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Why must some applications be port forwarded when using NAT when WEB traffic doesn't require it?

Hi,

Does anyone know why file sharing applications like Emule, EDonkey, Bittorrent require port forwarding when used over a NATted network? I understand the principle that the incoming connection needs to be requirected to a specific internal (LAN) IP address to get to the correct client and I have successfully set this up on many occassions... but then I started thinking about web (HTTP Port 80/ 443) traffic and how that requests of this nature can be routed back to it's original client all over the same port, over NAT, and without the need for port forwarding. I'm assuming that the originating non-routable (LAN) address must be stored in each packet throughout it's life so it knows where to go when it gets back to it's native firewall on the way back in.

So I guess what I'm asking is 'What is the difference between this standard Web traffic and traffic generated by these file sharing programs'? Couldn't file sharing programs employ the same technology to reduce the set-up overhead and remove the requirement for complex port forwarding setups?

Any thoughts and comments appreciated.

Edd

Reply to
edd
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Here you go.

If you had a machine running a WEB server and wanted to expose the site to the public Internet, then guess what you have to do?

formatting link
Duane :)

Reply to
Duane Arnold

Actually, they only require ports opened due to the way programmers wanted to FORCE you to share what's on your computer. In the early days you could host/not-host without any problems, it was only after they found that most people were leeches and not contributing that they changed the code so that you have to provide in order to get.

Since none of the programs you mention are free of spyware, stop using them and start paying for what you need.

Reply to
Leythos

There is no spyware in any Bittorrent client I have seen. But Bittorrent does require you to host any pieces of the file you are downloading.

Reply to
CyberDroog

Thanks for the link and the response. Unfortunately that doesn't tell me anything I don't already know.

I guess I'm more intersted in the actual packet content and the differences in work done within the TCP/IP stack(s) which allow some packets to be routed back to their originating machine (IP address or MAC address etc), over NAT, and without the need for port forwarding (web traffic for example).

Any ideas appreciated.

Edd

Reply to
EdD

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