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VOIP with QoS and TOS

Discussion in 'DD-WRT Firmware' started by dududa, May 27, 2006.

  1. dududa

    dududa Network Guru Member

    I want to ensure, that my ATA devices for VOIP has alway max priority. I tried everything with QoS. QoS by IP, by Services and by MAC. But if uTorrent is running on an wired Client, I can't telephone. Even if I set Torrent-Ports to Bulk.
    But it seems, that QoS doesnt work.
    Is there anywhere a good Guide on how to configure QoS for optimal VOIP?

    And is it possible to make QoS identify packets by their ToS (Type of Service) in their packet-header?

    thx for good help!
  2. eric_stewart

    eric_stewart Super Moderator Staff Member Member

    I'm assuming that you have set the parameters (in the QoS setup screen) for upstream bandwidth? I have a VoIP adapter (a Sipura SPA200) from Bell Canada and haven't had any issues.

    Just a thought....

  3. will792

    will792 Network Guru Member

    There are many options in QOS configuration and somehow some work well for some people while not for others. I know that older versions of WRT54G and WRT54GS can have priority by port while newer ones cannot. The easiest criteria for QOS packet identification is MAC. Some people expressed opinion that Broadcom CPU is not fast enough for more sophisticated processing. Some have luck with L7 or port type identification.

    You'll find tens and tens of QOS guides for VOIP. At the same time you'll see that the same settings did not work for many people.

    There is a possibility that instructions are not correct. Example UP and Down settings are recommended at 80%-90% of real throughput. If somebody has 10000/2000 service and sets his/her router QOS speeds to 8000/1600 it is totally different from someone with 1300/328 service and 1040/260 QOS setting. Many discussions do not even mention the service speed.

    My best guess (after reading conflicting information) is that QOS margin (service speed - QOS speed set in router) has to be at least 100 - 130 Kbps for VOIP use. The problem for me is that I do not want to sacrifice 130Kbps of upload speed when I do not use VOIP. I set QOS margin to 80Kbps which does not preserve voice quality during FTP uploads but does not kill it completely.

    Check dd-wrt.com forum for QOS discussions. There is plenty of material to read. It is like advertisement on my commuter train: "Everyone on this train has a stock tip. The problem is you do not know who is right."

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