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04/04/2007, 14h39

UDP checksum is very simple. Just use binary sum over 16-bit words and
then the result should be inverted. Disregard any carry out bit. In
your particular example the sum is:

1110011001100110
+ 1101010101010101
----------------------------
16-bit sum (NO carry) 1011101110111011
one's complemented: 0100010001000100

What UDP puts in its header in checksum field is: 0100010001000100.

My first reply was incomplete so apologize for that. You will be fine
with your homework or midterm. For further reading you may refer to:
http://www-net.cs.umass.edu/kurose/transport/UDP.html

04/04/2007, 14h39	#6
martinmk Messages: n/a Hébergeur:	Re: UDP checksum calculation UDP checksum is very simple. Just use binary sum over 16-bit words and then the result should be inverted. Disregard any carry out bit. In your particular example the sum is: 1110011001100110 + 1101010101010101 ---------------------------- 16-bit sum (NO carry) 1011101110111011 one's complemented: 0100010001000100 What UDP puts in its header in checksum field is: 0100010001000100. My first reply was incomplete so apologize for that. You will be fine with your homework or midterm. For further reading you may refer to: http://www-net.cs.umass.edu/kurose/transport/UDP.html