I've answered the questions in-line below. Anyone reading this, the original header from Lee Badman is removed for readability (it appears at on the original email at the end):
As 11ac looms on the horizon and our AP counts have gone from 4 to 50 to 600 to 3500, I think it's natural to think "is there a better way than changing out 3,500 of these things"... and so I ponder simple basics like: - What would 3,500 APs reduce to for arrays? In general, you'll get a ratio of 2.5:1 array:access point. The larger the number of LARGE OPEN SPACES the higher that ratio will be. Conversely, since Xirrus' smallest "array" is a two-radio unit, if you have areas where a single radio is needed, you have to go with the dual. Note that the larger units support an external antenna, while the smaller (2 radio) units do not. We have used this for outside coverage (ie use 3 radios for inside coverage, while "stealing" the 4th radio for outside, using an external antenna). - What would a building with say 125 APs typically reduce to with arrays? A building with 50? A building with 3? So, generalizing again, you'll need about 40ish arrays (XR4) to cover where you used to have 125 AP's, 15-20 arrays to replace 50 AP's and 1 or 2 arrays for the 3. This is a very big generalization. Physical properties are physical properties. The Xirrus antennas are directional, but that won't always equate to more powerful. If you couldn't get a single AP to go through a wall, chances are the Xirrus won't either. However, if you need 4 or 5 AP's to cover a relatively unobstructed area, a single Xirrus 4 will do. - How much existing AP wiring might happen to be in the right place to support arrays? We had to rerun about 30% of our cables and move another 30%. Again, this is very building/construction specific. We did not have to rerun everything. This assumes 5e or better cabling though. We did rerun any Cat5's, whether in the right spot originally or not. One of the advantages of the Xirrus model is the leveraging of your wired infrastructure better (an array/AP still has to connect to your wired network someplace!). With the single AP model (802.11n) you can either connect the AP at 100Mbs and oversubscribe the line, or connect at 1Gbs and undersubscribe it. If you have 4 AP's, that's 4 x 1Gbs ports you are chewing up in your closet. With an array, you connect the array to your switch at 1Gbs (XN4) for the 4 x 300Mbs radios to share. That's 1 port on your switch. - Would the clients notice any difference between a traditional AP deployment and an array-based WLAN if both properly designed? That depends on your authentication model. If you go with a flat network, it would be seamless. If you utilize Dynamic VLAN'ing, you'll need to have the users in RADIUS (802.1x). That would require client configurations, but it would allow you to break up your wireless network into better broadcast domains. If your SSID's are local rather than global to your network, DVLAN's aren't needed. - With 3,500 APs, a fleet of controllers, and 16K plus clients, an effective management strategy is as important as any marketing foo foo about AP performance (to me). How good, buggy, and complete has Xirrus' management platform been? Ok, XMS is pretty good. Remember that the Xirrus model is distributed, not central so there is no controller. On the face of it, it seems like a management nightmare having to deal with all units individually. Conversely, the central model means all traffic has to go back to the controller. The reality is, most traffic goes back defacto to a common point anyway, so the "controllers are bad" argument doesn't hold with me. But managing the arrays isn't an issue. You can push full or delta changes out to all or subsets of arrays via XMS. If you aren't considering XMS, I wouldn't go with Xirrus. With XMS, there is no advantage/disadvantage of their model over, say Aruba. - What has been extremely satisfying about Xirrus beyond reduced AP locations? The value of reducing the number of devices goes w/o saying .. fewer devices to maintain; fewer Ethernet uplink ports chewed up; less cabling. The Xirrus arrays do use more juice (I haven't started using the 2-radio units yet, so I don't know if they are 802.11af standard or not, but the XR4's require are larger PoE brick or the multi-unit. You won't be able to use your switches' PoE). - What are the warts? The company is a victim of its own success. Its growth does make procurement slow (this could just be because, as an entity of the Commonwealth, we are limited to whom I may purchase from) and on-site support challenging to schedule (they have turned over a few SE's. Every one of them have been excellent though, but they don't have enough so getting their time sometimes means waiting two weeks). OTHER One thing to be aware of - Xirrus EXCELS at high-capacity wireless networking. If you have large spaces that needed many AP's for proper coverage and capacity, you can't do any better than Xirrus. However, you need to decide if your goal is capacity, coverage or a combination. And, as with any wireless, you need to decide if you are going to support 2.4GHz regardless of an 11ac implementation. I would design for 5GHz though and turn down the juice for the 2.4GHz if you use it. Feel free to contact me directly or here, if you have any other questions. I'll be at the Annual Conference next month too, if you are attending. -Brian Please- no calls from Xirrus. Or any other vendor. Or integrator. I already have corporate contacts with most WLAN companies and am not shopping at this point, only gathering data to satisfy my own curiosity. Thanks- Lee Lee H. Badman Wireless/Network Engineer, ITS Adjunct Instructor, iSchool Syracuse University 315.443.3003 ________________________________________ From: The EDUCAUSE Wireless Issues Constituent Group Listserv [[email protected]] on behalf of Brian Helman [[email protected]] Sent: Wednesday, October 03, 2012 9:13 AM To: [email protected]<mailto:[email protected]> Subject: Re: [WIRELESS-LAN] Xirrus- anyone ever made the switch? Lee, we moved to 100% Xirrus a few years ago. I'd be happy to discuss. I'll send a more detailed reply to the group later (in a meeting now). If you have any other specific questions, feel free to add them and I'll answer as best I can when I'm back at my desk. FYI, we have about 300 arrays and will be adding another ~50 in the coming year. Thanks, Brian ________________________________________ From: The EDUCAUSE Wireless Issues Constituent Group Listserv [[email protected]] on behalf of Lee H Badman [[email protected]] Sent: Wednesday, October 03, 2012 8:51 AM To: [email protected]<mailto:[email protected]> Subject: [WIRELESS-LAN] Xirrus- anyone ever made the switch? Am wondering if anyone with hundreds or thousands of APs on this list has ever ditched it all and moved to Xirrus? Would like to hear how it went and is going for you either on list or off. Thanks- Lee Lee H. Badman Network Architect/Wireless TME Information Technology and Services (ITS) Syracuse University 315 443-3003 ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
