TCP/IP Protocol Suite
A network protocol is a standard for communication between computers. TCP/IP stands for Transmission Control Protocol/Internet Protocol. We refer to TCP/IP as a suite of protocols, actually it is a system comprised of several protocols, each with specific functions. The two primary protocols serve the following functions:
- IP – is responsible for moving packet of data from computer to computer. IP forwards each packet based on a four byte destination address (the IP address). The Internet authorities assign ranges of IP numbers to different organizations. The organizations assign groups of their numbers to others.
- TCP – is responsible for verifying the correct delivery of data. Data can be lost on the network. TCP detects errors or lost data and requests retransmission until the data is correctly and completely received.
- There are many other protocols in the TCP/IP suite with specialized functions for
discovering routes from computer to computer, including RIP, OSPF, and IGRP.
Every computer on the Internet has a unique IP Address which is a 12 digit number in the form of 987.654.321.001. If it doesn’t look like a 12 digit number, such as 188.8.131.52 we can assume the first numbers are zeros – 098.076.001.005. An IP address could be compared to a phone number for a computer.
Packet Switching Network
Have you ever ordered a large item and it arrived in separate packages? After opening the packages and reading the instructions you had to assemble it. Data sent over the Internet and over local networks is broken up and sent in separate packages called packets. When all of the packets arrive at the destination, they are assembled with instructions from the TCP/IP protocol. If a packet is lost or corrupted, the TCP protocol can ask the sending computer to resend the packet instead of the whole file.
There are many advantages to packet switching. If a large file was sent as a single packet instead of breaking it up, one small error would require resending the whole file. A large file would have to complete sending before another computer could use the transmission medium (the wire or fiber optic it is traveling on). This would lead to delays and congestion. If a particular route the packets are traveling on becomes congested or goes down, the routing protocol can find an alternative route for the remaining packets without the sender or receiver even knowing.
Servers and Clients
You may hear the terms server and client or client/server architecture used in technical computer documentation. There is nothing mystical about clients or servers; the terms describe a computer’s function more than its physical design. Your desktop PC is probably a client but it could be a server if it had server software on it.
A server is a computer that provides services to other computers. A client is the computer requesting the services. The term server is also used to describe software running on the server computer, such as a web server, a database server, an email server, a DHCP server, and so on. A server computer could be dedicated to only one server-type service, such as a web server, or could provide multiple services, such as an email server, a web server, a database server, and so on.
Server computers generally use more expensive, higher quality components to ensure reliability and redundancy. A typical server will have multiple hard drives, the thing in your computer that stores the data, and they will continue operating without a hitch if one of the drives fails. They may be connected to battery backups in the event of a power failure and may even have a backup power converter to take over if one fails. They typically have large amounts of memory and fast CPU’s, the processor brain of the computer. However, today’s desktops have very powerful CPU’s and the same components may be used in a server or a client computer. Whenever you surf the web your client computer requests web pages from a web server. When you check your email, you are retrieving it from an email server. Many smaller businesses have a server in their offices that may provide a centralized storage area for files, run a database application, and could potentially host (store and deliver) your web page and email. But it is recommended that you pay someone else to host your website and email unless you or someone in your business is technically proficient and understands the business of running servers on the Internet.