Threat Prevention Severely Degrades ISP Download Speed when Tested in Succession

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Threat Prevention Severely Degrades ISP Download Speed when Tested in Succession

DS920+ DS215J,
  1. RT2600ac
  2. MR2200ac
Operating system
  1. Windows
Mobile operating system
  1. Android
Recently I upgraded some Ethernet from the PC>Router and started doing some Speed Tests with Ookla & Others. Two months ago my ISP "gifted" us a Speed Increase from 200>500Mbps. Not expecting to see any differences with the new CAT 7 Cables, the first Test came in a 550Mbps... Great.. And then I started Testing again after each test cycle, as the numbers looked lower at the onset. Sure enough the Speed would start off at 500+, then I would watch the Speed rapidly decrease during that 15 Seconds of the Download portion of the Test.. no consistency in numbers but it could go as low as 77 or less. I threw on other Cables with no change. I changed Ports and everything else I could think of. I then bypassed the Router connecting the PC directly to the Modem... and I was surprised to see Solid 525Mbps Speeds. To eliminate any other factors, I called my ISP and they changed the Modem due to its age (2 years) and the tech was kind enough to Test every link in the chain with his Analyzer and could find no issues. As everything now pointed to the 2600, I logged a Ticket with Synology and after phone calls and e-mails asking me to change various settings, and after a few days of tests the next to last was "Turn OFF Threat prevention".... Once that occurred, the Speed issue was resolved. The culprit (maybe?) is my USB Flash Drive. For the 1.5 years owning this, I had always had a Class 3 95 Write Speed SD Card installed (borrowed from my camera) and saw no issues. Recently I saw a post about the "Best" Flash Drive and it recommended the Kingston DataTraveler Kyson 32GB High Performance USB 3.2 Metal Flash Drive... I ordered and installed it, again with no issues to my knowledge. Synology Logs showed they were only seeing (7.355 MB/s vs a recommended 15MB/s)... The Kingston claimed 60Mbps Write. I called Kingston and a great rep did some digging and found that ONLY the 64 & 128Mbps have the 60Mbps claimed Speed... NOT the 32. So much for the Specs found on Amazon. Kingston is sending me a higher revision Number Model to test. And the "Recommended" Flash Drives on the Synology Site? Most of them are obsolete and/or unavailable. If you are running Threat Prevention, Have you done repeated, successive Speed Download Tests? Do yours Degrade when doing these repeated Tests?? And what specific USB Flash Drive are you using?

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I found that TP (for 2600 router) reduces torrent downloads to about 20% of the ISP internet download rate I get when not using TP. TP reduces downloads from 25 MB/s to 5 MB/s. The only solution is to go to TP/Setting/Device and uncheck the device you are downloading to so that its packets are no longer inspected. When I do that I get the maximum download my ISP provides. The drawback of course is that IP does not inspect packets directed to the device. For me, it's not a big deal, and I just turn TP back on for that device when I'm done.

I was curious if the 6600 would have the same TP bottleneck or if its processor was fast enough to keep up with the packet inspection to provide 25 MB/s.
I was curious if the 6600 would have the same TP bottleneck or if its processor was fast enough to keep up with the packet inspection to provide 25 MB/s
In my testing, 6600 had no penalty with TP active while testing it over 1G fiber.
Thank you for sharing your experience... This one was weird enough as it appears very few have ever seen how the Speed just drops in those seconds. Are you using a "Fast Write" USB? The 6600 does have a faster processor and its hard to justify upgrading as my 2600 is just 2 years old at this point. I too wonder if the 6600 has the same issues with TP....
I should add there is a Knowledge Center Article on Router caused Slow Download Speeds, but it does NOT address the USB Flash / SD card as a contributor to this issue:

I used to use a SanDisk Ultra USB 3 thumb drive as the storage used by TP and other bits on the router. That died from what I assumed was the heat and proximity to the router, so that it couldn't dissipate. I've been using a USB 3 WD Element HDD since then and haven't noticed a slow down, and I use TP.

Our Internet connection is 380/36 Mbps. Can't say how this router will continue to perform if I had 1 Gbps Internet. I would try an external USB 3 SSD most likely.

Just now, from my Mac on Ethernet.
Don’t have high speed internet to test, but I can confirm that SD Cards can degrade over time.

I’m now running on M.2 card in USB3, and just recently we determined that trim is being applied once a month to ext USB Port on a SSD.
My max is 200/20 but no difference w/wo TP.

One thing than can cause speed issues is T3/T4 errors in your modem is on cable. You might look for those in your event log of modem.

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Only if that combination is not using split DNS. If that device is in full tunnel, then yes, it's fine. TP...

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