Unicast or Multicast

[damona]

There are other threads about this.


Assume a 8 port switch with wireless network, assume the Controller/Transmitter (e.g. Raspberry Pi) is on port 1


Multicast-ing without IGMP-Snooping Switch
- Packet Multicast Packet received on one port sent to the other 7 ports and the wireless network.
- Effectively the same as broadcasting
- All Devices hanging off the switch, need to process the packet i.e. open it up and determine if an action is required. Each individual device will have a limit on how many packets/actions it can process without dropping any packets/actions. You could assume a E.131 design to support a single Universe would not need a lot of cpu/chip processing power and big maybe might be the first device to drop packets/actions.

Multicast-ing with IGMP-Snooping Switch
- E.131 Device now and then should send a packet to say I am interesting in hearing about these multicast packets with these Multicast IP address. The switch builds up a table of Multicast IP address to Switch Port. e.g. it would learn Port 2 is DMX Universe 10, Port 3 DMX Universe 5, Port 4 DMX Universe 6, Port 5 DMX Universe 15, Wireless DMX Universe 5,9&3. (not that you want many DMX universe on wireless)
- Effectively Unicast (really bad way to put it)
- If a Multicast IP address does not have a mapping (because the device did not send out the I want to hear this), all ports will get the Multicast Packet.

I Recommend the LinkSys LGS308 Switch. 8 Ports and 12VDC 1amp, so you can spread your switches around the house/yard. If you are running 12VDC you can then use the same power supply as your lights use.

Wireless ADSL Router (not connected to ADSL/Telephone) i.e. use it as a DHCP Server and a Wireless access into Raspberry Pi so you can upload your new shows.


[SIZE=x-small]Wireless ADSL Router, one port only ->[/SIZE] (port 1) LinkSys LGS308
-> (port 2) Raspberry Pi (output)
-> (port 3-7) E131 Devices
-> (port 8 ) Second LinkSys LGS308
The assumption here is the old ADSL route does not support IGMP Snooping i.e. do not plug a Multicast-ing Raspberry Pi into it directly

 

[rvenegas]

I got this switch available for my next set up.
http://www.tp-link.us/products/details/cat-42_TL-SG1024.html#overview

 

[dgirard]

while my display use's the same network as all the household computers,
Unicast is best for my setup.
i have noticed that if the rasp pi is sending data to a unicast ip thats not there, there will be issues in stuttering.
besides that i ran 50,000 channels last year nicely..
an could still stream stuff to the tv sets without issues..

i tryed multicast an basicly the whole house network fell over an died till i turned it off..

i also have all my gear with set IP numbers, so it made things a no brainer to me..

but everyone to there own setup realy

Unicast to a device not on the network can kill your transmissions... Especially with the ip stack on the pi. Basically it retries over and over to find (arp) the device and gets in the way of other traffic.

Multicast over wifi tends to flood the airwaves.