VOIP QoS sanity check


For VOIP customers on PMP450 platform, we currently enable High Priority channel and assign a CIR of 256kbps on the upload and download.

Then on the Diffserv tab we assign DSCP 46 a priority of 7. We use Grandstream adapters which use DSCP 46.

Am I missing anything in this configuration?

For Priority Precedence, should I put Diffserv first, or does it matter much?



Yes, Diffserv should be first if you're using DSCP priority. 

One thing to note which we've run into is:

1) You have to make sure customers arne't flagging non-voip traffic as DSCP 46. Some torrent apps do this and some VoIP (skype) clients do. 

2) You have to make sure your backhauls respect and prioritize this if you're hitting cap on any of them.


Thanks Tim.

That's interesting about other application using DSCP 46.

I assume a packet capture will pick this up?

Hhow do you combat this?

Thinking about it though, we only configure High-Priority channel on our VOIP customers so this shouldn't be too much of a problem.

On the AP's, I assume just giving DSCP 46 a priority of 7 and prioritising Diffserv should be enough?


Yes, setting DSCP to 7 should be fine, anything 4+ goes high priority if I remember right. 

In terms of other applications we've seen some file sharing and chat apps do it. No real easy way to combat this unless you have a firewall on site that can reflag packets based on destination and you know what the IP's of the sip servers are. 

You can see if it's working correctly by going to Statistics > Data VC and see the CoS 1 VC see if they counting up as you would expect.

Definitly check your backhauls for if they care about DSCP and respect it too because we had early problems where AP's were prioritizing traffic right but then it hit a backhaul up the chain from a small micro site and had PL at the backhaul. 


Hey guys we have this set up as described above, but seems the radios get rid of the code point setting on reboot ? and the priority setting ?