PC Help Jansant - A Guide to TCP/IP

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TCP/IP Guide

Transmission Control Protocol Internet Protocol (TCP/IP) is actually a suite of protocols rather than 2 suggested by the name. TCP/IP is the protocol suite that drives the internet and many networks large and small. In a TCP/IP network computers do not have names, they have a number which is the computer address. When you type a web address such as http://www.google.com, the name is resolved by a Domain Name Server to googles IP address. This way people don't have to remember confusing numbers to surf the web. Because each computer connected to a network must have a unique IP address, there are methods for a single computer on a network to share it's IP address with other computer on it's local network, this is the gateway computer. Without this there would soon be no addresses for new computers to join the internet. IP addresses are broken into classes for different uses such as for use on the internet, or for use within a private network. Therefore a large organisation with hundreds of computers connected to the internet via a private network can all use the same IP address to access the internet.

An IP Address is a 32bit address broken into 4 octets and can be expressed either in binary or in decimal. No octet can contain all 0's or all 1's (0 or 255)

11010100 00001111 10010000 00001100 or 212.15.144.12

An IP address is further broken into two, to represent the network address and the computer address. Which part is the network address and which part is the computer address is determined by the subnet mask. All computers on the same network must have the same subnet mask, but they must have different computer addresses. Even if two computers are on the same physical network but have different network addresses, they will not be able to communicate with each other. So it is possible for computers to share the same physical network but be on different logical networks.

Main TCP/IP Address Classes

Class A address range is from 1.0.0.0 to 126.0.0.0 and the default subnet mask is 255.0.0.0. A class A address has a possibility of 126 networks, each network has the possibility of 16,777,214 hosts.

Class B address range is from 128.0.0.0 to 191.255.0.0 and the default subnet mask is 255.255.0.0. A class B address has the possibility of 16,384 networks, each network has the possibility of 65,534 hosts.

Class C address range is from 192.0.1.0 to 223.255.255.0 and the default subnet mask is 255.255.255.0. A class C address has the possibility of 2,097,152 networks, each network has a potential 254 hosts.

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