Firewall Rules / (RFC's?), how to integrate them.

[element-x]

Here's what I'm asking exactly:

For example...

An SMTP server running on port 25, is this server supposed to accept any source-port to the matching destination-port 25? or is it restricted to say, 1024+?

I'm looking for information not only relating to SMTP servers, but DNS,POP3,HTTP and so on. Even if a vague idea of where to start was given, that would be much appreciated.


Thanks.

[Gaston]

This might come handy:

http://www.linux-firewall-tools.com/linux/faq/index.html

And then look under "Network Security Strategies"
and then "Port Level Filtering".

I also have the "Linux Firewalls" book from Robert Ziegler which
has helped quite a lot.

[filp]

Linux Firewalls - Second Edition

ISBN 0-7357-1099-6

Very good explenations of protocols and how to work firewalls around them. As well as lots of information about cool NAT stuff.

For more indepth protocol stuff "TCP/IP Illustrated, Volume 1. The Protocols" ISBN 0-201-63346-9 is excellent.

But we can keep talking about firewall if you want, it's pretty much all I do all day.

Seeya,
Filp.