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Author Topic: QOS and Dante  (Read 10424 times)

Helge A Bentsen

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QOS and Dante
« on: October 13, 2016, 02:50:54 am »

I'm trying to get my head around Dante and Quality of Service..

Several companies and Audinate themselves refer to QOS and that you have to choose a switch that supports it and configure it, but none I've contacted so far can tell me what it is and how to do it. The most common answer is "don't worry about it, it will take care of itself".

Now, I don't like that kind of answer.
So, what is QOS?
Do I need to worry about it in terms of Dante?
Do I need to set it up?

The switch in question is a Netgear GS716Tv3

Any help would be appreciated.
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Scott Holtzman

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Re: QOS and Dante
« Reply #1 on: October 13, 2016, 03:05:58 am »

I'm trying to get my head around Dante and Quality of Service..

Several companies and Audinate themselves refer to QOS and that you have to choose a switch that supports it and configure it, but none I've contacted so far can tell me what it is and how to do it. The most common answer is "don't worry about it, it will take care of itself".

Now, I don't like that kind of answer.
So, what is QOS?
Do I need to worry about it in terms of Dante?
Do I need to set it up?

The switch in question is a Netgear GS716Tv3

Any help would be appreciated.

Quality of Service is a generic term for any protocol or method that categorizes and prioritizes traffic on a network.

QoS on a LAN is very simple as you have control over each component.  You simply need to make sure it all matches.

QoS over a WAN is much more complicated but not relevant to your question.

QoS mechanisms exist at Layer 2 and Layer 3 however again since we are talking about a Layer 2 switch I will confine my comments to that specific scenario.

The first and most important thing to understand is QoS only occurs when an interface is congested (presented with more traffic than it can process).  Congestion can occur at speeds less than media however modern switches are generally "wire speed" for all intents and purposes.

For layer 2 the switch supports manual QoS, this scheme you set the priority on a port by port basis.  Higher priority ports will have their Ethernet frames forwarded first in the event of congestion.  If you are not using VLAN's this is all you need to do. 

If you are using VLAN's the switch supports 802.1p protocol.  A table exists that maps QoS information from the source host to different priorities.  I believe there are 8 priorities.  You should be able to program that value in the hosts and then setup the table in the switch to match.

All switches must match

The most important thing to consider is that if your network is not congested QoS is not required, nor will it do anything.  QoS policies are only in effect during congested states.

Let me know if you have any questions.

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richard_cooper

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Re: QOS and Dante
« Reply #2 on: October 13, 2016, 05:38:48 am »

I'm trying to get my head around Dante and Quality of Service..

Several companies and Audinate themselves refer to QOS and that you have to choose a switch that supports it and configure it, but none I've contacted so far can tell me what it is and how to do it. The most common answer is "don't worry about it, it will take care of itself".

Now, I don't like that kind of answer.
So, what is QOS?
Do I need to worry about it in terms of Dante?
Do I need to set it up?

The switch in question is a Netgear GS716Tv3

Any help would be appreciated.

I presume you've seen Audinate's FAQ on the subject. If not here's the relevant bit.

Quote
What is Quality of Service (QoS)?

Quality of Service (QoS) is a feature of managed switches, which ensures that certain types of network packets (e.g. clock sync and audio packets) get preferential treatment and are "moved to the front of the line" ahead of other traffic. This is achieved by attaching a priority number to each packet, which is then used by the switches to ensure that high priority packets get processed before lower priority packets.

When do I need to use QoS in a Dante network?

QoS is required when using Dante in networks that have 100Mbps devices and is optional in networks with Gigabit devices. We recommend that QoS be enabled in all Dante networks in order to ensure proper operation under all possible conditions.

How does Dante manage QoS?

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 many 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.

How does Dante use DSCP / Diffserv priority values when configuring QoS?

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 below shows how Dante uses various Diffserv Code Points (DSCP) packet priority values:

PriorityUsageDSCP LabelHexDecimalDecimal
HighTime critical PTP events CS7 0x38 56 111000
MediumAudio, PTP    EF 0x2E 46 101110
Low(reserved) CS1 0x08 8 001000
NoneOther traffic    BestEffort 0x00 0 000000

This Page on Yamaha's site describes the setup process for a specific Cisco switch. I'm not aware of any guides for other switches, but given the number of switches out there....

In my experience, which is in the realms of up to 100-150 channels using Yamaha/A&H/DVS type kit, there is no down sides to having properly set up QOS.

