As someone who reviews networking products, I generally receive a couple of emails from readers every day, and most of them, in one way or another, are asking about the basics of networking (as in computer to computer; I am not talking about social networks here).
A typical wireless router with LAN ports for Ethernet-ready devices and antennas for Wi-Fi clients.
(Credit: Dong Ngo/CNET)
Don't get me wrong; I appreciate emails, because, at the very least, they give me the impression that there are real people out there amid the sea of spam. But I'd rather not keep repeating myself. So instead of saying the same thing over and over again in individual emails, I'll talk all about home-networking basics, in layman's terms, in this post.
Advanced and experienced users won't need this, but for the rest, I'd recommend reading the whole thing. If you want to quickly find out what a networking term means, you can search for it here.
1. Wired networking
A wired local network is basically a group of devices connected to one another using network cables, more often than not, with the help of a router — which brings us to the very first networking term.
This is the central device of a home network that you can plug one end of a network cable in to. The other end of the cable goes into a networking device that has a network port. If you want to add more network devices to a router, you'll need more cables and more ports on the router. These ports, both on the router and on the end devices, are called local-area network (LAN) ports. They are also known as RJ45 ports, named after the plug shape itself. The moment you plug a device in to a router, you have yourself a wired network. Networking devices that come with an RJ45 network port are called Ethernet-ready devices. There's more on this below.
Note: technically, you can skip a router and connect two computers together using one network cable to form a network of two. However, this requires manually configuring the IP addresses or using a special crossover cable for the connection to work. You don't really want to do that.
The back of a typical router; the WAN port is clearly distinguished from the LANs.
(Credit: Dong Ngo/CNET)
Local-area network (LAN) ports
A home router usually has four LAN ports, meaning that out of the box, it can host a network of up to four wired networking devices. If you want to have a larger network, you will need to resort to a switch (or a hub), which adds more LAN ports to the router. Generally, a home router can handle up to about 250 networking devices, and the majority of homes and even small businesses don't need more than that. There are currently two main speed standards for LAN ports: 100Mbps Ethernet (or about 13MBps), and gigabit Ethernet, which caps at 1Gbps (or about 125MBps). In other words, it takes about a minute to transfer a CD's worth of data (some 700MB or about 250 digital songs) over a 100Mbps Ethernet connection. With gigabit Ethernet, the same job takes just about 5 seconds. In real life, the average speed of a 100Mbps Ethernet connection is about 8MBps, and a gigabit Ethernet connection is somewhere between 45 and 80MBps. The actual speed of a network connection depends on many factors, such as the end devices and the speed of the hard drives within, the quality of the cable, the amount of traffic and so on.
Rule of thumb: the speed of a network connection is determined by the slowest speed of any party involved. For example, in order to have a wired gigabit Ethernet connection between two computers, both computers, the router they are connected to and the cables used to link them together all need to support gigabit Ethernet. If you plug a gigabit Ethernet device and a 100Mbps Ethernet device in to a router, the connection between the two will cap at the speed of the 100Mbps Ethernet.
In short, LAN ports on a router allow Ethernet-ready devices to connect to one another and share data. In order for them to access the internet, the router may also need to use a wide-area network (WAN) port.
A typical CAT5e network cable.
(Credit: Dong Ngo/CNET)
Wide-area network (WAN) port
Generally, a router has just one WAN port (some business routers come with dual WAN ports, so you can use two separate internet services at a time). On any router, the WAN port is always separate from the LAN ports, and often comes in a different colour to distinguish itself. A WAN port is exactly the same as a LAN port, just with a different usage: to connect to an internet source, such as a broadband modem. The WAN allows the router to share that internet connection with all of the Ethernet-ready devices connected to it.
Note: since most internet connections are slower than 100Mbps, you can generally get by with only a 100Mbps WAN port. Top-end routers these days tend to come with a gigabit WAN port, and, considering the roll-out of the Australian National Broadband Network (NBN), it might be a sound investment. Decent WAN-to-LAN speeds also become important when you start daisy chaining routers.
