Difference Between Policy Map Bandwidth and ETS

[richardmaxw]

Hi,

On a Cisco router, I can specify how much bandwidth each class gets, like this:

Router(config)#class-map test
Router(config-cmap)#match cos 3
Router(config-cmap)#exit
Router(config)#policy-map test
Router(config-pmap)#class test
Router(config-pmap-c)#bandwidth percent 30

I'm reading about ETS (Enhanced Transmission Selection) and it says it also allocates bandwidth to each class of service on a link. So, I'm unsure what the difference is between the two. In other words, how is ETS different from traditional QOS?

Also, I've been searching for documentation covering how to set up ETS on a Cisco device, but couldn't find anything. Do you need to set it up on a Cisco device or do you just run lldp tlv-select dcbxp to allow automatic setup for ETS? Who sets the percentage of bandwidth in the conversation?

Thanks,

Rich

[Joseph W. Doherty]

Laugh, so what is traditional QoS?  Reason I laugh, over the years there has been lots (and lots) of kinds of QoS support across Cisco switches and/or across Cisco routers.

From looking at Wiki's entry for ETS (Wiki ETS), ETS just appears to be a high level dot1Q spec defining multiple queues for egress traffic (w/o, it appears, even defining a specific algorithm for dequeuing).

What ETS would do, would, I suspect, depend very much on the platform.

I further suspect, ETS helps provide a framework and/or specification, of how CoS tags might be used across multiple queues.

The biggest difference, "traditional (Cisco) QoS" might be more focused to using L3's ToS, while something like ETS focuses on L2's CoS.

Personally, I would say ETS appears to be a form of AQM (active queue management), and a part of QoS (the latter including anything that allows/support a defined quality of service).