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Home Networking Basics

from http://news.cnet.com/8301-17938_105-57485724-1/home-networking-explained-heres-the-url-for-you/

by Dong Ngo

As the guy who reviews networking products, I generally receive a couple of e-mails from readers a 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.)

Don’t get me wrong, I appreciate e-mails because, at the very least, it gives 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 e-mails, 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, and 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.

Router: This is the central device of a home network that you can plug one end of a network cable into. 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. The moment you plug a device into a router, you have yourself a wired network. Networking devices that come with an RJ45 network port are called Ethernet-ready devices. 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.

LAN ports: A home router usually has four LAN ports, meaning 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: Ethernet, which caps at 100Mbps (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 (around 700MB or about 250 digital songs) over an Ethernet connection. With Gigabit Ethernet, the same job takes just about 5 seconds. In real life, the average speed of an Ethernet connection is about 8MBps, and of 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, 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 an Ethernet device to a router, the connection between the two will cap at the speed of Ethernet, which is 100Mbps.

In short, LAN ports on a router allow Ethernet-ready devices to connect to one another and share data. In order for them to also access the Internet, the router needs to also have a Wide Area Network (WAN) port.

WAN port: Generally, a router has just one WAN port. (Some business routers come with dual WAN ports, so that one could 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 color 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 connect to the Internet and share that connection with all the Ethernet-ready devices connected to it.

Note: Since most Internet connections are slower than 100Mbps (a fast cable connection, for example, is about 50Mbps down and about 6Mbps up), an Ethernet-rated WAN port is sufficient in most cases. However, Gigabit Ethernet routers tend to also come with a Gigabit WAN port. That said, switching from an Ethernet router to a Gigabit Ethernet router generally doesn’t translate into faster Internet speeds, but only helps devices within your local network (LAN) to connect to one another faster.

Broadband modem: Often called a DSL modem or cable modem, a broadband modem is a device that bridges the Internet connection from a service provider to a computer or to a router, making the Internet available to consumers. Some providers offer a combo device that’s a combination of a modem and a router, or wireless router, all in one.

Network cables: These are the cables used to connect network devices to a router or a 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 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
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, or 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 sometimes are 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.

Access point: 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).

Wi-Fi client: A Wi-Fi client or WLAN client is a device that can detect the signal broadcast by an access point, connect to it, and maintain the connection. (This type of Wi-Fi connection is established in the 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 the Ad hoc mode. However, similar to the case of the crossover network cable, this is rather complicated and inefficient, and is far less used than the Infrastructure mode.

Wi-Fi range: This is the radius distance an access point’s Wi-Fi signal can reach. Typically, a Wi-Fi network is most viable within about 150 feet from the access point. This distance, however, changes based on the power of the devices involved, the environment, and, most importantly, the Wi-Fi standard. A good Wireless-N access point can offer a range of up to 300 feet or even farther. The Wi-Fi standard also determines how fast a wireless connection can be and is the reason Wi-Fi gets complicated and confusing, especially when the Wi-Fi frequency bands are mentioned, which I just did.

Frequency bands: 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, 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.

Depending on the standard, some Wi-Fi devices use one of the two bands, while others use both. Following are the existing Wi-Fi standards, starting with the oldest:

802.11b: This was the first commercialized wireless standard. It offers a top speed of 11Mbps and operates only on the 2.4GHz frequency band. The standard was first available in 1999 and is now totally obsolete; 802.11b clients, however, are still supported by access points of later Wi-Fi standards.

802.11a: 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.

802.11g: Introduced in 2003, the 802.11g standard marked the first time wireless networking was called Wi-Fi. The standard offers the top speed of 54Mbps but operates on the 2.4GHz band, hence offering better range than the 802.11a standard. It’s still used in many mobile devices, such as the iPhone 3G and the iPhone 3Gs. This standard is supported by access points of later standards.

802.11n or Wireless-N: Available starting in 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, one for each band. There are two types of dual-band routers: selectable dual-band routers that can operate in one band at a time, and true dual-band routers that simultaneously offer Wi-Fi signals on both bands.

On each band, the Wireless-N standard is available in three setups: single-stream, dual-stream, and three-stream, offering cap speeds of 150Mbps, 300Mbps, and 450Mbps, respectively. This in turns 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).

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 1,300Mbps) when used in the three-stream setup. The standard also comes with dual-stream and single-stream setups that cap at 900Mbps and 450Mbps, respectively. (Note that the single-stream setup of 802.11ac is as fast as the top three-stream setup 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 then 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 I’ve seen so far is 42MBps, provided by the Asus RT-AC66U, which is close to 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. That means 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.

3. More on wireless networking
In wired networking, a connection is established the moment you plug the ends of a network cable into the two respective devices. In wireless networking it’s more complicated than that.

Since the Wi-Fi signal, broadcast 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 the WPA 2 being the most secure, while WEP is getting obsolete. WPA 2 (as well as WPA) offers two ways to encrypt the signal, which are Temporal Key Integrity Protocol (TKIP) and Advanced Encryption Standard (AES). The former is for compatibility (allowing legacy clients to connect); the latter allows for faster connection speeds and 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.

Wi-Fi Protected Setup or 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 2 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.

Wi-Fi Direct: 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. Now other Wi-Fi clients can also access that Internet connection. Wi-Fi Direct is actually most popularly used in smartphones and tablets, where the mobile device shares its cellular Internet connection with other Wi-Fi devices, in a feature called personal hot spot.

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, in some places, such as that corner in the basement, a Wi-Fi signal can’t reach, either because it’s too far away or because 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 end. There are some routers on the market, such as the D-Link DHP-1320, that have built-in support for power line, meaning you can skip the first adapter. More on power line devices can be found here.

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.


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