A data compression algorithm used in cisco devices, developed by STAC Electronics (now Hi/fn, Inc.) and based on the Lempel-Ziv algorithm. LZS is in Cisco's Link Access Procedure, Balanced (LAPB), HDLC, X.25, and Frame Relay. The Cisco IOS uses an optimized version of LZS that provides pretty good ratios but requires manic-hamster CPU cycles.

LZS searches the input data stream for redundant strings and replaces them with a shorter token. It creates dictionaries of the string matches and tokens that are pointers into the previous data stream. The dictionary is used to replace the redundant strings found in the new data streams.