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must select “Enable WINS Resolution” and manually enter the IP address(es) of the WINS server(s) on each client computer. Fig.10 shows how to do this. As with DHCP, it pays to have a more than one WINS server to ensure network reliability. Domain Name Server (DNS) Fig.9: here’s how to set up the WINS configuration on a Windows 95/98 client computer if you have a DHCP server. er automatically updates its database whenever computers are added to or removed from the network. When a client computer needs to resolve a NetBios name, it contacts the WINS server, which then hands out the IP address for that name. In effect, WINS is the dynamic equivalent of an lmhosts file. Because a client computer always attempts to contact a WINS server first for name resolution, the need for query broadcasts or lmhosts file checking is eliminated. Setting up WINS WINS is installed on an NT Server machine in exactly the same way as DHCP. After that, it’s a matter of config­ uring each of the client computers to use WINS for name resolution. If you’re also using DHCP, this can be used to supply the primary (and secondary, if it exists) WINS server address to client computers that ask the DHCP server for an IP address. This saves you from having to type in the WINS server address(es) on each of the client computers. Fig.9 shows how to set up the WINS Configuration on a Windows 98 client Fig.10: if you don’t have a DHCP server, you will have to enter the IP address(es) of the WINS server(s) on each client computer, as shown here. computer if you have a DHCP server. It’s just a matter of selecting the “Use DHCP for WINS Resolution” option. Of course, you must also use the DHCP Manager to supply IP addresses to the WINS servers and to hand these out to the clients. If you don’t have DHCP, then you Fig.11: Example hosts File For Windows 98/NT                127.0.0.1 192.168.1.1 192.168.1.20 192.168.1.40 192.168.1.80 8  Silicon Chip localhost lister.reddwarf.home rimmer.reddwarf.home starbug.reddwarf.home holly.reddwarf.home Oh, no! – not another naming system! Well, yes but this one’s somewhat different from WINS because it allows your system to look up, or “resolve”, a domain name (eg, www. microsoft.com) and translate this to an IP address. Currently, this would give you 207.46.130.14 as the IP address for Microsoft’s web site. In practice, this means that a web site on the Internet can be given a friendly address and you don’t have to worry about typing in its IP address. Instead, a Domain Name Server (DNS) looks up the IP address for you. You don’t have to worry about installing a DNS if you only wish to access the Internet, since this will be taken care of by your Internet Service Provider (ISP). However, you may want to set up a DNS if you wish to run a private intranet. Alternatively, if the network is only small and you are using static IP addresses, you can resolve domain names using a hosts file. This works in a similar manner to an lmhosts file (which resolves computer or NetBios names), except that you list the host names next to the IP address. Fig.11 shows a sample hosts file. Note that, as with lmhosts, you must select the Enable DNS option in the TCP/IP Properties dialog box for Windows 95/98. A similar situation applies to Windows NT. By the way, Windows NT server’s implementation of DNS allows direct look-up of the NetBios names from WINS. If this is enabled, it can make quite a powerful system whereby users are able to find others either by their NetBios name (eg, “Rimmer”) or by their Fully Qualified Domain Name (eg, www.siliconchip.com.au). Finally, this article should only be considered as an introduction to DHCP, WINS and DNS. TCP\IP addressing is really quite a complicated subject and you can buy complete textbooks on this topic. And, of course, it all becomes much more complicated when you throw in a SC dial-up adapter. The BreezeNet demonstration system came with an SA-10D Station Adapt­er, an AP-10D Access Point, an SA-PCR PC Card and several external antennas but you can order individual components to suit your special requirements. The laptop computer came from SILICON CHIP. Wireless networking without the hassles Designed for use in professional installations, the BreezeNET wireless networking system is a cinch to install and get going. You don’t need any special driver files with this system; you just plug it into standard network cards and hubs and it works. By GREG SWAIN Want to network different buildings in a school, a univers­ity campus or a factory? A wireless LAN (local area network) can make