3Com MSR 50 Series, Configuration Manual

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51
T
ERMINAL
A
CCESS
C
ONFIGURATION
Introduction to
Terminal Access
Terminal access refers to the connection of a terminal to a router through an
asynchronous interface for data exchange with a front-end processor (FEP) or
another terminal through the router.
Three types of network devices are used in terminal access:
■
Terminal: A terminal is a character device generally connected to another
device through a serial interface cable. A user inputs characters by using the
terminal keyboard. Then, the characters are transferred to another device
through the serial interface cable. After processing the characters, the device
returns the result to the terminal, which then displays the result on its screen.
■
Terminal access initiator (hereinafter referred to as initiator): An initiator sends a
TCP connection request and serves as the client of the TCP connection.
Generally, a router is used as an initiator
■
Terminal access receiver (hereinafter referred to as receiver): A receiver
responds to a TCP connection request and serves as the server of the TCP
connection. A receiver can be an FEP or a router. An FEP is a system installed
with an application program for banking, postal service, taxation, customs, civil
aviation, and so on. An FEP can be a Unix server or a Linux server.
Once a TCP connection is established, the router, functioning as either the
terminal access initiator or receiver, can transparently transmit the data from the
terminal to the peer over the TCP connection. Transparent means that no manual
or extra operation is required.
Introduction to Terminal Access Types
Three types of terminal access are used in different applications: true type terminal
(TTY) access, Telnet terminal access, and remote terminal connection (RTC) access.
TTY terminal access and Telnet terminal access are used to help implement services
between a terminal and an FEP, with a router being the initiator, the FEP being the
receiver. The difference between them is the way of establishing a TCP connection
between the initiator and the receiver. RTC terminal access is used to monitor
terminal data. It is initiated by a router and received by another router. The
following describe the three types of terminal access:
Introduction to TTY Terminal Access
The initiator and receiver of TTY terminal access are a router and an FEP. The
service terminal is connected to the router through an asynchronous serial
interface. The router is connected to the FEP through a network. Application
services run on the FEP. The FEP interacts with the router through the ttyd
program, and the router pushes the service display to the service terminal. The