Chapter 2: networking – Technicolor - Thomson Network Router User Manual

Page 22

Chapter 2: Networking

Chapter 2

Example: The Wireless Cable Gateway offers a number of built-in web pages which you can
use to confi gure its networking side; when you communicate with the networking side, your
communication is following this path.

Each packet on the Internet addressed to a PC in your home travels from the Internet down-
stream on the cable company’s system to the WAN side of your Wireless Cable Gateway. There it
enters the Cable Modem section, which inspects the packet, and, based on the results, proceeds
to either forward or block the packet from proceeding on to the Networking section. Similarly,
the Networking section then decides whether to forward or block the packet from proceeding on
to your PC. Communication from your home device to an Internet device works similarly, but in
reverse, with the packet traveling upstream on the cable system.

Cable Modem (CM) Section

The cable modem (or CM) section of your gateway uses DOCSIS Standard cable modem technol-
ogy. DOCSIS specifi es that TCP/IP over Ethernet style data communication be used between the
WAN interface of your cable modem and your cable company.

A DOCSIS modem, when connected to a Cable System equipped to support such modems,
performs a fully automated initialization process that requires no user intervention. Part of this
initialization confi gures the cable modem with a CM IP (Cable Modem Internet Protocol) address,
as shown in Figure 3, so the cable company can communicate directly with the CM itself.

Networking Section

The Networking section of your gateway also uses TCP/IP (Transmission Control Protocol/ Internet
Protocol) for the PCs you connected on the LAN side. TCP/IP is a networking protocol that pro-
vides communication across interconnected networks, between computers with diverse hardware
architectures and various operating systems.

TCP/IP requires that each communicating device be confi gured with one or more TCP/IP stacks,
as illustrated by Figure 4. On a PC, you often use software that came with the PC or its network
interface (if you purchased a network interface card separately) to perform this confi guration. To
communicate with the Internet, the stack must also be assigned an IP (Internet Protocol) address.
192.168.100.1 is an example of an IP address. A TCP/IP stack can be confi gured to get this IP

DCW725 book file.indb 20

10/6/04 11:17:22 AM