QoS configuration - can someone check my work?

[Jesse_Ohlsson]

We're an Extreme shop, and I'm the new-ish engineer here. I'm tasked with configuring up a replacement X440 switch stack to replace some old Cisco 3560 switches. I was taking configuration queues from one of our existing Extreme user access
switch stacks. In so doing, I think our existing QoS configurations are incomplete.

Here is what I found in the existing stack from which I'm duplicating configurations:
The switch has two QoS profiles created by default: QP1 and QP7. On this switch, two additional QoS profiles were created:

create qosprofile "QP5"

create qosprofile "QP6"



Then, the QoS profiles QP1, QP5, and QP6 were applied to all ports:

configure qosprofile QP1 minbw 0 maxbw 20 ports 1:1-48,2:1-47,3:1-47,4:1-47

configure qosprofile QP5 minbw 0 maxbw 100 ports 1:1-48,2:1-47,3:1-47,4:1-47

configure qosprofile QP6 minbw 0 maxbw 100 ports 1:1-48,2:1-47,3:1-47,4:1-47

On this stack, ports 1:48, 2:48, 3:48, and 4:48 are a LAG for the switch uplinks.

That seems a curious configuration, since the default profile QP1 is now limited to using a maximum of 20% of an egress port available bandwidth. Also, by defining no minimums, it is possible for traffic in QP5 or QP6 to take all available port bandwidth.

Later, the switch uses LLDP to instruct the VoIP phones to tag voice traffic with VLAN 606, and mark it with DSCP 63, the highest possible value for DSCP. From what I've used elsewhere and what I've read about it, VoIP traffic, while it needs certain minimums, isn’t the highest priority of packets, and doesn’t need to be stamped with such a high DSCP value.

However, this is as far as the QoS in that production access switch setup goes. In this configuration, the QoS profiles are created and assigned to the ports. But, the switch never examines ingressing traffic to apply a QoS profile to it.

I confirmed this by observing the result of the show port 1:48,2:48,3:48,4:48 qosmonitor command to see into what queue traffic was being placed:



Slot-1 X440Stack.1 # show port 1:48,2:48,3:48,4:48 qosmonitor

Qos Monitor Req Summary Fri Sep 9 16:43:26 2016

Port QP1 QP2 QP3 QP4 QP5 QP6 QP7 QP8

Pkt Pkt Pkt Pkt Pkt Pkt Pkt Pkt

Xmts Xmts Xmts Xmts Xmts Xmts Xmts Xmts

===============================================================================

1:48 0 0 0 0 0 0 0 0

2:48 29000235 0 0 0 0 0 0 601287

3:48 29855741 0 0 0 0 0 0 59808

4:48 90251869 0 0 0 0 0 0 60342



There is some QP8 traffic, which confused me. But, I suspect that is switch management traffic. The default queue, QP1, seems to be reflecting all user port traffic. No packets are being put into QP5 or QP6.

On the new X440 stack I'm configuring, here’s what I’ve done with its QoS configs:

First, I created QoS Profile QP6:



create qosprofile "QP6"



Then, I enabled DSCP examination and disabled ToS examination on all user ports, (not the uplinks):



enable diffserv examination ports 1:1-47,2:1-47,3:1-47

disable dot1P examination ports 1:1-47,2:1-47,3:1-47



I applied QoS profile QP6 to all user ports:



configure qosprofile QP6 minbw 5 maxbw 10 ports 1:1-47,2:1-47,3:1-47



The goal here is to give VoIP traffic a minimum of 5% and a maximum of 10% of each port’s available bandwidth. VoIP traffic isn’t high bandwidth, but it does need a reserve, and it needs priority to reduce latency and jitter. Those minimum and maximums may be a bit high. I checked sFlow data I'm collecting from the production user access switch I'm using as an example, and I never see any traffic to/from the VoIP phones that exceeds 1% of the bandwidth reported by sFlow.

