Re: IP BW computation in RTP stream analysis

["RUOFF LARS" <Lars.Ruoff () alcatel-lucent com>]

...and with reading the source code it looks even more like what Martin
said:

tap-rtp-common.c
(http://anonsvn.wireshark.org/viewvc/trunk-1.2/tap-rtp-common.c?view=mar
kup):

        /* Calculate the BW in Kbps adding the IP+UDP header to the RTP
-> 20bytes(IP)+8bytes(UDP) = 28bytes */
        statinfo->bw_history[statinfo->bw_index].bytes =
rtpinfo->info_data_len + 28;
        statinfo->bw_history[statinfo->bw_index].time = current_time;

        /* Check if there are more than 1sec in the history buffer to
calculate BW in bps. If so, remove those for the calculation */
        while
((statinfo->bw_history[statinfo->bw_start_index].time+1000/* ms
*/)<current_time){
                statinfo->total_bytes -=
statinfo->bw_history[statinfo->bw_start_index].bytes;
                statinfo->bw_start_index++;
                if (statinfo->bw_start_index == BUFF_BW)
statinfo->bw_start_index=0;
        };
        statinfo->total_bytes += rtpinfo->info_data_len + 28;
        statinfo->bandwidth = (double)(statinfo->total_bytes*8)/1000;
        statinfo->bw_index++;
        if (statinfo->bw_index == BUFF_BW) statinfo->bw_index = 0;

Lars
 


________________________________

        From: wireshark-users-bounces () wireshark org
[mailto:wireshark-users-bounces () wireshark org] On Behalf Of Martin
Visser
        Sent: mercredi 18 novembre 2009 12:52
        To: Community support list for Wireshark
        Subject: Re: [Wireshark-users] IP BW computation in RTP stream
analysis
        
        
        Without reading the source code, it looks to me to be pretty
much a sum of the size (in kilobits) of the previous 1 seconds worth of
RTP packets in that direction on that stream. (I *think* it is just the
IP size (header + payload) but not the layer 2 frame. So effective it
shows a moving average bit rate over a one second window. You can tell
it is done this way as see the IP BW "ramp up" at the beginning of each
session. (Of course you should  read the code to confirm this exactly). 

        Regards, Martin
        
        MartinVisser99 () gmail com
        
        
        
        On Wed, Nov 18, 2009 at 9:06 AM, Josephine Kakande
<jnkakande () gmail com> wrote:
        


                Hello,
                
                Can anyone tell me what formulae/equations are used to
compute the the IP BW (in kbps) for Wireshark RTP stream analysis?
                
                Thanks,
                Josephine
                
                
                
        
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