Help with QoS settings for VoIP

Discussion in 'DD-WRT Firmware' started by Sellitna, Dec 14, 2005.

  1. Sellitna

    Sellitna Guest

    I have searched these and the forums but have not been able to find much definitive information, so I am posting to ask for help with setting my QoS up to maximise call quality on my VoIP service.

    I have a WRT54G v3 running DD-WRT v23b2 std (the latest 12/12 build). Connected to it is a Sipura 3000 ATA as well as up to five PCs, some wired and some wireless. My SPA-3000 registers with my service provider's voice service, so my VoIP traffic consists of SIP registration and RTP voice traffic (configured to transfer on ports 16384-16482).

    I have a 512/128kbps ADSL connection - not the fastest around, but my understanding is that it should be possible to get VoIP working reasonably well. The SPA-3000 is configured to use the G729 codec for the lowest bandwidth requirements, but the next step is to get the QoS working to minimise interruptions when other data is being transferred.

    I ran speed tests on my connection and they came out around 440/104. I have enabled QoS on my router and set the uplink and downlink speeds to 90 and 360kbps respectively. I have left "Optimize for Gaming" unchecked as I have not found any clear description of what it does.

    Where I become really confused is in which level(s) to use in the remaining settings. I have configured the Ethernet ports so that the SPA-3000's port is at Premium and the others are Standard. I have not touched MAC or Netmask priorities because I have seen mixed reports about whether one or the other works, and because rather than slowing an entire PC I would like to differentially prioritise different types of traffic (which is the whole point of QoS). So, instead I have tried to work with the service priorities.

    Using the built-in L7 services, I have set FTP and bittorrent to Bulk and SIP to Premium. However, I cannot see an option for RTP. This seems to be a potential problem because the RTP traffic contains the critical data (the voice content). So, instead I added a new service for RTP, defined as being TCP&UDP traffic on ports 16384-16482. I set this to Premium.

    Based on my testing these settings do not seem to be working well. I am having issues with call packet loss during calls and the quality clearly degrades when I am uploading and/or downloading. I am aware that downlink QoS is quite limited in its effectiveness, however my ISP provides prioritisation of incoming voice traffic and so I am surprised at the extent to which downloads have affected calls.

    I would appreciate any comments, suggestions, or pointers to further information about the QoS on this router and in particular with this firmware. I have looked at the DD-WRT Wiki but its QoS page is pretty basic. Please let me know if you can think of anything I might try to improve my configuration.

    Thanks in advance.
  2. danr

    danr Network Guru Member

    I am using MAC QoS, since I tried port based QoS and it didn't work. I was then told that only certain versions of hardware actually work with port based QoS. MAC based QoS works great for me. No voice dropouts at all in either direction on my VOIP phone calls.

    I have my TA's MAC on Premium and don't have any other MACs listed (ie they'll be defaulted at Standard).

    I also have not read what the "optimize for gaming" is for. I do have it set on for now... I have read that the overall bandwidth would be lower if that is set... but I don't know what the advantage of that settings is. I checked the box, since in both gaming a VOIP, the packet timing is crucial.
  3. bigjohns

    bigjohns Network Guru Member

    port qos only worked on a few versions of the router. IP (192.168.x.x/32) or MAC is the only way to make it work now.

  4. brucebeh

    brucebeh Network Guru Member

    ahhh wow.

    that's nice thing to know, let me add the MAC of my VOIP box right now and we'll see how this goes..

    EDIT: Now filtering with mac address, WOW! Works PERFECT, I can upload and download full and my Voip will have NO affect at ALL!

    Thankyou soooooo much John, and DD-WRT! Great great great great firmware!
  5. daenigma

    daenigma Network Guru Member

    I thought you could use service level filtering without MAC or Port filtering...
  6. bigjohns

    bigjohns Network Guru Member

    Service level sets levels for the entire "network" wired and wirelessly, and are less (at least it appears to be) effective than assigning a specific priority to a device - especially in the case of VOIP.

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