Often called an ADSL or cable modem, a broadband modem is a device that bridges the internet connection from a service provider to a computer or router, making the internet available to consumers. Some providers offer a device that's a combination of a modem and router, or wireless router, all in one.
These are the cables used to connect network devices to a router or switch. They are also known as Category 5 cables, or CAT5 cables. Currently, most, if not all, CAT5 cables on the market are actually CAT5e, which is capable of delivering gigabit Ethernet data speeds. The latest network cabling standard currently in use is CAT6, which is designed to be faster and more reliable than CAT5e. The difference between the two is the wiring inside the cable and at both ends of it. CAT5e and CAT6 cables can be used interchangeably, and in my personal experience are basically the same, except that CAT6 is more expensive. For most home usage, what CAT5e has to offer is more than enough. In fact, you probably won't notice any difference if you switch to CAT6, but it doesn't hurt to use CAT6, either, if you can afford it.
Now that we're clear on a wired network, let's move on to a wireless network.
2. Wireless networking: standards and devices
Each of the Wi-Fi networks that a client (such as an iPhone) detects generally belongs to one access point.
(Screenshot by Dong Ngo/CNET)
A wireless network is very similar to a wired network, with one big difference: devices don't use cables to connect to the router and one another. Instead, they use wireless connections, known as Wireless Fidelity (Wi-Fi) which is a friendly name for the 802.11 networking standard supported by the Institute of Electrical and Electronics Engineers (IEEE). This means wireless networking devices don't need to have ports, but just antennas, which are sometimes hidden inside the device itself. In a typical home network, there are generally both wired and wireless devices, and they can all talk to one another. In order to have a Wi-Fi connection, there needs to be an access point and a Wi-Fi client.
An Access point (AP) is a central device that broadcasts the Wi-Fi signal for Wi-Fi clients to connect to. Generally, each wireless network, like those you see popping up on your smartphone's screen as you walk around a big city, belongs to one access point. You can buy an AP separately and connect it to a router or a switch to add Wi-Fi support to a wired network, but generally you want to buy a wireless router, which is a regular router (one WAN port, four LAN ports and so on) with a built-in access point. Some routers even come with more than one access point (see dual-band router, below).
A Wi-Fi client or WLAN client is a device that can detect the signal broadcasted by an access point, connect to it and maintain the connection (this type of Wi-Fi connection is established in Infrastructure mode, but you don't have to remember this). Most, if not all, laptops, smartphones and tablets on the market come with built-in Wi-Fi capability. Those that don't can be upgraded to that via a USB or PCIe Wi-Fi adapter. Think of a Wi-Fi client as a device that has an invisible network port and an invisible network cable. This metaphorical cable is as long as the range of a Wi-Fi signal.
Note: technically, you can skip an access point and make two Wi-Fi clients connect directly to each other, in Ad hoc mode. However, similar to the case of the crossover network cable, this is rather complicated and inefficient, and is used far less than Infrastructure mode.
This is the radius distance that an access point's Wi-Fi signal can reach. Typically, a Wi-Fi network is most viable within about 45 metres from the access point. This distance, however, changes based on the power of the devices involved, the environment and obstructions and, most importantly, the Wi-Fi standard. A good Wireless-N access point can offer a range of up to 90 metres or even farther. The Wi-Fi standard also determines how fast a wireless connection can be, and is the reason that Wi-Fi gets complicated and confusing, especially when Wi-Fi frequency bands are mentioned.
These bands are the radio frequencies used by the Wi-Fi standards: 2.4GHz and 5GHz. The 2.4GHz band is currently the most popular, meaning that it's used by most existing network devices. That, plus the fact that home appliances, such as cordless phones, also use this band, makes its signal quality generally worse than that of the 5GHz band, due to oversaturation and interference.
A typical web interface of a D-Link wireless router that allows users to customise their Wi-Fi network.
(Screenshot by Dong Ngo/CNET)
This was the first commercialised wireless standard. It offers a top speed of 11Mbps, and only operates on the 2.4GHz frequency band. The standard was first available in 1999, and is now totally obsolete, while 802.11b clients are still supported by access points of later Wi-Fi standards.
