Network Monitoring: Application Level

As discussed in the PIPVIC deliverable "Collection and Analysis of Mbone Traffic Statistics", there are three possible places at which it is possible to take loss measurements: application level, IP level and link level. This page discusses application level monitoring, using RTCP reception reports.

The audio and video tools used in the PIPVIC project are based around the IETF standard real-time transport protocol (RTP), and the associated RTP control protocol (RTCP). The control protocol, RTCP, is used to convey information about each participant to all other participants: it is, for example, the means by which the personnal names displayed by the media tools are distributed.

Each application periodically multicasts an RTCP reception report to the group. This reception report includes, for each active sender, summary statistics for packet loss and jitter since the last report. By plotting the information contained in these reception reports, it is possible to display an overview of the network performance during a conference.

The graphs below show the reception quality observed, at UCL, during the project meeting held on Friday 1st May 1998. There is one graph for each participant sending video during the meeting. Within each graph, there is a row for each receiver, with a coloured bar indicating the quality that receiver was reporting. This bar is green if less than 5% packet loss was observed, orange for 5-10% loss, and red when more than 10% loss occured. Periods where no reception reports were received are white. This could mean one of two things: either the source stopped transmitting, or the reception report packets were lost.

Apologies for the size of the text in these graphs: if I scale them up big enough the make the text easy to read, the files become huge and we run out of disk space on our web server....

Note:

Readers may also be interested in the Mbone loss measurements taken by Mark Handley, which show a couple of different ways of measuring similar statistics.
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Colin Perkins, 4 May 1998.