[Winpcap-users] determinist / speed up the transmission with winpcap ?

[Loris Degioanni]

WinPcap skips the protocol layer, but it still relies on the low part of 
the NDIS stack to transmit packets. In other words, it doesn't talk with 
the network card directly, but:

1. performs a transition from user mode (packet.dll) to kernel mode 
(npf.sys). This is normally quite slow.
2. gives the packets to NDIS, which delivers it to the NIC driver for 
transmission. This is normally quite fast (microseconds), but the NIC 
driver may introduce arbitrary latencies that are not under the npf.sys 
control.

If you don't need to be interactive, you can buffer the packets during 
the transaction from user mode to kernel mode (pcap_sendqueue* 
functions). This improves things a lot.

Loris


Soft Prodel wrote:
> Hello All developers,
> 
>  
> 
> - excuse first for my bad English...-
> 
>  
> 
> I would like to know if with winpcap used with windows XP (pro) ,i can 
> be determinist for the timing.
> 
>  
> 
> each milliseconde,(using the multimedia timer),i send a request to a 
> server with UDP/IP protocol. at this moment i use traditional 
> AsyncSocket windows API's.
> 
> but all the layers, stacks of windows take time and is not determinist. 
> when i decide to send a frame, the most of the time, the frame is 
> emitted on the network 1, 5, 10, 50 ms after and sometimes, when i 
> stress the PC, 250 ms later !!!.
> 
> i know that XP is not a Real-Time operating system, but i try to speed 
> up the transmission at least at 2 or 3 ms.
> 
>  
> 
> is winpcap able to skip all the system latency ?
> 
> i think yes because it bypass all the layers but what with the HAL 
> layer... ?
> 
> or any person have information about to how to make ?
> 
>  
> 
> The application is for fast communicate with I/O system. without real 
> time system like RTX or others. 
> 
>  
> 
> Thanks for attention.
> 
>  
> 
> Best Regards.
> 
>  
> 
> Laurent.
> 
> 
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