3Com 10014299 manual channel delimitation parameters, Parameter Meaning

Configure X.25 201

X.25 protocol can multiplex multiple virtual connection over a real physical link between DTE and DCE, also called virtual circuit (VC) or logical channel (LC). X.25 can establish up to 4095 virtual connections numbered from 1 to 4095. The number that can be employed to identify each virtual circuit (or logical channel) is called logical channel identifier (LCI) or virtual circuit number (VCN).

Strictly speaking, virtual circuit and logical channel are two different concepts. However, they are not much different at the user side.

X.25 protocol divides the logical channel into 4 areas. (listed here in numerically increasing order): Permanent virtual circuits (PVCs), Incoming-only circuits, Two-way circuits, Outgoing-only circuits.

According to the X.25 recommendation proposed by ITU-T, DCE selects an available logical channel with a smaller number from the “one-way incoming call channel range” and “two-way channel range” to initiate a call, while DCE selects an available logical channel with a larger number from the “one-way incoming call channel range” and “two-way channel range” to initiate a call. Thus, we can avoid the case that one side of the communication occupies all the channels, and minimize the possibility of call collision.

In X.25 protocol, six parameters are employed to delimit the four sections, as shown in the diagram below.

Figure 62 X.25 channel delimitation

1

Permanent virtual circuit

LIC

Incoming-only channel

HIC

Unused

LTC

Two-way channel

HTC

Unused

LOC

Outgoing-only channel

HOC

Unused

4095

For the meanings of these six parameters, please refer to the following table.

Table 236 X.25 channel delimitation parameters

Parameter	Meaning
LIC	Lowest Incoming-only Channel
HIC	Highest Incoming-only Channel
LTC	Lowest Two-way Channel
HTC	Highest Two-way Channel
LOC	Lowest Outgoing-only Channel
HOC	Highest Outgoing-only Channel

Perform the following task in the interface view: