O'Reilly logo

Sams Teach Yourself Network Troubleshooting in 24 Hours, Second Edition by Jonathan Feldman

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

TCP Versus UDP

Germane to the theory behind firewalling is the idea that connections can be limited based on the service being offered or sought. Because each TCP/IP service has a unique socket number that it listens to (remember from the telephone analogy that a port is the extension number that the service person for the company answers), it’s reasonably easy for a router or proxy server to limit connections to these ports. Because limits are placed on the port numbers themselves, it follows that the service is also limited. This means that you can pick and choose among the services that might travel in or out of the firewall.

Actually, services ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required