Introduction To IP Addressing

In order to allow global communications among all devices in the Internet, the identifier is used at the network layer for delivery from host to host. It is identical to the telephone system which the telephone numbers consist of the country code and area code as part of the identifying scheme. The identifier in the network layer is called Internet address or IP address with 32-bit address (IPv4). IP addresses are unique in which each address defines one and only one connection to the internet. IP addresses are also universal where the addressing scheme must be accepted by any hosts connected to the internet. IP address is also known as logical address.

                IPv4 consists of 32-bit address which means it can support to 2³² devices (4,294,967,296) in the world. However, almost 600 million are reserved and cannot be used for public routing [2]. The addresses are allocated to countries by the Internet Assigned Numbers Authority (IANA) via the Regional Internet Registries (RIRs) [2] and we can clearly observe via
 https://en.wikipedia.org/wiki/List_of_countries_by_IPv4_address_allocation.
Some addresses are shown in Table 1.

Table 1

We can get information regarding to our IP address by typing ‘ipconfig/all’ in Command Prompt as shown in Figure 1. Make sure your computer is connected to the Internet before you run the prompt. As shown in Figure 1, apart from getting an IP address of your computer, you can also know the Physical Address of your computer and other information. Physical address or MAC Address is an Ethernet address which uniquely identifies computers and interfaces. It is burned into Read-Only Memory (ROM) in the Network Interface Card (NIC). MAC address consists of 48-bits and is expressed as 12 hexadecimal digits, such as 0000.0c12.ab89 or 00-00-0c-12-ab-89. Figure 2 shows the division of MAC address into two parts; the first six hexadecimal digits are the manufacturer or vendor identifier and the remaining six hexadecimal digits represent the serial number or other value administered by the manufacturer. MAC address works at Data Link Layer in OSI model.

Figure 1 IP configurations in Command Prompt

Figure 2 MAC address

Compared to MAC address, IP address works at Network Layer in OSI model. When we deal with the internet, we refer to the TCP/IP model instead of OSI model. However, IP address is in the same layer for both models but with different name, Network layer in OSI model, Internet layer in TCP/IP model. The differences between TCP/IP and OSI model is shown in Table 2.

Table 2 Differences beween TCP/IP and OSI model

IP addresses are expressed in decimal numbers such as 10.8.240.13. IP addresses are categorized into five classes as depicted in Table 3. For the public addressing scheme, only Class A, B and C are used. Class D is utilized for multicast network while Class E is reserved for future or experimental purposes. We can identify the class of our IP address based on the first value by referring to Table 3. For instance, my IP address as shown in Figure 1 is 10.60.101.59. Because my IP address begins with 10, it is in decimal range of 0 to 127 which means the IP address is in Class A. Identifying the classes are important to develop a local network for assigning devices in the network. However, this is not discussed here.

Table 3 IP Address Classes

 Nowadays, IP addresses are running out due to the large amount of networks that have been allocated. The problem we face today, more than one computer and smartphone are used for one home. Even, the electrical and mechanical appliances are being enabled for Internet access these days. Thus, some addresses that had been blocked for reserving special purposes before, are currently used for private networking. Followings are the ranges and the amount of private IPs:

10.0.0.0 - 10.255.255.255                              16,777,216

172.16.0.0 – 172.31.255.255                         1,048,576

192.168.0.0 – 192.168.255.255                     65,536

Private IP addresses are also known as ‘Non-Routable Addresses’. Do not be surprised if these private IP addresses can be the same as your neighbors'. Routers recognize the private address belongs to our network and never forwards the packet to other networks if it is not necessary. However, we still require a real address from the router. Network Address Translation (NAT) is performed by a router to change private IP address to real IP address if the packet needs to be sent to the internet.

In the future, the use of Internet might be widely used by more than 4.2 billion of devices. In order to overcome this problem, IPv6 has been defined and developed. IPv6 uses 128-bits rather than the 32-bits currently used in IPv4, which means it can support number of devices as much as 2¹²⁸. Compared to IPv4, IPv6 represents its number by using hexadecimal numbers. For further reading, feel free to check the link https://en.wikipedia.org/wiki/IPv6_deployment.

References:

[1] www.ciscopress.com

[2] https://en.wikipedia.org/wiki/List_of_countries_by_IPv4_address_allocation

[3] https://en.wikipedia.org/wiki/IPv6_deployment

Written by:

Siti Sara Binti Rais