Wi-Fi hotspots

A wireless access point mounted on a streetlight pole in Toronto, part of a Wi-Fi network that covers public places in the city's downtown core.

People who travel with their computers now take it for granted that they can connect to the internet wirelessly from hotel rooms, airports and coffee shops. But what actually happens when you log on to a wireless hotspot?

Hotspots use a wireless data communications standard called Wi-Fi or 802.11, also found in office networks. Wi-Fi comes in three main flavours: 802.11b, 802.11g and 802.11a.

The original version, 802.11b, can transmit data at 10 megabits per second (about the same speed as the fastest home internet connections at the moment). The newer 802.11g and 802.11a versions are even faster, at 54 megabits per second.

The b and g standards are most popular, says Bilal Kabalan, general manager of national hotspot operator Fatport Corp. in Calgary, because 802.11b appeared first and 802.11g is compatible with it. 802.11a uses a different frequency, incompatible with the others. Some wireless hotspots, such as Fatport's, support all three standards, he adds.

Hardware

To use a hotspot, your laptop computer or other mobile device must support one of these Wi-Fi standards. Newer laptops come with this capability. To add it to older ones, you can buy a Wi-Fi card that plugs into a slot in the machine. It's essentially a radio transmitter and receiver coupled with networking electronics.

The hotspot itself relies on wireless access points and a router. An access point is a gadget that is connected to a network, receiving and transmitting Wi-Fi signals to and from nearby wireless gadgets such as laptops, handhelds and VoIP Wi-Fi phones. The router is the piece of hardware that provides network security and routes traffic to and from the internet.

If you have a wireless network at home you probably have a device that is a combined router and wireless access point in a single box. A small public or private hotspot may have something very similar, but wireless access points have a range of only 30 to 50 metres and can handle just 30 to 50 users each, Kabalan explains — more than enough for the average home traffic, but not sufficient for a busy restaurant, a train station or convention center, for example.

For a larger area or to handle more users, a hotspot operator can use more than one wireless access point. These may be separate devices spread throughout the coverage area and connected to a single router (often called a gateway when it is separate from the access points) that controls the flow of information to and from the internet.

Finding a hotspot

The wireless router in a hotspot continuously broadcasts its Service Set Identifier or SSID to tell nearby wireless devices it is available for connections. A Wi-Fi-equipped computer scans for broadcast SSIDs and displays a list of the networks it detects as a list of available nearby networks. If you've used a hotspot or other Wi-Fi connections, you've seen this list and selected a network from it.

When you choose to connect, says Kabalan, your computer sends the hotspot a unique identifier called its Media Access Control (MAC) address. In some networks you must also supply a password at this stage — you may have the password for your home or office network stored in your laptop for easy connection. But hotspots often skip this password in favour of a login screen. Your basic connection to the wireless network is established without a password, but the first time you try to open a website, in place of what you asked for you get a page asking you to sign on to the hotspot service and provide either an existing user ID and password or a credit card for payment.

This is called a captive portal. Normally, once you're connected to a network router and you send a request to load a web page, the router simply passes it in the right direction until it travels over the internet to the server that hosts that page, which sends the page back to you. But when you log onto a hotspot, the first time you request a website, the hotspot doesn't pass the request on. Instead it sends you the logon page, forcing you to log on (and in many cases pay a fee) before you can start browsing the internet.

Performance and privacy

Though the connection from your computer to the hotspot is wireless, the rest of the path from the hotspot to the internet — known in the business as the backhaul — usually isn't.

Usually the wireless router is connected to a high-speed wired connection, but through the hotspot you're sharing that capacity with whoever else is logged on at the same time. This is why hotspots can sometimes have slower web-surfing performance than home internet connections, even though Wi-Fi itself is capable of high speeds.

Which brings up the issue of security and privacy. Computers on an office or home network can see each other, and may have access to the contents of each other's hard drives. A common way to prevent this from happening on a hotspot, Kabalan explains, is to divide the wireless network into multiple virtual local area networks, or VLANs. Each customer who connects gets a VLAN with no one else on it, and the connection can be protected using encryption.

That raises a question: What about those other people banging away on their laptops at nearby tables in the coffee shop? How does the hotspot keep their traffic separate from yours? Can they see what you're doing?

The answer to that last question is no, unless they know more than most of us about snooping on networks. But you'd still be wise to think twice about using hotspots for sensitive communications, such as banking and e-commerce activity, since anyone with the knowledge and desire to snoop Wi-Fi networks is more likely to do it at a busy hotspot (and you never know who might be looking over your shoulder in a public place, too).