10GE TOR port buffers (was Re: 10G switch recommendaton)

Nick Hilliard nick at foobar.org
Fri Jan 27 18:51:20 CST 2012


On 27 Jan 2012, at 23:08, bas <kilobit at gmail.com> wrote:
> Im my (our) busines model _is_ the internet connectivity...
> We could give the customer double the port capacity, if they were
> willing to pay, but in real life they do not care...
> 
> While all respondents replies hold truth a (technial business) logic.
> None shed a light why there isn't  TOR box that does 10GE deepbuffers

There are a couple of reasons for this: first, dropping the amount of buffer space decreases the cost of the hardware.  Secondly, you really only need large buffers when you need to shape traffic.  Shaping traffic is important if you're down stepping from a faster port to a slower port (this is a common use case for a blade switch like a c6500), or else if you're running qos on the port and you need to implement sophisticated queuing and policing.  You can't run qos effectively without having generous buffers which is why LAN switches typically have very little buffer space and metro Ethernet switches typically have lots.

In the case of a tor switch, the use case is typically in a situation where you're not downstepping from a higher speed to a lower speed, and where you don't really need fancy qos.  So as its not generally needed for the sort of things that tor switches are used for, its not added to the hardware spec. 

Nick 


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