QoS configuration

[JaWe]

Hi everyone,
I need an advice from you how to setup QoS in our network. in the attachment you will find our running config from our core switch and a RC from a "downstream" switch.
Let me explain our situation. Since several months, we make use of voip. The users setup a call either via softphone (software on desktops) or via a voip phone (tadicom). The connect to the telephonessytem with udp port 16400+. Each phonecall uses an unique udp port. Each phonecall uses the last used udp port increment with 1.
I configured a voice vlan (vlan-52) and connected the telephonesystem to a untagged vlan 52 port. The clients (softphone and tadicom phones)are connected to the downstream switch on vlan-50. The downstream switch is connected to the core-switch via fiber. Both sides of vlan-50 are tagged.
The quality of our phonescalls aren't very good at all. So, QoS can help me to bring up the quality to a higher level.
I read a lot of the qos possibilities but don't know what the best solution is in our situation.
Shall I use DSCP, or only prioritize vlan-52 or prioritize with the ip address of the telephone system.
Thanks in advance...

[Mohieddin Kharnoub]

Hi

I've noticed that you don;t have Vlan52 on the downstream switch, but anyway, you just need to
run the following command under Vlan52 (or Voice Vlan) to make it higher priority for better QoS

core(config)#vlan 52
core(config-vlan52)#qos priority 7
core(config)#wri mem

And run this command on the Core switch and on all the edge switches that are used to connect phones (or softphones).

Good Luck !!!

[Mohieddin Kharnoub]

More information about this kind of setup that you have, and for more practices:

ftp://ftp.hp.com/pub/networking/software/6400-5300-4200-3400-AdvTrafficMgmt-Oct2006-59906051-Chap08.pdf

Good Luck !!!

[JaWe]

Hi,
Thanks for your reply.
Our softphones will stay in vlan 50. So, I have to prioritize traffic from a softphone in vlan 50 to vlan-52 and visa versa. When I follow the commands you suggest, then only traffic within vlan52 will get prioritezed. Should I make use of the known udp ports, to classify the traffic and prioritize on this?
Thanks in advance...

[Mohieddin Kharnoub]

Hi

Use then QoS priority 7 for both Vlan50 and 52 because both Vlans need high priority, and i don't think the UDP priority is reasonable to be setup in your scenario.

Switch(config)#vlan 52
Switch(config-vlan52)#qos priority 7
Switch(config-vlan52)#exit
Switch(config)#vlan 50
Switch(config-vlan50)#qos priority 7
Switch(config-vlan50)#exit
core(config)#wri mem

Good Luck !!!

[JaWe]

Hi, Thanks again for you reply.
I still got a question about it.
The softphone client's run on a desktop. So, there's also other traffic within vlan-50. I think the problem still exist when I prioritize all traffic in vlan-50 because all data will get the same priority. Isn't it?
What do you think of prioritize traffic with the destination/source of the telephone system? (qos device-priority priority 7)?

[Mohieddin Kharnoub · Accepted solution]

Hi

You are totally right, both Data and Softphone actually will have priority 7 and that we don;t need.
Your suggestion in this case to prioritize based on UDP but the question is, do you have a list of UDP ports you will use?

So i agree with you in regards the Device Priority, because this option assigns an 802.1p priority to all IPv4 packets having the specified IP address as either a source or destination, and in your Case i believe its a destination IP to your VoIP Server or Media Gateway (whatever the IP for the VoIP Service you have).

Switch(config)#qos device-priority priority 7.

Good Luck !!!

[JaWe]

Hi, I will set it up like that way (with device priority). But its not my favourite solution because other traffic (important traffic) will get some disadvantage effects, isn't it (its going to be )?

Because of digital industrial applications integration in our network, the need of prioritize traffic wil get more and more in the near future.
So, is there any kind of guideline where to look at on how to configure qos with multiple qos rules?
Thanks again!

[Mohieddin Kharnoub]

Hi

I just want to clarify something, when you prioritize some kind of traffic say voice, that doesn't mean you are killing the data traffic with low priority, because its default to normal (value=0), unless you change it to lower value =1 or lowest =2.

With my experience, the IP phone usually use less than 100k of your bandwidth, even the softphones, and its really a low number even with high priority i don't think it will affect your data traffic - its my opinion anyway :)

Good Luck !!!