Sufficient Buffer Sizes

Wed Jan 3 19:49:36 UTC 2024

Thus spake Mike Hammett (nanog at ics-il.net) on Tue, Jan 02, 2024 at 05:02:22PM -0600:
> While attempting to ascertain how big of switch buffers I needed in a 100G switch, I rediscovered this article where I first learned about switch buffers.
> 
> https://fasterdata.es.net/network-tuning/router-switch-buffer-size-issues/#:~:text=Optimum%20Buffer%20Size&text=The%20general%20rule%20of%20thumb,1G%20host%20across%20the%20WAN.
> 
> It suggests that 60 meg is what you need at 10G. Is that per interface? Would it be linear in that I would need 600 meg at 100G?

We've tried to be clear about the use cases where these guidelines
apply.  In these sets of articles, we are primarily describing issues
prevalent between many scientific research and education environments
where traffic can be dominated by multiplexing a low number of high-BDP
machine-machine flows, such as from a telescope array to a supercomputer
one continent away.  

Numbers here are not one-size-fits all, and are not necessarily
characteristic of what you would want to do for multiplexing say a
bazillion flows from cdns to homes all within ~10ms rtt.  That said, if
you dig in and understand where the numbers are coming from, the
principles apply.

Dale