The only time QOS has appeared to help, was a setup where lots of large files were moved over the Dante network, which sometimes caused audio dropouts.  HOWEVER in moving to have QOS the switches were changed from cheap desktop ones to something much more suitable, so any number of factors could have been in play.

My own rule of thumb is to not worry about it on networks with just Dante present, but to try and have it for mixed networks. Most of the time, however, I'm just using my own pre configured switches, which are set up with QOS for Dante anyway.

Your switch looks like it supports the needed stuff, so you may as well set it up IMHO.
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David Sturzenbecher

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Re: QOS and Dante
« Reply #3 on: October 13, 2016, 09:29:31 am »

If you are on Dante only network, you don't even need a managed switch. A simple dumb switch with no EEE or the ability to turn it off is sufficient.


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Mac Kerr

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Re: QOS and Dante
« Reply #4 on: October 13, 2016, 10:52:04 am »

I'm trying to get my head around Dante and Quality of Service..

Several companies and Audinate themselves refer to QOS and that you have to choose a switch that supports it and configure it, but none I've contacted so far can tell me what it is and how to do it. The most common answer is "don't worry about it, it will take care of itself".

Now, I don't like that kind of answer.
So, what is QOS?
Do I need to worry about it in terms of Dante?
Do I need to set it up?

The switch in question is a Netgear GS716Tv3

Any help would be appreciated.

In a network that only has Dante traffic on it QoS does nothing. There is no need to think about it. The only thing to watch for on a Dante only network is that no switch goes into EEE mode, if your switch has it, turn it off. If you are sharing your network with other traffic you can follow the instructions on the Yamaha site for setting up QoS, which will make sure that Dante timing data goes with the highest priority, and audio data with the next highest.

Mac
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brian maddox

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Re: QOS and Dante
« Reply #5 on: October 13, 2016, 01:08:29 pm »

In a network that only has Dante traffic on it QoS does nothing. There is no need to think about it. The only thing to watch for on a Dante only network is that no switch goes into EEE mode, if your switch has it, turn it off. .....
Mac

This. 

It's also critical to make sure it's turned off on EVERY switch on your Dante Network.  Recently did a load in on a job where my client chose to install all new Cisco switches thoughout my Dante Primary network [since that made the Fiber interface simpler] without realizing that those switches default to EEE ON.  There were some other issues during the setup that masked the effect of that until first day of show when i suddenly noticed that i had serious DANTE clocking issues on 2 of the 8 Dante Fiber networks coming into my Master Control.  Turned off EEE on the switches on those fiber networks but that didn't fix the issue.  It was only when we went through and turned off EEE on ALL the switches [there were about 20 on the network in total] that the issues completely disappeared.
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Samuel Rees

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Re: QOS and Dante
« Reply #6 on: October 13, 2016, 02:31:01 pm »

This. 

It's also critical to make sure it's turned off on EVERY switch on your Dante Network.  Recently did a load in on a job where my client chose to install all new Cisco switches thoughout my Dante Primary network [since that made the Fiber interface simpler] without realizing that those switches default to EEE ON.  There were some other issues during the setup that masked the effect of that until first day of show when i suddenly noticed that i had serious DANTE clocking issues on 2 of the 8 Dante Fiber networks coming into my Master Control.  Turned off EEE on the switches on those fiber networks but that didn't fix the issue.  It was only when we went through and turned off EEE on ALL the switches [there were about 20 on the network in total] that the issues completely disappeared.

20 switches is a wilder Dante network than I have done, for sure!
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Mac Kerr

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Re: QOS and Dante
« Reply #7 on: October 13, 2016, 02:40:32 pm »

20 switches is a wilder Dante network than I have done, for sure!

Not me! ;-)

Mac
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Riley Casey

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Re: QOS and Dante
« Reply #8 on: October 13, 2016, 02:43:26 pm »

Its easier than you might think to get to those kinds of numbers which is why getting the basics down is so important when using Dante gear

FOH console rack =two switches
Monitor console rack = two switches
RIO one rack = two switches
RIO two rack = two switches
video world RIO rack = two switches
Record mix rack = two switches

And we haven't even gotten to the locations in the other halls that are cheaper to reach with 2000 ft of fiber and a couple of rented RIOs than to run copper.

20 switches is a wilder Dante network than I have done, for sure!
« Last Edit: October 13, 2016, 03:37:15 pm by Riley Casey »
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Samuel Rees

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Re: QOS and Dante
« Reply #9 on: October 13, 2016, 02:46:55 pm »

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Re: QOS and Dante
« Reply #9 on: October 13, 2016, 02:46:55 pm »


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