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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 (M AC)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.