I have a customer with d-link AP's in four separate co-located buildings (hotel rooms). The Building are all linked (wired) with Ethernet.
The d-link AP's are not working so well. So, I was going to suggest he replace them with commercial AP's. Maybe even double the AP coverage in each building too. (And, you have to have commercial AP's for that.)
Does anyone have any feed back on the Allied Telesys AT-WA7400?
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Anyone have any feedback on them? Any other units you like better?
One AP per hotel building is not enough. You'll probably need at least one AP per floor (depending on type of construction).
I'm suprised they work at all. How many walls are you going through between the AP and the guest's laptop? If it's more than one, you're going to have problems no matter what hardware you select.
Good idea, especially since this is a commerical operation.
Baloney. I can put a generic junk access point (or wireless router acting as an access point), next to the most exotic commercial access point I can find (Sonicwall), and as long as the TX power and antennas are the same, the range will be very close. In fact, I've done exactly that to justify using cheapo hardware to customer that insisted on blowing his budget on acronyms and buzzwords. You may get a few more feet of range or penetration using commercial quality hardware, but no way are you going to get double.
No experience with this unit. Looking at the specs, it looks like a dual radio 802.11a and 802.11g access point, with impressive management and monitoring features. Lots of flexibility and control. However, nothing in the specs that I can see claims any better range or penetration. Such a box will certainly make it easier to manage and troubleshoot, but that's not what you're looking for.
I don't like to make specific recommendations on hardware unless I know how it's going to be used, the network topology, expected traffic, number of users, building layout, available expertise, and of course the size of the budget.
For other vendors, look at: Cisco, 3com, Proxim and Sonicwall. Also look at "wireless switch" offerings. See:
Also, please read the Intel Wireless Hotspot Guide that has disappeared from Intel's web pile and that I've illegally archived (don't tell Intel) at:
There's a huge amount of good info in there on setting up a WLAN.
I am going to walk the premises next Tuesday. Go over their blue prints too.
Question: do you know of a piece of test equipment I can use to test signal strength of the current d-link's in the problem areas that the customer has tagged for me? (I guess I could make a crude measurement with a laptop.)
Hmmmm. I wonder if all the d-links in the various (four) buildings are using the same channels.
The customer may also just need to put UPS'es on all his AP's: sometimes it is just that easy.
No. I have scripts that will crash literally anything. If it doesn't crash the AP, it will do the same to the router. For example, starting a file sharing program with hundreds of IP ports (streams) active, that will run the AP and router out of buffer space. Many of the WEP cracking tools are also inadvertant AP crashers. If your system doesn't have any QoS or Bandwidth Management, and you have an asymmetrical DSL or cable connection, then any user that is uploading heavily, will saturate the upstream bandwidth. That will cause the ACK's from downloads to get lost, making downloading slow or impossible. (Hint: You need Qos).
Incidentally, I have some of my wireless router set to reboot nightly to avoid such problems. It seems to work and I haven't had any complaints since I started doing that. Perhaps a $10 digital lamp timer might be a better fix?
I am going to do the walk and blue print next Tuesday. I know there are four buildings (~200 rooms) and that a couple of them are multistory. I am not sure if it is a wood or steel (struts, etc.) either.
The AT-WA7400 is only $300.00. I did not think it would blow the bank.
I was looking for something that did not get a lot of complaints from the users and did not jam all the time. Basically, I was looking at spending a few more dollars to more reliability.
Thank you!
I am in process of reading it. It is a bit vague in spots. But, I don't think it was meant for a radio design engineer like myself. More of a non-techie user. Their convention hall example applies the closest, but they are not tell me things like max users per AP, signal strength to avoid swamping other AP's, etc., etc.. I guess it is time to start reading the AP's spec's.
On Mon, 11 Feb 2008 15:51:32 -0800, Jeff Liebermann wrote in :
[cough cough] I doubt that you can crash a Cisco Aironet access point with a script, and if the router is a serious Cisco as well, then you're going to have your work cut out for you there too.
On Tue, 12 Feb 2008 00:06:29 GMT, ToddAndMargo wrote in :
The complaints tend to be associated with low-end routers that go into never never land for no good reason (e.g., too many filesharing connections. The best solution IMHO is to use access points, not routers, and back them up with a serious commercial (e.g., Cisco) wired router.
Well, maybe you're right. I've never tried it with a Cisco AP. I probably should have said "...will crash most low end access points and wireless routers". Also, it's more than just scripts, but I don't wanna leak any details.
