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Deco X20 ethernet backhaul disallows large file downloads

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Deco X20 ethernet backhaul disallows large file downloads

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Deco X20 ethernet backhaul disallows large file downloads
Deco X20 ethernet backhaul disallows large file downloads
2023-04-29 18:57:38
Tags: #Backhaul Method
Model: Deco X20  
Hardware Version: V1
Firmware Version: 1.5.0 Build 20210303 Rel 33690

My network:

 

  • AT&T Router (fiber)
    • Deco X20 main (ethernet 1)
      • Deco X20 satellite 2 (wifi backhaul)
        • Other devices (wifi)
      • Other devices (wifi)
  • SG-105
    • Deco X20 main (ethernet 2)
    • Deco X20 satellite 1 (ethernet backhaul)
      • Desktop (ethernet)
      • Laptop (wifi)

 

From the desktop and laptop, I cannot download large files with this network configuration.  Video conferencing and other streaming services work fine.  The problem only shows up when trying download a large file.  I believe I enountered the issue over both HTTP and FTP.

 

To help pinpoint the problem, I rearranged my network like this:

 

  • AT&T Router (fiber)
    • Deco X20 main (ethernet 1)
      • Deco X20 satellite 2 (wifi backhaul)
      • Deco X20 satellite 1 (wifi backhaul)
        • Desktop (ethernet)
        • SG-105 (ethernet)
          • Laptop (ethernet, wifi disabled)
      • Other devices (wifi)
    • Other devices (wifi)

 

With this configuration, I did not experience any limit on download file sizes from my laptop or desktop.  Note that the SG-105 is still between the laptop and my ISP in this configuration, so the problem is not the SG-105.

 

I played around with downloading files from Google Drive, and I found three interesting facts.  1) There is no upload limit.  I can upload files I cannot then download.  2) The maximum allowed size varies wildly but is consistent within a time window.  I was able to determine the max downloadable size as 514M, 90M, 3.8M, and ~500k at various points in time over about 30 minutes.  I haven't timed the length of the time window between max file size limit changes, but it's on the order of several minutes.  3) When the downloads fail, they fail immediately, no matter the file size, which leads me to suspect the something is explicitly rejecting large downloads.

 

How should I proceed?  I need the ethernet backhaul, because satellite 1 is on the other side of the house from the main Deco. I only have ethernet drops in the perimeter walls of the house, so there's no way to place the main Deco close to both satellites.  Without the ethernet backhaul, the bandwidth through furthest satellite drops below an acceptable level.

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#1
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6 Reply
Re:Deco X20 ethernet backhaul disallows large file downloads
2023-05-01 21:47:23

Hey  @templedf,

A few Questions:

 

  1. When you rearranged your network, did you have a better overall experience?
  2. What is the Operating Mode of Your Main Deco X20? AP Mode or Router Mode?
  3. Have you Enabled the Bridge or IP Passthrough Setting on your AT&T Router?

 

If the Router is in Router Mode, then the Switch will need to be placed within your network(downstream of the first Deco, meaning: AT&T > Deco Main> SG105 > Everything Else) Otherwise, there will be conflicts with which deco is attempting to connect to your modem to operate as the main node. In your current setup, it looks like you are trying to run a WAN connection directly to multiple nodes, however, the connection must first pass through a Deco to create a stable mesh.

 

It is also worth mentioning that when an  ISP gateway is in IP Passthrough or Bridge Mode, only one of the Ethernet Ports can be used at a time; but this may be different for fiber setups.

 

New Release - Kasa KS240: Smart Ceiling Fan Control and Dimmer Switch
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#2
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Re:Deco X20 ethernet backhaul disallows large file downloads
2023-05-01 23:01:06

  @Riley_S 

 

With the second network arrangement there were no limits on file download sizes, but the bandwidth available to my laptop and desktop were reduced by about 90% because of the distance between the satellite and the main Deco.

 

The main Deco is in router mode.

 

In both arrangements, the only thing plugged into the AT&T router is the main Deco.  Everything else connects to the main Deco either via wifi or through the SG-105.  I learned that lesson the hard way already.  In the first network arrangement, the ethernet backhaul works great in every way except that it limits my file downloads (but not uploads or streaming).

 

I originally thought the issue was with the SG-105, which is why I tried the second network arrangement.  The fact that the max file download size changes every few minutes is bizarre.  Could it be that the backhaul is trying to avoid overburdening the network, so it's capping download sizes based on some periodic average of the network traffic?  I can't come up with any other reason it would vary like that.

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#3
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Re:Deco X20 ethernet backhaul disallows large file downloads
2023-05-02 22:23:58

  @templedf,

It could be, but if there are no other devices sending data through the network, the drop should not nearly be as dramatic.

 

Two Things to Try Would Be to Change the DNS server to see it is specific to the service you are using

 

and to try setting your laptop as a high-priority device in the QoS settings. This should prevent any load balancing that would occur while downloading.

New Release - Kasa KS240: Smart Ceiling Fan Control and Dimmer Switch
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#4
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Re:Deco X20 ethernet backhaul disallows large file downloads
2023-05-02 22:47:40

  @Riley_S 

 

It's definitely not DNS, because I was able to download small files between failing to download large files.  DNS entries are cached, so if it worked once, it would keep working.  Also DNS timeouts take a while.  When a file fails to download, it's immediate.

 

I tested with the laptop set as priority.  It didn't make any difference.

 

This issue is 100% reproducible across multiple devices, so I'm certain that it's not some kind of localized effect.  If it were slowness or occasional dropped packets, I would have a good idea where to look, but this behavior where large file downloads fail immediately, only over the ethernet backhaul, is strange enough that I'm baffled.

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#5
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Re:Deco X20 ethernet backhaul disallows large file downloads
2023-05-03 22:12:57 - last edited 2023-05-03 22:14:01

  @templedf,

Interesting, I really would have though that setting a priority device would fix any issues related to the software dropping the speed. Have you considered that it may be some sort of fault in your ethernet cable?

 

The only real thing in common since you mention that everything else is working fine is that you are probably trying to push as much data through that cable as your nodes think it can handle; which may cause crosstalk or dropped packets when at capacity.

 

I would recommend testing the ethernet cable, or at least the satellite Deco by moving the satellite into the same room as the main Deco, wiring them together, and seeing if the behavior follows the Deco.

 

 

New Release - Kasa KS240: Smart Ceiling Fan Control and Dimmer Switch
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#6
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Re:Deco X20 ethernet backhaul disallows large file downloads
2023-05-06 23:07:03

  @Riley_S 

 

Nailed it!  It was the cable(s).  There are 4 cables in the circuit, and I was able to prove one of them was bad.  I still can't download anything over 1GB, but it's reliable below 1GB.  There are clearly other bad cables, but the 2 I couldn't rule out are in the walls, so they'll be hard to validate.  I can live with 1GB for now, and I know where to hunt if it stops being OK.  Thanks!

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Helpful: 2

Views: 465

Replies: 6

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