My Vigor router does not seem to be invoking QoS. I think the problem is that online status reports my connection downstream speed as 1.5Mbps - but my ISP plan has much less bandwidth.
Posted by Gabriel Yu on 15 April 2008 01:46 AM
Firstly, the situation with Downstream speed being reported as 1.5Mbps is due to the way Telstra have set up the DSLAMs in their telephone exchanges, which almost all ADSL1 customers are connected to.  Note that this situation applies in Australia only.   The Vigor modem detects this setting, and uses it as the basis for determining when QoS should be applied.

DrayTek are considering adding a 'Downstream Bandwidth' field to the GUI (similar to the Vigor 2100V/2900V models) which Australian users can over-ride.  There is currently a telnet command in Vigor 2800 (fw.6.3) which can change QOS bandwidth.
Secondly, the UPSTREAM bandwidth where the QoS is most important, for 2 reasons:
  1.  Upstream bandwidth is usually only a fraction of downstream bandwidth, and so is quicker to get congested; and
  2.  Your Vigor router can control what packets it will send out now, and what packets it will hold and send later - but it does not have the ability to control what your ISP's router sends to it (excepting to reject some packets). 
Thirdly there is a common misconception that QoS reserves bandwidth, effectively limiting other applications to the remaining bandwidth.  In fact, you should only see the effect of QoS when the bandwidth is congested.  QoS is an advanced networking topic which is difficult to explain in simple terms.
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