>Hi,
>
>I'm currently trying implementing a modified TCP state machine and I'm 
>going through the code looking for all the systems calls ( eg. the active 
>open calls and close connection calls) to TCP and all of it's outputs.
>
>Would anyone know of a document that already has this information?  I

Try "TCP/IP Illustrated vol. 2"  It fully describes the implementation
of the 4.4 BSD TCP/IP stack.  Volume 1 is a very good book as well..

>will also be tackling the IP stack as well, so any info on what systems 
>calls it receives and what it outputs would also be of great help.

What exactly are you interested in doing?

Chris Csanady