Understanding wireless networks - Linux Tutorial

- [Instructor] To connect to the internet, we need to use what's known as a router, or an internet gateway. These come in a range of types from simple, low-cost home appliances, to complex multifunction business devices. But nowadays, they all have the same basic functionality. A wired connection to an ISP, and the ability to connect multiple devices wirelessly. Desktop computers come with the ability to connect to both wired and wireless networks, as do laptop systems. However, tablets and mobile devices only connect wirelessly. So having a wireless capability is pretty much a must nowadays. And, of course, media technology, such as the Chromecast and Apple TV, depend upon wireless networks to operate. While this has become very much part of life, and many cities now offer what are known as wireless hotspots, as do libraries and social meeting places, such as Starbucks and McDonald's. As a technology, wireless communications has its limitations. Early wireless devices didn't have the same bandwidth as standard ethernet, and even the more recent high-power wireless systems continue to lag behind good quality ethernet. Wired devices connect using ethernet cables, and these are rated with a Cat specification. The most common cables are Cat 5, Cat 5e, and Cat 6. As we can see in this table, these provide quite substantial speeds. Wireless devices connect using what's known as Wi-Fi, the wireless networking protocol, which is defined in the 802.11 series of standards. These standards are continually being improved, with the early 802.11a, b, and g being superseded by 802.11n, and 802.11ac. And speeds are continually increasing. Note the anomaly of 802.11a, which has the greatest speed, but is pretty much limited to line of sight, and hence was never really that successful. Wireless deployments operate through one of 14 different channels, the exact number will depend upon the country and the protocol used. For instance, an 802.11g deployment would be in the 2.4 gigahertz range, and would have channels at 2.412, 2.417, 2.422, and up to 2.472 gigahertz. The specific channel used by clients may be preset or selected dynamically, depending upon the network performance at the time of connecting. With enough channels and spectrum use, the theoretical maximum speeds of the wireless standards are starting to approach the speeds achievable on a wired connection. With 802.11n and more recently 802.11ac, the speeds are quite sufficient to be acceptable, especially given the additional convenience of wireless. Connection to a wireless network requires that the laptop or mobile device connect to what is known as an access point. This is a device which has an existing connection through to the internet and broadcast its identity, offering client devices the opportunity to connect. We've all connected to access points. Every time we go into our computer, click on Wireless Networks, and select a network to connect to, we're communicating with the access point for that network. This has a name. It might be a good descriptive name such as Qantas Club, or it might be somewhat more cryptic. This is what's known as a service set identifier, or SSID. Associated with this is a BSSID, or basic SSID, which is its MAC address. Some security techs recommend hiding the SSID, but this offers no real security and is often an annoyance for the business. It's poor advice. Wireless access points usually require a network key in order to connect, or may connect directly, but request an internet login before allowing access. Some routers enable what is known as MAC filtering to limit access just to a known set of user devices. But this can be circumvented by an attacker just by running a software tool to change his or her MAC address to one that's connected. Encryption and authentication can be configured on a wireless LAN by selecting one of three options. Wired Equivalent Privacy, or WEP. Wi-Fi Protected Access, or WPA. And WPA2, a stronger variant of WPA. Wireless Protected Setup, or WPS, is a relatively new feature which allows a user to connect just by the press of a button the router. Security is ensured by virtue of having physical proximity to the router. Let's take a look at my router. I'm on the wireless LAN configuration page. We can see the access point, SSID, is TPG-83NJ, and it chooses its channel automatically. It's using the 802.11bgn protocol set, has WPA and WPA2 configured for security, and has WPS enabled. If I now click on the WLAN Filtering tab, I get the option to enable MAC filtering. I'll activate it. Here we see that we can either blacklist or whitelist MAC addresses. If I enter a MAC address and blacklist it, then that MAC address won't be allowed in. If I've selected whitelist, then only MAC addresses that are on the list will be allowed in. I don't activate this, because any attacker worth his or her salt would circumvent this control easily. Okay, I'll uncheck that and Logout.