problems with internet terms

[ltensail]

i also have slow download problem. i've read the topics with slow download problem but i don't know how to check if i have firewall. what's a router? how do i check if i have one? what about port forward?

[complich8]

ok, I'll try to give you a quick overview, see if you can follow along.

your computer has a network connection of some kind or another. That connection gets an address, which lets it talk to the rest of the computers on the internet. Every computer on the net has an address, called an "IP address" (IP is "Internet Protocol").

In addition, to allow multiple applications on your computer to use the same network connection at the same time, you have these things called "ports". It's basically just a place that a program can talk from or listen to. Ports are part of TCP and UDP (TCP is "Transmission Control Protocol", UDP is "Universal Datagram Protocol" ). Ports are specified by number, from 1-65535.

A firewall is an application or an appliance that decides what can go through and what can't. It allows access to things that it's told to, and doesn't allow access to things that don't. It's basically a wall in front of your "ports" -- so if you think of ports as windows to the outside of your house, a firewall is basically a big brick wall with a couple armed guards and some razor wire -- things that are allowed get in, things that aren't don't. Common firewall software includes windows xp's internet connection firewall, norton personal firewall, mcaffee personal firewall, tiny personal firewall, and zonealarm. Common hardware firewalls include pretty much every router on the market, because they all do NAT (which I'll talk about later). Brands to expect include Linksys, D-link, and Netgear.

A router is a device that figures out how pieces of data are going to travel on the internet. In terms of what most home users think of, it's what lets several computers (usually 2-4) share one internet connection (like a cable modem connection or something). So if you have a router, it'll be a device that your internet connection passes through that isn't your cable or dsl modem. Home user routers perform what's called NAT ("Network Address Translation") -- which means they make it possible for multiple computers to use one apparent IP address. If you're behind a NAT router you'll have an ip address that looks like "192.168.something.something" or "10.something.something.something" (where something is 0-255). Most home routers use 192.168.0.x or 192.168.1.x. Note that these address ranges are reserved by the standard that establishes IP addresses, so they aren't "real" addresses, in that no one person has them and they can't be seen by the actual internet.

NAT works by changing the source fields of packets you're sending to the internet in such a way that it looks like they're coming from the address of the router instead of the address of the computer. Then it tries to remember what computer sent what packets, based on a couple internals (like connection states, sequence numbers, etc). This works well for things responding to requests made from behind it, but doesn't allow for connections from the outside to go past it to the inside.

Port Forwarding is taking a NAT router and forwarding all of its incoming connections aimed at a certain port to a machine behind the router. This lets one of those reserved addresses get incoming connections, so you could do things like running a server or some sort.

All of this is relevant to bittorrent because .... if you've got a firewall (like zonealarm) that doesn't know that bittorrent should be allowed through it, a router (anything that NATs) that doesn't know what to do with incoming connections to bittorrent ports, so either case just drops the incoming data and ignores it. This means that you don't get those incoming connections, and as a result you're not going to be downloading at your best speeds.

Hopefully that clarifies internet technology jargon a bit for you.