Similar to 802.11b in terms of age, 802.11a offers a cap speed of 54Mbps at the expense of much shorter range, and uses the 5GHz band. It's also now obsolete, though still supported by access points of later standards.
Introduced in 2003, the 802.11g standard marked the first time that wireless networking was called Wi-Fi. The standard offers the top speed of 54Mbps, but operates on the 2.4GHz band, hence offering a better range than the 802.11a standard. It's still used in many mobile devices, such as the iPhone 3G or the iPhone 3Gs. This standard is supported by access points of later standards.
802.11n or Wireless-N
Available from 2009, 802.11n has been the most popular Wi-Fi standard, with lots of improvements over the previous ones, such as making range of the 5GHz band comparable to that of the 2.4GHz band. The standard operates on both 2.4GHz and 5GHz bands and started a new era of dual-band routers; those that come with two access points, with one for each band. There are two types of dual-band routers: selectable dual-band routers, which can operate in one band at a time; and true dual-band routers, which simultaneously offer Wi-Fi signals on both bands.
On each band, the Wireless-N standard is available in three set-ups: single stream, dual stream and three stream, which offer cap speeds of 150Mbps, 300Mbps and 450Mbps, respectively. This in turn creates three types of true dual-band routers. N600 (each of the two bands offers a 300Mbps speed cap), N750 (one band has a 300Mbps speed cap, while the other caps at 450Mbps) and N900 (each of the two bands offers up to 450Mbps cap speed). It's important to recognise that no single Wi-Fi client will ever receive these speeds: these ratings are the entire throughput that the router is capable of across all clients. Actual router-to-client speeds are significantly slower. An N900 router might, at best, get somewhere between 160Mbps (2.4GHz) to 240Mbps (5GHz), dependent on ideal situations.
Note: in order to have a Wi-Fi connection, both the access point (router) and the client need to operate on the same band, either 2.4GHz or 5GHz. For example, a 2.4GHz client, such as an iPhone 4, won't be able to connect to a 5GHz access point. In case a client supports both bands, it will only use one of the bands to connect to an access point, and when applicable, it tends to "prefer" the 5GHz band to the 2.4GHz band, for better performance.
802.11ac or 5G Wi-Fi
This latest Wi-Fi standard operates only on the 5GHz frequency band, and offers Wi-Fi speeds of up to 1.3Gbps (or 1300Mbps) when used in the three-stream set-up. The standard also comes with dual-stream and single-stream set-ups that cap at 900Mbps and 450Mbps, respectively (note that the single-stream set-up of 802.11ac is as fast as the top three-stream set-up of 802.11n).
Currently, there are just a few 802.11ac routers on the market, such as the Netgear R6300, the Asus RT-AC66U and the Buffalo WZR-D1800H, but it's predicted that the standard will be more popular by the end of 2012, when hardware devices such as laptops, tablets and smartphones with built-in 802.11ac become available.
Technically, the 802.11ac standard is about three times faster than the 802.11n (or Wireless-N) standard, and therefore is much better for battery life (since it has to work less to deliver the same amount of data). In real-world testing so far, I've found that 802.11ac is about twice the speed of Wireless-N, which is very good (note that the real-world sustained speeds of wireless standards are always much lower than the theoretical speed cap. This is partly because the cap speed is determined in controlled, interference-free environments). The fastest real-world speed of an 802.11ac connection that I've seen so far is 42MBps, provided by the Asus RT-AC66U, which is close to half that of a gigabit Ethernet wired connection.
On the same 5GHz band, 802.11ac devices are backward-compatible with Wireless-N and 802.11a devices. While 802.11ac is not available on the 2.4GHz band, for compatibility purposes, an 802.11ac router will also come with a three-stream (450Mbps) Wireless-N access point. In short, an 802.11ac router is basically an N900 router plus support for 802.11ac on the 5GHz band.
