[Bloat] Bufferbloat in switches and routers

David Lang david at lang.hm
Sat Apr 18 13:33:05 PDT 2015


On Sat, 18 Apr 2015, Ketan Kulkarni wrote:

> Hi,
> We have been talking about the bloated buffers mostly on the home routers.
> The Cisco PIE too has been standardized by docsis meant to be for cable
> modems
>
> I think we would have similar concerns for switches and routers. (E.g.
> cat3k switches or Cisco 5760 controllers just to name)

remember that bufferbloat shows up where there is a difference in bandwidth from 
one side of the router to the other (i.e. a bottleneck)

This is almost always going to happen at the edge of your LAN where you go from 
your Gig-E (or in a datacenter, possibly 10Gig-E to your WAN link. It can happen 
at places inside your datacenter, but isn't as likely

> I would like to know your views about what you think about it .
> Are the theories so far and the AQMs  (codel and pie) stand true for such
> devices too?

If they are bottlenecks, yes. If they are not bottlenecks it won't hurt (no 
queues will build up

> What would it take to measure the bloat levels of these devices? Do we
> still need to use the netperf wrapper to get the characteristics of such
> devices?

the same approach works. you may need beefier systems to generate sufficient 
load.

David Lang
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