Managing QoS for voice traffic

[James_A]

I've put this in the general switching and routing section because I'm dealing with EOS, EXOS and VOSS. I want to apply QOS to voice packets. For our sins we use CUCM, but some users (whose phones are connected to an X440-G2) are hearing brief audio glitches during calls. I can see congestion occurring on the switch ports the phones are plugged in to:

Slot-1 dblockr2x.16 # show port 1:43 qosmonitor congestion no-refresh
Port Qos Monitor
Port QP1 QP2 QP3 QP4 QP5 QP6 QP7 QP8
Pkt Pkt Pkt Pkt Pkt Pkt Pkt Pkt
Cong Cong Cong Cong Cong Cong Cong Cong
================================================================================
R2-39:> 6 0 0 0 0 0 0 0

although that was last week, now the counters have all gone to zero:

Slot-1 dblockr2x.15 # show ports 1:43 qosmonitor congestion no-refresh
Port Qos Monitor
Port QP1 QP2 QP3 QP4 QP5 QP6 QP7 QP8 
Pkt Pkt Pkt Pkt Pkt Pkt Pkt Pkt 
Cong Cong Cong Cong Cong Cong Cong Cong 
================================================================================
R2-39:> 0 0 0 0 0 0 0 0 

Anyway, I read a bunch of posts here and the manuals, and since the phone does correctly tag the packets with DSCP EF and 802.1p priority 5, I want to stick that in a higher priority queue, so ran:

create qosprofile "QP5"
configure qosprofile qp5 minbw 20 maxbw 100 ports all
configure dot1p type 5 qosprofile QP5

which should drop the traffic into QP5 based on the .1p value. I think this works, I can see traffic in QP5 using show port qosmonitor.

Now the hard part is getting the voice and control traffic coming the other direction correctly marked. The core is several 7400s in campus fabric, and the phone system runs as a number of VMs. I read the VOSS QOS guide and came to the conclusion that the default settings respect DSCP, but were probably being overridden by the 802.1p priority being set to the default of 0 (since it's just a normal vSwitch, not a vDS which has CoS/DSCP support), so on the ports going to the VMware servers, I set qos 802.1p-override enable so that the .1p priority is ignored and the DSCP is used. However, I can't tell if it's having any effect. I have spanned the traffic out of a Cisco phone and it doesn't seem to have worked, traffic from the server just has 802.1p priority set to 0.

There's also a Cisco 4331 which terminates the SIP trunk, that is connected to a C3, which goes to a B5, which goes to the 7400. I set qos 802.1p-override enable on the port the B5 goes to as well. The other way would be to do 802.1p tagging based on DSCP on the C3 or B5, but I haven't found the documentation to do that yet, am I going to have to fire up policy manager?

The SIP trunk comes in on a B5, vlan 102 so I ran this per https://extremeportal.force.com/ExtrArticleDetail?an=000080747:

vblock(su)->set policy profile 1 name "SIP Trunk" cos-status enable cos 5
vblock(su)->set policy rule admin-profile vlantag 102 admin-pid 1

I would have to go sniff that traffic to see if it sets DSCP correctly.

I think it's correct to summarise the various OS behaviours as EOS and VOSS generally respect 802.1p tags, whereas EXOS doesn't, and when any of them do, 802.1p overrides DSCP by default.

Anyway, does anyone have any ideas as to what might be going wrong or how to fix it?

[Chris_Mabie]

I've been doing a lot of reading for the Eos, and Exos Qos like you.  So take this with a grain of salt 🙂

Anyway, I read a bunch of posts here and the manuals, and since the phone does correctly tag the packets with DSCP EF and 802.1p priority 5, I want to stick that in a higher priority queue, so ran:

If the phone correctly marks 802.1p and DSCP, could you use something like below, wouldn't this code loaded on all EXOS switches for the DSCP values, force those packets to the higher level Qos profile?

create qosprofile "qp6"
configure qosprofile "qp6" use-strict-priority
configure diffserv examination code-point 46 qosprofile "qp6"
configure diffserv examination code-point 24 qosprofile "qp6"
enable diffserv examination ports all
disable dot1p examination ports all

From original post:
https://community.extremenetworks.com/communities/community-home/digestviewer/viewthread?GroupId=127&MessageKey=4e227601-64dd-4446-9c95-3049ee9833c1&CommunityKey=929e6d1f-141a-4b6d-b66e-7ebfd2f3f952&tab=digestviewer

For EOS:
I've found in the manual:
Extended ACLs can optionally be set to match a Diffserv codepoint (DSCP), IP precedence, or IP
Type of Service (ToS) value.

But still reading on how to create the extended ACL policy.