IEEE 802.2 LLC Header

 

Destination Service Access Point (DSAP) - a seven bit address with an eighth bit indicating if it is a specific address (0) or a broadcast address (1). The DSAP is not a station or MAC address; it designates the service control point where the message should be routed.

Source Service Access Point (SSAP) - also a seven bit address; the eighth bit is used to determine if the massage is a command (0) or a response (1). Like the DSAP, the SSAP designates a control point from which the message originated.

Control - Can be 8 or 16 bits long. Lenght is indicated by the first two bits. The 16 bit fields are used to exchange sequence numbers; the 8 bit fields are used for unsequenced information.

Data - the frame's payload.