QoS Config for Microsoft Lync 2013

Userlevel 1
Does anyone know how to configure QoS for Microsoft Lync? I know there is a Lync SDN for Dynamic QoS configurations and we will be using that in the coming months but I need something that i can configure right now to alleviate QoS issues. We set up a conference call between 2 sites over a VPLS circuit provided by AT&T. The Quality of the call was horrible. We have DSCP enabled on all ports and we have qosprofiles configured for audio and video. qp4 is video and qp5 is audio. The VPLS port is hard coded to 100Mbps full duplex. The circuit itself is a 50Mbps circuit. While in a call i see consistant packet drops when i run the command show port 1:24 congestion. i also see that QP5 and QP1 are the packets that are causing the congestion. QP5 causes most of the congestion.

This is what I have so far for configs:
configure ports 1:24 auto off speed 100 duplex full
configure ports 1:24 shared-packet-buffer 30

configure qosprofile QP4 maxbuffer 100 weight 1 (Default)
configure qosprofile QP5 maxbuffer 100 weight 1 (Default)

configure qosprofile QP1 committed_rate 24900 K peak_rate 50000 K ports 1:24
configure qosprofile QP4 committed_rate 20000 K peak_rate 40000 K ports 1:24
configure qosprofile QP5 committed_rate 5000 K peak_rate 8000 K ports 1:24
configure qosprofile QP8 committed_rate 100 K peak_rate 3000 K ports 1:24

configure diffserv examination code-point 26 qosprofile QP5
configure diffserv examination code-point 34 qosprofile QP4 (Lync Video)
configure diffserv examination code-point 40 qosprofile QP4
configure diffserv examination code-point 46 qosprofile QP5 (Lync Audio

show qosprofile port 1:24
Port: 1:24
QP1 CIR = 24900K PR = 50M MaxBuf = 100%
QP4 CIR = 20M PR = 40M MaxBuf = 100%
QP5 CIR = 5M PR = 8M MaxBuf = 100%
QP8 CIR = 100K PR = 3M MaxBuf = 100%

show qosprofile
QP1 Weight = 1 Max Buffer Percent = 100
QP4 Weight = 1 Max Buffer Percent = 100
QP5 Weight = 1 Max Buffer Percent = 100
QP8 Weight = 1 Max Buffer Percent = 100

one thing that I saw in the ports information details was this setting
QoS Profile: None configured

I'm not sure why the QoS profile is not configured if I have all these configurations above.

VPLS Bandwidth per sites
Site 1: 50Mbps
Site 2: 50Mbps
Site 3: 50Mbps

We have Lync deployed to a few users and in all of our conference rooms. If anyone could help me with a QoS Configuration that can hold us over until we get the Lync SDN deployed, that would be great.

5 replies

Userlevel 6
Hello Darren

I am not sure specifically for Lync but if you are using DSCP to assign the traffic to the queue and Lync sets the DSCP then it should be hitting the queue regardless. Note that all traffic with that DSCP will hit the same queue.

A few things to think about. I never mess with the buffer on the port not that you shouldn't but doing so really needs to have a good understanding of the traffic. I would open a case with GTAC on that to see if that is needed or if that is the correct value.

I see that you have set the CIR and Peak Rate. Have you tried a percentage of the port bandwidth to see if that changes the behavior? It may give you a little more bandwidth to see if it helps with the performance. I would start high on the allowed bandwidth make sure it works then slowly go down to see what the best value would be.

By default we look at assigning traffic to a Queue on ingress so if traffic is egressing the switch on 1:24 you need to enable the DSCP examination on the ingress port. so for example if you want traffic on port 1 to go into the correct queue on port 14 you need to enable DSCP examination on port 1 so the traffic will be placed in the correct queue as it egresses port 24. Look at the whole traffic flow.

Next look in the concept guide. DSCP is the lowest or second lowest in priority for QoS examination. If the packet has a .1Q value we will honor the traffic based on the .1Q before we look at DSCP. 1.Q examination in on by default. To resolve this you can either disable .1Q examination or use an ACL to look at the DSCP and put it into the queue. ACLs have the highest priority.

Lastly the port QoS profile is if you set that port into a qosp. It looks like you are using DSCP to assign the traffic not the port that it is ingressing on.

I hope that helps. Please provide more data as you test.

Userlevel 1
Hi Paul,
Thanks for the Reply. GTAC told me to raise the buffer speed because the congestion might be caused by traffic coming from ports with higher speeds. The tech did not give me much information on what percentage I should change it to so I only raised it 5%.

I am going to try and configure the min and maxbw on the port to
configure qosprofile egress qp4 minbw 1 maxbw 100 ports 1:24
configure qosprofile egress qp5 minbw 1 maxbw 100 ports 1:24
These numbers are based on a Lync Bandwidth Calculator that said I only need around 1Mbps for Video, less than 1Mbps for Audio, and A/V conference is 2Mbps. Now Lync doesnt have a DSCP code-point for Audio and Video, it seperates them to their individual code-points. Will this BW configuration satisfy the 2Mbps for audio/video or should I bump them both up to 2Mbps? Should the minbw and maxbw match my CIR and PR?

I have enabled diffserv examination on all ports and disabled dot1p examination on all ports. Is this what you mean when you say, "enable the DSCP examination on the ingress port"?

I am confused when you say disable .1Q examination. I cannot find anything in the concepts guide that says to disable .1Q examination. I found dot1p examination. Is that what you meant? If so, I did disable dot1p on all ports.
Userlevel 6
Hey Darren

Yes sorry it is .1p not .1Q was thinking to much to early in the morning. The min will guarantee the 1% bandwidth but the queue can burst up to 100% or to the highest bandwidth left over after satisfying all of the min values. So if you have two queues with a min of 1 % then any queue can burst up to 100% as long as there is no other traffic in those two queues. If there is traffic in those queues then any queue can burst up to 98%. Hope that makes sense.

If GTAC said to change the buffer that is fine just didn't want to change buffer for the fun of it 🙂

base on your queuing each queue will get a guarantee 1% of the ports bandwidth so you fullfil your 2Mmps.

I hope that helps
Userlevel 1
Since i have the CIR at 20Mbps and PR at 40Mbps, should the min and maxbw reflect that as well?
Userlevel 2
I just stumbled across a document for this that I couldn't find before when I specifically went searching. It does an excellent job of explaining the pieces.