Aggressive UDP flows

Gngogh

Hi,I am reading about the DBL feature on the Cisco 4500E which protect the buffers from filling up with traffic that is identified as nonadaptive or belligerent flows such as aggressive UDP flows. Since my curiosity doesnt stop here, i am trying to understand how the supervisor engine identify this type of traffic, which characteristics has this traffic appart from being UDP.

Is this UDP traffic only?

Can someone provide me with examples of aggressive UDP flows or any other flows that are marked as belligerent flows?

Regards
Gonçalo Reis

tunerX

High Definition video streamed over multicast.

The DBL works just by buffers and thresholds. If a UDP flow is taking a bunch of buffer space it will be dropped first based on threshold rates/PPS. Any high rate UDP flow is considered belligerent when buffers get full. So instead of just randomly dropping UDP/TCP traffic it will choose to prefer bulk dropping high rate UDP flows.

Gngogh

Hi tunerX,

Thank you for your explanation, i now understand that most of the non adaptive flows are just UDP packets that flood the network and end up consuming buffer space.

Do you know BTW if its possible to see which traffic is on the buffers and or which traffic has been dropped by protocol?

tunerX

I don't know if it is possible on a 4500E in a single system with any granularity. I would assume you could use netflow exports and synchronized clocks with a series of SNMPc collections/traps. It wouldnt be that accurate.

But as far as which packets in flow are in which buffer and receiving treatment... I don't think that is possible.