Date: Wed, 18 Sep 2002 08:49:52 -0700 From: "Justin C. Walker" <justin@mac.com> To: freebsd-net@FreeBSD.ORG Subject: Re: socket buffers Message-ID: <453BBE24-CB1E-11D6-891F-00306544D642@mac.com> In-Reply-To: <3D8895BE.F2F12CED@he.iki.fi>
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On Wednesday, September 18, 2002, at 08:03 AM, Petri Helenius wrote:
>
> I played around adjusting udp socket buffers for a while and noticed
> that if the input buffer is set to a value, packets start getting
> dropped
> when npkt*MTU > SO_RCVBUF so if a socket receives 100 byte packets over
> an ethernet interface of 1500 byte MTU and receive buffer of 100k the
> packets
> start dropping at less than 10k received data in a buffer.
This is, I think, normal behavior. Check Wright/Stevens (TCP/IP
Illustrated, V2), Ch. 2, where this is discussed (as I recall). A
socket buffer counts not only the valid data bytes enqueued, but also
the size of the mbufs used. The reasoning is clear: in order to avoid
having all the mbufs in the system end up on a single queue, because
very small packets are being received, counting mbuf space limits the
number of mbufs that can be sucked up by one direction for one socket.
Regards,
Justin
--
Justin C. Walker, Curmudgeon-At-Large *
Institute for General Semantics | It's not whether you win or
lose...
| It's whether *I* win or lose.
*--------------------------------------*-------------------------------*
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