last hop, then yes congestion is
not the main factor for packet drop. I am just wondering if that case is
always true in a multihop wireless network such as MANET.

- Sukanta

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From: Sanket Nesargi <[email-masked]>
Date: Mon, 31 Mar 2003 00:58:50 -0600 (CST)

Ankur,
	There was work done on this by our lab a couple of years back.

K. Chandran, S. Raghunathan, S. Venkatesan, and R. Prakash. A Feedback
Based Scheme for Improving TCP Performance in Ad Hoc Networks. IEEE
Personal Communication Systems (PCS) Magazine: special issue on Ad Hoc
Networks, Volume 8, Number 1, Pages 34--39, February 2001
http://www.utdallas.edu/~ravip/papers/tcpf.icdcs98.pdf

	It relies on feedback from underlying layers to improve the
performance of TCP in ad hoc networks.

	Thanks,
	- Sanket

> anybody send me useful links about this.

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All the world's indeed a stage and we are merely players, 
performers and portrayers,
each another's audience outside the gilded cage.
                                                     
Sanket S. Nesargi
Distributed Systems Lab
University of Texas at Dallas,
Richardson TX 75082				<[email-masked]>
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