I am running a router with Tomato firmware and I want to correctly configure QoS controls. The router establishes a PPPoE connection through the DSL modem in bridge mode. The Tomato QoS settings have an adjustment for "DSL Overhead Value - ATM Encapsulation Type".

But I'm not sure what type (if any) my ISP uses and they don't have the slightest idea either. I have tried all the above settings, but they significantly reduce the throughput. So I'm not sure if the settings are right for my ISP. Is there a way I can sniff the packets or something to figure out what encapsulation type is being used, if any?


1 Answer 1


If you have an ADSL/ADSL2/ADSL2+ connection you should put 40 as a value. This is the value I use. Doing this, you should be able to use your sync speeds as the bandwidth.

If you have acces to your modem, at Wan connection you should be able to see if you use LLC/Snap or VC-Mux. If LLC/Snap you should use 40 as I do. If VC-Mux you should use 32.

  • 3
    Why 40? What makes that specific choice the best for the OP, as opposed to any other of the choices? Note that the question asks "how to determine?", not "what to use?". Your answer would be better if you edit to explain the rationale, beyond "it's what I use". It would likely be even better if you also edit it to include how you reached the conclusion that 40 was the best choice.
    – user
    Commented Nov 23, 2015 at 19:57

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .