Wireless Networking    

Wireless computer networks have been around for a long time. Most have been based on radio wave technology, but some have used optical or infrared beams instead.
Hawaiian Islands
One of the earliest successful implementations, in place as early as 1970, was the "Aloha" network at the University of Hawaii. It used conventional radio-frequency transmitters and receivers to span distances between cities and Islands in Hawaii.

Of course, in order for computers to participate in any network, they must all agree on the precise meaning of the signals they exchange. Every detail of the radio or infrared beams that they exchange must be defined so that they can be translated into meaningful, unambiguous bits and bytes.

When groups of people get together to seek agreement on these details, they produce "Protocol Documents" that serve as guidelines for others. The most successful protocols are generally sponsored by influential trade associations or governments.

Since the early days of the "Aloha" network, the Wireless Networking industry has seen the rise of several protocols that have become popular, and as the science of computer networking has evolved, the most important and popular protocols have coalesced into a rich group of technologies that can interoperate with one another to varying degrees. These are generally known as the "WiFi" protocols.

WiFi Networks

The earliest "WiFi" networks used a protocol from the Institute of Electrical and Electronic Engineers (IEEE). The committee responsible for that work named it "Protocol 802.11" back in 1997, but it didn't become popular until 1999, when two newer, enhanced versions were created. These were named "802.11A" and "802.11B".

The "B" variant began to dominate, but as vendors began developing and selling related equipment, they found that consumers were reluctant to buy their devices until they were assured of compatibility across brands. Nobody wanted to buy network equipment without assurance that it would be supported into the future and that it would continue to work as other vendors entered the marketplace. An industry alliance was formed to evaluate and publish compatibility. The group felt that the old protocol names were too complicated, so they chose the nickname "WiFi", and they began to publish lists of equipment that could interoperate.

WiFi Router As technology has advanced, newer versions of the 802.11 protocol family have been published. Today's networks, based on Protocols 802.11g and 802.11n, can exchange information much faster and farther than the originals. The committees responsible for these new protocols made sure that they included provisions for communicating with older equipment by "falling back" to older, slower technologies when they encountered them on the same network. Thus the new 802.11n protocol knows how to slow down and communicate with older 802.11g equipment, and 802.11g equipment knows how, in turn, to slow down and communicate with 802.11b equipment.

Today, the "WiFi" logo enjoys a very good reputation. When present on a piece of network equipment, it indicates that the vendor has paid the WiFi Alliance to test and certify that the equipment works as advertised, and that it can be used with other WiFi equipment from other vendors. As a general rule today, consumers trust that any network equipment advertising "WiFi" compatibility can be purchased, installed, configured, and used with confidence in combination with other WiFi equipment, regardless of the underlying protocol details.

However, today's consumers will find 802.11b, 802.11g, and 802.11n equipment for sale on the same store shelves. Some vendors don't pay for WiFi certification, so the WiFi logo may not be present, even on good equipment that will interoperate according to the standards. Informed consumers can make better purchase decisions if they are aware of these basic protocol details.

802.11a: This older protocol isn't used very much, and there is little guarantee that newer equipment will interoperate with it. It also suffers from limited range (about 50 feet indoors). Some businesses actually LIKE that because it can contribute to privacy and eliminate certain problems related to radio interference, but there is little reason for today's consumers to purchase this equipment.

802.11b: This older, slower, limited-range protocol remains very popular, and it's the only popular wireless protocol that is compatible with virtually everything. Speeds range between 1 and 11 million bits per second, over distances of about 100 feet indoors or 300 feet line-of-site. You won't find very much new network equipment that's advertised as "802.11b" nowadays, but all of the newer items know how to slow down to use it. If you have an old 802.11b laptop computer or network adapter, you'll be able to use it at all public wireless "hotspots" whenever you are within about 100 feet of the hotspot antenna. Although 802.11 speed is too slow for High Definition local video between your TV and adjacent PC, it's fast enough to fully exploit your Internet connection. If you are just surfing the web or exchanging email, you'll be fine with this. Skype telephony, and even YouTube and Hulu video can be acceptable if you don't frustrate easily.

