|Lesson 4|| TCP/IP addresses and classifications |
|Objective||Describe TCP/IP Addresses and how they are classified.|
A TCP/IP address is a unique address that identifies a computer that is connected to a network. A network can be a LAN, or it might be
your ISP (internet service provider). An IP address consists of a 32-bit number represented as a four-part number with each part
separated by a period (like x. x. x. x). Each part is called an octet and has a value from 0 to 255. Octets are used to identify the
network address and the local host address and are always shown as decimal values (even though they consist of 32 binary values).
The diagram below illustrates the elements of the IP addressing scheme. In this diagram, the Network Number is shown as four octets.
However, it can be any number desired.
For example, if an IP address were 220.127.116.11, this is how that address actually looks in binary:
To accommodate an efficient numbering system, TCP/IP addresses are divided into five classes (A, B, C, D, and E). Classes are similar
to the telephone system's area code concept. Instead of assigning each telephone a unique number, telephones are grouped by area
code. Grouping in this way reduces the total number of digits required to identify a single phone (or in the case of TCP/IP, a single
computer). Instead of organizing users by area code, TCP/IP organizes users by network. The five classes of networks essentially
specify the maximum quantity of networks possible for a particular company.
An address's class can be identified by the first octet. The table below defines the first octets for each class and describes how
the octets are read to identify the network address and the local host address.
Notice that Class A dedicates its first bit position to a 0. Class B sets its first bit to a 1 and its second bit to a 0. The other
classes follow suit. Routers are designed to specifically read these patterns to determine the address class. Once known, the remaining
bits making up the 32-bit address can be read to determine additional information about the address.
Making sense of the numbers
For a real world example, consider your phone number again. It starts with an area code, then a local exchange. For example, if your
phone number is 415-555-1010, it tells the telephone company that you are in a particular region (based on 415), in a particular
neighborhood (based on 555), and on a particular street (based on 1010). Similarly, networks use identifiable IP addresses like the one
In the next lesson, you will learn about the purpose of subnet masks.
If your IP address was 18.104.22.168, your PC would be on a Class-A network. Additionally, assuming a simplistic network number system is
being used, that particular network would be Network number1, and your PC would be node number 3.
InterNIC is the agency that assigns public IP addresses
Tcp Ip Addresses Classifications