How to use QoS feature to set high priority for external VoIP service (e.g. an Engin Voicebox)?
Posted by Gabriel Yu on 15 April 2008 02:02 AM

The QoS function in DrayTek VoIP models is pre-configured to give priority to VoIP calls to/from the FXS ports built into the router.

However, if you don't have a "V" model; or have an external VoIP device connected on the LAN side of the router, this device needs special QoS configuration in your DrayTek Vigor router.

The following example shows a Vigor 2600G configured for an external ATA device on static IP Addresses 192.168.1.9. 

  1. In the routers Advanced Setup > QoS Control Setup page, tick the "Enable the QoS Control" box.
  2. Under Class Name, enter text to remind you what this rule is for. Under "Reserved Bandwidth Ratio" enter the percentage of bandwidth which should be allocated for this rule. Note that this percentage is only meaningful if you use 2 or three of these QoS rules. Click the [Advance] button.
  3. the > Advanced Setup > QoS Control Setup page will display, with only a single Empty entry.  Click the [Edit] or [Insert] button to enter the first entry.
  4. Tick the "Act" box, then click the [SrcEdit] button.
  5. Enter the IP Address(es) of the VoIP device(s).  This can be a single address, a range of addresses (as shown here) or a subnet.

    Click the [Apply] button to return to the QoS rule page.
  6. You do not need to change any other values. Service Type and DifServ CodePoint are provided for those customers who understand their meaning - the rest of us are asked to stick to the default values.

    Click the [Apply] button to return to the QoS Control Setup page
  7. Click the [OK] button to return to the Main Menu

There are a couple of points to note about the "Reserved_bandwidth Ratio" on the QoS Control Setup page:

  • QoS is activated when the actual WAN bandwidth used reaches 80% of the available bandwidth.  For an ADSL modem/router the available bandwidth is the synchronisation speed reported by the modem component.  For a Broadband router (Vigor 2100 or Vigor 2900) see here.
  • The built-in FXS ports (if any) get first priority and all the bandwidth they require. 
  • The Reserved_bandwidth Ratios allow you to set proportions of the remaining bandwidth (after the built-in FXS ports). For an example of how the Reserved_bandwidth Ratios work, please see here.
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