802.11g: This is similar to 802.11b, but it's 4 or 5 times as fast, delivering up to 54 million bits per second over the same distances. This is the dominant WiFi protocol at the time of this writing in 2009, and equipment prices have fallen dramatically. With a carefully located central antenna, a typical 802.11g router can serve the needs of most consumers, reaching even the remote corners of a large American home with performance that can fully exploit your Internet connection. Over short distances (50 feet or so) it can deliver acceptable performance between your TV, network disk drives, and PCs for audio and standard-def video applications. Internet telephony and compressed, Internet-based video services like YouTube and Hulu will probably be fine all throughout your house at standard definition.

802.11n: Scientists have discovered that they can put multiple WiFi transmitters and receivers into a single box, with multiple antennas, and that they can even take advantage of radio "echos" and "reflections" to transmit at higher speeds and over greater distances. 802.11n equipment takes advantage of this technology to achieve speeds up to 10 times as fast as 802.11g, with distances that range up to 300 feet indoors or 600 feet line-of-site.  At the time of this writing in 2009, the WiFi alliance is certifying interoperability of equipment from several vendors, based on a preliminary ("draft") standard document that is pending final approval by the relevant IEEE committees. Equipment prices are considerably higher than older equipment, but because this effort has been so popular, it is likely that future wireless equipment will continue to support that draft standard, and it is generally considered safe and prudent to purchase this equipment as part of a consumer network. With a carefully located central antenna, a typical 802.11n router can serve high-definition video and audio to TVs and PCs all throughout a large American home, and Internet applications can be accessed throughout adjacent yards and buildings at distances of 300 to 500 feet or beyond.

WiFi Network Equipment Types

Technology retail store shelves offer a wide variety of network equipment
If you go into any large technology retail store, you'll find shelves loaded with various types of network equipment. As of this writing in 2009, the industry has reached general agreement on the names that they apply to most of these items, based on either formal or informal definitions of functions. Most of today's equipment combines several separate functions into multiple-purpose boxes, but it's easier to understand the situation if we first think about simple, single-function devices. You'll find some of those too. Let's consider those single-function devices first. You may find these items:

Single-Function Items:

Broadband modem rear panel

Broadband Modems:
A - "Broadband Modem" - converts a DSL or Cable Internet signal from a telephone or TV cable to computer-compatible Ethernet. In its most basic sense, a Broadband Modem makes just ONE Internet address available for use by a single computer in your home or small office.

Basic Cisco RouterRouters: Routers are used to share a single Internet connection with multiple computers. The most basic, single-function "Router" has 2 separate Ethernet Interfaces on 2 separate network segments. It uses one of these 2 network segments to create a new, local, private LAN subnet that can be expanded to connect with several computers in your home or small office. It uses the other network segment to communicate with your ISP on a Wide Area Network (WAN) through a single IP address. It multiplexes all outbound Internet traffic from all of the local computers into that single ISP IP address so that your Internet Service Provider thinks you have only one computer sending data to the Internet, and when Internet traffic comes back in response to that outbound traffic, the router demultiplexes it and sends it back to the appropriate computer on the LAN subnet. You can learn a lot more about Routers from videos in the "Networking Fundamentals" section at AskMisterWizard.com. Pay particular attention to the two videos entitled "NAT Routers Part 1" and "NAT Routers Part 2".

Ethernet Switch Ethernet Switches: Ethernet Switches are used to expand a LAN subnet for use with additional PCs. The most common, basic, single-function Ethernet Switch has 5 or more Ethernet connectors, and each can be connected, via an Ethernet Cable, to a separate computer, or to additional Ethernet Switches for further expansion in - "daisy chain" - fashion.  All of the computers thus interconnected can then use Ethernet protocols to exchange information. If those computers also understand a higher-level networking protocol like IP, then their Ethernet messages can also contain distinct IP addresses and IP messages that a router can multiplex onto the Internet. Ethernet Switches are closely related to Ethernet Hubs, and both technologies can be used for the same purposes. You can learn a lot more about Ethernet Hubs and Switches from additional videos, using those titles, in our "Networking Fundamentals" section.

Wireless Access Point Wireless Access Points: A Wireless Access Point Receives Ethernet traffic from a LAN segment and broadcasts it over radio waves, where it can be picked up by computers equipped with Wireless Network Adapters.  A Wireless Access Point also receives radio messages from those PCs, converting them into Ethernet messages and applying them to the LAN segment. If those computers also understand a higher-level networking protocol like IP, then their Ethernet messages can also contain distinct IP addresses and IP messages that a router can multiplex onto the Internet. Thus a Wireless Access Point is very similar to an Ethernet Hub. You can see how we installed, configured, and used a Wireless Access Point by watching the video entitled "Adding a Wireless Access Point or 'Wireless Hub' to a wired Ethernet", which is available in our "Networking Fundamentals" section.

