Dummynet low bandwidth simulation
Ivan Voras
ivoras at fer.hr
Mon Apr 26 17:25:38 PDT 2004
Luigi Rizzo wrote:
> are you sure you aren't running out of mbufs ?
> netstat -m should tell you.
No, its not mbufs (such messages are shown on the console I believe and
I haven't seen them; also, running netstat -m states there's plenty of
buffers remaining).
> Additionally, note that the 250ms of delay are probably way too much
> for your config (you are adding 250ms each way, which makes a 500ms RTT,
> not accounting for transmission times -- i think normal values here
> are more like 150-200ms rtt), and possibly irrelevant given how
> large your queues are -- a full-size packet is 12000 bits or 200ms,
> you can have up to 20 queued...
Oh sorry, I pasted from a wrong shell script. I've been experimenting
with different values and am considering settling at 75ms, queue of 5.
I'm still not sure: how does the number of buckets influence the operation?
I don't think it's clear to me how would such large queues produce my
errors (connection reset by peer & broken pipe). Is this reasoning
correct: in the above case, 200ms*20 = 4s, so in the worst case the
packet from the end of a queue will travel 4s until it reaches its
destination. Is 4s enough for a timeout of some sort?
I've tried running on a different machine, running 4.9-release, and
there I also get this error (in large numbers):
Error: socket: address is unavailable.: Can't assign requested address
--
C isn't that hard: void (*(*f[])())() defines f as an array of
unspecified size, of pointers to functions that return pointers to
functions that return void.
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