["Aisling" <ashling.odriscoll@xxxxxx>]

Therefore if the round trip delay formula (according to rfc 3550) is
"A-LSR-DLSR" to use the figures from the original posters email, the
formula would be:

33511349861.1073741824 - 2321891328 -1?     With the MSW and LSW making
up the NTP timestamp?

Or should the tethereal timestamp also be considered?

Regards,
Aisling.

-----Original Message-----
From: ethereal-users-bounces@xxxxxxxxxxxx
[mailto:ethereal-users-bounces@xxxxxxxxxxxx] On Behalf Of Martin
Mathieson
Sent: 24 March 2006 14:59
To: proqui@xxxxxxxxxx; Ethereal user support
Subject: Re: [Ethereal-users] RTCP for VoIP QoS

David Grau Serra wrote:

> 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).
>
These fields and the way the calculation should be done, is described in

RFC 3550, section 6.4.1.

Ethereal already does this calculation for you (if the preference is 
turned on).  There have been fixes made to this calculation, the last of

which I believe was made after the last (0.10.14) release.

DLSR is defined as:

      "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."



If the DLSR is always 1, that indicates that either:
- the RTCP stack isn't filling the value in properly, OR
- it really is replying almost instantly after receiving a report from 
the other side.  This could be because:
    - both clients are sending reports at the same rate and they are 
almost exactly in sync
    - they are sending reports in response to an incoming SR rather than

on a timer (or some other trigger)

Note that the Last SR timestamp is formed by taking the middle 32 bits 
from the MSW and LSW fields.  Taken together they are the Most 
Significant Word and Least Significant Word or an NTP timestamp.

If you still can't get Ethereal to calculate the roundtrip delay 
properly, you could send me a capture and I'll take a look.

Regards,
Martin

> Does anybody know it?
>
> Many thanks.
>
> Regards,
> David Grau
>
> _______________________________________________
> Ethereal-users mailing list
> Ethereal-users@xxxxxxxxxxxx
> http://www.ethereal.com/mailman/listinfo/ethereal-users
>

_______________________________________________
Ethereal-users mailing list
Ethereal-users@xxxxxxxxxxxx
http://www.ethereal.com/mailman/listinfo/ethereal-users

-------------------Legal
Disclaimer---------------------------------------

The above electronic mail transmission is confidential and intended only
for the person to whom it is addressed. Its contents may be protected by
legal and/or professional privilege. Should it be received by you in
error please contact the sender at the above quoted email address. Any
unauthorised form of reproduction of this message is strictly
prohibited. The Institute does not guarantee the security of any
information electronically transmitted and is not liable if the
information contained in this communication is not a proper and complete
record of the message as transmitted by the sender nor for any delay in
its receipt.


-------------------Legal  Disclaimer---------------------------------------

The above electronic mail transmission is confidential and intended only for the person to whom it is addressed. Its contents may be protected by legal and/or professional privilege. Should it be received by you in error please contact the sender at the above quoted email address. Any unauthorised form of reproduction of this message is strictly prohibited. The Institute does not guarantee the security of any information electronically transmitted and is not liable if the information contained in this communication is not a proper and complete record of the message as transmitted by the sender nor for any delay in its receipt.