That said, let me restate the rule of thumb one more time: the speed of a network connection is determined by the slowest speed of any of the parties involved. This means that if you use an 802.11ac router with an 802.11a client, the connection will cap at 54Mbps. In order to get the top 802.11ac speed, you will need to use a device that's also 802.11ac capable.
A wireless router and USB client, both with their Wi-Fi Protected Setup button.
(Credit: Dong Ngo/CNET)
3. More on wireless networking
In wired networking, a connection is established the moment you plug the ends of a network cable in to the two respective devices. In wireless networking, it's more complicated than that.
Since the Wi-Fi signal, broadcasted by the access point, is literally in the air, anybody with a Wi-Fi client can connect to it, and that might pose a serious security risk. To prevent this from happening, and only let approved clients connect, the Wi-Fi network needs to be password protected (or in more serious terms: encrypted). Currently, there are a few methods used to protect a Wi-Fi network (called "authentication methods"): WEP, WPA and WPA 2, with WPA 2 being the most secure, while WEP is getting obsolete and is very insecure, as it has long been cracked. WPA 2 (as well as WPA) offers two ways to encrypt the signal: are Temporal Key Integrity Protocol (TKIP) and Advanced Encryption Standard (AES). The former is for compatibility (allowing legacy clients to connect), while the latter allows for faster connection speeds, is more secure but only works with newer clients. From the side of the access point or router, the owner can set the password (or encryption key) that clients can use to connect to the Wi-Fi network.
If the above paragraph seems complicated, that's because Wi-Fi encryption is very complicated. To help make life easier, the Wi-Fi Alliance offers an easier method called Wi-Fi Protected Setup.
Personal Hotspot is a feature made available by the Wi-Fi Direct standard. It temporarily turns the Wi-Fi client, an iPhone in this case, into a "soft" access point.
(Screenshot by Dong Ngo/CNET)
Wi-Fi Protected Setup (WPS)
Introduced in 2007, Wi-Fi Protected Setup is a standard that makes it easy to establish a secure Wi-Fi network. The most popular implementation of WPS is the push button. Here's how it works: on the router (access point) side, you press the WPS button. Now, within two minutes, you press the WPS button on the Wi-Fi clients, and that's all you need for them to connect to the access point. This way, you don't have to remember the password (encryption key) or type it in. Note that this method only works with devices that support WPS. Most networking devices released in the last few years do, however.
This is a standard that enables Wi-Fi clients to connect to one another without a physical access point. Basically, this allows one Wi-Fi client, such as a smartphone, to turn itself into a "soft" access point, and broadcast Wi-Fi signals that other Wi-Fi clients can connect to. This standard is very useful when you want to share an internet connection. For example, you can connect your laptop's LAN port to an internet source, such as in a hotel, and turn its Wi-Fi client into a soft AP. Other Wi-Fi clients can then also access that internet connection. Wi-Fi Direct is most popularly used in smartphones and tablets, where the mobile device shares its internet connection with other Wi-Fi devices in a feature called Personal Hotspot.
4. Power-line networking
When it comes to networking, you probably don't want to run network cables all over the place, making Wi-Fi a great alternative. Unfortunately, a Wi-Fi signal can't reach some places, such as that corner in the basement, either because it's too far away or there are thick concrete walls in between. In this case, the best solution is a pair of power-line adapters.
Power-line adapters basically turn the electrical wiring of a home into network cables for a computer network. You need at least two power-line adapters to form the first power-line connection. The first adapter is connected to the router, and the second to the Ethernet-ready device at the far corner. There are some routers on the market, such as the D-Link DHP-1320, that have built-in support for power line, meaning that you can skip the first adapter.
Currently, there are two main standards for power-line networking: HomePlug AV and Powerline AV+ 500. They offer cap speeds of 200Mbps and 500Mbps, respectively.
Power-line networking comes with a built-in warning: always make sure that you can return the product before you purchase it. This is because dependent on how your house is wired, it may not work for you at all. Power-line adapters work best when they're on the same electrical circuit, and don't like tricky things like power boards or surge protectors, either. In most cases, there's rarely a middle ground: it'll either work incredibly well, or incredibly poorly.