[Winpcap-users] EXT : WinPCAP Packet ordering

Gianluca Varenni Gianluca.Varenni at riverbed.com
Fri Feb 25 12:20:07 PST 2011

Packets will be put in the buffer respecting when the timestamp was generated.


-----Original Message-----
From: winpcap-users-bounces at winpcap.org [mailto:winpcap-users-bounces at winpcap.org] On Behalf Of Guy Harris
Sent: Friday, February 25, 2011 12:15 PM
To: winpcap-users at winpcap.org
Cc: neil.powell neil.powell
Subject: Re: [Winpcap-users] EXT : WinPCAP Packet ordering

On Feb 25, 2011, at 12:09 PM, Gianluca Varenni wrote:

> Finally (and even if you have two machines with a direct Ethernet cable, no switches/routers...) you can still "receive" packets out-of-order when running on a multicore system. The reason is that the NIC itself receives the packets probably in order, but then the NIC driver and OS will try to distribute the received packets among all the CPUs on the system. WinPcap (in its kernel driver) will receive packets concurrently on multiple cores, and will put all the packets in the same buffer. It has no way of knowing which packet was actually received first by the NIC (and has no way to control such behavior).

...and the packets will be time stamped early enough that they might not be put in the WinPcap buffer in time stamp order?  (If so, think of it as compatibility with Linux. :-)  That behavior has shown up on Linux MP machines as well - and, in the shiny new world of multi-core processors, lots of recent x86-based personal computers are MP, perhaps even the majority of them.) _______________________________________________
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