I see that while using the -sS option to stealth scan per se a particular TCP port, nmap attempts to send atleast 6 TCP packets ( with varying seq nos , window size etc ) to the same ip address . When the number of ip addresses being scanned is a large number ....it becomes very problamatic to finish the scan. Is there any way of curtailing this repeated packets?
These packets were picked up by a local sniffer ...and effectively makes each scan to consume atleast 20 seconds.

i'm not too sure, but i think it has to do this to make it stealth because if it just sent one packet, then the remote machine would know what was happening and where it was being sent from. If nmap sends several different packets then it can confuse the remote machine so it doesn't know it's you.

i think this is something along the right lines anyway...