Nortel Networks 553-3001-211 manual Lapb balanced class of procedure, Balanced configuration, Fcs

		Appendix A: LAPB Data Link Control protocol				Page 891 of 894
Table 275
LAPB frame structure
Flag	Address		Control	Information	FCS		Flag
01111110	8 bits		8 bits	unspecified	16 bits		01111110
				(no. of bits)
Legend:

Flag: Flag sequence – All frames start and end with the flag sequence. (A single flag is used as both the closing flag for one frame and the opening flag for the next frame.)

Address: Station address field – In command frames, the address identifies the station for whom the command is intended. In response frames, the address identifies the station from which the response originated.

Control: Control field – This field contains commands or responses and sequence numbers.

Information: Information field – Information may be any sequence of bits, usually related to a convenient character structure such as an octet, but may be an unspecified number (from 1 to 128) of bits unrelated to a character structure.

FCS: Frame check sequence.

LAPB balanced class of procedure

Applications which use ports on the QPC513 are automatically designated as BAC, 2, 8 (for example, balanced operation, asynchronous balanced mode class of procedure with optional functions 2 and 8 implemented).

Balanced configuration

A balanced configuration is one in which two combined stations have identical responsibilities for exchanging data and control information and for initiating error recovery functions, as shown in Figure 188 on page 892.

Combined station

A combined station has balanced link control capability and transmits both commands and responses to, and receives both commands and responses from the other combined station.

Circuit Card Description and Installation