General Protocol Suite Description
T ~ ~ ~ T _____Imagine three computers: A, B, and C. A and B both have radio equipment, and can communicate via the airwaves using a suitable network protocol (such as IEEE 802.11.) B and C are connected via a cable, using it to exchange data (again, with the help of a protocol, for example Ethernet). However, neither of these two protocols will be able to transport information from A to C, because these computers are conceptually on different networks. One, therefore, needs an inter-network protocol to "connect" them.
One could combine the two protocols to form a powerful third, mastering both cable and wireless transmission, but a different super-protocol would be needed for each possible combination of protocols. It is easier to leave the base protocols alone, and design a protocol that can work on top of any of them (the Internet Protocol is an example.) This will make two stacks of two protocols each. The inter-network protocol will communicate with each of the base protocol in their simpler language; the base protocols will not talk directly to each other.
A request on computer A to send a chunk of data to C is taken by the upper protocol, which (through whatever means) knows that C is reachable through B. It, therefore, instructs the wireless protocol to transmit the data packet to B. On this computer, the lower layer handlers will pass the packet up to the inter-network protocol, which, on recognizing that B is not the final destination, will again invoke lower-level functions. This time, the cable protocol is used to send the data to C. There, the received packet is again passed to the upper protocol, which (with C being the destination) will pass it on to a higher protocol or application on C. Often an even higher-level protocol will sit on top, and incur further processing.
An example protocol stack and the corresponding layers:
| Protocol | Layer |
|---|---|
| HTTP | Application |
| TCP | Transport |
| IP | Internet/Network |
| Ethernet | Data Link/Link |
| IEEE 802.3u | Physical |
Read more about this topic: Protocol Stack
Famous quotes containing the words general and/or description:
“‘A thing is called by a certain name because it instantiates a certain universal’ is obviously circular when particularized, but it looks imposing when left in this general form. And it looks imposing in this general form largely because of the inveterate philosophical habit of treating the shadows cast by words and sentences as if they were separately identifiable. Universals, like facts and propositions, are such shadows.”
—David Pears (b. 1921)
“An intentional object is given by a word or a phrase which gives a description under which.”
—Gertrude Elizabeth Margaret Anscombe (b. 1919)