QOS/DSCP configuration Question

[jhoffmann015]

Hi all,

This one is way beyond my current knowledge - I am setting up a digital audio network that utilizes Dante as the audio transport.  To do this, I am configuring a 3750X switch with 2 vlans - Data and Dante.  Data will provide audio control data, and Dante will carry the actual audio streams.

The specs say to create VLANS (did that), enable IGMP Snooping (Did that), and it also uses QOS.  I do not know past auto qos how to specify the QOS settings, and reading some of the literature out there isn't helping my AV brain much.  There's lots that I can make this Cisco switch do, but this isn't one of them lol

Here's what the spec says:

QoS: QoS stands for “Quality of Service” and in simplest of terms it is a feature that allows a network switch to prioritize data based upon its type and purpose. QoS standards were created to ensure reliability of audio on a data network in applications such as telephony, conferencing, and VOIP. Dante uses these same standards to prioritize audio, clocking info, etc. Symetrix recommends QoS be enabled in all Dante networks. Will Dante work without QoS enabled? Many times the answer is yes, but if there are Dante related issues, the first thing that should be checked is whether QoS is enabled. Dante uses standard Voice over IP (VoIP) Quality of Service (QoS) switch features to prioritize clock sync and audio traffic over other network traffic. QoS is available in both inexpensive and enterprise Ethernet switches. Any switch that supports Diffserv (DSCP) QoS with strict priority and 4 queues, and has Gigabit ports for inter-switch connections should be appropriate for use with Dante. The QoS feature must have a trust mode option, which needs to be set to DSCP (diff serve) for Dante. Trust mode refers to the type of QoS tagging of the packets which allows the network to properly prioritize the different types of packets. DSCP (Diffserv) is the layer 3 QoS tagging which Dante uses. CoS is a layer 2 Trust mode that is not compatible with Dante. Switches prioritize packets using what are called DSCP/Diffserv values. Although Dante packet priority values have been chosen to make it simple to configure QoS with many switches, some switches require special configuration to recognize and prioritize specific DSCP values.

The table in the page below details the QOS settings but set up for the SG300 series switches, which I am not using:

http://www.yamahaproaudio.com/global/en/training_support/selftraining/dante_guide/chapter2/04_qos_settings/

I know this is very broad and I am potentially asking a lot but could someone at least point me in the right direction?

thanks!

[Joseph W. Doherty · Accepted solution]

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The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

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Posting

Reading the thread, I would strongly suggest you retain a consultant on QoS.

For a 3750X, I would recommend you leave QoS off until such time as you engage a consultant, because a 3750X's default QoSsettings can actually be more adverse than having QoS disabled on the device.

Or, for a 3750X, you might try it's autoQoS feature, which isn't too bad, if your traffic is like what Cisco's autoQoS model assumes it should be.  (NB: Your initial post's reference, noting usage of CS7 for some of your traffic, is NOT something Cisco's autoQoS would expect.)

Unfortunately, as Jon describes, although your question is reasonable, it requires much more information to address, and even if we could provide a perfect "do this" reply, QoS often requires monitoring and tuning to avoid degradation, over time.  The latter requires some additional understanding of the technology.

[jhoffmann015]

I actually did retain a consultant about an hour ago and we went through a few scenarios, including enabling auto qos voip trust to build the policy and class maps automatically, and also trying the devices with no qos enabled on the ports.  Dante requires QoS on a FE switch but it is "recommended" on a gigabit switch.  Since this is the only traffic on this switch, and the control traffic is negligible, we're going to see how we get on without the qos, then with autoqos in play.  

Thanks everyone for helping me work through this one - I have learned that although I can hold my own in a lot of Cisco configurations, QoS is NOT something I ever want to mess with!!  lol

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Ah, that's great!

Dante requires QoS on a FE switch but it is "recommended" on a gigabit switch.

Yea, I saw that, but what that really means Dante too needs a good QoS consultant.  (Also confirmed by their mention of using CS7.)

...QoS is NOT something I ever want to mess with!!

QoS can sometimes deliver "magic" results.  Because of it's apparent complexity, it's often ignored, which gives up what it can actually do for you.

QoS isn't really that difficult or complex, but there's much to know.  It's the kind of subject where the "devil is in the details", especially when you get into device configurations.

[ThusithaK1]

How did you go at the end?

Did you enable QoS or running without QoS?

Thanks