WHAT IS A NETWORK OR IP ADDRESS?

I. Definition of Network or IP address

  An IP address is a unique address that identifies a device on the internet or a local network. IP stands for Internet Protocol and describes a set of standards and requirements for creating and transmitting data packets, or datagrams, across networks. The Internet Protocol (IP) is part of the Internet layer of the Internet protocol suite. In the OSI model, IP would be considered part of the network layer. IP is traditionally used in conjunction with a higher-level protocol, most notably TCP. 

If you're wondering how IP works let me give you an information about it: 

 IP is designed to work over a dynamic network. This means that IP must work without a central directory or monitor, and that it cannot rely upon specific links or nodes existing. IP is a connectionless protocol that is datagram-oriented so each packet must contain the source IP address, destination IP address, and other data in the header to be successfully delivered.

 Combined, these factors make IP an unreliable, best effort delivery protocol. Error correction is handled by upper level protocols instead. These protocols include TCP, which is a connection-oriented protocol, and UDP, which is a connectionless protocol.

II. List of the IP versions numbers 

  

 During the development of the first version of the Internet Protocol, in the seventies of the previous century, the initial experimental versions 1 to 3 were not standardized. The first working version that was widely deployed was assigned version number 4. A separate protocol based on reliable connections was developed, and assigned version 5.IP version 7 was chosen in 1988 by R. Ullmann as the next IP version because he incorrectly assumed that version 6 was in use for ST-II. 

 However, ST-II had reused version 5 of the original ST protocol. When it became apparent, in the early nineties of the previous century, that IPv4 could not sustain routing in a growing Internet, several new Internet Protocols were proposed. The Internet Protocol that finally emerged was assigned version number 6, being the lowest free number greater than 4. The PIP protocol and TUBA protocol used versions 8 and 9, following version 7 for TP/IX.

III. Binary Digits of IP address

 You know that an IP address is numbers that represent a device on a network, as a mailing address represents your home's location. But in order to actually assign and use IP addresses, you must understand the format of these "numerical identifiers" and the rules that pertain to them.

In binary notation, all four octets are written in binary format.

Examples of IP address in binary notation are following: 

00001010.00001010.00001010.00001010
10101100.10101000.00000001.00000001
11000000.10101000.00000001.00000001

Examples of subnet mask in binary notation are following: 

11111111.00000000.00000000.00000000
11111111.11111111.00000000.00000000
11111111.11111111.11111111.00000000

In decimal notation, all four octets are written in decimal format. A decimal equivalent value of the bits is used in each octet.

Examples of IP address in decimal notation are following: 

10.10.10.10
172.168.1.1
192.168.1.1

Examples of subnet mask in decimal notation are following: -

255.0.0.0
255.255.0.0
255.255.255.0

In real life you rarely need to covert an IP address and subnet mask from decimal to binary format and vice versa. But if you are preparing for any Cisco exam, I highly recommend you to learn this conversion. Nearly all Cisco exams include questions about IP addresses. Learning this conversion will help you in solving IP addressing related questions more effectively

Except the base value, binary system works exactly same as decimal system works. Base value is the digits which are used to build the numbers in both systems. In binary system, two digits (0 and 1) are used to build the numbers while in decimal system, ten digits (0,1,2,3,4,5,6,7,8,9) are used to build the numbers.

In order to convert a number from binary to decimal and vice versa, we have to change the base value. Once base value is changed, resulting number can be written in new system.

Since IP address and subnet mask both are built from 32 bits and these bits are divided in 4 octets, in order to convert these addresses in binary from decimal and vice versa, we only need to understand the numbers which can be built from an octet or 8 bits.

A bit can be either on or off. In binary system on bit is written as 1 and off bit is written as 0 in number. In decimal system if bit is on, its position value is added in number and if bit is off, its position value is skipped in number.

IV. Classes of IP address

 

 Classful addressing is a network addressing the Internet's architecture from 1981 till Classless Inter-Domain Routing was introduced in 1993.

This addressing method divides the IP address into five separate classes based on four address bits.

Here, classes A, B, C offers addresses for networks of three distinct network sizes. Class D is only used for multicast, and class E reserved exclusively for experimental purposes.

Let's see each of the network classes in detail:

Class A Network

This IP address class is used when there are a large number of hosts. In a Class A type of network, the first 8 bits (also called the first octet) identify the network, and the remaining have 24 bits for the host into that network.

An example of a Class A address is 102.168.212.226. Here, "102" helps you identify the network and 168.212.226 identify the host.

Class A addresses 127.0.0.0 to 127.255.255.255 cannot be used and is reserved for loopback and diagnostic functions.

Class B Network

In a B class IP address, the binary addresses start with 10. In this IP address, the class decimal number that can be between 128 to 191. The number 127 is reserved for loopback, which is used for internal testing on the local machine. The first 16 bits (known as two octets) help you identify the network. The other remaining 16 bits indicate the host within the network.

An example of Class B IP address is 168.212.226.204, where *168 212* identifies the network and *226.204* helps you identify the Hut network host.

Class C Network

Class C is a type of IP address that is used for the small network. In this class, three octets are used to indent the network. This IP ranges between 192 to 223.

In this type of network addressing method, the first two bits are set to be 1, and the third bit is set to 0, which makes the first 24 bits of the address them and the remaining bit as the host address. Mostly local area network used Class C IP address to connect with the network.

Example for a Class C IP address:

192.168.178.1

Class D Network

Class D addresses are only used for multicasting applications. Class D is never used for regular networking operations. This class addresses the first three bits set to "1" and their fourth bit set to use for "0". Class D addresses are 32-bit network addresses. All the values within the range are used to identify multicast groups uniquely.

Therefore, there is no requirement to extract the host address from the IP address, so Class D does not have any subnet mask.

Class E Network

Class E IP address is defined by including the starting four network address bits as 1, which allows you two to incorporate addresses from 240.0.0.0 to 255.255.255.255. However, E class is reserved, and its usage is never defined. Therefore, many network implementations discard these addresses as undefined or illegal.

Example for a Class E IP address:

243.164.89.28

Limitations of classful IP addressing

Here are the drawbacks/ cons of the classful IP addressing method:

• Risk of running out of address space soon
• Class boundaries did not encourage efficient allocation of address space

Summary:

• An IP (Internet Protocol) address is a numerical label assigned to the devices connected to a computer network that uses the IP for communication.
• IP Address is divided into two parts: 1) Prefix 2)Suffix
• IP address works in a network like a postal address. For example, a postal address combines two addresses, address, or your area your house address.
• In a class A type of network, the first 8 bits (also called the first octet) identify the network, and the remaining have 24 bits for the host into that network.
• In class B type of network, the first 16 bits (known as two octets) help you identify the network. The other remaining 16 bits indicate the host within the network.
• In class C, three octets are used to indent the network. This IP ranges between 192 to 223.
• Class D addresses are 32-bit network addresses. All the values within the range are used to identify multicast groups uniquely.
• Class E IP address is defined by including the starting four network address bits as 1.
• The major drawback of IP address classes is the risk of running out of address space soon.
• Important rule for assigning network id is that the network ID cannot start with 127 as this number belongs to class A address and reserved for internal loopback functions.