RTP Statistics page provides detailed information about the established call is provided. When Quadro serves as an RTP proxy, this page displays two groups (legs) of RTP statistics. For example, when calling from an IP Phone attached to the Quadro's IP line to an external SIP destination or from one external SIP destination to another through the Quadro's Auto Attendant. Each group of parameters describes characteristics of a piece of RTP stream composing an overall SIP session. Normally, one leg describes the RTP stream from caller to the Quadro and the other leg describes the RTP stream from Quadro to the destination.
Quality - estimated call quality, which depends on RTP statistic. Below is the legend for Call Quality definitions on the displayed RTP Statistics:
very bad - RX Lost Packets > 20% or RX Jitter > 200
The Local and Remote fields indicate the two peers between which the RTP stream is transmitted. The characteristics in the table below describes to the piece of RTP stream between these peers.
Rx/Tx Codec - codec for received and transmitted RTP stream respectively.
Rx/Tx Packets - number of RTP packets received and transmitted respectively.
Rx/Tx Packet Size - size of RTP packet (payload) received and transmitted respectively.
Rx Lost Packets - number of lost RTP packets for received stream.
Rx Jitter - inter-arrival jitter is an estimate of the statistical variance of the RTP data packet inter-arrival time, measured in timestamp units.
The inter-arrival jitter is defined to be the mean deviation (smoothed absolute value) of the difference D in packet spacing at the receiver compared to the sender for a pair of packets. If Si is the RTP timestamp from packet i, and Ri is the time of arrival in RTP timestamp units for packet i, then for two packets i and j, D may be expressed as:
D(i,j) = (Rj - Ri) - (Sj - Si) = (Rj - Sj) - (Ri - Si)
J(i) = J(i-1) + (|D(i-1,i)| - J(i-1))/16, where J(i) is Rx Jitter for packet i.
Rx Maximum Delay - maximum variance (absolute value) of actual arrival time of the RTP data packet compared to estimated arrival time, measured in milliseconds.
If Si is the RTP timestamp from packet i, and Ri is the time of arrival in RTP timestamp units for packet i, then variance for packet i may be expressed as following:
V(i) = |(Ri - R1) - (Si - S1)| = |(Ri - Si) - (R1 - S1)|
Rx Maximum Delay = max V(i) / 8
RX Delay Increase Count - indicates the number of times the delay in jitter buffer is increased during the call.
RX Delay Decrease Count - indicates the number of times the delay in jitter buffer is decreased during the call.
Note: RTP Statistics is logged only when at least one of the call endpoints is located on the Quadro. For example, it will not be logged when:
calls incoming from or addressed to the IP lines or remote extension,
calls from an external user are routed to another external user through Quadro's routing rules.
In the first case, RTP statistics will be logged if remote extension or IP line user is calling locally to the Quadro's extension or auto attendant.
The Configure Call Quality Event Notification link leads to the Configure Call Quality Event Notification page where call quality control notification specifics can be configured.
The Configure System Events link leads to the System Events page where the methods of notification for each system event can be configured.