Table of Contents
Advertisement
Chapter 3: Networking
When a packet enters a network interface, it is offered to all the TCP/IP stacks associated with the device
side from which it entered. But only one stack can accept it — a stack whose configured Ethernet address
matches the Ethernet destination address inside the packet. Furthermore, at a packet's final destination, its
destination IP address must also match the IP address of the stack.
Each packet that enters a device contains source MAC and IP addresses telling where it came from, and
destination MAC and IP addresses telling where it is going to. In addition, the packet contains all or part
of a message destined for some application that is running on the destination device. IRC used in an
Internet instant messaging program, HTTP used by a web browser, and FTP used by a file transfer
program are all examples of applications. Inside the packet, these applications are designated by their port
number. Port 80, the standard HTTP port, is an example of a port number.
The Networking section of the router performs many elegant functions by recognizing different packet
types based upon their contents, such as source and destination MAC address, IP address, and ports.
Three Networking Modes
Your gateway can be configured to provide connectivity between your cable company and your home
LAN in any one of three Networking Modes: CM, RG, and CH. This mode setting is under the control of
your cable company, who can select the mode to match the level of home networking support for which
you have subscribed. By default, all units are set for the RG mode, however; your cable company may
change these defaults during device initialization.
Cable Modem (CM) Mode
Fig.46
55
Illustrations contained in this document are for representation only.
Advertisement
Table of Contents
