Wireshark · Wireshark-dev: [Wireshark-dev] Question regarding the DELAY

["Andreina Toro" <andreina.toro@xxxxxxxxx>]

Hi Mr. Ruoff, thanks for helping me with my thesis. What you explained me really helped, I talked to the people here and I´m going to analyze the "Mean Jitter". But I still have a confusion with the delay, you said: " You can take the average delay over the whole communication for example. But you should also monitor the maximum delay." I agree with you, and I have some questions about that.

 

Is the round-trip propagation delay  (A - LSR - DLSR) specified in Wireshark??

  

When I filter RTCP packets I can get specific information about them, I took some fields to ask you some questions... 

 

- Real-time Transport Control Protocol (Sender Report)

     Stream setup by H245 (frame 8)

    -Source 1

        Identifier: 1632266440

        SSRC contents

        Extended highest sequence number received: 35241

        Interarrival jitter: 560

        Last SR timestamp: 14635237 (0x00df50e5)

        Delay since last SR timestamp: 251396

            Frame matching Last SR timestamp: 447

        Roundtrip Delay(ms): 5

 

Is this Roundtrip Delay(ms) the (A - LSR - DLSR)  specified in the RFC-3550??.

 

And why not all the RTCP packets have this Roundtrip Delay? I read in that RFC that if no SR packet has been received yet from SSRC_n, the DLSR field is set to zero.? But why is this?

       Last SR timestamp: 0 (0x00000000)

       Delay since last SR timestamp: 0

 

How is the conversion done between "Delay since last SR timestamp: 251396" and the Roundtrip in ms??

 

Do I calculate the average delay with this Roundtrip Delay data?,

 

And another question, is there a way to get the maximum delay information with wireshak?

 

Thanks sooo much for your time!

 

Best Regards,

Andreina

 

Lars Ruoff <Lars.Ruoff@xxxxxxxxxx> escribió:

Hello Andreina,

First, the roundtrip delay we are speaking of is not directly the DLSR
field, but A - LSR - DLSR. (see RFC 3550 - page 40/41)
Again it is difficult to define what should be used for a QoS review.
You can take the average delay over the whole communication for example.
But you should also monitor the maximum delay.

best regards,
Lars

Andreina Toro wrote:
> Hi Mr. Ruoff, I was reading the RFC-3550 regarding "delay since last SR
> (DLSR): 32 bits", I know with Wireshark I can filter RTCP so I would be
> able to read this information, but how is the delay managed in a Quality
> of Service Review?. I mean, what has to be less than 150ms? the delay
> since last SR for every packet for every call? :0S How do you clasify a
> call to be one with an acceptable delay?
>
>
> Best regards!
> Andreina