jerryhatt
asked on
Cisco Access points - Speed expectations
Hi,
We have a site that uses 6 Cisco aironet 1200 access points, 4 of which are root points connected to ethernet and 2 are repeaters. Radio seems to be 802.11 G and A.
We are having issues where when a few computers are connected and browsing that everything seems to grind to a halt. This is greatly exaggerated if the computers are in the same room connecting to the same AP. Sometimes a reboot makes things better, sometimes not.
We have performed internal network speed tests at each access point and the average is around 20Mbps up and down with the repeaters giving slower performance at about 6-10Mbps.
Is it possible that these older access points can be becoming saturated with a few modern PCs streaming internet and transferring files over the network (such as a Mac backup using time machine)?
Also, when moving between access points and using skype phone over the wifi it often cuts off. Is this normal when switching APs?
Thanks.
We have a site that uses 6 Cisco aironet 1200 access points, 4 of which are root points connected to ethernet and 2 are repeaters. Radio seems to be 802.11 G and A.
We are having issues where when a few computers are connected and browsing that everything seems to grind to a halt. This is greatly exaggerated if the computers are in the same room connecting to the same AP. Sometimes a reboot makes things better, sometimes not.
We have performed internal network speed tests at each access point and the average is around 20Mbps up and down with the repeaters giving slower performance at about 6-10Mbps.
Is it possible that these older access points can be becoming saturated with a few modern PCs streaming internet and transferring files over the network (such as a Mac backup using time machine)?
Also, when moving between access points and using skype phone over the wifi it often cuts off. Is this normal when switching APs?
Thanks.
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If all of your devices are running at those speeds at the same time you are probably fine to leave them on. It's when you get a mix of G speeds (above 11mbps) and B speeds (below 11mbps) that the protection method is used. Idealy, having your clients transfer at a higher rate is better because of how wireless technology works, your ap can only hear 1 message at a time. Using faster rates means less time to communicate that message and leave others waiting. Sometimes you may not be able to achieve these higher speeds if other problems exist in your wireless network. The client device chooses what speed to shift up or down to based on received signal strength(RSSI), and error rate.
Doing a site survey would probably be best to make sure your channel usage pattern and wireless cell overlap is just right. such as make sure 2 aps on channel 1 arent right next to each other, spread them out. only use channels 1,6 and 11 since these dont interfere with each other but make sure 2 APs on the same channel are not right next to each other or you'll get interference and seriously degrade performance.
Just kinda rambling here but hopefully some of this info helps.
Doing a site survey would probably be best to make sure your channel usage pattern and wireless cell overlap is just right. such as make sure 2 aps on channel 1 arent right next to each other, spread them out. only use channels 1,6 and 11 since these dont interfere with each other but make sure 2 APs on the same channel are not right next to each other or you'll get interference and seriously degrade performance.
Just kinda rambling here but hopefully some of this info helps.
Different send/receive rates:
basic rate = 1 mbps. This is used for broadcast and beacon traffic. Should not be any higher.
Supported rates = 1 - 54Mbps is how low you'll go on send speed. You can set this to higher speed (24Mbps) if you have APs that interferece, together with lower output power on AP's. If you set this to 24Mbps, then clients connecting at 12 Mbps (du to low signal strength) will be disconnected
802.11b in 802.11a/g networks: it's true trat 802.11b clients (and even older legacy 802.11 clients) will force other clients into protected mode, as they don't use the modulation technology. However, most AP's nowadays will now use a more fair airtime algorithm, that will give 802.11a/g/n clients more air time than 802.11b - thus not influencing speed on 802.11a/g clients
When looking at roaming:
- you should, for a corporate network never use anything other than 802.1x. With 802.1x you authenticate to a 3rd party user database, like Microsoft AD via Radius or Cisco TACACS. The clue is that the wireless station will authenticate to the next AP before roaming, thus bbeing able to continue real time traffic. But then again, you need to have some degree of overlap between AP. overlap does not mean same channel (!!) but that AP's are visible.
You can also try to force clients to 802.11a (5Ghz) band rather than 802.11b/g (2,4Ghz) since it's far less interference in 5Ghz.
Even though a client is 5Ghz capable, it will connect with 2,4 Ghz as preferred band. The technique of tring to get cleint to connect on 5Ghz rather than 2,4 Ghz is controlled in AP's
basic rate = 1 mbps. This is used for broadcast and beacon traffic. Should not be any higher.
Supported rates = 1 - 54Mbps is how low you'll go on send speed. You can set this to higher speed (24Mbps) if you have APs that interferece, together with lower output power on AP's. If you set this to 24Mbps, then clients connecting at 12 Mbps (du to low signal strength) will be disconnected
802.11b in 802.11a/g networks: it's true trat 802.11b clients (and even older legacy 802.11 clients) will force other clients into protected mode, as they don't use the modulation technology. However, most AP's nowadays will now use a more fair airtime algorithm, that will give 802.11a/g/n clients more air time than 802.11b - thus not influencing speed on 802.11a/g clients
When looking at roaming:
- you should, for a corporate network never use anything other than 802.1x. With 802.1x you authenticate to a 3rd party user database, like Microsoft AD via Radius or Cisco TACACS. The clue is that the wireless station will authenticate to the next AP before roaming, thus bbeing able to continue real time traffic. But then again, you need to have some degree of overlap between AP. overlap does not mean same channel (!!) but that AP's are visible.
You can also try to force clients to 802.11a (5Ghz) band rather than 802.11b/g (2,4Ghz) since it's far less interference in 5Ghz.
Even though a client is 5Ghz capable, it will connect with 2,4 Ghz as preferred band. The technique of tring to get cleint to connect on 5Ghz rather than 2,4 Ghz is controlled in AP's
I'd recommended not using 802.1x on the network if it is segmented (voice on its own vlan) to be vo-wifi only (not corporate data network). Authentication takes longer with 802.1x than WPA personal because you are authenticating to an external database rather than locally on the AP. This can cause calls to drop.
@Zulazen: no no --- not necessarily. you can authenticate with the next AP before switching over to it, thus you're already authenticated when roaming to that AP.
802.11r - http://www.wi-fiplanet.com/voip/article.php/3776351/Introducing-IEEE-80211r.htm
802.11r - http://www.wi-fiplanet.com/voip/article.php/3776351/Introducing-IEEE-80211r.htm
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Another question I have is that there are options for the different speed rates and all of them seem to be set to 1mbps as required (basic) and the other speeds are all set to enabled.
They only use new laptops, macs and iphone/blackberries so I do not think that they jhave and B devices, should I switch off those speeds anyway?
Thanks.