View Full Version : Shaw CRC errors in files

05-26-2011, 06:55 PM
This is a rather odd issue that has baffled me for the past week or so.

The problem started when some compressed files did not decompress properly due to CRC errors. Downloading the same files a second or third time "fixed" that issue. This led me to believe the issue is network related.

So I downloaded several copies of an identical linux distro from different locations, and low and behold the MD5 checksums do not match either.

This issue seems to have started after I go the free "speed upgrade" from 15 to 25 Mbit/sec.

I don't believe it's my hardware since I would see other issues like random crashes and other odd behavior. This is not the case, and I can run something like WoW for 6 hours straight without a hitch.

I have not changed any soft or hardware, and I have downloaded TB's in the past year without ever having CRC extraction errors.

Anyone else has noticed anything similar lately?

05-28-2011, 04:15 PM
Have you tried bypassing your router? I had a similar prob and it was my Linksys router..I changed to another router and crc's went away. Determined router was sporadically causing CRC errors at first, then started occurring more frequently over a period of a few weeks. Other than that, hope you find out.

05-28-2011, 06:26 PM
That was my initial idea, and I do have 2 spare routers around for testing purposes.
I have flashed with the latest firmware and did a factory reset, we will see what happens.

In the meantime I will MD5 files to ensure they don't become corrupted when transferring them on my LAN.

06-29-2011, 08:06 PM
I finally figured out the problem, although I have no explanation for it.
These CRC errors only occur when using HTTP to transfer files. If you use HTTPS to transfer the same files you never get CRC errors. I tested this for Gigabytes and Gigabytes of data. The regular HTTP CRC errors are very prominent and I must not be the only one with this issue?? With prominent I am talking 1 out of every 5 files or so, which is extremely annoying.

I can only conclude the problem is with whatever Shaw does with the HTTP protocol. I am assuming they are either throttling, traffic shaping, or transparent caching and somehow that results in HTTP data not being transmitted properly.
I have tried the following, and unless I missed something my conclusion is correct :

3 different routers
2 different cable modems, Docsis 2 and Docsis 3.
Direct connection to either cable modem.
Changed all network cables.
Tried with 5 different computers.
Tried with xp, 7 and 2008 R2.
Tried with a couple of Linux distros.
Tried with different power bars.
Had Shaw technician verify line levels and signal quality.
Tried wired and wireless.
Tried all possible settings I could think off.

06-29-2011, 10:43 PM
If you do a traceroute using the same site but with http:// for one run and https:// for the other, are there any differences in the routing?

06-30-2011, 06:09 AM
No, they come from the same physical servers just with a http instead of a https protocol. I have tried many locations from all over the globe, always with the same results.
I thought it might have been a bad router somewhere out there, but it would need to be one on Shaw's network.

08-25-2012, 10:55 PM
They fixed this and it was good for months. Since yesterday the exact same issue is back. I smell traffic shaping since my download speeds are terrible.