Surveying Mess....uh, Mesh.By CWNP On 07/14/2008 - 5 Comments
Site surveying has finally standardized. The process is well-understood among industry professionals - though not always implemented properly. Just when we thought we had it whipped, we get a curve ball: mesh. Have you checked out systems from vendors like Ruckus, Motorola, Meru, Cisco, and Aruba that have the option to have mesh APs connecting back to root APs? This is a seriously nice feature, but have you thought about doing a manual survey for such an implementation? Let's explore that, shall we?
Let's call him Bill. Bill is cranking along, measuring RSSI values - perhaps doing active and/or passive surveys using leading-edge site survey tools from companies like AirMagnet and Ekahau. All is well. Then, the supervisor calls and says, "Hey Bill, don't forget that not only do the clients have to talk to the APs at a level good enough for voice, but the APs have to talk to each other - sometimes over multiple hops - good enough for voice as well. Also, the customer wants some redundancy in case one of the APs dies, so makes sure each AP can communicate with at least 2 other APs with voice-grade connectivity." Bill just looks at the ground, wondering if this is even possible. This "one-day" site survey could now take a week. Place, test, move, retest, move, retest, move again. Horrible.
How is Bill supposed to make sure the connectivity level between the APs is voice-grade? Certainly not with traditional survey tools. Now we have to bring a controller or some piece of management software into the mix. Once the APs are associated and configured, is the portal AP (wired) seeing the mesh APs (wireless)? How many mesh APs can be seen and at what RSSI values? At what connectivity rates are each of the mesh APs connected to each other and each portal AP? If a client transmits a voice packet to a mesh AP and it has to hop twice to get to the portal AP, is the latency too high? What if the data path changes on the fly due to unforseen changes in the RF environment? Holy smokes batman! How are we supposed to survey that?
I'm thinking that there will be two schools of thought on this topic:
1) Implement mesh APs in hard-to-wire areas, as coverage-gap-fillers (to save money on wiring), and for some minimal level of redundancy. This will mean that you do a traditional survey, then hose it up "somewhat" by throwing extra APs here and there as needed for whatever purpose suits your fancy.
2) Design the network from the ground up with a mesh edge in mind. This will be done without doing a manual survey up-front, and the manual survey will be done as a verification-of-coverage-and-capacity tool only. Cisco's stance on survey's is that they are not for design, but rather for verification of a design. I think this line of thinking will play nicely with this type of implementation.
I'd love to hear some feedback on what you guys think will happen to site surveying due to this new technology at the edge.