In Abilis CPX, PVC connections represent a permanent links between two logical channels of two communication ports; they also define the compression protocols to be used.
The main functions provided by the PVC connections are:
The PVC connections table is initially empty: it has to be configured if on the two communications ports are present PVC channels to be connected.
PVC connections activation is dynamic, so that any add, delete or change can be activated by using the commands C C and R PVC.
All the commands for PVC connections management are described in the section PVC connections of the chapter Commands relating to the Connection Oriented Router.
The following commands are available:
A PVCHere is an example of the command D PVC execution. Values shown for connections from 1 to 3 are interesting examples for displaying some features of the PVC connections, values of the connection 4 are the default ones of the command A PVC:
[18:14:08] ABILIS_CPX: D PVC
- Not Saved (SAVE CONF) -------------------------------------------------------
ID:0 ST:2 POI:301 SESI:1 PWI:7 COMP:MBIT
POO:302 SESO:1 PWO:7
ID:1 ST:2 POI:302 SESI:3 PWI:1 COMP:MBIT
POO:301 SESO:2 PWO:1
ID:2 ST:1 POI:301 SESI:1 PWI:2 COMP:NO
POO:302 SESO:4 PWO:2
ID:3 ST:2 POI:302 SESI:2 PWI:6 COMP:NO
POO:301 SESO:3 PWO:5
ID:4 ST:2 POI:NONE SESI:NONE PWI:2 COMP:NO
POO:NONE SESO:NONE PWO:2
The "Not Saved (SAVE CONF)" message is displayed every time the table is modified but not saved with the SAVE CONF command.
| ID: | Identifier of the PVC connection |
| no value | from 0 to 63 |
The identifier sets the activation sequence of the PVC connections. Adding, modifying and deleting commands also use it as reference to the PVC connection.
PVC channels activation starts from the lowest identifier until it reaches the last. As consequence, if there are two PVC connections wrongly using the same port and logical channel, then the one with the lowest identifier will be activated (ST:3), the other will be set as "not valid PVC connection" (ST:1).
Identifiers, in the PVC connection table, are kept in sequential order; when an identifier is added or deleted, the table is re-sorted.
PVC connections inserted or modified can be activated without restarting the Abilis CPX, by using the commands C C and R PVC.
| ST: | PVC connection state |
| 2 | 0, 1, 2, 3 |
It is the current state of the PVC connection. Default value is the connection state when it is added by using the command A PVC.
The meaning of the states is the following:
| State | Meaning |
|---|---|
| 0 | Undefined state. |
| 1 | PVC connection is not valid. Probable errors and/or parameters conflicts. |
| 2 | PVC connection has been set but not activated. IT will be activated on the next Abilis restart, or by executing the command R PVC. Even if the configuration is syntactically correct, eventual errors and/or conflicts in parameters will be detected only during its activating. |
| 3 | PVC connection is active. |
| POI: | Source port of the PVC connection |
| NONE | 1 - 999, NONE |
It sets the source port of the PVC connection.
The value "NONE" stands for "no port", it can be used to deactivate the connection without deleting it.
Distinction between source/destination port is meaningless for the PVC connection configuration, it is used only for distinguish the parameters "logical channel (SESI: e SESO:)" and "packet window (PWI: e PWO:)" relating to each port.
| POO: | Destination port of the PVC connection |
| NONE | 1 - 999, NONE |
It sets the destination port of the PVC connection.
The value "NONE" stands for "no port", it can be used to deactivate the connection without deleting it.
Distinction between source/destination port is meaningless for the PVC connection configuration, it is used only for distinguish the parameters "logical channel (SESI: e SESO:)" and "packet window (PWI: e PWO:)" relating to each port.
| SESI: | Logical channel number of the source port |
| NONE | 1 - 255, NONE |
It sets which logical channel of the source port is going to be used in the PVC connection.
The value "NONE" stands for "no logical channel", it can be used to deactivate the connection without deleting it.
The logical channel specified must be a PVC valid one, otherwise the connection will be set as "PVC connection not valid" (ST:1).
| SESO: | Logical channel number of the destination port |
| NONE | 1 - 255, NONE |
It sets which logical channel of the destination port is going to be used in the PVC connection.
The value "NONE" stands for "no logical channel", it can be used to deactivate the connection without deleting it.
The logical channel specified must be a PVC valid one, otherwise the connection will be set as "PVC connection not valid" (ST:1).
| PWI: | Packet window to be used for SESI: |
| 2 | from 1 to 7 |
It specifies which packet window is used for the logical channel specified in SESI: of the port specified in POI:.
Parameter is meaningful only for X25 ports type. If the input port is modified to a not X25 port type, the packet window is automatically set to 1.
| PWO: | Packet window to be used for SESO: |
| 2 | from 1 to 7 |
It specifies which packet window is used for the logical channel specified in SESO: of the port specified in POO:.
Parameter is meaningful only for X25 ports type. If the input port is modified to a not X25 port type, the packet window is automatically set to 1.
| COMP: | Compression protocol to be used |
| NO | NO, QLLC, MBIT |
It sets the compression protocol to use on data exchanging, once the PVC connections is established.
| Value | Meaning |
|---|---|
| NO | No compression protocol is associated to the PVC connection; data "pass transparent through" the Abilis CPX. It has to be used for PVC connections set on system different from the Abilis CPX, or for connections that don't have to be compressed. |
| QLLC | To the PVC connection is associated the QLLC compression protocol |
| MBIT | To the PVC connection is associated the MBIT compression protocol |
it is necessary that both parts of the same PVC connection set this parameter to the same value.
MBIT protocol has a system able to detect the protocol used by the counterpart. If they are not the same, Abilis CPX closes the PVC connection and generates a X25 RESET with F0,40 cause codes. However in internal diagnostics the RESET will be generated with F0,AA cause codes (Compression protocol not compatible).
QLLC doesn't have this system, so the error may not be immediately detected, causing the DTE to generate a RESET owing to not valid data.
it is also possible the Abilis detects the error before the DTE. Abilis will close the PVC connection and generate a X25 RESET with F0,40 cause codes. However in the internal diagnostics the RESET will be generated with F0,C2 cause codes (expansion error) or F0,C3 (Format of data compressed not valid).
Here are some examples, useful to distinguish the above-mentioned functions:
ID:0 ST:3 POI:301 SESI:1 PWI:7 COMP:NO
POO:302 SESO:1 PWO:7
| ID: | represents the PVC connection identifier to be used by the PVC connections management commands. |
| ST: | represents the current status of the connection. |
| POI: and SESI: | represent source port and logical channel. |
| PWI: | represents the packet window to be used for the source logical channel. |
| POO: and SESO: | represent destination port and logical channel. |
| PWO: | represents the packet window to be used for the destination logical channel. |
| COMP: | compression protocol to be used. In the example, no compression protocol is used. |
Abilis CPX is instructed to set a permanent connection between logical channel "1" of port "301" and logical channel "1" of port "302", without using any compression protocol, independently of what the parameters communications ports are set to.
Changes made on the PVC connections can be activated without restarting the Abilis CPX, by using the commands C C and R PVC.
ID:0 ST:3 POI:301 SESI:4 PWI:7 COMP:MBIT
POO:302 SESO:5 PWO:7
In this example, Abilis CPX is instructed to set a permanent connection between logical channel "4" of port "301" and logical channel "5" of port "302", using the MBIT compression protocol and packet window "7", independently of what the parameters communications ports are set to.
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