Physical Address

The physical address is also known as the MAC (Media Access Control) address or link address. It is the address of a node which is defined by its LAN or WAN. It is used by the data link layer and is the lowest level of addresses. MAC address is the unique address of a device. The size of a physical address is 48 bits (6 bytes). Below is the format of representing a physical address:

XX : XX : XX : YY : YY : YY, where 1 octant = 8 bits.

Example:

16 : 1A : BB : 6F : 90 : E5

The first 24 bits of a MAC address XX : XX: XX is decided by OUI (Organizationally Unique Identifier). It represents the identity of the manufacturer. The next 24 bits of a MAC address YY : YY : YY represents the unique identity of the device. It is assigned by the manufacturer. They represent NIC (Network Interface Card).

Below is a diagram representing the working mechanism of a physical address:

In the above diagram, we can see that there are two networks – Network 1 and Network 2. A1 is the sender and there are two receivers – D1 and D2. In case of physical address, receiver D1 receives the data but receiver D2 is unable to receive data. This is because receiver D2 does not belong to the same network as the sender A1 belongs to. Physical address can only be passed in the same network and not in different networks. The purpose of using Physical address is to identify devices in the same network.

Advantages

• Physical address can uniquely identify devices and deliver data packets accurately.
• We can restrict access to any network by allowing only those devices which have the authorized MAC addresses to connect. Thus, it can also be used for network security.

Disadvantages

• MAC addresses can be easily spoofed. Thus, the devices can easily gain unauthorized access to a network.
• As physical addresses cannot traverse through the routers therefore they can only be used in local networks and not between different networks.

We can connect two nodes in a network to communicate with each other with the help of addressing. There are four levels of addressing in a network employing the TCP/IP protocol physical address, Logical address, Port address, and Specific address.