Re: Lost UDP packets
Re: Lost UDP packets
- Subject: Re: Lost UDP packets
- From: Justin Walker <email@hidden>
- Date: Sun, 26 Sep 2004 20:39:46 -0700
On Sep 26, 2004, at 18:13, Jim Hunter wrote:
> Date: Sat, 25 Sep 2004 14:23:24 -0700
> From: Justin Walker <email@hidden>
> Subject: Re: Lost UDP packets
> To: Mark Hunt <email@hidden>
> Cc: email@hidden
> Message-ID: <email@hidden>
> Content-Type: text/plain; charset=US-ASCII; format=flowed
>
>
> On Sep 25, 2004, at 13:43, Mark Hunt wrote:
>
>>Since for any given lost packet, another receiver gets it, I think I
>>can rule out collisions.
I agree.
See below.
>>I'm still waiting on a meaningful netstat from my beta-tester, but
I'm
>>pretty sure the problem is in my receiving application. It's pretty
>>busy, so maybe my network thread (blocked in recvfrom) needs higher
>>priority?
Why are you ruling out either the NIC hardware or the driver being
the cause of the dropped packets? I don't see why the problem has to be
at the application level.
Agreed.
> Also, check stats on both sender and receiver(s). You haven't ruled
> out the sender yet, and at high packet generation rates, the CPU can
> easily overwhelm the driver send-queue limits (usually fairly small).
> For UDP, when this happens, the packets are dropped on the sending
end
> (without error indications; only the counters are updated).
It can't be the sender, since the "lost" packets are actually being
received on some other nodes. If the transmitter's send queue was being
overrun, then the lost packets would not be received anywhere.
Are the packets sent to individual addresses? I have reread the
thread, and can't tell for sure.
If the traffic is broadcast, the issues are much different than unicast.
Regards,
Justin
--
/~\ The ASCII Justin C. Walker, Curmudgeon-at-Large
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