sizing router buffers (Re: Software router state of the art )
swmike at swm.pp.se
Wed Jul 23 21:48:08 UTC 2008
On Wed, 23 Jul 2008, Kevin Oberman wrote:
> be of any use at all. This would require 3 GB of buffers. This same
> problem also make TCP off-load of no use at all.
3 Gigabyte? Why?
The newer 40G platforms on the market seems to have abandonded the 600ms
buffers typical in the 10G space, in favour of 50-200ms of buffers (I
don't remember exactly).
Aren't there TCP implementations that don't use exponential window
increase, but instead can do smaller increments, which I would have
believed would enable routers to still do well with ~50ms of buffering.
High speed memory is very expensive, also a lot of applications today
would prefer to have their packets dropped instead of being queued for
hundreds of milliseconds. Finding a good tradeoff level between the demand
of different traffic types is quite hard...
Also, DWDM capacity seems to get cheaper all the time, so if you really
need to move data at multigigabit speeds, it might make sense to just rent
that 10G wave and put your own equipment there that does what you want.
Mikael Abrahamsson email: swmike at swm.pp.se
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