[Winpcap-users] Slow receiving speed (40Mbps), and packet loss.

[Gianluca Varenni]

what I would probably do is use a hub between the two machines, and try to capture the packets from a 3rd machine. I would then look at the delay of all the packets, and try to understand where you lose packets.

Also, what is the frame rate?
I would also decrease the mintocopy value (pcap_setmintocopy) to a couple of kB and see if that helps.

Have a nice day
GV
  ----- Original Message ----- 
  From: Benoit 
  To: winpcap-users at winpcap.org 
  Sent: Sunday, October 19, 2008 5:43 AM
  Subject: [Winpcap-users] Slow receiving speed (40Mbps), and packet loss.


  Hello,

  I'm actually experimenting speed problem with the winpcap 4.0.1
  library. I'm doing a software to control a Camera IP and to receive
  frames from this one.
  The transmission protocol is done at the MAC layer for the moment and
  is the following one:

  1. PC_MAC    -> CAM_MAC: Ask for a frame.
  2. CAM_MAC -> PC_MAC   : Send a frame header packet (64 bytes).
  3. CAM_MAC -> PC_MAC   : Send a frame block packet (~1500 bytes).
     Repeat this operation 150 times until the whole image is
  transmitted, no ACK packet is used.
  4. CAM_MAC -> PC_MAC    : Send a "frame has been sent " packet (32 bytes)
  5. PC_MAC    -> CAM_MAC : Send a ACK packet ("frame has been
  received") packet (32 bytes), and go back to step 1.

  Doing this transmission protocol the speed is limited at 40Mbps which
  is very slow for real time video stream.
  I've tried to play with the timeout (pcap_open(...)) and with the size
  of the buffer (pcap_setbuff(...)) but the results are quite similar.
  To capture the packet I'm using the pcap_next_ex().

  Finally If i do the same thing with two cameras: The rate is still
  40Mbps but I'm loosing half of the packet. This mean for me that the
  bottleneck is my program in C++, but I don't know how to solve it...
  Maybe if someone has a good sample code with high speed transmission
  (~Gbps) it could be helpful to understand where my application failed.

  Thanks for your help

  --
  Benoit RAT
  www.neub.co.nr




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