Sender Restart Indicator – when sloppy senders meet picky receivers
Do you know why the RTP header has a sequence number? It is incremented packet by packet and is used to detect packet loss. If your phone detects a gap in the increasing sequence, then it knows that packets were lost along the way.
But what if the sequence number suddenly jumps back to 0? Doesn’t sound like a big issue? Well, it can be and has caused huge customers to suffer from one‐way audio. The reason is that the RTP standard does not define what to do if the sequence number unexpectedly decreases. Due to this, your phone may decide not to play out audio from packets with “funny” sequence numbers. All packets arrive – still there is silence.
Voipfuture Qrystal calculates hundreds of metrics and indicators for every stream in the network and for every 5 seconds in real-time. One is called “Sender Restart”. When needed, it makes life a lot easier for operations engineers.