Enterasys Networks CSX6000 - Manual (Page 252)

USER’S GUIDE
252 CyberSWITCH
X.25 R ESTRICTION F ACILITIES
These facilities are used to place restrictions upon incoming and outgoing X.25 calls.
B ARRING I NCOMING C ALLS
Allows to you bar X.25 calls coming in to the system. The default configuration is to not bar
incoming X.25 calls.
B ARRING O UTGOING C ALLS
Allows you to bar X.25 calls going out of the system. The default configuration is to not bar
outgoing X.25 calls.
X.25 M ISCELLANEOUS F ACILITIES
These facilities are used for fast select acceptance for incoming and outgoing X.25 calls. Fast select
is a calling method that allows the device to send a limited amount of information along with a “call
request packet” rather than after the packet.
F AST S ELECT A CCEPTANCE - I NCOMING C ALLS
Allows you to chose whether fast select acceptance should be done on incoming calls. The
default configuration is to not perform fast select acceptance on incoming calls.
F AST S ELECT A CCEPTANCE - O UTGOING C ALLS
Allows you to chose whether fast select acceptance should be done on outgoing calls. The
default configuration is to not perform fast select acceptance on outgoing calls.
After all of the above X.25 facilities have been specified, the configuration of the X.25 access itself
have been completed. You may now configure the virtual circuits associated with the X.25 access.
PVC C ONFIGURATION E LEMENTS
Once the above X.25 configuration elements have been configured, the associated virtual circuits
should be configured. Note that virtual circuits may be configured with any combination of SVCs
and PVCs, adding up to a maximum of 48 virtual circuits.
A PVC is similar to a dedicated line. At subscription time, the subscriber gives the network the
address to be associated with that virtual circuit. A logical channel is permanently assigned. From
that point on, no call set up is needed. Data to be sent to that destination are simply sent in data
packets using the assigned logical channel.
L OGICAL C HANNEL N UMBER (LCN)
X.25 uses LCNs to distinguish the connections between DTEs at either end of a communication.
These LCNs make it possible to send a packet into a packet-switched network at one end (with no
control over the packet’s journey) and then to pick the packet out at the receiving end. LCN values
for PVCs are obtained from the PPSN carrier.
N ONSTANDARD D EFAULT T RANSMIT W INDOW S IZE
The number of frames that a DTE can send without receiving an acknowledgment. Using modulo
128, the DTEs can send up to 127 frames without receiving an acknowledgment. Using modulo 8,
the DTEs can send up to 7 frames without receiving an acknowledgment. The default value for both
modulo 8 and modulo 128 is 2.