Enterprise QoS WFQ/FIFO/WRED

[frosty074]

After applying Cisco recommended QoS configuration to a WAN site router users experienced performance issues. The problem was resolved by changing the default queuing to WFQ - from WRED/FIFO. The Cisco documentation recommended FIFO/WRED for default traffic on a medium size WAN link >768Kb<2048Kb. REF:"Enterprise QoS Solution Reference Network Design Guide v3.3" PG 3-10.

Is it best to use WRED/WFQ rather than WRED/FIFO?

See attachments:

[mlund]

Hi

From my experience the best choice is WFQ on low speed links (below E1). Cisco default is to use WFQ on E1 and below and FIFO on higher speed. see this link

http://www.cisco.com/en/US/docs/ios/qos/configuration/guide/congstion_mgmt_oview.html

/Mikael

[Joseph W. Doherty]

What's "best" depends.

In general, getting the intended benefit out of WRED is very, very difficult, especially Cisco's implementation. I recommend you avoid using it, although it's handy for getting marked packets stats passing through a class.

FQ, also in general, is usually much, much better than FIFO. It's often safe to use it when you don't otherwise truly understand how to manipulate traffic with QoS. (There are excecptions, though.)

The problem you may have bumped into, I believe, Cisco's CBWFQ class-default FQ can keep other defined classes from obtaining their bandwidth guarantees on most Cisco CBWFQ supporting platforms.

A good CBWFQ template is:

policy-map CBWFQ

class LLQ

priority . . .

class scavenger

bandwidth # (minimum value, e.g. 1%)

class class-default

fair-queue