PortMaster 3 Stac Data Compression Module The PortMaster 3TM Stac compression module provides fast 4:1 data compression performance on ISDN and other PPP routed links. Up to 60 separate routed links can be supported simultaneously. The Stac compression module for the PortMaster 3 is a field-upgradeable option that plugs into a daughterboard slot on the main PortMaster 3 motherboard. Support is provided for RFC 1974 PPP Stac LZS Compression Protocol including both sequence number and extended mode error checking for full Microsoft Windows 95 interoperability. ComOS version 3.7 or later is required to support this module. The PortMaster 3 Stac compression module is ideal for providing end-to-end data compression throughput in conjunction with remote PortMaster Office Routers such as the ISDN Office Router and Synchronous Office Routers. RFC 1962 PPP Compression Control Protocol support provides for standards based interoperability with Lucent routers as well as with third party routers and terminal adapters. Check out this Customer STAC FAQ for Real-Life performance benefits and a Step-By-Step setup.