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The PC Pro guide to wireless

Posted on 28 Nov 2005 at 12:13

Network addresses

All modern networks, from your home LAN up to the Internet, now use the TCP/IP (Transfer Control Protocol/Internet Protocol) system to communicate; it's almost made all other network protocols obsolete. TCP/IP is a packet-switched networking system. This means data is divided up and sent from transmitter to receiver in small chunks. These packets of information can travel via different routes around the network and need to be routed to the correct destination. This is why the single most important concept in a TCP/IP network is the IP address. Every network adaptor - wired or wireless - on a network must be assigned a unique IP address for that network, so that data packets can find their way to the correct destination. Without exception, all wireless routers will by default handle that automatically via DHCP (dynamic host configuration protocol). The DHCP server in the router doles out an IP address to every wireless PC or device that tries to connect to it.

Gateways and DNS servers

As well as giving a wireless device an IP address, it also informs the device of three important bits of information it needs to communicate: the address of a gateway, the address of a DNS server and a subnet mask. The first two allow the device to communicate with the Net. A gateway is simply the IP address of the device that can route data to and from an external network; in the case of a home router, that external network is the Internet. So in the majority of cases, the gateway address is in fact the router's own IP address; it then acts as a broker, forwarding requests for web pages back and forth via a process known as NAT (network address translation).

A DNS (domain name system) server is one that a PC uses to translate 'friendly' web addresses (www.pcpro.co.uk, for example) into numerical IP addresses by which it can request web pages. The subnet mask is often the cause of confusion; it's a way of separating network subsegments. You don't need to worry about it, however - it's only of relevance to corporate-scale networks and doesn't impinge on getting your wireless network up and running.

Incidentally, NAT also acts as a safeguard in conjunction with any hardware firewall the router may have, since it means that external PCs on the Net can't get direct access to any given PC on your internal wireless network. This is in contrast to USB modems commonly supplied by ISPs, which place your PC onto the Internet directly and are an invitation to hackers.

Mac address

A second type of address you'll probably encounter is known as the MAC (media access control) address. Every standard Ethernet network device, including Wi-Fi access points and adaptors, has a unique hardware MAC address assigned to it at manufacture. For the end user, this is useful, because it allows MAC address-based security to restrict access to a wireless network.

NEW TECHNOLOGY

In the beginning - at least as far as consumers and small businesses were concerned - there was 802.11b, the first popularly adopted Wi-Fi standard. It offers a maximum theoretical throughput of 11Mb/sec, but in practice you're highly unlikely to achieve anything exceeding 5Mb/sec. Then came 802.11g to give a maximum theoretical throughput of 54Mb/sec, but again it's near impossible to achieve even a third of that in practice. But that isn't the only problem - variations in positioning and range make an enormous and unpredictable difference in the speed and reliability of both 11b and 11g wireless networks. This is particularly true in Europe as opposed to the US, where houses tend to be made of wood with thinner walls more easily penetrated by radio waves. Put joists, metal-reinforced concrete and so forth in its way and the results are unpredictable.