Types of addresses associated with the layers of TCP/IP model

In this article, you’ll learn about Types of addresses associated with the layers of TCP/IP model.

Each layer in the TCP/IP model uses an address for the efficient delivery of data between communicating nodes. The host-to-network layer (physical plus data link layer) relates to physical address, network layer relates to logical address, transport layer concerns with port address and application layer defines specific address. The description of these addresses is as follows: 

Physical Address

• It is the address assigned to a node by the network (LAN or WAN) in which it is connected.
• It is the lowest-level address that is included in the frames at the data link layer to identify the destination node. The size and format of physical address is highly dependent on the underlying physical network. That is, different networks can have different address formats.
• The most common physical address size is of 48-bits. Physical address is also known by other names including link address, MAC address and hardware address. 

Logical Address

• In an inter-networked environment connecting different networks having different address formats, the physical addresses are inadequate for communication. Thus, a universal addressing system is used that assigns each host in the network a unique address called logical address (also referred to as IP address or software address) which is independent of the underlying physical network.
• For example, in Internet, each host connected to the Internet is assigned a 32-bit IP address and no two hosts connected to the Internet can have the same IP address.
• It is the responsibility of the network layer to translate the logical addresses into physical addresses. 

Port Address

• The data link layer (using physical address) and network layer (using IP address) ensure end-to-end delivery of data, that is, data is reached the destination host. Now, since multiple processes may be running simultaneously on the host machine, there should be some means to identify the process to which data is to be communicated. To enable this, each running process on the host machine is assigned with a label what is known as port address.
• Using the port address, the transport layer ensures process-to-process delivery. In TCP/IP architecture, port address is of 16 bits. 

Specific Address

• Some applications such as e-mail and World Wide Web (WWW) provide user-friendly addresses designed for that specific address.
• Some examples of specific address include an e-mail address that helps to identify the recipient of that e-mail and URL of a website that helps to search a document on the web.