|  | 10.2 | Path Determination
| 10.2.2 | Network layer addressing

The network address helps the router identify a path within the network cloud. The router uses the network address to identify the destination network of a packet within an internetwork. In addition to the network address, network protocols use some form of host, or node, address. For some network layer protocols, a network administrator assigns network host addresses according to some predetermined internetwork addressing plan. For other network layer protocols, assigning host addresses is partially or completely dynamic/automatic. The graphic shows three devices in Network 1 (two workstations and a router), each with its own unique host address. (it also shows that the router is connected to two other networks - Networks 2 & 3).

Addressing occurs at the network layer. Earlier analogies of a network address include the first portions (area code and first three digits) of a telephone number. The remaining (last four) digits of a phone number tell the phone company equipment which specific phone to ring. This is similar to the function of the host portion of an address. The host portion tells the router to which specific device it should deliver a packet.

Without network layer addressing, routing can not take place. Routers require network addresses to ensure proper delivery of packets. Without some hierarchical addressing structure, packets would not be able to travel across an internetwork. In a similar way, without some hierarchical structure to telephone numbers, postal addresses, or transportation systems, there would not be a smooth delivery of the goods and services.

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