Debugging MS Teams Traffic

Skype client protocols

This page describes how Skype traffic can be analyzed with the Allegro Network Multimeter. The Skype client heavily relies on SSL for all control based traffic and RTP for all audio based traffic.

The Allegro Network Multimeter allows to search for traffic to the microsoft cloud, helps to analyze the response time of the SSL encrypted control traffic and the RTP analytics.

Skype control traffic

A simple way to get an overview of the response time of many skype server is the IP statistic table. Her you can use the freetext search for "skype" and select the the graph dialog: "tcp response time".

This graph shows you the delay of the tcp stack to confirm the reception for data. Please note that many tcp stacks wait a few milliseconds if there is no data to respond ( see [Wikipedia TCP delayed acknowledgment]. So any delay below above this value ( usually 40 ms ) shows a significant delay in the roundtrip time.

This can be done also for tcp retransmissions. If you have installed the Allegro close to the Skype client, this will indicate if the data sent to the Skype server required a retransmission on the WAN link.

Skype audio traffic

The Skype audio traffic is sent by RTP frames with encrypted content but not the RTP header. You can easily debug the RTP traffic with the RTP decoder output of the Allegro Network Multimeter.

To get an overview of which IPs have used RTP, you can use the Applications → RTP statistics.

You can also navigate directly to an IP Address and see all RTP connections of it.