Wireless LAN Adapter with USB Interface Wireless Network Adapters: A Wireless Network Adapter contains WiFi compatible radio transmitters and receivers, and converts those radio signals to and from USB or PCI signals that are compatible with modern personal computers. Sometimes these adapters are called "NICs", where "NIC" stands for "Network Interface Card". Without some kind of Wireless Network Adapters, a computer can't use a wireless network. Most modern PCs come with Wireless Network adapters built-in. At the time of this writing in 2009, most of these built-in, preconfigured NICs are based on 802.11g technology, so if you want to use 802.11n you'll probably need to pay extra for an external device. Operating system compatibility can be an issue here, so be sure that the device you purchase clearly advertises support for your chosen operating system! You can see how we used a built-in Wireless Network Adapter in a McDonald's fast-food restaurant to access a WiFi Hotspot by watching the video entitled "McWireless: Wireless Internet Access at McDonalds", which is available in our "Networking Fundamentals" section.

Wireless Ethernet Bridges: Wireless Ethernet Bridges, operating in pairs or in conjunction with a Wireless Access Point, can interconnect two separate Ethernet LAN segments.
Wireless Ethernet Bridge

For example, suppose a DSL Internet connection enters a home office equipped with an appropriate router and Ethernet Switch, where a printer and three separate computers reside:

Computer equipment in small office
Suppose that a distant bedroom at the opposite end of the same house has 2 more computers and another printer, all plugged into a separate Ethernet Switch.

Computer equipment in small bedroom

We would say that this home has 2 separate Ethernet LAN segments. The 2 computers in the bedroom could both use the bedroom computer, but they couldn't use the office printer, or share its Internet connection.

It is possible to string a long Ethernet cable between the office Ethernet Switch and the bedroom Ethernet Switch, but usually it is more convenient to do this without wires.

Long ethernet cable bridging segments

By installing a Wireless Access Point  in the office and a Wireless Ethernet Bridge in the bedroom, both LAN segments are joined.
2 Network Segments WiFi Bridged

Once the bedroom's Wireless Ethernet bridge and the office's Access Point are configured to communicate with one another, all 5 of the computers and both printers can be given IP addresses from the same subnet and shared, along with the Internet connection. Because modern console gaming hardware like "X-Box" and "Playstation" generally contain wired Ethernet connectors without any provision for WiFi, it is commonplace to use them with a Wireless Ethernet Bridge. This functionality is sometimes marketed as a "Wireless Game Adapter". Some Wireless Game Adapters are specifically "crippled" with technology that prevents their general-purpose use by PCs and other Ethernet devices, but most are fully compatible and can bridge Ethernet LAN segments for use by any kind of Ethernet equipment, in spite of their game-oriented names.

Wireless Print Server Wireless Print Servers: A Wireless Print Server allows you to share and access your printer without wires. The most basic Wireless Print Server would have a single USB or Parallel Printer port for connection with a single, nearby printer, and a radio transceiver with antenna for connection to a WiFi LAN through a nearby Wireless Access Point. It converts the appropriate radio signals into printer commands and data so that the printer can be located at any convenient place within WiFi radio range of the Wireless Access Point. Today's basic Printer Servers understand the IP protocol and are able to receive and interpret IP messages containing printer data so that IP-equipped computers throughout the home or small office can share the printer, even if the printer was not originally designed with WiFi in mind. If the home or small office router is appropriately enhanced with "Port Forwarding", it is even possible for the printer to receive and handle printing instructions from all over the Internet. You can learn a lot more about "Port Forwarding" from the video segment entitled "NAT Routers Part 3: Port Forwarding", which is available in the "Networking Fundamentals" section at AskMisterWizard.com.

