Some new Information from Apple's hotline an a resume of the previous findings.
First the news.
Apple phone support told, that some network files can get corrupted over time and should be deleted occasionally, especially if you have installed a new operating environment like Lion.
For that, switch OFF the wireless on the machine you want to tweak.
Delete from the system files:
* preferences.plist
* Networkinterfaces.plist
* com.apple.network.identification.plist
* com.apple.airport.preferences.plist
* (and any associated files like above that had ".orig" at the end)
Eventually you should also delete all related entry's from Keychain Access
Reboot and join the network again.
Nevertheless, there could be also different reasons for the problems one experience. For that a resume about the major issues....
In most cases, people blame on firsthand the obvious because they are mostly, by lack of knowledge, not able to see the coherence in a complicated infrastructure as wireless and networking is.
That's pretty normal and o.k. as well as a car driver mostly not have to have any knowledge about the regulations and functions of the fuel injection system.
I've discovered on many troubleshoots around wireless problems regardless of Apple, Linux or Windows, that (except a single reason became valid) in most cases it's a mix of minor issues what leads to major problems; e.g. constantly stream drop out, lousy speed, 3 stations work well but one wont, WiFi drop when a smart phone connects, up to total loss of the WiFi connection.
Although it's sometimes a rough job to find the reasons behind the trouble in networks it's always a fine idea first to eliminate all known or discoverable possible reasons.
What comes out so far?
- Corrupted or damaged configuration files on client.
- Different domains in the local network
- General radio problems in WiFi. Based on disturbance from interferences, obstacles in or reflections of the radio beam
- Mismatched settings on the network participants
- Problems with the 802.11b/g/n compatibility mode
- Hardware fault's or buggy drivers / firmware
...and of course there could be a lot more reasons.
On this I'll follow the numbering above and will also add a short description about possible reasons or a example in a not so technical manner for better understanding.
One may check, which possible solution or combination of solutions may best fit the own problematic.
#1 -> Corrupted or damaged configuration files on client.
Possible reasons: Time, Updates, Upgrades, accidentally power loss on running system and nearly countless more.
Solution: See entry of this post.
Alternative solution:
For those are a bit frightened to delete complete system configuration files. In many cases this "short version" will do the trick too.
* Switch OFF wifi on the affected machine.
* Delete all affected networks from the "known networks" list in System Settings
* Delete all keys pointing to these networks from Keychain Access
* Reboot
* Join network again.
#2 -> Different domains in the local network environment.
Description: In a network segment (your home network) all systems have to be member of the same local domain. This allows a clear name resolution (DNS) in the net. Most systems have a default set local domain name in the network configuration to ease joining a network with systems of the same bread.
Windows systems have by default set a own local domain like e.g. "workgroup" (depending on version or localisation). Mac's have by default set the local domain name as "local". Some Routers have by default set one of these, none or a different local domain name; e.g. in UK some BT-DSL/WiFi boxes provide "home" for the local domain name.
Reasons: If there different domains in the same segment (your network), name resolution trouble is programmed and that leads to unwanted network traffic, packet collisions and could at last force stations to disassociate from the network or get disassociated by access point (router) due to time out, bad or wrong response.
User experience: Slow and sluggish network, WiFi or iTunes/Video stream drop, lousy data transfer speed or being unable to open different Internet sites in the browser. Also observations like: My Windows box work well in my wireless but my Mac wont. At the office all is perfect but at home...
Solution: Configure ALL stations (clients) in your network to use the same local domain name, regardless of which name you choose. Eventually set up a second location (profile) for the particular network.
Attention!
If you want to use Apples new child "Airdrop" you must use "local" as the domain name, as Airdrop refuses to work with other local domains or with stations using not "local" for domain name.
