QoS Download

Packets are tested against the rules in the order specified -- rules toward the top have priority. As soon as a packet matches a rule it is classified, and the rest of the rules are ignored. The order of the rules can be altered using the arrow controls.

The Default Service Class specifies how packets that do not match any rule should be classified.

Each service class is specified by four parameters: percent bandwidth at capacity, realtime bandwidth and maximum bandwidth and the minimimze round trip time flag.

Percent bandwidth at capacity is the percentage of the total available bandwidth that should be allocated to this class when all available bandwidth is being used. If unused bandwidth is available, more can (and will) be allocated. The percentages can be configured to equal more (or less) than 100, but when the settings are applied the percentages will be adjusted proportionally so that they add to 100. This setting only comes into effect when the WAN link is saturated.

Minimum bandwidth specifies the minimum service this class will be allocated when the link is at capacity. Classes which specify minimum service are known as realtime classes by the active congestion controller. Streaming video, VoIP and interactive online gaming are all examples of applications that must have a minimum bandwidth to function. To determine what to enter use the application on an unloaded LAN and observe how much bandwidth it uses. Then enter a number only slightly higher than this into this field. QoS will satisfiy the minimum service of all classes first before allocating to other waiting classes so be careful to use minimum bandwidths sparingly.

Maximum bandwidth specifies an absolute maximum amount of bandwidth this class will be allocated in kbit/s. Even if unused bandwidth is available, this service class will never be permitted to use more than this amount of bandwidth.

Minimize RTT indicates to the active congestion controller that you wish to minimize round trip times (RTT) when this class is active. Use this setting for online gaming or VoIP applications that need low round trip times (ping times). Minimizing RTT comes at the expense of efficient WAN throughput so while these class are active your WAN throughput will decline (usually around 20%).

Specifying Total Download Bandwidth correctly is crucial to making QoS work. If you are using the active congestion then just set this to the maximum download speed your ISP will deliver. If you are using a PPPoE connection check your modem's webpage and set this to your DSL downlink speed.

If you are not using the ACC then you must establish what the minimum speed your ISP will deliver is and then set this number to that. In general ISPs do not provide a guaranteed minimum bandwidth so it will take some experimentation and frustration on your part to arrive at a number. One approach is to start with a number which is half of what you think it should be and then test your link under full load and make sure everything works. Then increase it in steps, testing as you go until QoS starts to break down. You also may see that after your testing QoS works for a while and then stops working. This is because your ISP is getting overloaded due to demands from their other customers so they are no longer delivering to you the bandwidth they did during your testing. he solution, lower this number. Entering a number which is too high will result in QoS not meeting its class requirements. Entering a number which is too low will needlessly penalize your download speed. Because of all these complication I recommned you use the ACC when possible. Note that bandwidth is specified in kilobit/s. There are 8 kilobits per kilobyte.

The active congestion control (ACC) observes your download activity and automatically adjusts your download link limit to maintain proper QoS performance. ACC automatically compensates for changes in your ISP's download speed and the demand from your network adjusting the link speed to the highest speed possible which will maintain proper QoS function. The effective range of this control is between 15% and 100% of the total download bandwidth you entered above.

While ACC does not adjust your upload link speed you must enable and properly configure your upload QoS for it to function properly.

Ping Target- The segment of network between your router and the ping target is where congestion is controlled. By monitoring the round trip ping times to the target congestion is detected. By default ACC uses your WAN gateway as the ping target. If you know that congestion on your link will occur in a different segment then you can enter an alternate ping target.

Manual Ping Limit- Round trip ping times are compared against the ping limits. ACC controls the link limit to maintain ping times under the appropriate limit. By default Gargoyle attempts to automatically select appropriate target ping limits for you based on the link speeds you entered and the performance of your link it measures during initialization. You cannot change the target ping time for the minRTT mode but by entering a manual time you can control the target ping time of the active mode. The time you enter becomes the increase in the target ping time between minRTT and active mode. You can see the limits ACC is using in the [] brackets next to ping time limits field.

Reset Fair Link Limit- If you need to force the Fair Link Limit back to its starting value (90% of Total Download Bandwidth), you can use this function. Note that if your network conditions are still unfavourable, ACC will step in and lower the FLL back to where it should be to keep your ping under control. ACC will raise your FLL on its own given enough demand for the link is presented and pings are reasonable.