What email address or phone number would you like to use to sign in to Docs.com?
If you already have an account that you use with Office or other Microsoft services, enter it here.
Or sign in with:
Signing in allows you to download and like content, and it provides the authors analytical data about your interactions with their content.
Embed code for: 13.2 Layer 2 Addressing
Select a size
13.2 Layer 2 Addressing
Layer 2 Addressing Section 13: Exploring the Packet Delivery Process The OSI data link layer (Layer 2) defines how data is addressed and formatted for transmission on the local LAN. Layer 2 addressing on a LAN is generally implemented as an Ethernet MAC address. To ensure unambiguous communication, every Ethernet station must have a unique MAC address. An Ethernet MAC address is a twopart, 48bit binary value that is expressed as 12 hexadecimal digits. Common MAC address formats include hyphenated hexadecimal 00059A3C7800, colondelimited hexadecimal 00:05:9A:3C:78:00, and period delimited hexadecimal 0005.9A3C.7800. Although IEEE 802.3 Ethernet has become the de facto standard for wired LANs, other Layer 2 LAN protocols have been used in the past, including the following: ARCnet ATM FDDI Token Ring MAC addresses are divided into two parts, a 3byte OUI prefix and a 3byte, vendor assigned suffix. Manufacturers of Ethernet NICs purchase OUIs from the IEEE. The 3 byte (24bits) of vendorassigned suffix yields 2 or about 16 million unique MAC addresses per OUI. As each new NIC is manufactured, a unique address is written onto a PROM chip on the card. Once a vendor assigns all of the unique suffixes, they must purchase another OUI from the IEEE before new MAC addresses can be assigned. 24 MAC addresses are associated with a particular NIC, regardless of its location or to which network that it is connected. If a NIC is plugged into a different local network, its MAC address remains the same. Ethernet NICs use the MAC address to determine if a message should be passed to upper layers for processing. When a device receives a frame, it looks at the destination address. If the device sees that the destination address for the frame matches its MAC address, it passes the data up to the application layer for processing. This is called unicast communication. If a device needs to communicate information to all devices on the local LAN, it addresses the frame to the broadcast address FF:FF:FF:FF:FF:FF (48 bits of binary 1s). Frames that have a destination address of FF:FF:FF:FF:FF:FF will be received by every device on the local LAN. Up Next: Layer 3 Addressing