#3 -> General radio problems in wireless networks based on disturbance from interferences, obstacles in or reflections of the radio beam
Description: The radio beams of a wireless are not Roentgen X-Ray based and therefore obstacles, interferences from other wireless systems or reflections of the radio beam could cause major disturbance of the wireless network and based on this, the data stream in the network.
Possible reasons:
- Obstacles like Walls, magnetic fields from live high voltage lines, antenna cable or insufficient shielded speaker systems. Metal frames or plating, furniture, bundled water pipes, dry construction plaster walls*, Humans* and much more.
- Interferences from other radio equipment like Bluetooth, cordless phones, neighborhood WiFi, cordless speakers, cordless doorbells, intercoms, ptt units, baby phone's, surveillance and alarm systems, commercial weather radar, some military equipment and so on.
*) Water is a big bar for radio. Plastered dry construction walls and Humans contain a lot of water.
One of the named possible reasons or any combination can cause major annoyance due to unwanted network traffic or packet collisions and could at last force stations to disassociate from the network or get disassociated by access point (router) due to time out or signal loss.
User experience: Heavy fading signal strength, slow and sluggish wireless connection iTunes/Video stream drop, lousy data transfer speed, total connection loss or only time relating disturbances here and there.
Solutions:
Placement of transmitter. Not flat at the wall. Not in a corner, not on the floor, not behind a furniture, not near of other radio sources e.g. cordless phones. Not near of anything that can reflect radio beams. Best: as high as possible; e.g. Airport Extreme mount on ceiling. Maximum possible line of sight to all stations respectively corners of the home.
Placement of stations: see above and below.
Placement of yourself: If possible not between your Mac' antenna(s) and the transmitter.
Radio interferences: Check that the channel you use have at least a 5 channel gap to the two strongest wireless networks around. If possible use the recommended overlapping free channels for your country for best performance. On 2.4GHz networks -> for US-1,6,11 and for Europe 1,5,9,13. If possible swap to 5GHz 802.11n only and force the stations supporting this to use only 5GHz. Disable 802,11a/b/g wireless if possible. Place cordless phone stations as far away from the router (access point) as possible. Eventually disable all radio transmitting equipment in the house. If the wireless then work better, enable one at the time to see which is the disturbing one. Don't forget leaking microwave ovens. A running faulty microwave may drown your complete wireless network at once and your neighbors WiFi too.
#4 -> Mismatched settings on the network participants.
Description: Self describing.
Reasons: New equipment in the network, differences between home and office/work settings.
Solution: Check and change to match. Eventually establish a second location (profile) in System Settings on that.
Remember: Contrary to marketing and promotion, Networking NEVER was easy Plug&Play and at least for the next few years it wont.
#5 -> Problems with the 802.11b/g/n compatibility mode.
Modern WiFi bases pretend to integrate every protocol regardless of age or used hardware in the connected stations. Pretty good idea from the viewpoint of a marketing department. Unfortunately. it could cause major problems in real wireless networks because mixing stone age 802.11a, cable LAN and lightning fast 802.11n 5GHz in the same network is a big challenge. Any minor disturbance in such a constellation may lead to major trouble. Aside from the fact, that the slowest participant in a network dictate the pace, some router's and client's chipsets have problems with that "compatibility mode".
Solution: If ever possible try to force your network on one (fastest) protocol only. If you need 802.11g (iPhone, iPod touch) try to fix your infrastructure on 802.11g 2.4GHz and 802.11n 5GHz or 2.4GHz only with the loss of the possible 5GHz speed.
#6 -> Hardware fault's or buggy drivers / firmware
What's to say? Give a bug report to Apple, wait for a fix with the next update or hope that your system is still under warranty. Eventually roll back to previous OS version or firmware.
Addendum for Airport Extreme or Time Capsule users.
If possible deactivate the "Guest Network". It constantly switches between 2.4GHz and 5GHz band for a maximum of user convenience. Unfortunately this may cause trouble if other disturbances are also in the wireless.
That's for now....
Happy networking - Lupunus
