Slow upload speed (but only to Dropbox). Dropbox is now unusable

[Verenhaul]

I've begun to experience this recently:

1: Uploads to dropbox are (as of about one week ago) consistently around 0.14 Mbps. This happens through desktop or web interface.

For perspective, that's a 300 baud modem from 1984 kind of speed.  It renders me unable to work using dropbox.

2: Speed tests of the line show consistent ~75 Mbps downstream rate / ~20 Mbps upstream rate.

3: If I try uploading the same file(s) to google Drive (or anywhere but dropbox), speeds are as-expected.

4: I have re-installed the dropbox app.  Prefs for everything, including Bandwidth, are at default, so please don't suggest it as a solution. 
 

Dropbox is the only destination exhibiting the problem.  Any help appreciated!
What kind of tests can I do to narrow things down?  Thanks in advance.

(UPDATE EDIT: 9 Nov)  It's not a fix, but a good clue: I have seen immediate return to expected upload speeds after connecting through a VPN. 
Another user below has also found respite by altering the MTU size in their router configuration.  Will update with new findings.

POSSIBLY suspecting a bad hop somewhere along the route between me and dropbox.  If it is, then How to remedy?

[Bill-working]

YES! - same thing happened to me. Both the desktop app AND the web page are extremely slow at uploading. First started October 21st. ISP is Fision Hotwire. Getting upload speeds only about 3,000 bytes per second. Forcing a connection through Verizon Wireless bypasses the problem. Have tried many other things. Other stuff works without a problem and internet speed is very good.

Definitely some kind of systemic problem in ISP connections or something. All of our computers started doing the same thing at the same time. Have bypassed the router and still the same thing.

DROPBOX - please investigate this and don't just say it is not your problem please?

[Bill-working]

Found a solution - I changed the MTU to my ISP in my router from automatic to 1428. There must be something along the path to Dropbox that cannot take normal sized 1500 packets. My Verizon connection was working and I thought it was because it was a different ISP path. But the Verizon cellular modem uses an MTU of 1428 so I tried that and it worked. I had already tried other MTU values but not that low.

[Verenhaul]

Thanks for the idea, BW. I might try it. How did you find this post?

-and can you tell me what kind of service you have and with what ISP?

Our circumstances may differ in ways that matter.

Also, it's still not a real solution.  It's a kludge; a risky band-aid to the actual problem.

If the user has to configure arcane settings in their router (potentially fouling up other services) to fix the problem, then dropbox has still not found a viable solution to a problem that only exists when accessing their service.

[Bill-working]

I had been searching several times for any information specific to this problem. At first I was only finding all the typical suggestions from the past. Then when I searched again I found your post which matched the problem I was having.

We have Fision Hotwire fiber ISP. Computers are behind a router. It is easy to change the MTU with the router.

Definitely only a temporary workaround. So far not seeing other problems by changing MTU TO 1428.

I don't think the problem is actually with Dropbox. It depends on the ISP and the path the packets take to get to Dropbox. I initially tested with Comcast connection and no problems.

Test your connection with file.io upload. It was having the same problem.

[IMightAsWellBashMyHeadIn]

Now here I was thinking I was the only one with dreadful upload speeds. For what it's worth I'm getting about 9Mb/minute.

I've only had this problem since Dropbox updated their web interface.

[Verenhaul]

Ah, cheers, then . I connected through a VPN and saw immediate restoration of transfer speeds, FWIW.
It’s not a fix, but it’s additional data that might point the way…?

My ATT “router” appliance is not feature rich(the five year old BGW 210-700), but I’ll see if it allows me to edit the IPv6 MTU. A network -savvy friend discovered that it’s likely as you seem to say: A device on one of the hops seems to be ill-configured.

Of course, that sounds like it’s genuinely not the domain of either my ISP or Dropbox…. In short, I can’t work and there’s no one to contact to “fix” the problem.

Anyone know how best to proceed if it turns out to be some random machine fouling up the path?

[Bill-working]

I don't know if you will be able to set the MTU for the WAN connection in that router/gateway. But what you are looking for is IPv4 MTU, not IPv6.

I had tried a VPN as a solution but it did not work for me. Once you leave the VPN tunnel you still pass through some regular IP routers to get to Dropbox. In my case it seems the problem was still happening between the VPN exit and Dropbox. In your case it sounds like you bypassed the problem spot while in the VPN tunnel so problem avoided.

If you could identify the specific routers causing the problem you could try to contact that company and tell them about the problem. That would be difficult and not worth the effort. One assumes that eventually the problem will get fixed!

[OrsonKane]

Since this morning when I try to sync, it looks like it will start but it doesnt, it shows on the status bar that it will take days to sync a few gigs and then just stops. From the web enviroment it does something similar, it starts to download but shows it will take days to do so and then just quits.

Tried other computers, other internet connections, even asked my friend and he gets the same, is all the same.

[OrsonKane]

Bill, you are a god, I wouldn't have thought of this in a million years, I just changed on my network settings and it worked, its amazing. I guess something changed on dropbox end and is affecting some users.