Subject: [manet] delay in sending the next packet in DSR

From: "Liaw, Yong Shyang - LIAYS001" <[email-masked]>
Date: Tue, 4 Feb 2003 15:34:02 +1030

Hi,

I have a question regarding DSR & would appreciate if any one can help.

In DSR, when sending data packet from the send queue, shall you wait for
(delay*no_hop) before sending the next data packet?
where delay is the time you wait for a reply from 1 hop away (i.e. 30ms),
	no_hop is the number of hops 

I find the Opnet's DSR model implements the above, but I could not find in the
DSR Internet-draft that said this for data packet (though there is some random
delay for sending reply packets). In this a bug? I would appreciate if you can
help me.

Thank you.

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From: Casey Carter <[email-masked]>
Date: Tue, 04 Feb 2003 14:43:35 -0600

This is a standard hack for ad hoc routing simulations that avoids 
interaction with ARP.  ARPs based on the BSD implementation have a 
single-packet buffer where they hold packets while performing address 
resolution.  Additional packets that arrive replace the packet in the 
buffer.  So, if you have a bunch of packets waiting for the route reply, 
and send them to the link layer all at once, ARP will drop all but the 
last if it does not already have an address mapping for the nexthop. 
 The hack is to guess how long an ARP request/reply cycle takes, and 
delay sending packets by cycle_time * #hops.

There is substantial discussion of this issue in my paper "ARP 
Considered Harmful: Manycast Transactions in Ad Hoc Networks" to appear 
in WCNC 2003 -- available at 
<http://mobius.cs.uiuc.edu/publications.htm>.  We discuss how ARP does 
not seem to integrate properly into ad hoc networks, and present an 
alternative that places responsibility for address resolution in the 
routing protocol, where it can be done with zero cost.

-- 
Casey Carter
[email-masked]
[email-masked]
AIM: cartec69