User`s guide

About the CSX200

10 CSX200 Family User’s Guide

Firmware Data Compression

The STAC Electronics Stacker LZS Compression algorithm provides a minimum of 2:1 ﬁrmware

data compression for the CSX200 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

CSX200, CSX400, and HSIM-W6 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.

HDLC

Cabletron Systems has provided the High-level Data Link Control (HDLC) protocol which is used

in conjunction with the WPIM-HDSL to conserve a user’s WAN bandwidth between two

Cabletron Systems products, over a point-to-point connection. Cabletron Systems products such as

the CSX200, HSIM-W6, and CSX400 must be in use on both ends of the WAN link for these

functions to work. The HDLC (RAW) protocol reduces the amount of overhead information that

needs to be contained within each data packet to direct it to its destination. This decreased packet

overhead provides the HDSL functions with more bandwidth to transfer user data.

DHCP and NAT

The Dynamic Host Conﬁguration Protocol (DHCP) and Network Address Translation (NAT)

method eliminates the expense of purchasing limited public IP addresses for each client on a local

network, and the need to re-conﬁgure a client if it is moved to a different network.

The CSX200 acts as a DHCP server that allows individual clients (PCs, network equipment) to

take turns using a range of private IP addresses (often referred to as local IP addresses), and

provides optional secondary setup features for these clients on a per-port basis. The CSX200

distributes these addresses dynamically assigning a local IP address to an individual client from a

range of 253 available addresses in its table on a ﬁrst-come-ﬁrst-served basis. This local IP address

is then “leased” for a predetermined amount of time, which is conﬁgured for the particular port.

Each Ethernet port provides DHCP services for one Class C subnet and secondary setup features

for individual clients that support the use of a default gateway, domain name and WINs server.

On the Wide Area Network (WAN) side, the Network Address Translation (NAT) routing method

is used to enable clients assigned with local IP addresses to use the public IP address(es) of the

CSX200 WAN interface(s) to access the WAN.