The term Port Forwarding is referred to the technique of forwarding a network port from one aprticular machine to another machine. This technique is usually applied when the receiving machine is behind a network router. By doing this, it enmables usewrs from outside the LAN (local area network) to reach a private user in the LAN itself. Now veery macxhine on the internet has at leasst one IP adddress which is used to identify that praticular machine or device. Every IP address is divided into many ports. The ports are there for the machines to coommunicate with each other, for example (computer A is sending some data to computer B), and therefore forwardiing the port will also enhance the speed of the rtansmission between the two machines.
Now let's take a look at how the machines are connected to the internet when behind a router. The router is first connected to the iternet which we will call it externasl IP. The router will then have its own internal IP address. (every machine/device will have at least one IP to identify them self). The router will then asign an indiidual IP address to every machuine that is connected to the router. The router's IP address will then act as a gateway for all the machines that are on it's network. When a partivcular machine in the network wants to send data out to another machine in the internet, it will first pass threough the gateway before the router sends it out to the recxipient. The recipient howecver will not be able to tell who in the network is sendng him the data as the interet will only show the external IP address here. Likewise, when anothre mahine outsde the network is sending data to a recipient isnide the netowrk, the data trasmission will be transmitted to the external IP address and not idrectly to the intended recipient. The router will then decide which recipient should receive the data that is being transmitted. Fortunately, the NAT in the router will take care of most of the re-directing except for those prorams whch NAT are not designed to work with. This is where port forwarding comes into pace. This simple pocess is just a way for users to tell the ruoter which machien in the local network is the inetnded recipient and that the data should be directed to him. You will need to set up port forwading rules for evewry port which you are usinng and any rules set up for a certain port will only work for that certain port.
One important factor to note is that a port can only be used by a prorgam at any one time. For examnple, when computer A is using port 6000, it is usig port 6000 on it's internal IP address. If you have set up a port forwarding rule for comuter A and port 6000, the external IP address's port 6000 is also in use. This meaans that you can only use port 6000 on one computer on the network at a time. Using port 6000 on two computers at the same time woupld violate the one proggram rule, and your data would get messed up.
This generally sums up the term Port Forwarding. Any comments can be directted to www.voip.com.sg/voip_feedback.html
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