[quagga-users 12566] Re: bgp - quagga-0.99.18

Ingo Flaschberger if at xip.at
Fri Nov 11 15:35:03 GMT 2011


Dear Alexis,

> On Nov 8, 2011, at 12:57 PM, Ingo Flaschberger wrote:
>>        +--------------------+
>> input ->|    1 mbit queue    |-> output
>>        +--------------------+
>>                            ^
>>                            |
>>                         small packet input
>> [...]
>
> There's rather more to the problem than what you do with small packets. 
> And if you think that "the queue" is just 1mbit, you're mistaken - just 
> at the level of one ethernet port's ring buffers, you could choose to 
> configure 4096*9000 bytes of buffering. That alone could produce ~300ms 
> of buffering on a gigabit interface. (Yes, that's generally unrealistic, 
> but 4k*1500 bytes is not, and that still amounts to 50ms.) And that 
> doesn't take into account the various other layers of buffering you may 
> have in your system. Stick ten or twenty routers in between source and 
> destination and you could have a real problem, if enough people make the 
> wrong choices.

at freebsd:
man ipfw
man dummynet

and the queue has 1 mbit!

ethernet-queues only fill if the router has not enough time to handle 
packets - and the you have other problems than only slow pings.

and the 1 mbit queue only fill if you have traffic more than 1 mbit; if 
not - it's nearly empty.
thats a queue - and no fixed time "delay", FIFO - not a shifting register.

Kind regards,
 	Ingo Flaschberger



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