3Com 56K manual HANDSHAKING, Error Control Data COMPRESSION, Throughput, Handshaking

HANDSHAKING, ERROR CONTROL,

12 DATA COMPRESSION, AND

THROUGHPUT

	This chapter contains information about:
	■	Handshaking
	■	Selective Reject
	■	V.90 Capabilities
	■	Error Control
	■	Data compression
	■	Getting maximum throughput
Handshaking	With each call, Business Modems go through a link negotiation process
	with the remote device. Another name for the negotiation process is
	"handshaking."

Business Modems default to V.90 modulation and try for the highest possible speed when they attempt to connect with another modem: 56 Kbps. If the remote device is not V.34-capable, a connection is made using the highest compatible modulation scheme (x2, V.34, V.FC, V.32 terbo, V.32 bis, and so on, down to as low as Bell 103, or 300 bps).

Selective Reject The Business Modem supports Selective Reject for analog calls. Selective Reject improves performance on noisy lines by reducing the amount of overhead incurred when the protocol must resend data due to errors.

When Selective Reject is active, only the frame that contained the error is resent, instead of the frame plus all of the following unacknowledged frames.