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Thread: Multicast and destination IP

  1. #11
    Frosty member
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    Quote Originally Posted by Jchuchla View Post
    Last I checked, the 682 doesn't do 512 channel universe boundaries. I thought you had to do 510 for those. That would explain why the last 29 pixels are wrong.
    This will depend on the version of firmware. With V5 firmware it can be specified if you want 510 or 512 per universe.

  2. #12
    Senior Elf member crees's Avatar
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    Quote Originally Posted by Rooster519 View Post
    Trying to set up a couple of PixelPop Tiny's and am having some misunderstandings. Everything is set to run in multicast and test fine through FPP, my issue comes when setting up the controllers in Vixen. When I select Streaming Scan and go to configure I can only put in the Unicast IP destination. Does multicast not use the IP address? If not how do you specify which controller gets what universe? I have 5 total PixelPops all except one stay within a single universe, so one of them has to cross a boundary.

    My theory is that I will set up a single output in vixen with with 3,072 outputs and just patch them in order per 512 count universe. Then just specify all my pixelpops to be universe 1 with different channel start points.
    sACN approach to DMX was to utilize Multicast as its main delivery mechanism. Its designed to take full advantage of the multicast stream by using multicast IP's derived from the DMX universe. So there is really no IP you need to worry about other than specify the universe and the program (vixen) will automatically create the multicast Group IP and send it out. Multicast is basically a one to many transmission allowing you to send data to multiple points that are interested. How does this work? In the proper world a Router or high end network switch uses a protocol called IGMP. Another term is IGMP snooping. These methods help register each physical port to a Multicast address they are interested in. Much like a Radio Station to those who want to listen to that station.

    The Valid concern with Multicast and Pixel Controllers, Multicast is suppose to make it somewhat easier but in reality requires the proper network equipment and clients to really effectively use it to its abilities. Now one curve ball situation with multicast and the pixel controllers we use, That is Multiple Universes. Because sACN rules require each universe has its own multicast address and this adds a level of complexity. Pixel controllers that handle more than one universe (most do) must listen not only to one multicast address but many. The challenge with this is if the router/switch is intelligent it may not allow all multicast traffic to reach each port. Thats why some controllers ask that you turn off IGMP or IGMP snooping so all multicast traffic must go to every port even if the device or controller wants it or not. Much like having to listen to multiple radio stations at the same time and only paying attention to the one you want.

    So this brings up a great topic. Which controllers support IGMP? I know espixelstick has a handy way to use IGMP and query/register the multicast adresses its wants to listen too but its doing this over wifi. The sans controller I believe uses the multiple sockets in the W5200 chip to register up to 7 multicast addresses. The Falcons I believe take in everything the network will forward to it but does not utilize IGMP (I could be wrong on that please correct me)

    Now lets Talk Unicast.... It just works. you specify the IP the Universe and move on to the next. Multiple universes to the same IP is the norm. Network Nerds like myself love it because the way unicast works is the most efficient way to ensure traffic only goes to the ports that need it.

    Good Topic!

    crees

  3. #13
    Santa's Helpers Jchuchla's Avatar
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    Quote Originally Posted by crees View Post

    Now lets Talk Unicast.... It just works. you specify the IP the Universe and move on to the next. Multiple universes to the same IP is the norm. Network Nerds like myself love it because the way unicast works is the most efficient way to ensure traffic only goes to the ports that need it.
    Except on WiFi. Because WiFi adds a mechanism for guaranteed delivery of WiFi, it does it by retrying, which means that it guarantees delivery, at the expense of timeliness. Which is bad for time sensitive data like sACN.

    The only controller that i'm aware of that fully complies with the IGMP standard (and therefore the sACN standard) is the PixLite. Falcons don't do it, SanDevices don't do it, RonP controllers don't do it. The ESPixelSticks do it in a cheating way, but it does work for the purpose. ESPixelSticks simply send out the IGMP membership requests at a regular interval. They don't participate in any other IGMP dialogs. But since there are IGMP membership requests going out, that's all the IGMP snooper needs to see.

  4. #14
    Senior Elf member crees's Avatar
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    Multicast and destination IP

    Right! Unicast espís = not good, you just need a good AP that can do it well like the ubiquity radios.




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    Last edited by crees; 11-03-2018 at 11:30 AM.

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