[c-nsp] Limiting Interface Traffic

[Tony]

Hi Bill,


--- On Wed, 6/10/10, Bill Blackford <BBlackford at nwresd.k12.or.us> wrote:

> I am trying to get a working
> configuration that can limit traffic bandwidth to a fixed
> rate in both ingress and egress directions on a given
> interface. I have customer handoffs that I'm linking at 1g
> and need to limit to 200M, 100M each, etc.
> 
> My platform is a fixed switch, Cisco 3750G. I know I can't
> apply a service-policy outbound (only inbound) so I'm
> looking at other options.
> 
> I've configured 'mls qos' 
> 
> I am testing with a single flow using Iperf (two hosts).

 
> 
> 3. Policy-map. Applying a policy-map as a service-policy
> input, I see that limiting is happening (ingress) but not at
> the rate I specified.
> Can policing input start to reach the configured limit when
> using multiple flows? IOW, I'm only getting 36M (not 200M)
> testing with a single flow.
> 

If you're testing with a single flow then that might explain the throughput you're seeing. Have you tried with multiple flows ? If what you're seeing is due to TCP backoff then you would expect to see the typical "sawtooth" line if you graph the traffic through the interface although 36M seems a little low, but might depend on burst parameters.

If you're not already, then I would suggest using UDP in iperf so that you can verify if what you are seeing is due to TCP behaviour. Using multiple TCP threads you should get closer to your full rate.

Also suggest that you test in one direction at a time and only then do both directions at the same time.


regards,
Tony.