MultiFunction Devices:

It is commonplace to combine two or more of the individual functions described above into a single box. When manufacturers do this, the functional lines often overlap or blur, resulting in the possibility of confusion when they choose names for the resulting equipment. Unfortunately, manufacturers tend to use the simple term "Router" for most of these combinations, so you'll need to study the published details to figure out the exact combination they are offering. A careful reading of the retail packaging is generally sufficient. Here are some of the combinations in common use today:

Router and Ethernet Switch combinedRouter and Ethernet Switch: Almost all consumer-grade routers today include an Ethernet Switch with 4 or more Ethernet connectors. Thus, at the back of the router, you'll generally see 5 Ethernet jacks. One will be labeled separately, and it will reference an "Internet" or "Internet-Facing" or "Upstream" or "Wide Area" connection. Connect that to your Broadband modem. The others will be grouped together, and an associated label will reference "LAN" or "Local" or "Downstream" connections. Use Ethernet cables to connect those to one or more PCs, printers, etc. Manufacturers will almost always use the name "Router" to describe this combination, and the general expectation is that any basic router will include a basic Ethernet Switch.

Router, Switch, and Access Point combinedRouter, Ethernet Switch, and Wireless Access Point: This combination is the same as "Router and Ethernet Switch", but it adds a Wireless Access Point so that you can connect one or more computers via WiFi in addition to those connected with Ethernet. You can use any practical combination of Ethernet and/or WiFi connections. Manufacturers generally use the name "WiFi Router" to describe this combination. It is also possible to bypass the Router portion of this kind of equipment, if you only need Ethernet Switch and/or Wireless Access Point.

Modem, Router, and Switch combinedModem, Router, and Switch: If you obtain your basic router from your Internet Service Provider, it will probably include modem logic that's compatible with their DSL or Cable connection. Like other routers, this logic almost always includes a  4-port Ethernet Switch, so you can connect it with 4 computers before you'll need to expand your Ethernet LAN subnet. This combination doesn't include a Wireless Access point, so every connection will be wired. Manufacturers are split on the name of this combination: sometimes they call it a "Broadband Modem", and sometimes they call it a "Router". Sometimes they call it a "Residential Gateway".

Modem, Router, Switch, and Access Point combinedModem, Router, Ethernet Switch, and Wireless Access Point: If you pay a premium to your Internet Service Provider you can get this all-inclusive combination. The modem logic will be compatible with the particular broadband technology supported by your ISP (DSL or Coaxial Cable). The Router will create a new IP subnet on which you can share your single Internet Address with several computers. The Ethernet Switch will expand that new subnet with several physical Ethernet connectors for wired PCs, and the Wireless Access Point will allow shared radio access to the resulting LAN segment. You can also buy these devices from retailers, but be sure to check the specs on the modem. Some support Cable only, some support DSL only, and some support both. Most manufacturers describe this combination as a "WiFi Router". Sometimes they call it a "Wireless Residential Gateway".

Combining or "Daisy-Chaining" - Multiple Devices

It's commonplace to - "Daisy Chain" - several of these devices in series. For example, if you were to obtain single-function boxes for all of the above functions, you could hook them all to one another like this:
WiFi Distribution in 5 Separate Modules
That basic, logical flow (Modem, Router, Ethernet Switch, WiFi Access Point) is retained regardless of whether the functional lines are contained within 4 separate network boxes, or in a single box.

Here's an example of that same functionality housed in 2 separate boxes:
WiFi NOC in 2 boxes, version 1

Modem, Router, and Ethernet Switch
2- Wireless Access Point.

Here's an implementation of the identical WiFi distribution architechture in 3 boxes:
WiFi Distribution Setup in 3 Boxes

2- Router and Ethernet Switch
3- Wireless Access Point

It is even commonplace to double-up some of those functions in the chain, like this:
WiFi Distribution Equipment in 2 Boxes, Option 2

Modem, Router, Ethernet Switch
2- Router, Ethernet Switch, Wireless Access Point

In this two-box case, TWO distinct, new subnets are created, and one is logically closer to the Internet than the other. The innermost new subnet, closer to the Internet, has wired access only, while the outer subnet has both wired access (through the Ethernet Switch in the second box) and WiFi Access. Managing two distinct IP subnets creates some interesting security implications: Internet traffic from BOTH subnets flows through the innermost one, and it can all be monitored by sophisticated technicians attached to that innermost LAN. The outermost LAN, however, never sees Internet traffic to or from the innermost LAN (but both segments can see any traffic exchanged between the Inner LAN and the outer LAN). You can learn a lot more about subnets and routers from the video clips in our Networking Fundamentals section.