Supporting QoS on NCUI and STMI cards

[donb01]

Do any of you gurus out there play with QoS? I'm trying to make sure everything is set right to take the most advantage of it between the phones, pbx and network, but I am in a live environment so there is only so much playing I can do.

In my NCUI and STMI cards the QoS parameters are set to the same as what is set in my phones - what I expect to see. We have VLANs set up for all the different locations that need VLANs set up, stuff in the switches, DHCP scopes, etc.

I have noticed in my snooping, at least in the NCUI card I was in this afternoon using WBM, that there is an option in the customer network settings called "Enable 802.1p/q tagging" that is set to "No".

I am wondering if that makes any difference, or whether that should be set to Yes to have the board be tagging the packets for QoS. I am afraid if I turn it on to try it that 200 phones will go down and something bad will happen, aso I don't want to just mess with it. If 200 phones go down in the middle of the night and then come back up all happy and joyful that's OK, but if 200 phones go down and I cant get them back online that would suck!!

Does anybody know if the QoS parameters being set means the board is actually processing and tagging all that stuff, or does that parameter on the customer network have to be enabled to have that happen?

Thanks!

Don Bruechert, Voice Comm Analyst II
CareTech Solutions @ Holy Family Memorial
Manitowoc, WI, USA

 

[Moriendi]

802.1 p/q is Layer 2 Cos and VLAN. You don't have to activate that if your VLAN config is done on your switch side with access ports. The 4K can use VLANs and not even know it. If you want to use the AMO config for VLANs and CoS the switch port needs to be a trunk port. If they are access ports you are not using this config. Check your CGWB and STMIB AMOs- is VLAN set to NO. Doesn't mean you're not using VLANs, it means the 4K doesn't know about them. Obviously doing it on the data switch side means no Layer 2 CoS bits are processed from 4K because it will only know about the VLAN.

The Layer 3 DSCP config 184/104 EF/AF31 is something else, that will be tagging fine without 802.1pq. If you configure a mirror port on your data switch and take a sniffer trace you will see the L3 diffserv markings are there.

Depending on your network config, activating layer 2 might kill everything, as the packets might suddenly get discarded or become invisible to the device looking for them. Undoing the change would bring them back, but you should speak to your data guys about the VLAN config before you do anything. I suspect you don't need it. You could set layer 2 marking but there's no point if the data switch discards/disregards it anyway.

You can see also see the packets headers with tcpdump from the platform, or a softgate if you have one. For stmi/ncui you can use a mirror port, although iptrace is much improved from Assistant and can be used to get some useful captures. You could also rcpap straight to Wireshark from the stmi/ncui.

If you are only wondering if you are not marking DSCP because 802.1pq is not enabled, the answer is no. They are different things. DSCP will be fine.

 

[donb01]

Thanks! They are all set to know, and we are using the DSCP as far as I know. The problem is the data guys are kids only a few years out of school and "We briefly covered that subject, but not to any depth." I have a tool called TotalView that is showing me a lot of problems on the network (discards due to insufficient buffers, some stuff implying the packets are too large and being discarded because the config doesn't obey the VLAN tagging, and assorted other areas in large quantities). When I brought up the discards and the overall slowness and bad performance of the network I was told "those discards really aren't that big of a problem, and why should we trust a piece of software that you just installed and it's telling us the network sucks?" My response was that if those packets were being re-transmitted that is a whole lot of extra bandwidth being used unnecessarily, and doesn't it slow down the PC because it has to wait, and put more load on the CPU of the switch because it has to deal with all the interrupts. So I'm trying to learn as much as I can about all this to try and discover what needs to be done and then explain to them how to do it. I found a website called cybrary.it that offers free Cisco training for prep for the test that I signed up for but haven't had (made) time to start yet.


Don Bruechert, Voice Comm Analyst II
CareTech Solutions @ Holy Family Memorial
Manitowoc, WI, USA