Справочное Руководство для Netopia 430 s

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6-2
Netopia ISDN Router Reference Guide
AppleTalk is a protocol set for local area networks developed by 
Apple Computer. While initially applied to the LocalTalk cabling 
system for connecting Macintosh computers and LaserWriters, it 
has been expanded to use other cabling systems, such as Ethernet, 
as well as the dial-up telephone networks and packet switching 
systems. LocalTalk was originally known as the AppleTalk Personal 
Network system.
Each computer or peripheral device (printer, fax, file ser ver) 
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,” “TechSpor tsWriter,” or “2nd Floor Apple-
Share”--but your application also knows the node addresses of all 
these devices.
When you send information, commands, or requests to a printer, 
ser ver, 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 for wards 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 star tup. Although a Macintosh that is star ting up 
will tr y to use its previous address, the address will often be 
different ever y time you restar t. 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 ISDN Router, into an internetwork (often 
shor tened to internet). Because devices on different networks can 
have duplicate node numbers, AppleTalk tells them apar t according 
to an additional par t of their addresses: the network number.