Cisco Cisco Unified MeetingPlace Audio Server Manual De Mantenimiento
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Cisco MeetingPlace Audio Server 5.2 Customer Engineering Guide (for Cisco MeetingPlace 8106)
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Chapter 4 Configuring the 8106 Server
Configuring the system
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Handles packets out of sequence — In some cases, various delays can cause consecutive packets to
be received out of sequence. A jitter buffer provides an opportunity to put these packets back into
the proper sequence.
be received out of sequence. A jitter buffer provides an opportunity to put these packets back into
the proper sequence.
•
Handles missing packets — A jitter buffer makes it easier to handle missing (as opposed to just late)
packets. When the software determines that the packet is missing, it provides a reasonable
approximation for the missing packet. This assumes that the sender enables redundancy support
(RFC 2198).
packets. When the software determines that the packet is missing, it provides a reasonable
approximation for the missing packet. This assumes that the sender enables redundancy support
(RFC 2198).
•
Handles overruns and underruns — When clocks are not synchronized, there are occasional packet
overruns or underruns (depending on whether the far end clock is faster or slower). The jitter buffer
allows for a more graceful way of dealing with these.
overruns or underruns (depending on whether the far end clock is faster or slower). The jitter buffer
allows for a more graceful way of dealing with these.
Jitter buffer configuration
There are two jitter buffer parameters that you can configure:
•
Jitter buffer minimum size — The jitter buffer automatically adapts to changing jitter values, but a
minimum value needs to be defined. The default value is 100 milliseconds. This is a reasonable value
for most installations, but some customer environments may do better with a different value. The
“blade” command allows for values from 1-1000 milliseconds.
minimum value needs to be defined. The default value is 100 milliseconds. This is a reasonable value
for most installations, but some customer environments may do better with a different value. The
“blade” command allows for values from 1-1000 milliseconds.
A smaller value reduces the noticeable voice delay, but increases the risk of missing packets that
degrade voice quality. A smaller value can be considered for customers’ IP networks that are:
degrade voice quality. A smaller value can be considered for customers’ IP networks that are:
–
small geographically
–
few hops
–
high bandwidth
A larger value can provide better voice quality, but the increased delays may become annoying for
users. A higher value can be considered for customers’ IP networks that are:
users. A higher value can be considered for customers’ IP networks that are:
–
large geographically
–
many hops
–
potential bandwidth bottlenecks
•
Jitter buffer optimization — The jitter buffer optimization factor controls how quickly the jitter
buffer can react to network jitter. The “blade” commands allows for optimization factor values from
0-12 and the value defaults to 7.
buffer can react to network jitter. The “blade” commands allows for optimization factor values from
0-12 and the value defaults to 7.
At the highest setting, the jitter buffer quickly tracks to the maximal network latencies and stays
there, thus minimizing packet error rates but also maximizing delays. At the lowest setting, the jitter
buffer increases delay only to compensate for clock drifts and soon decays to its minimal setting
again. Mid-range values (such as a default value of 7) provide a reasonable middle ground that is
appropriate for most customers.
there, thus minimizing packet error rates but also maximizing delays. At the lowest setting, the jitter
buffer increases delay only to compensate for clock drifts and soon decays to its minimal setting
again. Mid-range values (such as a default value of 7) provide a reasonable middle ground that is
appropriate for most customers.
Example of jitter buffer configuration
buffer optimization factor to 9. This example is modifying the blade in slot 6.