Broadband Telecommunications Handbook, Second Edition
A blockbuster overview of broadband updated and expanded to reflect the latest technologies.
TABLE OF CONTENTS Broadband Telecommunications Handbook, Second Edition
IP Addressing
Now that we have a handle on the protocols that are going to be used, let's take a look at the structure and significance of addressing and then we will discuss how routing is done.
The addressing scheme is important for obvious reasons. Addressing is used by the routers to find the destination for the IP packets. One could imbue the routers with God-like knowledge of the network, or the router could have a simple table to use to look up the next hop. If there is no entry in the table, then send it to the default router. The whole Internet works because of this default route mechanism. If any device doesn't know how to return a packet, it sends it to the default router, known as the default gateway.
Routers Versus Gateways
A point of clarification is needed about routers and gateways. In the Internet community, routers and gateways get a little confused. In the previous discussion, we use the term router almost exclusively. As pointed out, in the Internet community, it is referred to as the default gateway.
The Internet terminology started before terms were standardized. A gateway was a box that sat between two networks. Therefore, it was natural to refer to routers, especially ones connecting different networks as gateways.
Today, a router is a box that operates at the network layer, reads IP addresses, and chooses the best hop it can find to the destination network. A gateway is a device that handles...
Copyright The Mc-Graw-Hill Companies, Inc. 2002 under license agreement with Books24x7
