The Internet connection starts with the Internet Service Provider or ISP. This is the company that you pay at regular intervals to get your Internet connection. Popular ISPs include Comcast, ATT, Cox, Earthlink, Sonic, and Time Warner. The Internet signal comes into your home and connects with a wire to the modem. Usually, the ISP provides the modem either free of charge or on a rental basis. This is the extend of your ISP's involvement. After this, it is your responsibility to provide your own distribution of this Internet connection by means of routers and access points. Think of the router as a splitter that enables more than one computer to use the same Internet connection. The access points are boxes that relay the Internet signal with wifi signals so that end devices like smart phones and laptops can join the network and get to the Internet without being tethered to the router with a network cable.
A collection of routers and access points that make up your local network is a distribution system. There are different types of distribution systems that can be setup according to your needs and what is possible. Each has advantages and disadvantages. If cost is not an issue and it's possible to run network wires through the coverage areas, the best setup is mesh wired distribution system. You will understand why this is after you have read what is below.
The most basic is the wired distribution system. As seen in the graphic, all of the access points are connected to the router with its own dedicated network cable. The incoming Internet signal to all of the APs is via this wired connection. This enables the APs to relay a very good signal. If possible, this is how your local network should be setup to ensure that your wifi devices get the best Internet signal. If you have a bunch of wireless routers that you want to act as APs, you need to turn off the routing function in them or else you will have one mess of a network. In general, there should only be one device that acts as a router in a network.
A variation of the wired distribution system is one where each of the APs has two network jacks. Therefore as seen in the picture, AP1 gets its Internet signal from the router and then relays this signal to AP2 with a network cable. AP2 then does the same with AP3. This daisy chain of network connection looks different than the previous wired distribution system physically, but functionally, each AP still provides great Internet signal.
Sometimes it is not possible to run a network cable between each AP. Therefore the relay signal has to be over the air. When this is done, we have a wireless distribution system as seen in the graphic below. The dotted lines represent the wireless communication between the APs. You also see that AP1 only communicates with AP2 and not AP3. AP3 only communicates with AP2 and as such indirectly communicates with AP1. Setting up a WDS is a bit more complicated because each AP has to be programmed to only accept the incoming signal from its upsteam AP. Therefore, AP2 can only accept the signal from AP1, and AP 3 can only accept the signal from AP2. This means if AP2 is offline, AP3 will not get any Internet signal, resulting in computers in the range of AP3 not getting any Internet access. Moreover, the Internet speed is cut in half as the signal is relayed. This means any computers getting their Internet from AP2 only get half of the speed compared to if they get it from AP1. This also means any computers getting the Internet from AP3 get 1/4 the original speed coming out of the router. This is why WDS should only be setup no more than 5 APs. If AP6 is needed, it should get its incoming signal via a network cable either from the router or from one of the APs much closer to the router in this chain.
WDS has no redundancy in the participating APs. This means when one AP fails, the distribution system is broken. The offline AP has to be replaced or fixed before all the down the line APs can get the signal. In a mesh WDS network, all APs communicate with each other in a non-daisy chain way. When one AP goes down, another will take over its role as long as the replacement is within range of the source signal. In a sense, a mesh network can self heal. For a mesh network to be effective, you need to pepper APs in strategic locations to maximize overlapping signals. This is why a mesh WDS network is more robust, but it is also more expensive because you need to deploy more APs. There can also be a mesh network where all the APs are connected to the router with a network cable. When an AP is offline, the flow of the Internet signal is rerouted. For example, if AP2 is offline, AP1 will communicate with AP3 via their wireless connection. While the Internet connection is maintained, the computers connected to AP3 still have their Internet speed cut in half. This self healing only works if the signal from AP1 is strong enough to reach AP3. This is why in a mesh network, the APs are placed in strategic spots to maximize this rerouting when one or more APs fail. In a sense, the Internet itself is the largest mesh network of all networks. The Internet does not shut down when one or a few Internet routers fail.
Of course, you can mix and match these network setups. You can have a WDS at one part of the network and a mesh one at another part as long as the IP addressing scheme does not create any conflict, that is, as long as data knows where to flow to reach its destination, the mixed network would be fine. Basically,mesh is used at locations where there is a high demand for wireless access. The APs in such an area also have higher horse power to handle more simultaneous connections.
There are other variables to consider in addition to the topology. The processing power of the APs, the frequency they use, and how to handle the backhaul are just a few. In a WDS, usually the backhaul, the communications between the APs, are handled with the 5GHz frequency because of that frequency's higher throughput compared to the 2.4GHz. Distribution systems are complex networking schemes but with good understanding and good planning, they can be made to work even in the most demanding of situations like large coverage areas or high data usage demands.
If you like to play around with mesh wireless network without having to pay too much money, then Open-Mesh is the best solution. You can get an access point from them as little as $75. It used to sell an even cheaper model, so you can probably find these on some retailer who still has this cheaper model in stock. Unfortunately, as of this writing, these APs, even the high end models, do not support features like scheduling and auto-RF. Scheduling is when you program the APs to turn on and off their signal at a certain time of the day or day of the week. Auto-RF lets you choose what channel to transmit or the APs choose it for you based on the channel that has the least interference. Currently, these Open-Mesh APs are stuck at channel 5 for the 2.4GHz and 144 for the 5GHz. Open-mesh tech support told me that these two features are in the works and should be available by the end of the year. It would be hard press for anyone to say that these 2 features are not important. They are important to have a cleaner signal and stronger security.
