Specifications

Installation and Operation Manual Chapter 6 Diagnostics and Troubleshooting
IPmux-24 Ver. 1.5 Detecting Errors 6-11
Parameter Description
Jitter Buffer
Overflows
The number of seconds with at least one jitter buffer overflow event since the last clear.
Explanation:
In steady state, the jitter buffer is filled up to its middle point, which means it has the space to hold
an additional similar quantity of packets. Overflow is opposite phenomenon of the Underflow, i.e.,
when a big burst of packets reaches the IPmux (a burst with more packets than the Jitter Buffer can
store), the buffer will be filled up to its top. In this case, an unknown number of excessive packets
are dropped and hence IPmux initiates a forced underflow by flushing (emptying) the buffer in order
to start fresh from the beginning. An overflow situation always results in an immediate Underflow,
forced by the IPmux. After the buffer is flushed, the process of filling up the buffer is started again,
as explained above (“Underflow” section).
An overflow situation can be a cause of:
• A big burst of packets, filling up the buffer completely. The burst itself can often be a cause of
some element along the IP network queuing the packets and then transmitting them all at once.
• Too small jitter buffer configuration.
• When system isn’t locked on the same clock, it will lead to a situation in which data is clocked out
of the jitter buffer at a rate different from the one it is clocked into. This will gradually result in
either an overflow or underflow event, depending on which rate is higher. The event will repeat
itself periodically as long as the system clock is not locked.
Recommendations:
Check network devices and try increasing jitter buffer configuration.
Check system’s clocking configuration
Make sure the same amount of TS for bundle is configured on each side of the IPmux-24 application,
and that the “TDM bytes in frame” parameter is identical in both IPmux-24 units
Max Jitter
Buffer
Deviation
The maximum jitter buffer deviation (msec) in the interval (300 sec). This is the maximum jitter level
IPmux-24 had to compensate for in the selected interval.
Time Since
(sec)
The time elapsed, in seconds, since the beginning of the selected interval.
6.2 Detecting Errors
Power-Up Self-Test
IPmux-24 performs hardware self-test upon turn-on. The self-test sequence
checks the critical circuit functions of IPmux-24 (framer and bridge). The self-test
results are displayed via the Diagnostics menu.
³ To display the self-test results:
1. From the Main menu, select Diagnostics.
2. The Diagnostics menu appears (see
Figure 6-5 ). From the Diagnostics menu,
select Self Test Results.
The Self Test Results screen appears (see
Figure 6-6 ).