Since the arrival of BT TV we noticed an interesting/annoying behaviour with our WiFi. All of the non-FreeView channels are streamed to the YouView box over the internet. As mentioned in the last post, to get this to happen I needed to enable an IGMP proxy on our DrayTek Vigor 2860ac router. This lets the YouView box join the multicast group for the channel we want to watch. Initially this appeared to be all that we needed to do. However we found that when watching an HD channel delivered this way all WiFi traffic ground to a halt. Wired computers and gadgets didn't have a problem, but anything connected via WiFi would essentially see their data connection time out. The WiFi itself was still up and broadcasting, and our phones and tablets could see the signal, but with no data traffic. Switching to a streamed SD channel got the WiFi working again, so initially I thought this was a bandwidth issue, with the YouView box commandeering all the available broadband bandwidth. However according to the router's traffic graph an HD channel is only about 6.5Mbps, leaving more than enough bandwidth for other devices. And all the wired computers were able to use the internet just fine, so bandwidth wasn't the issue.
A knowledge base article from DrayTek states that only the IGMP proxy on their routers "need typically be enabled on a home network". However the router offers two optimisation settings for IGMP; Snooping (the ability to only forward multicast packets to LAN sockets that have devices that have subscribed to that multicast group) and Fast Leave (the ability to stop forwarding multicast packets when it detects there are no more multicast group subscribers). These two options "could be useful on larger networks or networks with a large quantity of IGMP packets that could limit normal LAN throughput".
I guess we have one of those networks then, although DrayTek don't specifically mention WiFi in their article. Our YouView box was already connected to a different LAN socket on the router to the other wired devices, and by enabling both IGMP Snooping and Fast Leave the ability to simultaneously watch streamed HD channels and surf the internet on our phones and tablets was restored. My best guess is that previously when the YouView box subscribed to a multicast group, the multicast packets for that channel were sent to all connected wired and wireless devices, which swamped the WiFi. Now they're not even going to the other wired connections let alone the wireless connections.
A knowledge base article from DrayTek states that only the IGMP proxy on their routers "need typically be enabled on a home network". However the router offers two optimisation settings for IGMP; Snooping (the ability to only forward multicast packets to LAN sockets that have devices that have subscribed to that multicast group) and Fast Leave (the ability to stop forwarding multicast packets when it detects there are no more multicast group subscribers). These two options "could be useful on larger networks or networks with a large quantity of IGMP packets that could limit normal LAN throughput".
I guess we have one of those networks then, although DrayTek don't specifically mention WiFi in their article. Our YouView box was already connected to a different LAN socket on the router to the other wired devices, and by enabling both IGMP Snooping and Fast Leave the ability to simultaneously watch streamed HD channels and surf the internet on our phones and tablets was restored. My best guess is that previously when the YouView box subscribed to a multicast group, the multicast packets for that channel were sent to all connected wired and wireless devices, which swamped the WiFi. Now they're not even going to the other wired connections let alone the wireless connections.
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