Hi all list,
My presentation: I am david grau and I am from barcelona. Excuses for my poor english.
My project objective is monitor and evaluate a wireless VoIP (SIP) peer to peer session by analysing RTCP control stream and filtering performance parameters such as jitter, delay and packet loss. These values will be dynamically plotted in order to provide a visual synopsis of network health.
I use a command line network sniffer (tethereal) to capture the relevant control packets i.e. RTCP sender and receiver reports. (tethereal -i 2 -p -c 100 -V -R "rtcp").
I parse the RTCP sender and receiver reports to filter out values for jitter, delay and packet loss.
The parsing code is working in Java.
The softphone is X-Lite.
I show you part of the parsing:
TIMESTAMP (From tethereal)
18:31:01.248701000
SENDER REPORT
MSW: 3351349861
LSW: 1073741824
Sender's packet count: 2
Sender's octet count: 320
RECEIVER REPORT
Cumulative number of packets lost: 0
Extended highest sequence number received: 0
Interarrival jitter: 0
Last SR timestamp: 2321891328
Delay since last SR timestamp: 1
TIMESTAMP (From tethereal)
18:31:01.280097000
SENDER REPORT
MSW: 3351349861
LSW: 1206885810
Sender's packet count: 4
Sender's octet count: 640
RECEIVER REPORT
Cumulative number of packets lost: 0
Extended highest sequence number received: 0
Interarrival jitter: 0
Last SR timestamp: 2321893359
Delay since last SR timestamp: 1
I know how can I calculate jitter and the packet loss rate.
My problem now is how can I calculate delay (round trip delay).
I don't understand why the "Delay since last SR timestamp" is always 1.
I don't know how it works the "MSW" and "LSW" (Timestamp).
Does anybody know it?
Many thanks.
Regards,
David Grau
