Cabletron Systems HSIM-W6 manual Hdlc, Dhcp and NAT

Chapter 2: About the HSIM-W6

HDLC

Cabletron Systems has provided the High-level Data Link Control (HDLC) protocol which is used in conjunction with the Inverse Multiplexing (IMUX) feature and 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 HSIM-W6, CSX200, 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 IMUX and 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 HSIM-W6 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 HSIM-W6 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 an predetermined amount of time, which is configured for the particular port. The Ethernet port provides DHCP services for one Class C subnet and secondary setup features for individual clients 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 HSIM-W6 WAN interface(s) to access the WAN.

NOTE

A private or “local” network is referred to as a sub network that is using private or “local” IP addresses. An “outside” network refers to a Wide Area Network (WAN) commonly known as an Internet where registered public IP addresses are required.

HSIM-W6 User’s Guide 11