Taming piggish flows via QoS

pnicolette · ‎06-29-2007

We have 10Mbit Metro Ethernet TLS between sites that use 100Mbit internally. Of the various QoS types available in Cisco midrange routers & 2960/3550 switches, can any enforce that no single flow use more than, say, 7 Mbits? And can that rule adjust after business hours so backups get 100%

Pavel Bykov · ‎06-29-2007

Yes.

For speed restriction, use per-class policing.

For minimum bandwidth reservation, use "bandwith" command.

e.g. for minimum 1 Mbit and maximum 7Mbit

policy-map test1

class test-class

bandwidth 1024

police 7000000 26000

For backups, use timed ACLs.

http://www.cisco.com/en/US/tech/tk543/tk759/technologies_tech_note09186a00801aa69d.shtml

pnicolette · ‎07-02-2007

Thank you for the quick response and link to timed ACL info.

If I understand the example, policing per class will restrict total bandwidth available to an ACL-defined group or "class" of flows. Can Cisco QoS create a per-flow restriction which applies to ANY SINGLE flow?

This is different from limiting a predefined flow or list of flows, and also different from limiting the summed bandwidth of multiple flows. It's more like creating an individual class for every new flow and imposing a standard constraint. If Cisco QoS cannot do this yet, might it be considered in future?

andrew.burns · ‎07-04-2007

Hi,

The feature you need is UBRL (User-Based Rate Limiting) but it's only available on the Sup720 - you probably won't ever see it on the low end switches because it's PFC3 based but you never know.

HTH

Andrew.