Streaming device causing network-wide issues

[canooten]

I'm having sporadic issues on my home network.  I've found the culprit and can remove the device to solve the issue, however I'm curious as to what exactly causes the issue I'm seeing.

Over the last several months, I've had a handful of random instances where my entire network goes down.  By that I mean that every connected device either loses internet connectivity or loses its network connection (IP address changes from legit DHCP or static address to auto assigned IP). 

The first time this happened it took quite a bit of trial and error to finally narrow down the issue to a Tivo brand streaming device.  I have an OTA Tivo device for viewing and recording over the air TV along with a couple of network devices that can stream stored recordings over the network to different displays in the house.  One of these devices is what causes the issue -

https://tivoidp.tivo.com/tivoCommunitySupport/s/article/TiVo-Mini-Product-Information

When I ID'd the issue I left that device off of the network and all was well again.  Some time later I decided to plug it back in to see if the problem persisted.  At that time, things worked fine.  The device itself functioned and the network as a whole stayed up. 
Some months later, the entire thing crashes again, and the same device seems to be the cause of it all.  Unplug that device and all other devices reconnect.  Plug it back in and usually within minutes, no connectivity.

Obviously my fix is to remove the device, but I'm just curious what can cause an issue like this?

[Dieselboy]

Hello and welcome

Usually in networks, a source device will transmit to a destination device. This destination is understood by the destination IP address. The network device is then responsible for "switching" this traffic between source and destination only. Network "switches" create a wire connection between these two devices; lots of information left out but this is a simple description.
With this switch, it is mostly not possible for another 3rd network device to see the traffic that is going on between the described source and destination devices.

The case of a streaming service say netflix for an example, your TV will reach out to netflix and a psuedo channel will be opened up between your TV and netflix. Again it's not really possible for a 2nd TV in your home to watch the same netflix as the 1st TV because of the psuedo 1-1 channel that is established between your TV and netflix. Again, lots of info missing and I am simplifying a lot here to try and give a brief explanation. The only way for a 2nd TV to watch the same netflix here is for each subsequent TV to log in to netflix and establish their own 1-1 connection with netflix.


It's worth noting at this time that HD TV can take up quite a bit of bandwidth. I recall 1080p consuming about 1.5mb/s one-way but when I just googled right now I found a Cisco whitepaper on webex meetings that suggests 1080p consuming around 4-6mb/s. Ref https://www.cisco.com/c/en/us/products/collateral/conferencing/webex-meetings/white_paper_c11-691351.html
the table under Bandwidth vs Resolution, Cisco Devices

Before going on further, it's wise to know what bandwidth your network has. I'm assuming if it's not that old that you're using 1GB wired connections. This equates to around 125mbit/s. This will be fine for your streaming but there will be an issue with only 100MB connections because 100mb equates to 1.25mbit/s (unless I am misremembering as it's early then I hope to rely on my peers to kindly correct me).
If you are using wifi here, this could be an issue because wifi is a half duplex medium for the most part therefore the more devices on the channel (connected and associated devices as well as your neighbours devices that may be trying to connect or are scanning for wifi channels). Furthermore, connected wifi devices that have a weak signal strength further reduce the throughput because there needs to be longer "air time" given to those devices to allow them time to transmit/receive data.


So with the above context, then we have the tivo device. A quick google shows that the tivo likely supports multicast traffic. Multicast allows multiple TVs to receive streams from a single source. This is great if you want to have mutliple tv's viewing the same content from a single source but not-so-great if your network does not understand or support multicast.

Why? Well remember above where I said that it was not possible to have multiple TVs view the same netflix without each TV establishing its own connection to netflix as an individual? This is because they establish that 1-1 connection. With multicast, this doesnt happen but instead, the destination IP is a multicast IP address.

In networks that do not understand multicast, they do not know where the destination device is on the network. So what happens is this traffic is actually broadcast flooded out all ports to ensure that because the destination is not know, it will still get to the destination because of flooding. Every network device will receive these packets from TIVO.
Unfortunately, if your bandwidth is low then this is going to consume bandwidth OR even impact devices that arent suited to receiving it.


Now lets hypothesise that your network consists of a simple home modem/router with wifi and you have a single subnet of 192.168.1.0 - 192.168.1.255 address range. Whether you are on the wifi or on a cable connection you receive an IP in this range. Every device will be receiving a copy of the stream. I think it's easy to see how the network can be swamped with load, especially on low bandwidth connections, or even the modem itself can become swamped if it has low amount of RAM and CPU for processing the traffic.

For mitigation of this, you would need to look at how you have built up your network and what network devices you have. A diagram will be helpful here. 
You could also try going into the settings menu and turning off multicast on the tivo to see if this helps, or even compare this tivo with the others that you have to see if the settings are different between them.
You could check your network device guides to see if they support IGMP which is mutlicast support. This can stop the flooding of the traffic while still using multicast for the benefit.

Hope the above is helpful to at least give some insight.

[canooten]

A diagram will be helpful here. 

I've attached a simple sketch - nothing overly complex and no other issues to speak of. 

I follow that HD streaming can definitely cause issues, but in this case there is no streaming going on.  The problem happens simply because this specific Tivo Mini devices is plugged into the network.  It even happens when the device is in standby mode.  Plug it in, all network traffic halts and devices lose credentials within minutes - unplug it and everything reconnects and functions correctly.

I'll look at the settings and research multicast.  I believe this Tivo system functions soley on that feature though.  The overall function of the mini is to stream content from the central DVR box to different displays on the network.  The Mini units do not function on their own.  I would think disabling that would cripple the system, but I will look into it. 

Also, I have 2 of the mini boxes on the network.  The other does not cause issues, which makes me think there could be a problem with the one in question.  I very well may need to simply remove it from the mix totally.  I'm just trying to wrap my brain around how a single device, in standby mode, can cripple an entire network by simply being connected to it. 

[deanwebb]

If it's a malfunctioning box, it could be pumping out static to fill the bandwidth available - acting exactly like a jammer.

[canooten]

If it's a malfunctioning box, it could be pumping out static to fill the bandwidth available - acting exactly like a jammer.

That's a possibility.  I'll do factory reset on the unit and see if it gives me any other issues going forward.  At least I know what's causing the issue and the fix is as easy as unplugging from the switch.

[Dieselboy]

I follow that HD streaming can definitely cause issues, but in this case there is no streaming going on.  The problem happens simply because this specific Tivo Mini devices is plugged into the network.  It even happens when the device is in standby mode.  Plug it in, all network traffic halts and devices lose credentials within minutes - unplug it and everything reconnects and functions correctly.

I 100% guarantee that there is *something* going on when it is plugged in. A wireshark capture will tell you what you need. Maybe, when it's plugged in, the box is simply streaming a menu screen with moving content to prevent TV screen burn-in. Or maybe it's just faulty and is doing the jammin'. Pic for reference