Bay Networks 3395A, Configuration Manual

Page: 139 / 146

Flow Control
893-826-A A-9
Figure A-5. State diagram for dial-in/dial-out modems that do not support RNG
Flow Control
Model 3395A server ports provide a flow control capability. This capability
allows the port to inform the asynchronous device (such as a terminal, PC, or
modem) to which it is attached to stop or start transmitting as required to
prevent data loss. Similarly, a port will stop or start transmitting on request of
the device to which it is attached. Model 3395A servers support two modes of
flow control: software flow control and hardware flow control.
Software Flow Control
Software flow control is implemented using ASCII XON and XOFF characters
to start and stop transmission, respectively. The server port can both assert and
observe these flow control characters. Using XON/XOFF flow control, the
receiver that wants to stop a transmitter sends the transmitter an XOFF
character. To start the transmitter, the receiver sends an XON character.
The use of XON/XOFF flow control can cause a problem with some data
transfers, such as binary files, where the XON or XOFF characters may be data
that needs to be passed to the connected partner on a session. In this situation,
you can disable flow control, use hardware flow control, or set the session to
Passall.
DCD not observed
for 120 seconds,
increment failed
call count
Make dial-out
connection
No data,
no DCD
observed
for 60s
Port not logged
in within 120s
Port logged in
DCD not
observed
within 15s
DCD
observed
within 15s
Receive
data, no
DCD
Observe
DCD
high
Failed
call
count
equals
password
limit
Observe
DCD
high
Port
logged
out
DCD not
observed
for timeout
period
Deassert
DTR
Assert
DTR
Wait for
login
Wait 15s
for DCD
Run
Start
Assert
DTR,
allow data
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