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DesignAV
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Video over IP

Tue Sep 10, 2019 3:52 pm

Hi all, clearly this is a newbie question...

I've tried to simplify the problem down to it's essential elements - it hides well over 40 hours of post-installation discussion and investigation, and a very unhappy client :-(

I am using CRS328-24P-4S+RM switches to build a video over IP local network. The Switches all have RouterOS 6.44.1. I am using Crestron's NVX video over IP protocol. (Which is similar to MPEG2 I am led to believe).

There is no other traffic on the network apart from a small number of occasional control packets. The local network does not route to any other network segment.

We have 4 rooms - with a switch in each room. Three of the switches are handling three video encoders, and three video decoders each. ( 9 sources and 9 sinks so far). The fourth switch has 4 encoders and 4 decoders. So that's a system total of 13 sources and 13 sinks.

The encoders are generating data at about 200 Mb/s

Switch 4 also runs DHCP.

Switch 1 & Switch 2 connect directly to Switch 4.
Switch 3 connects to Switch 4 via Switch 2. [Because of the way the rooms are laid out - its too far to get Switch 3 to connect directly to Switch 4]
Sketch.png
I hope the sketch works for you...

Switch 2 to Switch 4 is the longest link at about 30 metres, but it IS reporting 10G line speed, and we are using a tested Hellerman CAT 6a cable (for testing) on this link.

The Controller commands the decoders to subscribe to the appropriate encoders. No more than 4 encoders would be active at any one time, and no more than six of the decoders would be subscribing.

The encoders use multicast addressing.

The question is 'why doesn't this just work'?! I don't seem to be getting enough throughput on some combinations of encoder and decoder. For example, combinations that would have to traverse between Switch 2 and Switch 4 don't work, whereas Switch 2 to Switch 3 routes DO work. Any route that only has to traverse a single switch works.

'It works' means there is a 1020p60 image being transferred, whereas 'it doesn't work' means there in no, or only an intermittent image.

Does anyone on the forum have any observations or comments as to what might be wrong? On paper, there ought to be ample throughput.

Thanks all - Jeff
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mkx
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Re: Video over IP

Tue Sep 10, 2019 5:12 pm

Are you using IGMP snooping? If yes, try to disable it and see if things start to behave.

The problem is that for IGMP snooping to work one needs multicast router present (IGMP querier). If there isn't one, then IGMP snooping only works reliably if there's single switch between source and sink ...
BR,
Metod
 
CVXDEV
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Re: Video over IP

Wed Sep 11, 2019 5:20 pm

Hi -
how are the Switches connected to each other, are the red cables in your sketch Fiber or Copper?
I had/have similar performance problems when using fiber ports on the CRS - just for testing using the LAN ports & Copper might be worth to try...
 
DesignAV
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Re: Video over IP

Wed Sep 11, 2019 6:23 pm

Hi -
how are the Switches connected to each other, are the red cables in your sketch Fiber or Copper?
I had/have similar performance problems when using fiber ports on the CRS - just for testing using the LAN ports & Copper might be worth to try...
Thanks - the red links are copper, using the 10G module.
 
DesignAV
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Re: Video over IP

Wed Sep 11, 2019 6:24 pm

Are you using IGMP snooping? If yes, try to disable it and see if things start to behave.

The problem is that for IGMP snooping to work one needs multicast router present (IGMP querier). If there isn't one, then IGMP snooping only works reliably if there's single switch between source and sink ...
I'll try that tomorrow! Thanks.
 
CVXDEV
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Re: Video over IP

Fri Sep 13, 2019 10:52 am

Since I am dealing with a similar set-up / problem I am quite interested in the progress.
Did disabling the IGMP snooping improve something?

Additionally, did you do a Bandwidth-Test (via Winbox) between your switches? I have 2 CRS connected via Fiber, but only get ~400 Mbps on UDP (&also loose a lot of packages), and even lower on TCP (~90Mbps) and wonder if other people have the same issue.
 
DesignAV
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Re: Video over IP

Mon Sep 16, 2019 5:18 pm

I'm pretty sure we established that an IGMP Querier had been established. It was only visible at the bridge level though.

We had plenty of bandwidth - just the curious breakdown of reception at around 5 minutes.
 
Amm0
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Re: Video over IP

Tue Sep 17, 2019 3:17 am

If you posted the configuration, it help get to the bottom of this. Other than IGMP Snooping, random suggestion is that STP might be tripping up someplace - you diagrams has no loops but the actual network may?

If this just one big, flat L2 network (which is typically the case if using multicast/video switching), SwOS might be a better choice to use on those devices. With ROS and bridges, you have to make sure things don't get on the routing "slow path" and/or hardware offload is working. If you not create VLAN'd network, ROS may be overkill. You can also use 1 ROS, and 3 SwOS since it seems you do need DHCP someplace, which is only in ROS.

Now if you need ROS for some other reason, you can also install the multicast package (see https://wiki.mikrotik.com/wiki/Manual:Routing/Multicast) which tell you a little more about IGMP stuff (and allow IP routing of multicast if that's what you needed) if you still suspect that causing an issue.

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