CertiGuide to Network+  9  Chapter 0100:  Network Protocols       9  III  Protocol Suite Characteristics

III  Protocol Suite Characteristics 1 Packet Format

Each protocol suite has a unique format for logical addresses for the devices on the network. These logical addresses are used at the OSI Model’s Network Layer (and above) to identify the devices on the network. Whereas the format for hardware (MAC) addresses is standardized, and the same format of MAC address is used by all protocols that need to reference the NIC device, the designers of each protocol family have the option of creating another logical addressing scheme that works optimally for their purposes. Similarly, a network interface card (NIC)’s MAC address almost never changes. But its logical address may change when the PC (containing that NIC) is moved to a new LAN segment on the 4^th floor, from its old location on the 2^nd floor.

For example, a NIC might have a MAC address of “00-48-60-21-41-EB”. If the computer containing that NIC is communicating with a network using TCP/IP protocols, the network admin might assign it a logical address of 199.97.31.1.

If the computer is communicating with a network using NetBEUI protocols, the network admin might assign it a logical address of “MIKEY”. As you can see, the format of the unique logical address is completely up to the protocol suite designers, and it is independent of the MAC address.

III  Protocol Suite Characteristics 1 Packet Format