TCP vs UDP Throughput

I am trying to figure out why I am consistently getting lower throughput with UDP than with TCP. Here is the setup: I have two 1.6ghz systems (XP & 2000) connected via a 100mbit connection. I have tried using NetIQ's Chariot software, as well as Iperf to verify my results.

With TCP, I get an average throughput of about 94mbps. With UDP, I only get about 54mbps.

Any idea why? Thanks for any help you can give.

Sounds to me you are monitoring the amount of bandwidth being utilized with each protocol as TCP is connection oriented and will perform a 3-way handshake and thus use more bandwidth and UDP is connectionless and will just send and let layer 4 figure out if it made it or not. What exactly are you doing that gives you the option to change from udp to tcp as the transfer protocol? and are you sure you are measuring the speed of the transfer or the amount of bandwidth being used. This would actualy make sense if you are copying a file from a USB drive as it will only transfer at 50 Mbps the rest of what you would be seeing is the TCP overhead on the link. also you would want to make sure you are running everything in full duplex as you will not get collisions.