Appendix: Monitoring Practices - BridgeTech VB20 User Manual

2. Appendix: Monitoring Practices

This Appendix summarises a few useful monitoring practices.
RTP Monitoring
When running video inside an RTP wrapper it is possible to exactly deduce the number
of dropped IP frames due to network issues. This is possible as a result of the 16-bit
sequence counter inside the RTP header. When the protocol mapping is nTS/RTP the
RTP parameters RTPdrop, RTPdup, RTPooo and RTPlag will be updated and the
corresponding alarms Packet drops:N, Duplicate packets:N and Out of order
packets(lag:N) are fired (if not switched off).
Note that the probe will perform out-of-order corrections before RTP packet loss
analysis is performed.
Example of RTP sequences and their effects on monitoring:
..., 10, 11, 12, 13, 14, 17, 18, 19, ...
2 dropped packets (15-16)
..., 10, 12, 13, 16, 17, 18, 19, ...
1 and 2 dropped packets (11, 14-15)
..., 10, 11, 15, 12, 14, 16, 18, 19, ...
2 dropped packets (13, 17)
1 out of order packets of order 3
(1512)
Default Monitoring
When the protocol mapping is nTS/UDP, meaning there is no RTP information in the
multicast stream, there is no easy way to isolate and register network-induced errors.
Assumptions can be done by performing continuity counter analysis for the content of
each received UDP-frame on the fly. The probe will note CC-errors (CCerr) and
generate corresponding alarms (CC skips:N).
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Sequence Effect
Monitoring page: RTPdrop:+2
Alarms & events: RTP Packet drop: 2
Monitoring page: RTPdrop:+3
Alarms & events: RTP Packet drop: 3
Monitoring page: RTPdrop:+2
Monitoring page: RTPooo:+1
Monitoring page: RTPlag: 3 (at least)
Alarms & events: RTP Packet drops: 2
Alarms & events: RTP out of order
packets (lag:3)
PROBE USERS' MANUAL VERSION 5.0
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