Chapter 2: About the HSIM-W6
10 HSIM-W6 User’s Guide
Inverse Multiplexing
Cabletron Systems Inverse Multiplexing (IMUX) feature provides enhanced throughput for users
by doing each of the following:
•The IMUX function evenly distributes a data packet stream from the LAN interface through the
two WAN interfaces on the HSIM-W6. Since the data traffic is equally shared between the two
Full T1 interfaces, each with 1.5 Mbps throughput, the total throughput over the logical link is
3 Mbps, or 6 Mbps full-duplex operation with the optional hardware compression module
(CSX-COMP/ENCR) installed in the HSIM-W6.
•The IMUX function passes packet sequence information over the WAN using the Point-to-Point
Protocol (PPP) to support data coherency on both ends of the link.
•Data packet streams received by the WAN interfaces on the other end of the WAN link are then
recombined, ordered, and transmitted to the LAN interface.
•The IMUX function is fully configurable using QuickSET, which is discussed in the Bridging
and Routing Configuration section of Chapter 4 and the MIB Navigator command set
discussed in Chapter 6.
Firmware Data Compression
The STAC Electronics Stacker LZS Compression algorithm provides a minimum of 2:1 firmware
data compression for the HSIM-W6 over PPP and Frame Relay. Firmware data compression is
supported in software on each WAN interface for line speeds of up to 256 Kbps per WPIM, which
is equivalent to four DS0 channels. To use data compression, compatible equipment, (such as the
HSIM-W6, CSX400, and CSX200 or other vendors’ equipment which conforms to the applicable
standards), must be in use at both ends of the WAN link. This firmware method of data
compression is used as the default, if the hardware compression module is not installed.
NOTE Cabletron Systems products that support Inverse Multiplexing (IMUX), such as the
HSIM-W6, CSX400, and HSIM-4T1, must exist on both ends of the WAN link for the
IMUX function to work.
Both bridging and routing functions are disabled when using the IMUX function.