LAPB Parameters

The LAPB layer parameters are:

Ack Timer (T1) (t1_timer)

The period, in tenths of a second, during which the LAPB software expects to receive an acknowledgment to an outstanding I-frame or during which LAPB expects a response to a sent unnumbered frame. The valid range for values of this parameter is between 1 and 3000.

P-bit Timer (pf_timer)

The period, in tenths of a second, during which the LAPB software expects to receive a frame with the F-bit set to 1 in response to a command with the P-bit set to 1. This value should be less than that specified for the Ack Timer. The valid range for values of this parameter is between 1 and 3000.

Reject Timer (reject_timer)

The period, in tenths of a second, during which the LAPB software expects to receive a reply to a sent Reject frame. The valid range for values of this parameter is between 1 and 10000.

Busy-state Timer (busy_timer)

The period, in tenths of a second, during which the LAPB software waits for an indication of the clearance of a busy condition at the other end of the link. The valid range for values of this parameter is between 1 and 30000.

Link Idle Timer (idle_timer)

The period, in tenths of a second, during which the LAPB software expects to receive a frame from the other end of the link. If this timer expires, the Poll/Final cycle--which might result in link disconnection--is initiated. A zero value disables this function. The valid range for values of this parameter is between 0 and 32000.

Max. RR Delay (rr_ack_delay)

The maximum delay, in tenths of a second, before transmitting a delayed Receiver Ready. The value for this parameter must be significantly lower than the Ack Timer value. The valid range for values of this parameter is 0 to 3000.

Max Tries (N2) (n2_count)

The maximum number of times that an I-frame (information frame) is sent following the expiration of the Ack Timer, the P-bit Timer, or the Reject Timer. It also limits the number of times Receive Ready with P-bit set is sent when the remote side is busy and the Busy Timer expires. The valid range for values of this parameter is 1 to 255.

Max UnACKed IPDUs (unack_max)

The maximum number of unacknowledged I-frames that can be received before the Receive Ready acknowledging those I-frames must be sent. The valid range for values of this parameter is 0 to 127 for modulo 128, and 0 to 7 for modulo 8.

Transmit Probe (local_probe)

The position within a window at which the LAPB software sends an I-frame with the P-bit set, to ask for an acknowledgment from the receiver. The valid range for values of this parameter is 0 to 127.

MLP Priority (mlp_priority)

This parameter appears in the LAPB and WAN Parameters window when the Link Type is set to MLP in the Link Editor Window. In this instance, to access the LAPB and WAN Parameters window, you must call up the MLP Parameters window, then double click on the SLP you want to configure. For more information, see "MLP Parameters".

This parameter defines how many unacknowledged frames can be sent on one line before the next line is used. Setting this correctly forces traffic to be distributed between the lines in an MLP link. The values you set depend on the absolute speed of each line, and on the relative speeds of your lines. In general, don't set an MLP Priority of less than 3. If your lines operate at 64kbps, or more, you should increase the MLP Priority.

The following combinations of values provide efficient (90%) line use in two-line MLP configurations:

• For two 64Kbps lines, set the MLP Priority for each line to 10. In the MLP Parameters window, set the MLP Window and MLP Guard to 25. See "MLP Parameters" for more information.

• For one 512Kbps line and one 128Kbps line, set the MLP Priorities to 30 and 5, respectively. In the MLP Parameters window, set the MLP Window to 40. See "MLP Parameters" for more information.