the job easy and often costs less than a conventional wired LAN. When you think about it, a wireless LAN has a lot of advan­tages. First and foremost is the fact that you don’t have to install cabling – a job that’s often frustrating and awkward (try running cable under concrete paths and roadways, for example). On the other hand, a wireless LAN can easily bridge the gap between computers, be they in different rooms, on different floors or in different buildings! Second, unlike wired LANs, your computers are no longer tied to a particular point. When you have a wireless LAN, they can be easily moved from one location to another. A wireless LAN even permits “roaming”, which can be very useful if you want to trundle a laptop around a warehouse or factory floor, for exam­ ple. Third, a wireless system makes it easy to connect addi­tional computers to the network, anywhere and at any time. All you have to do is connect the appropriate transceiver to the computer, configure it as for a conventional wired LAN, and you’re in business. BreezeNET PRO.11 The BreezeNET PRO.11 system is intended for professional installations. Unlike some wireless networkSeptember 1999  9 EXISTING WIRED LAN REMOTE WIRELESS LAN SA-40 HUB ACCESS POINT (AP-10) SA-PC SA-10 SA-10 ing systems, it’s easily connected to a conventional wired LAN (Ethernet) and is not restricted for use as a standalone system. This means that you could use BreezeNET to “connect” one or more computers to a conventional wired LAN, or to “connect” several individual wired LANs together. These wired networks could be on different floors of a building or even in different buildings, for example. You can also use BreezeNET to connect several wireless cells together and to connect these to a wired LAN. BreezeNET operates at 3Mb/s (maximum) in the licence-free 2.4GHz band and has a range of 50-200 metres in office environ­ments or about 600 metres in free air using the standard 2dBi external antennas. This increases to about 800 metres in free air using a 6dBi omnidirectional external antenna and to 2.4km with an 18dBi unidirectional antenna. Actually, it’s possible to push the range out to about 30km by employing booster amplifiers and low noise amplifiers (LNAs) to drive separate highgain transmit and receive antennas. These amplifiers and antennas are all part of the BreezeNET equipment lineup. Of course, when you’re talking about this sort of range, the services of WIRED ETHERNET ACCESS POINT 1 ACCESS POINT 2 ACCESS POINT 3 OVERLAPPING CELLS Fig.2: two or more access points can be positioned to create overlapping cells. This allows a workstation (eg, a laptop) to be moved across cells without losing its network connection. It also allows a workstation in an overlap area to communicate with two Access Points for load sharing and, if necessary, to extend network coverage. 10  Silicon Chip Fig.1: BreezeNet can be used to create a stand-alone wireless network or to link a wireless network to an existing wired LAN, as shown here. Each Station Adapter (SA-10, SA-40) plugs into a conventional network card which makes the system easy to set up. an RF engineer are required to ensure correct installation and compliance with regulations. In its most basic form, the Breeze­ NET system consists of an SA-10 PRO.11 Station Adapter, an AP-10 PRO.11 Wireless Access Point and the necessary antennas. You don’t have to open up the computers to install either of these units – they both plug into the existing Ethernet “backbone” using Cat.5 cable. In practice, this means that the PCs to be networked must be equipped with conventional network interface cards (NICs), exactly as for conventional wired LANs. And of course, it’s also necessary to install the relevant networking protocols (eg, NetBEUI, TCP/IP, etc), set up workgroups and computer names, and share drives and printers in the conventional manner. For laptops, you need the SA-PCR PRO.11 Wireless PC Card Adapter. This clever little device features twin retractable antennas and plugs into a PCMCIA Type II expansion slot on the laptop to provide mobile network access. Unlike the SA-10 station adapter, which connects to an existing network card, this device is the network card, as well as a radio transmitter. Connecting it up The SA-10 Station Adapter is connected to the PC’s network interface card (NIC) via a standard Cat.5 network cable. You can use one station adapter for each PC but if you have several machines close together, it makes more sense to use the SA-40 adapter. This is similar to the SA10 but it has four ports on the back, which means that it also functions as a conventional 