The X.25 level 2 ports (LAPB)

[18:42:32] ABILIS_CPX: D P PO:201 .

PO:201 ------------------------------------------------------------------------
LAPB   LOG:NO       lowpo:1      lapb:DTE       FW:7
       T1:3000      T2:0         T3:0           N1:144       N2:10

Usually this parameter makes possible to activate/deactivate logging functionalities of meaningful events of the port as well as the detection and signalling of alarms in case of critical events.

The following table shows the available options and the related functionalities usable by the parameter:

Option	Meaning
D	Recording of the driver state changes and/or the meaningful events in Debug Log.
S	Recording of the driver state changes and/or the meaningful events in System Log.
A	Periodic detection of possible alarms. The detected alarms can be displayed with the command ALARM VIEW or by the analogous command available on the UTILITY of the LCD display of the front panel.
L	On alarm detection, acoustic signal generation plus a message on the LCD display. This function depends on activation of alarms detection by the "A" option.
T	Generation by the SNMP Agent of Abilis CPX of SNMP traps corresponding to any change of the driver state and/or occurring of meaningful events.

Beside the already described options the following values are also allowed:

Option	Meaning
NO	It means that all the logging functionalities, alarms detection and generation, above mentioned, are disabled.
ALL	It means that all the logging functionalities, alarms detection and generation, above mentioned, are enabled.
+E	This option added to one or more of the previous ones, extends its (their) set of meaningful events. The value "ALL+E" activates all the options and extends the set of meaningful events. The value "NO+E" is meaningless so it is ignored.

Options can be combined together.

Some examples:

• setting "LOG:DS+E", activates the extended logging functions for Events Log and System Log;
• setting "LOG:STA", activates the extended logging functions for System Log, SNMP traps generation and periodic detection of alarm states;

By using the characters "+" e "-" as prefix of one or more options is possible to add or delete one or more functionalities without setting from the scratch the value of the parameters.

Some examples:

let's suppose the current value of the parameter is "LOG:DSTA", by setting "LOG:-A", the periodic detection of eventual alarm states is removed, leaving unchanged all the remaining options; in such way the final value of the parameter will be "LOG:DST";

let's suppose the current value of the parameter is "LOG:ST", by setting "LOG:+DA", the logging function of the events on the Events Log and the periodic alarm detection are added to the already activated options; in such way the final value of the parameter will be "LOG:DSTA".

The changes made on this parameter are immediately activated, without the need of initialisation commands.

It sets the Abilis CPX lower level port, which can only be a SYNC, MLM, ML or PLINKE port type.

The value "NONE" is used to isolate the LAPB port

It allows to choose the level 2 behaviour between DTE and DCE.

The ports of the two devices that faces each other, that is the two ports connected through the line, must be configured complementary. It means that connection will work only if one is DCE and the other is DTE.

Network ports are usually set as DCE therefore user devices ports have to be set as DTE. As a result, Abilis CPX ports connected to a public network will be set as DTE while those connected to a user device will be set to DCE.

This parameter allows to establish a logical link between level 2 DCE and DTE: signal position on the interface connector is modified only changing the interface modules of the proper port and, if necessary, the link cable.

So, remember to implement the physical adaptation using interface modules and, if necessary, suitable cable.

It sets the size of the Level 2 window.

It must match the value set for the port at the other side of the line.

Usually it is set to 7.

It sets the maximum time to wait between sending a frame and receiving its acknowledge.

It sets the time to wait for sending the acknowledge frame.

This value is in relationship with the one defined in the parameter T1: through following the rule: T2 < T1/2.

It sets the time interval for sending connection maintenance frames.

This value is related to the one set in the parameter T1: through the following rule: T3 > T1*2.

It sets the maximum LAPB frame size.

It sets the maximum number of transmission attempts of level 2 frames before closing the link.

If it runs over, the link is closed and subsequently a new connection attempt occurs.

[18:42:32] ABILIS_CPX: D S PO:201 .

PO:201 ------------------------------------------------------------------------
LAPB   STATE:CONNECTED
       -----------|---INPUT---|--OUTPUT---|-----------|---INPUT---|--OUTPUT---|
       T1-UP      |           |0          | T1-DN     |           |0          |
       REJ        |1          |0          | FRMR      |0          |0          |
       N2-OVER    |           |0          | N1-OVER   |0          |           |
       INFO       |2414       |2419       | BADF      |0          |           |
       UNK-ADD    |0          |           |
       ------------------------------------------------------------------------

[18:42:32] ABILIS_CPX: D SE PO:201 .