I then defined the DSCP mapping, which will place any ingressing packet marked with a DSCP value of 40 into QP6:



configure diffserv examination code-point 40 qosprofile QP6


Finally, I used LLDP to instruct the VoIP phones how to tag and mark voice packets:



configure lldp port 1:1-47,2:1-47,3:1-47 advertise vendor-specific med policy application voice vlan Voice603 dscp 40



I disabled LLDP on the uplink ports, we don’t need that protocol there.



Now, I think I got this right. Can I ask you guys to check my work?

Thanks,

Jess

[Scott_Singer1]

Jesse,

I would mirror an edge port and use Wireshark to look at the packet header. It doesn't sound like the packet is being marked.

Also, you can usually set the DSCP manually within the phone configuration to ensure it's being marked correctly for testing. You'll need to figure out how to get into a manual configuration mode on the phone though.

Regards, Scott

[Jesse_Ohlsson]

I have high confidence this is so. The switch is doing exactly what it's told, as is the IP phone. I'm trying to figure out why the phone is ignoring the LLDP advertisement.

[Chad5]

Hello Everyone,

since this article is about 3 years old, things may have changed on the recent EXOS load. I am on 22.6.1.4 and 30.2.2.17.

I am using X440G2 and X450G2. My end devices are tagging DSCP for voice, video and signalling (46, 34 and 24). I just want the switches to prioritize the traffic into correct Queues.

By Default, I can see QOS profiles QP1 to QP8 already created. I understand QP1 is default and QP8 is switch traffic. 

I see all ports by default are strict-priority, which is fine.

I also see that diffserv examination is setting the Queues as per Scott’s email. 

CodePoint->QOSProfile mapping:
        00->QP1 01->QP1 02->QP1 03->QP1 04->QP1 05->QP1 06->QP1 07->QP1
        08*>QP1 09*>QP1 10*>QP1 11*>QP1 12*>QP1 13*>QP1 14*>QP1 15*>QP1
        16*>QP1 17*>QP1 18*>QP1 19*>QP1 20*>QP1 21*>QP1 22*>QP1 23*>QP1
        24*>QP1 25*>QP1 26*>QP1 27*>QP1 28*>QP1 29*>QP1 30*>QP1 31*>QP1
        32*>QP1 33*>QP1 34*>QP1 35*>QP1 36*>QP1 37*>QP1 38*>QP1 39*>QP1
        40*>QP1 41*>QP1 42*>QP1 43*>QP1 44*>QP1 45*>QP1 46*>QP1 47*>QP1
        48*>QP1 49*>QP1 50*>QP1 51*>QP1 52*>QP1 53*>QP1 54*>QP1 55*>QP1
        56->QP8 57->QP8 58->QP8 59->QP8 60->QP8 61->QP8 62->QP8 63->QP8
 

So, I was going to simply change the mappings for DSCP 46 to QP6, DSCP 34 to QP4 and DSCP 24 to QP3.

However, looking at qosmonitor, I saw traffic in almost all queues, I didn’t expect that with the default config, anyone can explain?

for example, my uplink:

port,QP1, QP2...etc

1:50    14171144084       53010      250705       26000      452582     1288002           0    66238477
 

It's all default config so really no config to paste.

Any  help would be appreciated. Must be missing something very basic.

[FredrikB]

Hi!

You probably see traffic in all queues because packets are tagged with 802.1p. Check out these commands on your switch:

Slot-1 sw21.3 # show dot1p
   802.1p Priority Value     QOS Profile     Ingress Meter
           0                 QP1
           1                 QP1
           2                 QP3
           3                 QP3
           4                 QP5
           5                 QP5
           6                 QP5
           7                 QP8
Slot-1 sw21.4 # show dot1p replacement
 QOSProfile    VPri
        QP1 -> 0
        QP3 -> 2
        QP5 -> 4
        QP8 -> 7

Your output may well be different from the above.

/Fredrik