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LOCAL AREA NETWORK CONNECTIONS 8-15
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— It can give outside users access to the LAN and the hardware and software resources that reside
there.
— It can provide LAN users with access to the lines and trunks attached to communications system.
• Second, it can let LAN nodes communicate with nodes in other networks.
• Third, for LAN nodes, the communications system can provide switched access to the LAN server
when direct access through the usual LAN links is blocked.
Communication Between the LAN and Outside DTEs
LAN nodes must be intelligent enough to understand and regenerate LAN protocols. Therefore, network
nodes are most often PCs or other hosts. Outside terminals usually access the LAN through a circuit-
switched, dialed-up connection. The connection links the terminal with a gateway PC that is both a LAN
node and an extension on the communications system. The gateway must be executing software that can
translate messages between the LAN’s protocol and the outside terminal’s protocol.
LAN
GATEWAY
PC
7400A
MODEM
POOL
D
C
P
E
I
A
S75/S85/G1/G2
A
N
A
L
O
G
D
C
P
OUTSIDE PC
(OFF-PREMISES)
OUTSIDE PC
(ON-PREMISES)
MODEM
7400B
ADU
Figure 8-6. Outside DTE Access to LAN
The general configuration for communication between the LAN and outside DTEs is shown in figure 8-6.
The configuration can be applied to the connection of any outside terminal to a StarLAN, Ethernet, or token
ring LAN. However the software that runs on the gateway PC to provide access for outside terminals
varies with the type of LAN and the operating system it uses. The following table lists some packages that
run on the gateway PC to provide access for outside terminals. Note that any of the operating systems
shown in the table can run a StarLAN, token ring, or Ethernet LAN.
Table 8-4. Gateway PC Software
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