[quagga-users 12568] Re: bgp - quagga-0.99.18

Alexis Rosen quagga-users at alexis.users.panix.com
Sat Nov 12 21:36:47 GMT 2011


On Nov 11, 2011, at 10:35 AM, Ingo Flaschberger wrote:
>> 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!

I quoted the words "the queue" for a reason - I was not talking specifically about any one particular queue- as I'd hoped the rest of the post, which was mostly talking about ethernet ring buffers, made clear. I was talking about all of the buffering that's done on the system.

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

You've entirely missed the point. I was talking about maximum packet handling capability of quagga routers. In other words, the type of situation where your router may indeed not have enough time to handle all the packets, at least momentarily. It's exactly those types of situations that may encourage people to use too much buffering.

/a


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