Справочник Пользователя для Netopia PN Series

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Reference Guide
Each computer or peripheral device (printer, client, file server) 
connected to a network is called a node and has a unique node 
address, which can be any number from 1 to 254. Whenever you 
open the Chooser or any application that communicates with other 
computers on your network, your application compiles a list of all 
node names and addresses. All you see are the names --- for 
example, “Paul’sMac,” “TechSportsWriter,” or “2nd Floor 
AppleShare” --- but your application also knows the node addresses 
of all these devices.
When you send information, commands, or requests to a printer, 
server, or another workstation, your application formats the 
information into units known as packets. It then attaches the 
correct address to the packets and sends them to the AppleTalk 
software on your computer, which forwards the packets across the 
network. Packets also include a return address, so the receiver will 
know where to reply.
If the cabling of your network were a street system, then a node 
address would correspond to a building’s street address. Node 
addresses are not permanent. Each AppleTalk device determines its 
node address at startup. Although a Macintosh that is starting up 
will try to use its previous address, the address will often be 
different every time you restart. This dynamic node addressing 
scheme prevents conflicts when devices are moved between 
networks and simplifies the administrative tasks of a network. If you 
have only one network, the node address alone is all the 
information AppleTalk needs to send a packet from one computer to 
another.
However, networks can be connected together through routers, 
such as the Netopia Router, into an internetwork (often shortened 
to internet). Because devices on different networks can have 
duplicate node numbers, AppleTalk tells them apart according to an 
additional part of their addresses: the network number.
The Router assigns a unique network number to each member 
network. In terms of the city street metaphor, the network number is 
similar to the name of the city. Putting a network number together 
with a node number fully specifies the address of a node on an 
internet.