Wireshark-users: Re: [Wireshark-users] End to End VoIP delay calculation (Interarrival jitter)
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From: capricorn 80 <cool_capricorn80@xxxxxxxxxxx>
Date: Fri, 27 Nov 2009 14:44:13 +0000

 Hi !

  Thanks for your responses. @ martin.r.mathieson: I tried alot to understand but may be I dont have much expertise in this case :(.
  .Now I am doing like this that I have run wireshark on computer and computer is synchronized with ntp server. I am looking for interarrival calculation.

This is my readings from wireshark: (The IP addresses i mentioned is dummy one).

113.100.26.222 is computer
61.216.159.110 is asterisk server

 No     Time            Source              Destination         Protocol     Delta time
-------------------------------------------------------------------------------------------
 28    24.646137    113.100.26.222        61.216.159.110    RTP         0.031826
 Arrival Time: Nov 23, 2009 23:50:32.660458000
 Sequence number: 7867
 Timestamp: 365000

--------------------------------------------------------------------------------------------
 29    24.656106    113.100.26.222        61.216.159.110    RTP          0.009969
 Arrival Time: Nov 23, 2009 23:50:32.670427000
 Sequence number: 7868
 Timestamp: 365160
--------------------------------------------------------------------------------------------

 30    24.675980    113.100.26.222        61.216.159.110    RTP         0.019874
 Arrival Time: Nov 23, 2009 23:50:32.690301000
 Sequence number: 3771
 Timestamp: 422060
---------------------------------------------------------------------------------------------
 31    24.685764    61.216.159.110        113.100.26.222    RTP         0.009784
 Arrival Time: Nov 23, 2009 23:50:32.700085000
 Sequence number: 3767
 Timestamp: 421420

----------------------------------------------------------------------------------------------
 32    24.695953    113.100.26.222        61.216.159.110    RTP         0.010189
 Arrival Time: Nov 23, 2009 23:50:32.710274000
 Sequence number: 7870
 Timestamp: 365480

-----------------------------------------------------------------------------------------------
 33    24.704766    61.216.159.110        113.100.26.222    RTP         0.008813
 Arrival Time: Nov 23, 2009 23:50:32.719087000
 Sequence number: 3768
 Timestamp: 421580

-----------------------------------------------------------------------------------------------

 Please if you help me in telling that how can I calculated the Interarrival jitter in steps in that case. I shall be very thanksful to you.

Regards,




Date: Thu, 26 Nov 2009 09:23:21 +0000
From: martin.r.mathieson@xxxxxxxxxxxxxx
To: wireshark-users@xxxxxxxxxxxxx
Subject: Re: [Wireshark-users] End to End VoIP delay calculation

There is the RTCP roundtrip network propagation delay.  If the necessary reports are present and properly formatted, there will be an expert info item for any calculations that may be made. You will need to enable this calculation in the RTCP dissector preferences.

Here is the extract from RFC 3550, section 6.4.1, that describes how the calculation should be done:

delay since last SR (DLSR): 32 bits
      The delay, expressed in units of 1/65536 seconds, between

      receiving the last SR packet from source SSRC_n and sending this
      reception report block.  If no SR packet has been received yet
      from SSRC_n, the DLSR field is set to zero.

      Let SSRC_r denote the receiver issuing this receiver report.

      Source SSRC_n can compute the round-trip propagation delay to
      SSRC_r by recording the time A when this reception report block is
      received.  It calculates the total round-trip time A-LSR using the

      last SR timestamp (LSR) field, and then subtracting this field to
      leave the round-trip propagation delay as (A - LSR - DLSR).  This



Schulzrinne, et al.         Standards Track                    [Page 40]


RFC 3550                          RTP                          July 2003


      is illustrated in Fig. 2.  Times are shown in both a hexadecimal
      representation of the 32-bit fields and the equivalent floating-

      point decimal representation.  Colons indicate a 32-bit field
      divided into a 16-bit integer part and 16-bit fraction part.

      This may be used as an approximate measure of distance to cluster
      receivers, although some links have very asymmetric delays.


   [10 Nov 1995 11:33:25.125 UTC]       [10 Nov 1995 11:33:36.5 UTC]
   n                 SR(n)              A=b710:8000 (46864.500 s)
   ---------------------------------------------------------------->
                      v                 ^

   ntp_sec =0xb44db705 v               ^ dlsr=0x0005:4000 (    5.250s)
   ntp_frac=0x20000000  v             ^  lsr =0xb705:2000 (46853.125s)
     (3024992005.125 s)  v           ^
   r                      v         ^ RR(n)

   ---------------------------------------------------------------->
                          |<-DLSR->|
                           (5.250 s)

   A     0xb710:8000 (46864.500 s)
   DLSR -0x0005:4000 (    5.250 s)

   LSR  -0xb705:2000 (46853.125 s)
   -------------------------------
   delay 0x0006:2000 (    6.125 s)

           Figure 2: Example for round-trip time computation






On Thu, Nov 26, 2009 at 2:48 AM, Martin Visser <martinvisser99@xxxxxxxxx> wrote:
As RTP in each direction is unacknowledged (you have a unidirectional stream going each direction) there is no way to determine end-to-delay from that. I think the best you can do is look at the SIP request/response time as an estimate.

Regards, Martin

MartinVisser99@xxxxxxxxx


On Wed, Nov 25, 2009 at 4:31 AM, capricorn 80 <cool_capricorn80@xxxxxxxxxxx> wrote:

 Hi!

  (Sorry for repeating my question)

 I am looking to calculate the end-to-end delay between two soft phone/hard phone. I have asterisk server and configured ntp server on the same machine and synchronized it with ntp pool.
 
 I have seen that Wireshark can be used to check the jitter. But I am not sure how can i calculate the end to end. 

May be this is not related to the mailing list topic but please help me if anyone has some information.

Regards,


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