3Com MSR 50 Series Configuration Manual page 745

Introduction to Terminal Access 745
Data encryption
Due to the extensive use of terminal access in banking systems, the requirements
of data security become higher and higher. The terminal access data encryption
function can be used to encrypt the data transmitted between the router and FEPs
to improve data security.
As shown in Figure 223, data is transmitted in ciphertext between Router A and
the FEP. Router A and the FEP that runs the program ttyd are responsible for data
encryption and decryption. At present, the advanced encryption standard (AES)
encryption is supported.
Figure 223 Data encryption procedure between the router and the FEP
Automatic link establishment
The terminal access feature supports the automatic link establishment function.
You can enable this function and configure the automatic link establishment time
in terminal template view. When the terminal is in the "ok" state (meaning the
physical connection is normal), the initiator automatically establishes a TCP
connection to the receiver after the specified period. If the automatic link
establishment function is disabled on the terminal, a link needs to be established
manually. In this mode, the initiator establishes a TCP connection to the receiver
only after you enter a character on the terminal.
Automatic link teardown
The terminal access feature supports the automatic link teardown function. You
can enable the function and configure the automatic teardown time for the
terminal in terminal template view. When the terminal device and the initiator are
disconnected from each other, the terminal enters the "down" state. Then after
the specified period of time, the initiator automatically tears down the TCP
connection to the receiver. In this case, the TCP connection remains active if the
automatic link teardown function is disabled.
One-to-one access
In one-to-one access, each terminal communicates with the FEP through a TCP
connection to achieve optimum communication quality and highest
communication speed under various link states. High terminal echo rates can still
be achieved over low-speed links through parameter adjustments. Frequent and
massive printing needs of users can also be satisfied in this mode.