Re: Packet loss in IP/UDP Stack?

[Martin Rauh]

The UDP packet loss went away by setting the rmem_max and rmem_default
in /proc/sys/net/core on the receiving linux box to about 80 percent of the
size of the
transfered file (~50MB).

Many thanks for the fast help!

greetings,

Martin Rauh

Andi Kleen wrote:

> On Fri, Jan 26, 2001 at 07:01:12PM +0100, Martin Rauh wrote:
> > Hi folks,
> >
> > It seems that we are loosing packets in the UDP stack.
> > Somebody might think that this is not astonishing, but
> > the packets are not lost at the network layer. They seem to get
> > lost in the IP/UDP Layer of the receiving box.
> >
> > We have got the following configuration:
> > Two linux boxes (P4, 733 MHz, 256 MB RAM, kernel 2.4.0)
> > are directly connected with two syskonnect sk98xx
> > gigabit ethernet cards. We are sending a file from one host to the other
> >
> > with UDP. About half of the file is lost in the receiving application.
> > But according to the statistics in /proc/net/dev no errors (fifo, frame,
> > dropped...)
> > occured in the network layer. Even the transmitted and received
> > data at the network layer (tx-bytes, -packets) are identical
> > to the amount of the transfered file (plus network overhead).
> >
> > Doas anybody know where the loss occurs? Is there a loss at the
> > network layer or in the higher protocol layers?
>
> UDP by default has 64K buffer and drops packets when it overflows.
> You can check that using netstat -s.
> You can increase it use the SO_{SND,RCV}BUF socket options and/or the
> net/core/[rw]mem_* sysctls.
>
> -Andi
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