I have a very strange issue which is causing problems playing videos over a wireless-n network. Playing the videos causes the network to drop out after a short period. Sometimes this only lasts for 2-3 seconds, which just causes a video stutter. Other times the drop out is more permanent and takes nearly a minute to recover, unless the wireless radio is switched off and back on, whereupon reconnection occurs.
Running a continuous ping during this results in timeouts when the connection drops. The connection is more likely to recover within 2-3 seconds if the video is paused as soon as the problem occurs.
I have so far tested and established the following facts (note: all speeds are given in bits not bytes)…
1. The direction of the file transfer doesn’t matter, it can be to the client or from the client (e.g. from A to C or from C to A). It can also be initiated by the client, or by the other end of the transfer (i.e. initiated by C). 2. The file transfer can be to a different computer from the source of the video, or the same, it always has the same “protective” effect. (i.e. file is streaming from C to A, file copy is from B to A)
Playing just 1 video with a bitrate of 2Mbps doesn’t seem to exhibit the issue? 2 Videos with a total of 4Mbps do suffer. Videos up to and including 13Mbps all exhibit the same issue. Higher rates haven’t been tested but I expect them to have the same problem.
4. There are no other nearby wireless networks effecting network performance,
and file transfers work reliably at approx 70Mbps so the connection is not bandwidth limited.
5. Increasing the buffer in WMP to 30 seconds has no benefit. Furthermore the judders in video playback still occur at the same time as the ping timeouts so the buffer doesn’t even seem to be working?
6. The router firmware is up-to-date, and it has had the wireless board replaced without resolving the problem. The issue also occurred with older firmware.
7. The drivers for the wireless cards are up to date. The issue also occurred the same with older drivers.
8. When the connection cuts off it cuts off ALL wireless clients, even those not involved in the streaming so the issue *seems* likely to be at the router end of the connection, not the client end? (i.e. when streaming from C to A, B is also cut off temporarily)
9. A web-download at ~300k/sec (2.4Mbps) doesn’t offer the same protective effect as the ~70Mbps file transfer.
10. The issue occurs even if the client (a laptop) is on battery or plugged in. So it seems unlikely to be power-management related?
11. Disabled IPv6 without any benefit
12. Tried streaming video from both Windows 2003 (server C) and Windows 7 (desktop D) hosts without change, so problem isn’t related to SMB 2.0
13. Tried playback with a variety of players including Media Center 7, Windows Media Player 12 x64, Windows Media Player 12 x86, MPC-HC x64 and VLC – all exhibit the problem
14. Upgrading to an Intel 6300 wireless card makes no difference
15. The distance from router makes no difference
16. The problem happens faster the more intense the traffic
17. The problem happens significantly less with a shorter wireless key
My best theory is that the router has an obscure issue where it is reducing wireless speed when it detects that the connection is under low usage, but this low speed state isn’t sufficient for the peaks of required bandwidth in variable bit rate video streams and goes into some kind of error state which is only relieved when the video playback is halted. Copying a file is sufficiently intensive to prevent this state being entered, but a web-download isn’t.
Next I’d like to try one of the laptops with Windows XP as the OS instead of Win7, altho I don’t expect this to help. Then I’d like to try a different router / wireless-n WAP which if my theory is correct will cure the problem. Sadly I don’t have a source of a wireless-n WAP or router at the moment.
If anyone has any other ideas for things to try/test, or has a similar problem please get in touch!
Update 1 (5/Jan-2011)
I’m not the only person experiencing this. Googling shows up a range of other people who have had similar issues but as yet no solutions. List of links below…
Update 2 (23-March-2011)
I’ve updated various parts of the post, and added a series of links below.
I’m at a point now where I need to test my laptop with a different Wireless-N network. If it works then I think I can conclude there is a problem with my router. If it doesn’t work then there is something wrong with either Intel wireless cards, or with Dell Studio laptops!
http://www.sevenforums.com/network-sharing/110061-windows-7-wireless-connections-drop-out.html – Sound similar, but not quite the same. My adaptor still sees wireless networks as far as I can tell
http://forums.whirlpool.net.au/archive/1300843 – Some people saying its Intel cards, but others saying changing card didn’t help. Nothing conclusive.
http://forums.lenovo.com/t5/W-Series-ThinkPad-Laptops/INTEL-5100-5300-Network-Dropouts-Disconnects/m-p/97708 – Another speculating about Intel drivers, but still with an unresolved issue, so not very helpful
http://forums.smallnetbuilder.com/showthread.php?t=1997&page=3 – Similar sounding problem with a Belkin router. Problem resolved by replacing router.
Update 3 (30-May-2011)
I’ve tested the laptop connected to 2 more wireless-n networks. It works without any issue. In conclusion there is either a fault with the draytek or there is an incompatibility. Having already sent the draytek back once before I am rather disappointed that draytek failed to resolve the issue.
If you’re thinking of getting a Draytek, consider an alternative. I can recommend the Netgear DGND3700
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