Installing and Administering PPP

Chapter 4 77
Common pppd Options
Compression
• The modem or CSU/DSU communication device does not support
data compression.
PPP link compression over modems that support V.42bis compression
may provide no performance advantage, except in cases where the link’s
bandwidth is limited by slow serial interfaces.
Predictor-1
Predictor-1 compresses typical binary data 1.5:1, absorbs relatively little
of the host’s CPU, and adds very little latency to interactive traffic. It is
well suited to achieving even better performance from higher-speed
synchronous PPP connections.
Stac Compression
The Stac LZS algorithm for data compression is an Internet Engineering
Task Force (IETF) compression standard for PPP. The algorithm can
maintain an average 2:1 compression ratio and, depending on the type of
data that is being compressed, the ratio may be as high as 3:1 or 5:1 .
The Stac LZS algorithm is based on the Lempel-Ziv algorithm and is the
same as that used in Stac Electronics retail software.