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Q.921/Q.931 Timers
November 2009 332
Q.921/Q.931 Timers
An application can change the default behavior in Instant ISDN
Software Level 2 and Level 3 parameters by issuing ENABLE_
PROTOCOL.
L4L3mENABLE_PROTOCOL contains an IISDN_L2_CONST
structure that defines Level 2 parameters and an IISDN_Q931_
TIMERS structure that configure Level 3 timers. The IISDN_Q931_
TIMERS structure is only valid when the Level 3 mode (l3_mode)
value in the message is IISDNl3modQ931. Table 15 and Table 16 list
the parameters for both structures.
When altering these values, refer to the system specification for the
switching system to which you are connecting the Brooktrout
Controller for valid timer and window values. Level 2 timers are
specified in 1 millisecond “ticks;” Level 3 timers in 100 millisecond
“ticks.”
Note: Dialogic strongly recommends that you use the default values
for Level 2 and Level 3 parameters and internal buffers.
Failure to do so might result in a system irregularity. If you do
need to change the configurations and buffer sizes, call
Dialogic Technical Services and Support first and seek
consultation. Internal buffer sizes for different Brooktrout
Controller configurations are found in IISDN.h.
Table 15. Q.921 Timers (Level 2 Parameters)
Data Type Mnemonic Definition
IISDN_L2_
LAP_
CONSTS
12 Setting a field to 0 causes the default value to be
used. Some timers have two possible default values
depending on whether or not the line is a BRI (set
by the q931_cnfg.basic_rate flag.
unsigned
short
t200 Maximum retransmission time. Default value is
1000 (1
second).
unsigned
short
t201 Minimum retransmission TEI Identity check.
Default value is 1000 (1
second).
unsigned
short
t202 Minimum TEI Identity request. Default value is
2000 (2
seconds).
unsigned
short
t203 Maximum link inactivity. Default value is 30
seconds. For NET-5 signaling, this timer should be
set to 10 seconds. BRI default is 10000 (10
seconds).