About the CSX20010 CSX200 Family User’s GuideFirmware Data CompressionThe STAC Electronics Stacker LZS Compression algorithm provides a minimum of 2:1 firmwaredata compression for the CSX200 over PPP and Frame Relay. Firmware data compression issupported in software on each WAN interface for line speeds of up to 256 Kbps. per WPIM, whichis equivalent to four DS0 channels. To use data compression, compatible equipment, (such as theCSX200, CSX400, and HSIM-W6 or other vendors’ equipment which conforms to the applicablestandards), must be in use at both ends of the WAN link. This firmware method of datacompression is used as the default, if the hardware compression module is not installed.HDLCCabletron Systems has provided the High-level Data Link Control (HDLC) protocol which is usedin conjunction with the WPIM-HDSL to conserve a user’s WAN bandwidth between twoCabletron Systems products, over a point-to-point connection. Cabletron Systems products such asthe CSX200, HSIM-W6, and CSX400 must be in use on both ends of the WAN link for thesefunctions to work. The HDLC (RAW) protocol reduces the amount of overhead information thatneeds to be contained within each data packet to direct it to its destination. This decreased packetoverhead provides the HDSL functions with more bandwidth to transfer user data.DHCP and NATThe 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 localnetwork, 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) totake turns using a range of private IP addresses (often referred to as local IP addresses), andprovides optional secondary setup features for these clients on a per-port basis. The CSX200distributes these addresses dynamically assigning a local IP address to an individual client from arange of 253 available addresses in its table on a first-come-first-served basis. This local IP addressis 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 featuresfor 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 methodis used to enable clients assigned with local IP addresses to use the public IP address(es) of theCSX200 WAN interface(s) to access the WAN.
