Has MaxFreeTcbs been obseleted?

I'm currently studying the effects of various settings on a file servers performance. One of the TCP/IP registry options that is documented (scarcely), is the MaxFreeTcbs setting. Supposedly this setting is used to decide how many Transmission Control Blocks (TCB) to pre-allocate from non-paged pool. In theory this also has the effect of limiting the amount of concurrent TCP connections the server can sustain.

I loaded up poolmon, and noticed that each time a TCP connection was negotiated, a 456-byte allocation was made from the non-paged pool using the pooltag TCPT. There appeared to be a few TCBs pre-allocated, but only about 5. After that, they were allocated when the TCP connection was created.

What I noticed on a Windows Server 2003 R2 server is that this MaxFreeTcbs setting now appears to have no affect. I set the value to 10, and still able to create 500 simultaneous connections with a tool called PCATTCP. Each of them matched up to an allocation on the TCPT pool tag.

Interesting, nothing mentioned anywhere about this. Also, many of the TCP performance guides still make reference to this key.

Has anyone else run into this? Is this a change to the way TCP/IP works in the Scalable Networking Pack?

-M