Where to set up QoS "ef" tagging?

Posted on 2012-09-12
Last Modified: 2012-10-02
Hi Experts,

We have our ISP set up QoS using DSCP "ef" for tagging site-to-site VOIP in order to prevent  choppy voice qty. But we still got the issue intermittently. While further investigating, the ISP found there is no voice traffice with a tag 'ef' flowing so they want us to set up the 'ef' tagging in the phone system. But our phone system provider doesn't know how to. That makes us think maybe it should not be the phone system where to set up the tag. In our LAN we have an IAD which is ISP's property and is not accessible to us. Other than that are Cisco ASA, Switches, etc. None of them is configured with QoS.

So the question comes down to be: where to set up traffic tagging so the ISP's QoS can identify the "ef" tagging and prioritize it?
Please help.
Question by:Castlewood
    LVL 10

    Expert Comment

    You can do it on the Cisco switch. What type of switches in what kind of architecture do you have (if you have please add sketch of your network)? If we know the type we might give you a hint on how to do it. You might want to try out auto-qos if it exists in your Cisco IOS version.

    What type of phone system/phones do you have? Possibly it can be done there as well.

    Author Comment

    We finally used Wireshark to see that the phone system actually does 'ef' tagging on the voice traffic while received by the switch (HP v1810) but the tag is stripped by the switch while transmitted. So the question comes down to be, how to set up the HP V1810 switch not to change the packet?
    Please help.
    LVL 10

    Accepted Solution

    When reading google about the switch you see a lot of talking about QoS but none of the links or manuals I have read says something about how HP does this or even how you have to configure the switch to allow QoS.

    I know that some switches do a remarking to DSCP 0 if they are not configured to allow the passing of the QoS markers but I have not read anything like this with the HP switch. Where did you mirror your Voice traffic so you could see the stripping of the DSCP? Can you post the pcap file?

    Author Closing Comment

    We ended up using the IP address for QoS criteria. It works.

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