However, I've got an AIR-AP1231G-A-K9 on order for a customer which I might try next week, time permitting. About $250 refurbished. I've also read rumors of various high end outdoor mesh and non-mesh access points getting crashed by probes, scans, ARP floods, MAC generators, and exploits. Some routers and AP's have watchdog timers, which helps recover from such attacks.
Look for aluminum foil backed insulation in the walls and ceilings. That blocks wireless (and cellular) traffic almost completely.
One of the tricks I use is to "illuminate" the outside wall of a hotel or motel from a nearby building or pole. Penetration through the glass windows are MUCH better than through inside walls. This requires directional antennas with a very controlled pattern. Look into sector antennas or if you wanna build your own, AMOS or Franklin antennas. For example:
Good price for such a unit. I just bought a used Cisco AIR-AP1231G-A-K9 for about $250 (used) with the PoE adapters. I know that it's not fair comparing new and used prices, but I tend to buy what little Cisco I use on the used (refurbished) market. There are 4 more used 1231 AP's on eBay for about the same price. Plan on having a spare handy. I also suspect that you'll need more than 4 radios to cover 200 rooms in multiple buildings and floors.
Once you get away from commodity hardware (Linksys, Dlink, Belkin, Netgear), the overall quality and reliability improves. However, since the (used) price of an access point is about equal to the cost of a service call, methinks you'll do better to get something that can be remotely managed (and remotely rebooted). Also, my coffee shop routers increased dramatically in reliability since I started rebooting them nightly. Same with running some of them off gel cell batteries and chargers to isolate them from flaky AC power.
It's also a bit old. It doesn't cover much of today's high fashion wireless technology, such as MIMO, roaming, QoS, and MultiMedia. However, it covers the basics, such as wall penetration, channel layout, and system sizing.
If you want technical, I can bury you in heavy reading. The IEEE Communications Society (ComSoc) procedings are great, but very very very dense. Are you sure you want it more technical?
Max users per AP is limited by the MAC address (bridging) table. Most small routers can barely handle a few users. See chart at:
Some of the bottom of the line models are so bad, that they crash when they fill up the MAC address table (because they don't expire entries). The ARP table (MAC address to IP address) table also tends to fill and crash when full. Never mind running out of DHCP IP leases. Buffers is also a problem. Each user will open some number of IP sockets. Each socket requires a buffer. If the AP has too many users, or too many open sockets, it will run out of buffer space. How it handles running out of buffer RAM varies by implementation. Small AP's and routers are made for, ummm... small number of users.
With better AP's and wireless routers, you get considerable relief with lots more working RAM and faster processors. The table and buffer problems may still be there, but the larger memory size means that you see them less frequently. You'll probably find the connection limit in the specs. As I vaguely recall, the Cisco 1241 will do 2000 connections. Many university systems regularly handle well over 100 connections per AP, although many of these connections are idle and not moving traffic.
Incidentally, you might find:
of interest. That's the local university wireless network. If you click on a building it will show the wireless coverage in the building. It does NOT show the location of the wireless access points, or their number, but it will give you a very rough idea of how much area a single access point is expected to cover. There are about
The 2nd thing to go is the memory. I forgot what was first.
See:
Q. How many clients can associate to the AP? A. The AP has the physical capacity to handle 2048 MAC addresses. However, because the AP is a shared medium and acts as a wireless hub, the performance of each user decreases as the number of users increases on an individual AP. Ideally, not more than 24 clients should associate with the AP because the throughput of the AP is reduced with each client that associates to the AP.
So overall do you think it is more cost-effective to use low-end APs with external watchdog hardware? This has been my solution so far (snmp controlled power supply).
How many entries do you suppose are involved in that case?
Most of these products have more RAM than high-end unix boxes of ten years prior, which could easily manage hundreds of arp entries, and why would an AP need an arp table for the wireless interface (see below)?
On an access point?
What sockets are opened for users on access points?
I just need to understand what functionality is involved here; shouldn't an AP just do layer 2 bridging? With a smidgen of instrumentation that might require IP? This presumes that all security is handled offboard and the AP only bridges.
Depending on your answers, I would ask why more folks don't build their own APs on standard hardware. I have always assumed that reliable but low-cost APs are sufficient for the basic bridging functions expected of an AP and should be able to service as many connections as the PHY and data paths permit.
On Mon, 11 Feb 2008 21:32:53 -0600, msg wrote in :
Layer 2 bridging uses a database to keep track of MAC addresses. See . To quote Jeff: "Max users per AP is limited by the MAC address (bridging) table." He then segued into talking about routers. Ignore that for bridging.
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