Appendix B: TCP/IP-In-Depth

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B.3 TCP/IP Addressing and Architecture

The anarchic nature of TCP/IP is purposefully designed directly into its architecture. In contrast to the host-based network architectures of the time, TCP/IP proved to be useful on a variety of systems without a central controlling system. With TCP/IP, there is no central authority. Nodes communicate directly among themselves, and each maintains complete knowledge about the available network services. If any host fails, none of the others know or care (unless they need data from the down machine, of course).

In order to identify themselves in this peer-to-peer environment, nodes are given explicit addresses that not only identify the computer, but the network segment that it is on as well. For example, the address specifies node number 20 on network 192.168.1. Another node on the same network segment might be numbered 21, and so on. Networks and the nodes on them are separate entities, with separate numbers.

Undisplayed Graphic

Figure B.1: TCP/IP addresses consist of a network address and a node address. Each node on a network is numbered uniquely, and each network on the Internet is also numbered uniquely. This provides a unique 32-bit address for each device on the Internet.

Routers perform the task of moving traffic between networks. A node that needs to send data to another node on another network will send the data to a router, and the router will then send the data on to the destination node. If the destination isn't on an directly-connected network, the router will send the data to another router for delivery.

For more information about 32-bit addressing, refer to section 1 Binary Addresses, Octets and Network Classes. For more information on address availability, refer to section 2 Addressing Limitations and section 3 Internet-Legal versus Private Addressing. For information on how to allocate addresses, refer to section 4 Sub-Net Masks.

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