About tcp_fastimo() and tcp_slowtimo()

[kwl02r]

Dear all,
I just follow the book "TCP/IP illustrate vol 2" to understand more 
about TCP timer. In the book, tcp_fastimo() is invoked each 200 ms to do 
delay ack job and tcp_slowtimo() is invoked each 500 ms to do the rest 
of other tcp times. But at the last version of FreeBSD source code, I 
couldn't find tcp_fastimo() anymore and  tcp_slowtimo() is quite 
different compared with source code present at book. My questions are:
At the new FreeBSD:

1. Did delay ack time still be detected each 200ms? Which function do 
this job? If not, can anybody help to describe some detail things about
delay ack time at freebsd source code.

2. The new tcp_slowtimo() following is invoked each 500ms, but seems 
only detects tcp_keepintvl timer, how about other timers (eg. SYN, 
FIN_WAIT ..)
void
tcp_slowtimo()
{
	int s;

	s = splnet();

	tcp_maxidle = tcp_keepcnt * tcp_keepintvl;

	splx(s);
}
3. Did TCP timer (detect 200 or 500 ms each time) doing the same job 
under the LINUX kernel?
4. Any web or book can find detail describe at source code about TCP 
timer under both FreeBSD and Linux kernel?

Thanks

Calvin