3Com 56K manual Getting Maximum, Throughput results, When

Getting Maximum Throughput 12-9

Possible dictionary sizes:

Bits	Entries
9	512
10	1024
11	2048

Your modem uses an 11-bit, or 2048-entry dictionary, but they can reduce its size to accommodate a remote modem that uses a 9- or 10-bit dictionary.

■ Maximum string length of each entry. As the dictionary fills, your modem deletes the oldest unused strings.

	V.42bis compression is more efficient than MNP5 compression, in part
	because it dynamically deletes entries that are no longer used. In
	addition, it works better with files that are already compressed. These
	include.ZIP files and 8-bit binary files.
	MNP5 compression should NOT be used with binary files because it adds
	data to the files, which lessens throughput. (The additional data is
	stripped when the file is decompressed by the remote modem.) When
	transferring such files, it's best to set the modem to &K3 (See the
	information in data compression). This allows V.42bis compression to
	work dynamically with the compressed data, but disables MNP5.
Getting Maximum	The following guidelines should help you to make the most of the
Throughput	Business Modem's advanced performance features. In many instances,
	experimentation and experience will indicate what works best for your
	applications.
Maximum	■ The communications software allows fixing the serial port rate higher
throughput results	than the connection rate, by setting the software to 115200, 57600,
when:	or 38400 bps and setting the Business Modem to &B1.
	If the software automatically switches serial port rates to follow the
	connection rate, the Business Modem's serial port rate must be also
	set to follow the connection rate for each call, &B0, and throughput
	will be limited.