Wireshark-users: Re: [Wireshark-users] use of -z io,stat
From: Sake Blok <[email protected]>
Date: Wed, 29 May 2013 23:19:58 +0200
Stuart,

If you would have used frame.time_delta, it would have worked, however, tcp.time_delta is a delta time within the TCP conversation, so if there are more TCP sessions at the same time, you can end up with more time delta in the io stat then the capture time.

Example:

Frame 1, tcp stream 0, frame.time_relative = 0.000, frame.time_delta = 0.000, tcp.time_delta = 0.000
Frame 2, tcp stream 1, frame.time_relative = 0.100, frame.time_delta = 0.100, tcp.time_delta = 0.000
Frame 3, tcp stream 0, frame.time_relative = 1.000, frame.time_delta = 0.900, tcp.time_delta = 1.000
Frame 4, tcp stream 1, frame.time_relative = 1.100, frame.time_delta = 0.100, tcp.time_delta = 1.000

Sum frame.time_delta = 1.100, sum tcp.time_delta = 2.000

Cheers,
Sake


On 26 mei 2013, at 17:42, Stuart Kendrick wrote:

> I'm trying to teach myself how to use the '-z io,stat' options in tshark
> 
> I was imagining that the following would tell me how many seconds the trace covers
> 
> tshark -r sample-http.pcapng -o tcp.calculate_timestamps:TRUE -qz "io,stat,0,SUM(tcp.time_delta)tcp.time_delta"
> 
> =============================================
> | IO Statistics                             |
> |                                           |
> | Interval size: 11.1 secs (dur)            |
> | Col 1: Frames and bytes                   |
> |     2: SUM(tcp.time_delta)tcp.time_delta  |
> |-------------------------------------------|
> |              |1               |2          |
> | Interval     | Frames | Bytes |    SUM    |
> |-------------------------------------------|
> |  0.0 <> 11.1 |    216 | 45453 | 23.817352 |
> =============================================
> 
> capinfos sample-http.pcapng
> File name:           sample-http.pcapng
> [...]
> File size:           53 kB
> Data size:           45 kB
> Capture duration:    11 seconds
> [...]
> 
> But apparently not:  '23.817352' does not equal '11 seconds'
> 
> https://vishnu.fhcrc.org/wireshark/sample-http.pcapng
> I'm using wireshark 1.10.0rc2
> 
> What am I not understanding about this '-z io,stat' feature?
> 
> --sk
> 
> Stuart Kendrick
> FHCRC
> 
> P.S.
> 
> My actual use case will be more complex than this.  This trace was taken next to the Client.  
> I want to calculate how much time the Client spent thinking:
> tshark -r sample-http.pcapng -o tcp.calculate_timestamps:TRUE -qz "io,stat,0,SUM(tcp.time_delta)tcp.time_delta and tcp.dstport==80"
> 
> and how much time the Network + Server spent thinking:
> tshark -r sample-http.pcapng -o tcp.calculate_timestamps:TRUE -qz "io,stat,0,SUM(tcp.time_delta)tcp.time_delta and tcp.srcport==80"
> 
> To give myself insights into how much of the total transaction time the Client is contributing versus that of the Network + Server.
> 
> But I figure that if I cannot even persuade tshark to sum every value in the DeltaT column, then I'm not ready to progress to the real-world use case.
> 
> 
> P.P.S.
> The Average function gives me a plausible answer:
> 
> tshark -r sample-http.pcapng -o tcp.calculate_timestamps:TRUE -qz "io,stat,0,AVG(tcp.time_delta)tcp.time_delta"
> 
> =============================================
> | IO Statistics                             |
> |                                           |
> | Interval size: 11.1 secs (dur)            |
> | Col 1: Frames and bytes                   |
> |     2: AVG(tcp.time_delta)tcp.time_delta  |
> |-------------------------------------------|
> |              |1                |2         |
> | Interval     | Frames |  Bytes |    AVG   |
> |-------------------------------------------|
> |  0.0 <> 11.1 |    473 | 349155 | 0.050354 |
> =============================================
> 
> 
> But when I sanity-check this calculation using Excel, I see a different result:
> 0.023518s
> 
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