4-port hub. Basically, the SA-40 allows up to four PCs to be connected to the hub to form a small wired LAN. It then provides these four stations with wireless access to a remote wired LAN and/or to other wireless stations. Wireless access points Each wireless network must have at least one AP-10 Wireless Access Point within its coverage area. The AP-10 manages the wireless LAN and is really the “brains” of the system. It keeps a list of known “wireless” stations and it deals with any messages it receives in several different ways (depending on the sources and destination of those messages). First, if a message that’s destined for a wireless station is received from the wired LAN, the AP-10 relays the message to that station. However, if the message has a destination address that it doesn’t recognise (eg, if the message is intended for another wired station), the AP-10 ignores the message. On the receiving side, if the AP-10 receives a wireless message that’s addressed to another wireless unit, it relays the message to that station without forwarding it to the wired LAN. And if it hears a message whose address it doesn’t recognise, it assumes that the message is for a station on the wired LAN and forwards it on accordingly. This might all seem unnecessarily complicated but it serves a very useful purpose: it minimises broadcast traffic, both on the wired LAN and at an RF level, and that means faster network operation. In operation, the AP-10 Access Point keeps a single address for each SA-10 station adapter and up to four addresses for each SA-40. These addresses are registered with the AP-10 when the very first messages are transmitted from the adapters. This means that the SA-10 won’t work properly if you attempt to connect it to more than one PC (eg, via a hub) or, in the case of the SA-40, to more than four PCs. In any case, the station adapters are not designed to plug into hubs; instead, they must be connected directly AP-10D WB-10D SA-40 SA-10 AP-10 AP-10 SA-PC SA-10 SA-PC Fig.3: the WB-10 PRO.11 wireless bridge allows LAN segments in adjacent buildings to be connected. These segments can be either wireless or wired, or a mixture of both. Ranges of up to several kilometres are possible, depending on the antenna system used. to the NICs in the PCs. By contrast, the AP-10 is designed to plug into a network hub. It can also be connected directly to a single PC but in that case you must use a Cat.5 crossover cable. By adding extra access points, the range of the wireless LAN can be greatly extended. Each access point covers a certain area (or cell) and by overlapping adjacent cells, the user is free to roam between them without network interruptions – see Fig.2. In operation, the stations within the cells choose the best Access Point to communicate with. They then automatically switch from one access point to the next as the user moves between cells. It’s also possible to co-locate several AP-10s to share the network traffic in heavily congested locations. The stations inside the common coverage area are automatically equally divided between the Access Points, so that the load is shared equally. Workgroup bridge What if you want to connect wired networks located in sepa­rate buildings or on separate floors? BreezeCOM have that covered too, in the form of the WB-10 PRO.11 Workgroup Bridge. This device plugs into the local network and transmits traffic to the second remote network via an AP-10 Access Point. In this way, a central LAN could be connected to one or more remote LANs; eg, on a university campus. Technical details By now, it’s obvious that a lot of technology is built into this system to ensure reliable and efficient wireless For laptops, the SA-PCR wireless PC card functions as both a network card and a radio transmitter. It features twin antennas which can be retracted when not in use, to prevent damage. September 1999  11 Both the SA-10 Station Adapter (left) and AP-10 Access Point can be fitted with dual-diversity antennas to ensure reliable radio communications. The receiver circuitry monitors the relative signal stengths from the two antennas and automatically switches to the antenna with the best signal. networking. So let’s take a brief look at some of the other technical details of this system. First, both the SA-10/40 and AP10 units are equipped with dual-diversity antennas. In operation, the receiver monitors the relative signal stengths from the two antennas and automatically switches to the antenna with the best signal. This technique effectively combats problems due to multipath propaga­tion and changing signal conditions (eg, when a user with a laptop computer moves about). BreezeNet also uses “Frequency Hopping Spread Spectrum” (FHSS) technology to eliminate interference from other equipment using this band and between adjacent units. The technology makes it virtually impossible for someone else to eavesdrop or to access an existing network using similar wireless LAN equipment. In addition, the system complies with the IEEE 802.11 Wire­less LAN standard which means that it can operate with other wireless LAN products which comply with this standard. Software setup The rear panel of the SA-10 Station Adapter has a single RJ-45 socket (the SA-40 has four). This connects via a standard Cat.5 cable to the network card in the computer. The monitor (MON.) socket allows the unit to be connected to the serial port of a PC so that it can be configured using the embedded SNMP (Simple Network Management Protocol) software. 12  Silicon Chip Although the BreezeNet PRO.11 wireless networking system operates immediately after installation, it’s best to change some of the internal settings. This is done for security reasons, as much as any thing else. In summary, you configure the Station Adapters and Access Points using the embedded SNMP (Simple Network Management Proto­col) software. This involves connecting the MON jack on the rear panel of each item to the COM port on the PC using the supplied cable and then running a terminal emulation program such as HyperTerminal. Each AP-10 Access Point on the Brief Technical Details Wired LAN Interface Compliant with: Physical Interface: Ethernet/IEEE 802.3 CSMA/CD standard. 10BaseT for AP-10 Access Point, SA-10/40 Station Adapters & WB-10 Wireless Bridge; PC Card Type II/ PCMCIA 2.1 for SA-PCR/PCD PC Card Adapters Wireless LAN Interface Compliant with: IEEE 802.11 CSMA/CA wireless LAN standard Radio Specifications Type: Frequency hopping spread spectrum (FHSS) Frequency Range: 2.4-2.4835GHz Antenna Diversity: Two antennas selected on a per packet basis Range 2dBi External Antennas: 50-200 metres from Access Point to Station Adapter in an office environment; about 600 metres in free air Other Antennas: 2.4km with 18dBi unidirectional antenna; up to 30km depending on external antenna and regulations Data Rate Over the air 3Mb/s, 2Mb/s & 1Mbs; 15Mb/s aggregate with overlapped cells (maximum number of co-located Access Points = 15) network must be given the same “network identifier” (ESS ID) or password. This prevents unauthorised access by third parties, unless they happen to know what the password is. Alternatively, you might want to separate two adjacent wireless networks by deliberately giving the Access Points dif­ferent passwords. In addition, you can set different frequency hopping se­quences for each Access Point, to minimise channel collisions, and configure a range of other parameters such as whether to use one or both antennas. Unfortunately, we didn’t get the chance to evaluate this aspect of the BreezeNET system, since we were supplied with a demonstration system only. This included an SA-10D Station Adapt­er, an AP-10D Access Point, an SA-PCR PC Card (for laptops), several external antennas, two plugpack power supplies and a manual. We plugged it in as directed and it all worked, just like that! The manual, by the way, is quite comprehensive and includes sections on Planning & Installing Wireless LANs (including multi­ ple-hop installations), Accessory Installation, Wireless LAN Concepts and Radio Signal Propagation. There are also tables showing the various antennas available and the expected ranges for various data rates (3Mb/s, 2Mb/s & 1Mb/s). Where to get it This 8.5dBi unidirectional external antenna gives a range of about 2.4km in free air. The price of all this technology doesn’t come cheaply but as previously pointed out, this equipment is intended for profes­sional installa- A comprehensive range of external antennas is available for use with the BreezeNet wireless networking system. This 6dBi omnidirectional antenna gives a range of about 800 metres in free air. tions. And in many situations, it will be far cheaper to install a wireless network (eg, to link buildings) than a wired network. You can expect to pay around $2030 for the SA-10 Station Adapter, $3010 for the SA-40 Station Adapter and $3640 for the AP-10 Access Point. For further information on the BreezeNet PRO.11 wireless networking system, point your web browser to: www.breezecom.com The equipment is sold locally by Namlea Data Systems, 22 Cleg St, Artarmon, NSW 2064. Phone (02) 9439 6966; fax (02) 9439 6965 or email: SC ndson­line<at>namlea.com.au September 1999  13