Constant LAN traffic flood between Echo devices on UDP port 55444

[cinergi]

Hello,

I have multiple Echo devices in my home, and I see a constant LAN traffic flood between some of them even when they're idle. This goes on 24 hours a day. For example, here is a Wireshark dump between an Echo and an Echo Show 5 in just 1/4 of a second:

3 0.002627 10.10.65.203 10.10.65.235 UDP 60 55444 → 55444 Len=8
7 0.004818 10.10.65.235 10.10.65.203 UDP 60 55444 → 55444 Len=16
22 0.043388 10.10.65.203 10.10.65.235 UDP 60 55444 → 55444 Len=8
23 0.045924 10.10.65.235 10.10.65.203 UDP 60 55444 → 55444 Len=16
75 0.083424 10.10.65.203 10.10.65.235 UDP 60 55444 → 55444 Len=8
76 0.085826 10.10.65.235 10.10.65.203 UDP 60 55444 → 55444 Len=16
82 0.124841 10.10.65.203 10.10.65.235 UDP 60 55444 → 55444 Len=8
83 0.126838 10.10.65.235 10.10.65.203 UDP 60 55444 → 55444 Len=16
85 0.165571 10.10.65.203 10.10.65.235 UDP 60 55444 → 55444 Len=8
86 0.167665 10.10.65.235 10.10.65.203 UDP 60 55444 → 55444 Len=16
87 0.205569 10.10.65.203 10.10.65.235 UDP 60 55444 → 55444 Len=8
88 0.207565 10.10.65.235 10.10.65.203 UDP 60 55444 → 55444 Len=16
92 0.247903 10.10.65.203 10.10.65.235 UDP 60 55444 → 55444 Len=8
93 0.249998 10.10.65.235 10.10.65.203 UDP 60 55444 → 55444 Len=16
95 0.287927 10.10.65.203 10.10.65.235 UDP 60 55444 → 55444 Len=8
96 0.289018 10.10.65.235 10.10.65.203 UDP 60 55444 → 55444 Len=16

Unplugging the Echo devices stops the traffic, but as soon as I plug them back in, the traffic resumes. What is this for? There is no reason for it, especially when the devices are idle. The rate is approximately 300-400 packets per second - not reasonable!

Thanks

[jwlv]

Notice that the length of each packet is 8 or 16 bytes (or maybe bits - your data doesn't say). And it's UDP instead of TCP. Based on what little information this data shows, it is likely to be the spatial perception. A few bytes of data is hardly a "constant LAN traffic flood."

What's that you say? Read this: https://www.theverge.com/2018/7/25/17613832/amazon-alexa-echo-spatial-perception

I don't see a problem with this, no matter how many hundreds, or thousands, or millions of packets go between your Echo devices. If you're worried, then unplug it.

But let's say it is a million packets that goes through each day. Well, a million packets x 8 bytes is still only about 8MB (1MB if your data is actually in bits and not bytes), which is about the size of a typical MP3 track that you might stream through Spotify. A typical 2-hour Netflix movie is about 6000MB. In a full year of this constant Echo traffic, it would be less than a single 2-hour Netflix movie. Do you still see a problem or a traffic flood?

[cinergi]

Thanks!  Interesting article regarding the spatial perception feature.  I did a bit of research as well, and there are a few others (not many) that have reported this issue.  Another possibility is that it's a time synchronization for the multi-room audio feature, especially since UDP port 55444 seems to be used for "time sync".

It's not just the packet size that matters, it's the rate as well (packets per second or pps).  A large number of small packets can place more load on a network than a smaller number of large packets with a higher total data rate.  This is why networking equipment specifications are given not just in Mbps, but also in pps.  In the streaming audio/video example, the packet size would be close to the 1500-byte maximum.

In this particular case, my equipment can handle the load, but it's an unnecessary inefficiency.  As someone with an engineering background, I hate inefficiency.  I therefore moved all of my Echo devices into my IOT WLAN with layer-2 segregation between clients, and separated from my main LAN on its own VLAN.  This stopped the extraneous traffic, and the Echo devices continue to work fine - I see no difference in functionality.  However, I don't use the multi-room audio feature and my Echo devices are far enough apart that determining which one should answer an "Alexa" query (via spatial perception) is not an issue.  Works for me.

Thanks,
cinergi