Yes, Sparse mode is what you need. If you have Mikrotik routers at your sites, you'd want to get the Multicast package installed on the routers (at least those which would transit your multicast streams). You'll have a bit of work to setup PIM, particularly related to the Rendezvous Point. Cisco has a quasi-automatic way of doing it, but on Mikrotik you'll have to do it manually. Essentially, the RP (rendezvous point) is a router that can see all the multicast you have and all the routers between the RP and any device that would request the multicast stream need to have PIM running. Those routers will listen for IGMP join requests and send the requested multicast group (i.e. stream) towards the direction of the requestor. Also, make sure you allow all the PIM-related communications as well as IGMP messages in the input chain of the Mikrotiks. PIM is similar to OSPF or LDP in that it uses unsolicited UDP multicasts to create neighbor relationships and IGMP's are also multicast.

If you have switches between the routers and the AP's, if they're managed switches and they support IGMP snooping, you'll want to turn that on so it only sends multicast out ports that are towards a requestor. If they're not managed or don't support IGMP snooping, they'll just send whatever multicast comes into them out all ports.

In the APs, I don't know exactly how Cambium handles multicast, but generally, multicast data is sent at the lowest (or low) MCS rate in wireless APs so it is more reliable. In this case, you'd want the multicast to be sent over the air at a high MCS rate so there was enough bandwidth for the stream. In UBNT, it's called Multicast Enhancement.

The trick for you is getting something on the requestor end that knows what to do with a multicast stream. You can test it using VLC on a computer by joining the multicast group by telling VLC to open a network source with a URL like "udp://239.255.255.20:8100" (insert your multicast group IP and port here). VLC will send the IGMP join request, IGMP-aware router will hear it, and start sending it to VLC. The quickest way to test it is to be on the same L2 network as a Mikrotik and see if you get the stream. If PIM is working, you should. Then you can try to get behind an IGMP-aware RG (i.e. router) and see how it works for you. You'll also be able to watch the mechanics of PIM work, too, which is kind of cool.

On the device-side of things, I don't think Firesticks, Apple TVs or Roku's support multicast video, only HLS. Even if they did, you'd need some kind of UI that had a mapping between channels and multicast groups/ports (i.e. Channel X is at multicast group address Y and port Z) and tune to it. I think you'd need some kind of a true set top box like an Amino to have it pull multicast.

You could deploy a Wowza server. It could transmux the multicast streams into HLS streams and be a streaming media server (I'm ignoring scaling this at the moment). But if the video codec was something typical of IPTV (MPEG2 with AC3 audio), then just transmuxing it won't likely be of any help because the video bitrate would be too high. You'd also need to transcoded at least the video to H.264 so the bitrate was reasonable (the AC3 audio can stay, all the above devices can deal with that). Obviously I'm making a lot of assumptions about your situation, but you get the idea.


Jesse DuPont

Owner / Network Architect
email: jesse.dup...@celeritycorp.net
Celerity Networks LLC / Celerity Broadband LLC
Like us! facebook.com/celeritynetworksllc

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On 2/23/22 2:43 PM, Steven Kenney via AF wrote:
Yeah just read up on it sounds exactly what I need.  It basically is a pull mode which is exactly what I'm looking for.  So if it is a pull, I'm going to need to get it to something to pull from.  

Its time to RTFM methinks.. :) 

On Wed, Feb 23, 2022 at 4:40 PM Chuck McCown <ch...@go-mtc.com> wrote:
This might be a clue:
PIM Sparse Mode (PIM-SM) is a multicast routing protocol designed on the assumption that recipients for any particular multicast group will be sparsely distributed throughout the network. In other words, it is assumed that most subnets in the network will not want any given multicast packet.
 
Sent: Wednesday, February 23, 2022 2:32 PM
Subject: [AFMUG] Multicast Over Wireless
 
So we are delivering IPTV unicast at the moment but I do have the ability to receive all the multicast streams.  So I had been toying with the idea of actually using Multicast over wireless. 
 
I can get the multicast to the towers without an issue.   Once it hits a Cambium AP (either 450 or ePMP) I'm not entirely sure how I can deliver this to my customers because the totality of the streams are in excess of 1Gbps.  So being a bit new to multicast it makes me wonder how you could get an end user device to join a multicast stream...without a set top box.
 
So we use Fire Sticks,  Roku, Apple TV all over the top.  I don't think the app even supports multicast yet.  But I've been told it can be done, potentially at the router. 
 
Is this madness or is it really possible?  How would a home router be able to convert and request joins of streams and deliver it unicast to multiple devices in the LAN?
 
I definitely need to read up in IGMP in detail as to its sparse and dense modes.  Right now we'd be receiving it all in dense mode. 
 
Anyone out there actually successfully deliver multicast via Cambium at this scale? (over 1Gbps stream data)
 
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    Steven Kenney

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