QoS policing question

[mark.tutton]

Hi,

I am trying to understand when Policing is used what scheduling policy is used, ie what factors decide when queue AF11,12,13 should be serviced before AF21,22,23 queue. I know that packets once in their policed queue may be subjected to random drops (depending on their drop precedence) and RED, but I do NOT know what mechanism the router uses to decide on which of the queues the next packet should be taken from and placed on WAN interface.

Any help would be great. Thanks

[Joseph W. Doherty]

What you're asking is very, very broad. QoS features vary much by platform and IOS version. Even default QoS operation can change across IOS versions.

Generally, most Cisco devices only provide either a single FIFO queue, or for routers with slower serial links, WFQ default. Everything beyond that normally requires explicit configuration.

What a platform/IOS provides is documented in the corresponding reference manuals. Why to use certain features are documented/explained in various technotes, white papers, QoS design guides, and/or QoS books.

[Istvan_Rabai]

Hi Mark,

As Joseph mentioned, this is an extensive topic.

I think what you are looking for is called congestion management or queuing and scheduling.

I have looked up for you the QoS configuration guide. Look for Congestion Management.

http://www.cisco.com/en/US/docs/ios/qos/configuration/guide/12_4t/qos_12_4t_book.html

Cheers:

Istvan

[mark.tutton]

Hi Istvan,

Great, that papers exactly what I am looking for.

Thanks for your time and effort.

regards

Mark