Black Box Gigabit Smart Switch Eco Fanless, LGB2118A manual Media Access Control MAC MAC Addressing

Chapter 4: Basic Concepts and Management

Table 4-2. SSAP address field

options.

OxAAAA	SNAP
0xE0E0	Novell® IPX
0x F0F0	NetBios
0xFEFE	IOS network layer PDU
0xFFFF	Novell IPX 802.3 RAW packet
0x4242	STP BPDU
0x0606	IP
0x9898	ARP

LLC type 1 is a connectionless service, LLC type 2 is a connection-oriented service, and LLC type 3 acknowledges a connectionless service and has three types of LLC frames for all classes of service. Figure 4-3 shows the format of the Service Access Point (SAP).

Figure 4-3. SAP format.

For more information about SAP, refer to the IEEE 802.2 standard.

4.3 Media Access Control (MAC)

4.3.1 MAC Addressing

A LAN is composed of many nodes. To exchange data among these nodes, each node must have its own unique address to identify who should send the data or should receive the data. In the OSI model, each layer provides its own way to identify the unique address in some form, for example, IP address in network layer.

The MAC belongs to Data Link Layer (Layer 2). The address is a 48-bit long and locally unique address. Since this type of address applies only to the Ethernet LAN media access control (MAC), it is referred to as a MAC address.

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