Routers and Switches For WLAN

For the most part, routers, switches, and hubs are not actually wireless, but are included here because they nevertheless form the basis of the wired LANs that underlie infrastructure and hybrid networks. Furthermore, wireless access points frequently include router technology along with their wireless relay and addressing technology.

Virtually all vendors of wireless networking equipment offer at least one product that combines an access point with a router, resulting in a single small box featuring three or four ports for Ethernet cables, another port for broadband modem hookup, and the wireless components required by the access point, including the antenna.

Routers and switches perform different functions. Today you’ll hear the word router more often than switch when it comes to sales of home and small-office networking equipment, but in reality most cable/DSL routers also are switches.

The difference is quite simple: routers connect two or more networks together and pass data between or among them, while switches provide interconnection among computers in a single network and isolate streams of traffic from each other so that signals make it from origin to destination without any other PC on the network having access to them.

Another component, called a hub, is an even simpler piece of equipment, functioning like a switch by allowing communication among the PCs on the network, but unlike a switch allowing only one communication stream at a time.

As mentioned, today’s access point products often combine AP and router technology. Much less publicized is the fact that they also operate as network switches, even though the switch component is every bit as important as the router component. The main reason for this exclusion?

Simply, in common language about computers, router and switch have begun to mean the same thing, although at even the first technical level they do not. When non-technical people start using computer terminology, the terminology tends to become less specific and therefore easier.

Which, of course, is only natural. Even so, the official name of these products tends to include both elements: for example, Linksys offers a product called the “EtherFast Cable/DSL Router with 4-Port Switch.”

Then again, the company also offers a combination AP/router/switch that it calls, simply, the “Wireless-B Broadband Router” with no mention of either switch or AP in the name.

Figure below shows a typical product combining all three technologies.

D-Link Tri-Mode Dualband 4-Port Wireless Router combines support for 802.11a, 802.11b, and 802.11g.

Your fully constructed wireless infrastructure network consists of the following components:

  • Clients: There’s not much point having a network without computers to network together.

In networking, these computers are called clients. Your clients can be desktop PCs, notebook PCs, personal digital assistants (PDAs), and even devices such as printers, network hard drives, and hardware firewalls.

Each device on the network gets its own unique network address, and the network hardware and software use that address to ensure that traffic destined for that device reaches it.

  • Network Adapters: Any client connecting to the network through the wireless components needs a wireless LAN adapter. Any client connecting via cable needs an adapter with a port for that cable (typically Ethernet).
  • Internet Gateway: Depending on the type of Internet connection you have, this component goes by different names.

You can have high-speed dedicated lines (T3, for example), and various other access types at various costs. We assumes that you have what has come to be called broadband Internet access, which currently comes in three forms: Cable, DSL, and Satellite (a fourth type, Wireless Broadband, is on the horizon).

For these types, the Internet gateway is the modem to which you attach your incoming DSL, cable, or satellite signal.

The modem receives signals through this connection and transmits them to your network through its Ethernet port, connected via Ethernet cable to the next component of your network. Here, that component is a router/switch or access point.

  • Router: You can connect your PC directly to your Internet gateway, in which case it becomes part of the cable or DSL network. Users with only one computer typically do so.

However, if you want to share the Internet connection with other computers, you must create a separate network. In such a case, you need a router to handle traffic between the two networks.

You can buy a separate router, or you can set up a Windows PC to act as a router by engaging Windows’ Internet Connection Sharing feature. This latter type of system has two disadvantages.

However: you must leave it running to provide connectivity to other clients, and the PC itself is directly subject to intrusion (hackers, viruses, and other bad things) from the Internet. For those reasons, a separate router works better.

Like access points, routers come in many shapes and sizes, but today’s typical broadband router contains one Ethernet port for incoming cable or DSL traffic and four outgoing Ethernet ports (sometimes more, sometimes fewer), each of which can connect to a different client.

These routers also act as switches, and many act as access points.

  • Switch: You can buy a separate switch, but usually you would do so only if you add wired clients to your network to the point where you run out of Ethernet ports on the router/switch device.

We refers to routers and switches almost exclusively as routers, in keeping with the more common terminology today, and with the fact that switches and routers are often combined in a device sold as a router.

  • Access Point: An access point is a client on your network. The access point (AP) enables wired communication on your network, and indeed operates as the starting point of your wireless LAN, but the AP connects to the rest of the network via Ethernet cable.

It connects to the switch, which in turn connects to the router. In many cases today, however, the three components are combined in one, for the sake of convenience and usability. But for configuration purposes it’s important to realize that they still function as separate units.

Think of an AP/router/switch product as the equivalent of a single-piece stereo system, as opposed to a multiple-component stereo that a network of separate router, switch, and AP would approximate, and you have the idea.