PO:201 ------------------------------------------------------------------------
LAPB   --- Cleared 027:07:02:55 ago, on 14/04/2000 at 11:07:27 ----------------
       -----------|---INPUT---|--OUTPUT---|-----------|---INPUT---|--OUTPUT---|
       T1-UP      |           |0          | T1-DN     |           |0          |
       REP        |0          |0          | INFO      |2414       |2419       |
       RR         |1456       |1688       | RNR       |0          |0          |
       REJ        |1          |0          | FRMR      |0          |0          |
       SABM       |1          |0          | UA        |0          |1          |
       DISC       |0          |0          | RD        |0          |0          |
       DM         |0          |0          | BADF      |0          |           |
       N2-OVER    |           |0          | N1-OVER   |0          |           |
       SHORT      |0          |           | UNK-ADD   |0          |           |
       ------------------------------------------------------------------------

This is the current state of the LAPB driver.

Driver	States	Meaning	Values shown in
			System Log	Events Log	LCD Display
LAPB	DOWN	Port is not active.	down
	DISCONNECTING	Waiting for disconnecting. The port sent a DISC frame and it is waiting to receive an UA or DM frame.
	FRMR	FRMR has been sent.	frmr
	CONNECTING	Waiting for level 2 connection. The port sent a SABM frame and it is waiting to receive an UA frame.	cg
	CONNECTED	LAPB is active. The port sent a SABM frame and received an UA frame, or vice versa.	CONN
	WAITING	The LAPB port is blocked	wait
	ERR	Software error. Please contact the Abilis assistance.	NA

The counter T1-UP (OUTPUT) is incremented every time the Abilis CPX does not receive, within the time interval set in the parameter T1:, the acknowledge of INFO frame sent while the driver is in the CONNECTED state

High values, but especially growing, of this counter could mean a bad quality of the transmission line. However they indicate errors in the received data. A bad quality turns into a performance lowering and possible breaks down of the connection.

The counter T1-DN (OUTPUT) is incremented every time the Abilis CPX does not receive, within the time interval set in the parameter T1:, the acknowledge of frame sent while the driver is in the connecting/disconnecting phase.

Since LAPB tries indefinitely to contact the counterpart, this statistic may increase just because the counterpart is switched off. However if you are sure that counterpart should be reachable, increasing value definitely indicates that the LAPB connection cannot be established indicating a line fault or DTE/DCE wrong configuration.

The counter REJ (INPUT) is incremented every time a REJ frame is received, while the counter REJ (OUTPUT) every time a REJ is sent.

High values, but especially growing, of this counter could mean a bad quality of the transmission line. However they indicate errors in data received by the counterpart which in turn are data transmitted by the local LAPB. A bad quality turns into a performance lowering and possible breaks down of the connection.

The counter FRMR (INPUT) is incremented every time Abilis CPX receives a FRMR frame, while the counter FRMR (OUTPUT) every time a FRMR frame is sent.

FRMR should always be 0 as they signal protocol violations. Every FRMR is always followed by a complete link reset with all X25 channels forcedly closed.

The counter N2-OVR (OUTPUT) is incremented every time the maximum retransmission number, set in the parameter N2: has been reached.

The counter N1-OVER (INPUT) is incremented every time the port receives a frame, whose size is bigger than the one set in the parameter N1:.

The counter INFO (INPUT) is incremented every time the Abilis CPX receives an INFO frame. The counter INFO (OUTPUT) is incremented every time an INFO frame is sent.

The counter BADF (INPUT) is incremented every time the Abilis CPX receives a frame, whose type is unknown.

The counter UNK_ADD (INPUT) is incremented every time the Abilis CPX receives a frame, whose address is unknown.

The counter REP (INPUT) is incremented every time the Abilis CPX receives a repeated frame.

The counter REP (OUTPUT) every time the Abilis CPX repeats the transmission of already sent frames.

The counter RR (INPUT) is incremented every time a RR frame is received, while the counter RR (OUTPUT) every time a RR frame is sent.

The counter RNR (INPUT) is incremented every time a RNR frame is received, while the counter RNR (OUTPUT) every time a RNR frame is sent.

The counter SABM (INPUT) is incremented every time a SABM frame is received, while the counter SABM (OUTPUT) every time a SABM frame is sent.

The counter UA (INPUT) is incremented every time a UA frame is received, while the counter UA (OUTPUT) every time a UA frame is sent.

The counter DISC (INPUT) is incremented every time a DISC frame is received, while the counter DISC (OUTPUT) every time a DISC frame is sent.

The counter RD (INPUT) is incremented every time a RD frame is received, while the counter RD (OUTPUT) every time a RD frame is sent.

The counter DM (INPUT) is incremented every time a DM frame is received, while the counter DM (OUTPUT) every time a DM frame is sent.

The counter SHORT (INPUT) is incremented every time the port receives a frame, whose size is smaller than the fixed minimum value.

This variable shows the CPX port number which the SNMP trap refers to.

This variable shows either the port type which the trap refers to (in this case LAPB) and the description eventually associated to it.

This variable shows the current state of the LAPB port driver which the trap refers to. The following table shows the relationship among the state value stored in the SNMP variable and the ones obtained executing the command D S.

This variable stores the elapsed time (in cent of second) from the system start to the SNMP trap event occurrence.

This value is usually shown in SNMP consoles as days:hours:minutes:seconds.