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Chapter 2: Networking
Example: The Wireless Cable Gateway offers a number of built-in web pages
which you can use to configure 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
downstream 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
technology. DOCSIS specifies 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 configures 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
provides communication across interconnected networks, between computers with diverse
hardware architectures and various operating systems.
TCP/IP requires that each communicating device be configured 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 configuration. 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 configured to get this IP
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Chapter 2
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