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Questions on Class Of Service

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Questions on Class Of Service

Can anyone advise me on using Class Of Service.

I have a mixture of Allied Telesyn AT8024 switches at two remote sites and Procurve 410x switches in the main site. The remote sites are linked using a wireless bridge and a BT EPS8 connection which is also bridged. The vlans run over tagged ports on the switches either side of the bridges.

I need to try to improve the quality of IP phone connections. I have vlanned the ip phones and brought the wireless bridge connection into my main routing switch, an HP4104. I use static routes on my servers, the Avaya Telephone switch and the main gateway router to provide routes back.

The Allied Telesyn cannot handle quality of service but they do handle Class Of Service. I read that the HP switches also handle CoS. Can I use this to give greater priority to voice traffic across the mix of switches? Can I use a mix of QoS and CoS across the switches where possible?

And finally how do I set this up? Which ports would need to be prioritised and in which direction? How high a priority setting should I give the different ports?

Many Thanks
Matt Hobbs
Honored Contributor

Re: Questions on Class Of Service

Very quickly, with the 4100 I believe you need to set the ports that the IP phones are on to a higher priority (6)

Syntax: interface qos priority < 1 .. 7 >


Since the 4100 only does Port-Based Priority - the phones themselves would need to be plugged directly into the switch on their own port with no PC connected via the phone. Otherwise both PC and phone will get the same priority value.

Assuming that the other devices leave the tagged packets alone and don't change the values, this should work fine.

Your voice VLAN needs to be on the same VLAN ID throughout your network and tagged throughout all the uplink ports.

Re: Questions on Class Of Service

Thanks for the reply.

To clarify I only need to increase the priority on the ports the ip phones are directly connected to. I do not need to touch the vlan tagged ports at all?

Currently the phones are working fine with the existing vlans. I am really just trying to tweak a little better performance.
Matt Hobbs
Honored Contributor

Re: Questions on Class Of Service

Yep, that's exactly right, you only need to increase the priority on the ports the phones are connected to.

Re: Questions on Class Of Service

Great. I have done this on the AT switches it just remains to be seen if the HP Procurves honor their CoS tags.

Many Thanks for your help