Seamless Roaming

TIntruder · 02-23-2004

Has anybody set up multiple APs in a home/building so that seamless roaming between APs is supported in XP?

I have done this previously with Cabletron/Enterasys products, but it appears that this feature is now an additional product requiring license and unlock code on each AP.

I don't need the sophistication of the Enterasys RoamAbouts (multiprotocol, multiple encryption/authentication, SNMP etc.) and would like to do this with inexpensive APs such as Linksys, DLink, Netgear.

Potentially using 4 APs, Upstairs SW, Upstairs NE, Downstairs NW, Downstairs SE, how would you configure this?

I do not want to have to join each network in-turn, nor do I want to have DHCP on each, but get it from a central router.

Any ideas?

Thorn · 02-23-2004

The APs all have to be on a common subnet, have a common SSID, and have SSID broadcast enabled. The laptops should then roam to the strongest signal. The central router needs to be on the same subnet, too.

gmiller220 · 02-24-2004

In your case I WOULD run network cable to each of the access points. Having them as repeaters will reduce your total bandwith and I'm guessing by a whole bunch since the area you are trying to cover isn't all that large for four aps.

In short: run a backbone

Twisted · 02-24-2004

As far as I know roaming is not an issue with windows XP, but unless you have a huge house the problem my be that your wireless setup may be fighting it's self.

Let me explain;

With the exception of the Orinoco card/AP, I have yet to see any setting for Distance Between APs, which handles when the wireless card starts roaming. Without this the card will attempt to stay connected to an AP for as long as possible, until the signal drops, then it starts looking for another AP.

One way around this in a heavy AP density, is to set your minimum level of service to say 5Mb, or 11Mb forcing the client to search for a new AP sooner.

Orinoco ccrds and APs rock for this, besides the level of service setting, the AP density has High Medium and Low.

Most APs have some type of feature to allow for fast roaming, which involves one AP keeping track of when a client moves between APs and I believe handling ARP updates to the switch.

It is preferable to have all your APs on the same switch.

TIntruder · 02-24-2004

The Orinoco features are also present in the original Cabletron/Enterasys cards.

On the RoamAbout 2000 AP, this was simple to set up. All you did was configure the APs identically and plug them in where you wanted (they support PoE too, which is helpful for placement) and voila! seamless roaming in an office.

You could walk around between AP cells and not drop the connection OR BE BOTHERED WITH THE DAMN XP POPUP about multiple APs available.

I'm not quite sure what "gmiller" is getting at, as APs will obviously be attached to the network.
Perhaps you mean to use some of the new/fancy "repeater/extender" units?

I would consider that except accessories like repeaters, bridges, print servers, video servers are all at full price, often over $100 while 802.11b equipment is DIRT CHEAP with cards as low as $10 and routers for $20. Even 802.11g is as low as $30 for the card and $50 for the router. And the AP/Routers have far more capability than the accessory products.

The weak point of XP with respect to roaming is the tendency for it to go "fishing" for alternate APs whenever your primary signal is weak.
For instance, in one corner of my house, the signal is "fair" or "good" but often I get the message about "One or More Wireless NEtworks are Available" because XP sees my neighbor's AP which has an even weaker signal. Then I have to choose my own network in order to continue.

Basically, I want ROAMING to work without ANY interaction on my desktop.

So for instance, if I had 4 WAP11 or similar:

Same channel
Same SSID
Same WEP KEY
No DHCP on AP...DHCP on Router or server

This ought to work?

edweird · 02-24-2004

There's actually a 802. something spec that applies to roaming between AP's.

When your client thinks the signal from the AP it's currently associated with is too weak, it then channel scans for the same SSID on the other channels. While this is happening, the AP it was associated with buffers any data for that client. If the client finds a stronger signal on the same SSID, but different AP, it will associate with it. The new AP uses the 802. something spec to send a broadcast on that network segment telling any other AP's that it now has the client(this may have to do with the wireless NIC's MAC). The original AP sees this broadcast and forwards the data it was bufferring for the client to the newly associated AP, and it goes on to the client. Any network gear in the middle has to support the protocol and not block it.

There were some issues with a client using Orinoco stuff which supported this, but a file transfer that was running would bomb out when roaming. Other stuff that was less particular and could tolerate a retry on the data wouldn't drop when roaming. Turned out it was the Cisco switches at the customer site needed the option to support/pass this AP roaming protocol turned on. Changes were made in the switches and roaming worked well at all times.

Using older AP's (like the Compaq AP400) which didn't support this roaming feature would also create a similar situation. The solution required AP upgrades in the area where most roaming was occuring.

