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I'm trying to configure traffic control on my TP-LINK TD-W8960N modem router. From what I can see in the configuration screen I have to set a maximum upload and download speed for the WAN, which is set to the line's maximum. Then I have to specify rules for different IP ranges, being able to select protocol, ports, a precedence, and min/max upload/download speed.

My questions are: What is the meaning of the min and max speeds? How is the total speed distributed? What if one PC is idle, can the rest use up it's bandwitdh?

The manual was of no help.

Here's a screenshot of the rule creation page:

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This is only a "guess" ... but I suspect "min" is the "reserved bandwidth"... meaning that if you have a 10-mbt connection... and you set something to have a "minimum" of 2mbt, and even if it's not being used... nothing else can use over 8mbt.

max, is probably defining a "maximum" burstable bandwidth... meaning that if you set a maximum of 2mbt on a particular protocol/port/ip/whatever... then that protocol/port/ip/whatever can never exceed 2mbt... even if you have 10mbt of bandwidth.

Setting up "traffic shaping" rules is quite of a challenge... there is no simple way to say "if there's enough bandwidth use 10mbt... otherwise reserve 2mbt for yourself". This is true in all aspects of networking... not just limited to tp-link devices.

  • Sure, that makes sense. But what if the sum of min bandwidth's exceed the total? And where does precedence come in? Do all the minimums get reserved first, or is it traversed by precedence first? Of course I don't expect you to know about this particular implementation, but maybe know about what is standard in these cases :) Thank you!
    – Guido
    Feb 10 '12 at 21:42
  • Honestly, everyone has their own standard when it comes to traffic shaping. Most expensive devices will let you setup tier'd filters which you can class bandwidth into different categories and allocate bandwidth on each level in the tier... etc... One important piece of advise. A router does not know how much bandwidth you have overall... the closest guess is that it has the maxiumum port-speed. (i.e. 100mbt, 1-gigabit... 10mbt... 54mbt... etc...) For TC to be effective, you need to be able to tell the router how much you have (i.e. 8mbt) and then restrict bandwidth fir specific reasons
    – TheCompWiz
    Feb 10 '12 at 21:48

I'm only guessing as well. But since these devices run linux inside them, this settings probably use a form of traffic shaping found in linux called Hierarchical Token Bucket. you can learn more about it here: http://luxik.cdi.cz/~devik/qos/htb/manual/theory.htm

In short, the min bandwidth is the guaranteed bandwidth this ip(s) will receive when the connection is saturated. The sum of all min bandwidth, in all rules, should never be bigger than your total bandwidth.

When your connection is not saturated, the devices using the network will receive extra bandwidth up to the max bandwidth you set. They will receive this extra bandwidth proportionally to their min bandwidth.

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