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QoS (Quality of Service) Questions
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Quality of Service (QoS) allows the user to make better use of limited bandwidth by allocating appropriate priorities and bandwidth to different service types or hosts. It is particularly useful when using VoIP or other situations where you need to reserve bandwidth for a particular application (or protocol). Consider the situation where you are having a VoIP (Voice over Internet Protocol) conversation with a friend when a workmate sends an email with all his holiday photos attached. Suddenly there is more data than the modem can send immediately, and a queue forms as the modem tries to send all that data. This is not a problem for emails, but VoIP requires the VoIP packets to arrive in a fairly steady stream, and soon your friends VoIP device will be unable to compensate for the delays - resulting in your friend hearing your voice chopped up with gaps between. In this example, with QoS enabled your router would give VoIP packets high priority, and send them almost immediately; while the email/file transfer packets would be fitted between the VoIP packets. Result is that the VoIP conversations remain high quality with your friend noticing no disruption at all - but the email takes a bit longer to send. Q. Is QoS available on all Draytek models ? No, QoS is a new feature which DrayTek has committed to providing on 2600plus, 2600G, 2600V series', 2900 series and above - but the firmware is not yet available (at time of writing this) for all these models. QoS will not be added to 2500 series, 2600/We/W/X models, 2200 series or below. Q. How to use QoS feature to set high priority for Vigor built-in VoIP service? 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. We recommend you keep QoS enabled to assure your Voice quality. Simply tick the "Enable the QoS Control" box in the routers Advanced Setup > QoS Control Setup page. If you are using a 2100 or Vigor 2900 model, you will also need to tell your router the bandwidth (speed) of your internet connection; as discussed below. What Bandwidth should I set for my Vigor 2100V or 2900V ? The Vigor 2100 and 2900 models connect to the internet via an external modem connected by 10 or 100Mbps Ethernet cable; and hence do not know how much bandwidth is actually available from the modem to the ISP. Normally this isn't a problem, but when the bandwidth starts to become congested the Vigor's QoS needs to start prioritising traffic to ensure that VoIP quality does not degrade. DrayTek recommend setting the WAN Inbound and WAN Outbound Bandwidths to 80% of the bandwidth provided by your ISP. Commonly ISP bandwidth is referred to as two numbers (e.g. 1.5M/256, 512/128 or 256/64), with Downstream bandwidth (pages and files coming "in" to you) the first number, and Upstream bandwidth (your page request going "out" to ththe second (and usually smaller) number. For example a 512/128 ADSL account has 512Kbps downstream and 128Kbps upstream bandwidth, and Draytek recommends you enter 410 into "WAN Inbound Bandwidth" and 102 into "WAN Outbound Bandwidth". Note that the default value of 10,000 represents the speed (10Kbps=10,000Kbps) of the Ethernet cable between your Vigor router and the external modem - which is a lot faster than the modem's connection to your ISP.
Q. What types of traffic can QoS be applied to ? DrayTek have pre-defined all the common protocols. Click the BASIC setup button and select which protocols are to be grouped in that class.
If you need to prioritise a custom data type, or traffic to/from a particular device, just click the ADVANCED setup button, and you can define your own custom data type.
Where is the Manual for the QoS functions ? If you bought your router recently, the QoS section should be included in the Documentation on the CD which came with your router. Alternatively, the QoS chapter of Vigor manual can be downloaded
from our website at Q. How to use QoS feature to set high priority for external VoIP service? 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 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 NBS's Vigor 2600VGi configuration for our Vodtel MOSA IP PBX units which use VoIP between units. The MOSA devices in our head office have been given static IP Addresses 240-254 within the 192.168.124.x private subnet.
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