Ed

02-23-2004	#1 (permalink)
TIntruder Registered Member Join Date: May 2002 Location: Oregon Posts: 163	Seamless Roaming Has anybody set up multiple APs in a home/building so that seamless roaming between APs is supported in XP? I have done this previously with Cabletron/Enterasys products, but it appears that this feature is now an additional product requiring license and unlock code on each AP. I don't need the sophistication of the Enterasys RoamAbouts (multiprotocol, multiple encryption/authentication, SNMP etc.) and would like to do this with inexpensive APs such as Linksys, DLink, Netgear. Potentially using 4 APs, Upstairs SW, Upstairs NE, Downstairs NW, Downstairs SE, how would you configure this? I do not want to have to join each network in-turn, nor do I want to have DHCP on each, but get it from a central router. Any ideas?

02-23-2004	#2 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,430	The APs all have to be on a common subnet, have a common SSID, and have SSID broadcast enabled. The laptops should then roam to the strongest signal. The central router needs to be on the same subnet, too. __________________ Thorn "Read Altas Shrugged. Compare it to today. Repeat as necessary"

02-24-2004	#3 (permalink)
gmiller220 People are dumb Join Date: Aug 2002 Posts: 466	In your case I WOULD run network cable to each of the access points. Having them as repeaters will reduce your total bandwith and I'm guessing by a whole bunch since the area you are trying to cover isn't all that large for four aps. In short: run a backbone __________________ "Got Google???" It does a Wifi Good

02-24-2004	#6 (permalink)
edweird Registered Member Join Date: Apr 2002 Posts: 5	There's actually a 802. something spec that applies to roaming between AP's. When your client thinks the signal from the AP it's currently associated with is too weak, it then channel scans for the same SSID on the other channels. While this is happening, the AP it was associated with buffers any data for that client. If the client finds a stronger signal on the same SSID, but different AP, it will associate with it. The new AP uses the 802. something spec to send a broadcast on that network segment telling any other AP's that it now has the client(this may have to do with the wireless NIC's MAC). The original AP sees this broadcast and forwards the data it was bufferring for the client to the newly associated AP, and it goes on to the client. Any network gear in the middle has to support the protocol and not block it. There were some issues with a client using Orinoco stuff which supported this, but a file transfer that was running would bomb out when roaming. Other stuff that was less particular and could tolerate a retry on the data wouldn't drop when roaming. Turned out it was the Cisco switches at the customer site needed the option to support/pass this AP roaming protocol turned on. Changes were made in the switches and roaming worked well at all times. Using older AP's (like the Compaq AP400) which didn't support this roaming feature would also create a similar situation. The solution required AP upgrades in the area where most roaming was occuring. Ed Last edited by edweird : 02-24-2004 at 02:49 PM.

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02-24-2004	#4 (permalink)
Twisted Registered Member Join Date: Dec 2003 Posts: 185	As far as I know roaming is not an issue with windows XP, but unless you have a huge house the problem my be that your wireless setup may be fighting it's self. Let me explain; With the exception of the Orinoco card/AP, I have yet to see any setting for Distance Between APs, which handles when the wireless card starts roaming. Without this the card will attempt to stay connected to an AP for as long as possible, until the signal drops, then it starts looking for another AP. One way around this in a heavy AP density, is to set your minimum level of service to say 5Mb, or 11Mb forcing the client to search for a new AP sooner. Orinoco ccrds and APs rock for this, besides the level of service setting, the AP density has High Medium and Low. Most APs have some type of feature to allow for fast roaming, which involves one AP keeping track of when a client moves between APs and I believe handling ARP updates to the switch. It is preferable to have all your APs on the same switch.

02-24-2004	#5 (permalink)
TIntruder Registered Member Join Date: May 2002 Location: Oregon Posts: 163	The Orinoco features are also present in the original Cabletron/Enterasys cards. On the RoamAbout 2000 AP, this was simple to set up. All you did was configure the APs identically and plug them in where you wanted (they support PoE too, which is helpful for placement) and voila! seamless roaming in an office. You could walk around between AP cells and not drop the connection OR BE BOTHERED WITH THE DAMN XP POPUP about multiple APs available. I'm not quite sure what "gmiller" is getting at, as APs will obviously be attached to the network. Perhaps you mean to use some of the new/fancy "repeater/extender" units? I would consider that except accessories like repeaters, bridges, print servers, video servers are all at full price, often over $100 while 802.11b equipment is DIRT CHEAP with cards as low as $10 and routers for $20. Even 802.11g is as low as $30 for the card and $50 for the router. And the AP/Routers have far more capability than the accessory products. The weak point of XP with respect to roaming is the tendency for it to go "fishing" for alternate APs whenever your primary signal is weak. For instance, in one corner of my house, the signal is "fair" or "good" but often I get the message about "One or More Wireless NEtworks are Available" because XP sees my neighbor's AP which has an even weaker signal. Then I have to choose my own network in order to continue. Basically, I want ROAMING to work without ANY interaction on my desktop. So for instance, if I had 4 WAP11 or similar: Same channel Same SSID Same WEP KEY No DHCP on AP...DHCP on Router or server This ought to work?