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IF YOU HAVEN'T NOTICED, the cost of setting up a local area network has fallen considerably: 10Base-T network cards (ISA or PCI) can be found for under $30, and an 8-port minihub (essentially an amplifier) can cost you less than $50. For notebook computers, a "PC Card" or PCMCIA network adapter will be about $70. Add a few "patch cords" of appropriate lengths ($3 to $20) and you can interconnect several machines. By using the "peer-to-peer" networking built into Windows 95, Windows 98, Windows NT, and yes, even Windows for Workgroups 3.11, you can share resources between the interconnected computers. For three machines you could probably set up a 10Base-T network for about $150. 10Base-T moves data at 10 megabits per second through wires that are similar to telephone wires, but instead of four conducting wires in the cable there are four pairs of wires, each pair spiraling (or twisting) around its mate. The twists perform a shielding function that protects the signal from electrical interference. Lastly the connecting plugs at the ends of the wire are not the same as on a regular telephone (RJ-11 plugs/jacks). The RJ-45 plug/jack has eight prongs and is somewhat wider. 10Base-T wiring must meet a specification known as "Category 5," or "Cat-5" for short. This configuration will deliver data transfers between machines on the network at approximately 250 times faster than the 40 kbps you might expect to get with a "56K" modem connection. For those of you with slightly deeper pockets, a newer technology, 100Base-T, can move data at 100mbps instead of 10mbps. Adapters cost about twice as much, hubs about three times as much, and they still use Cat-5 wiring. A home network based on 10Base-T should serve you quite well unless everyone in the house is moving huge quantities of data, such as video and/or sound clips. Usually a shared resource is taken to mean media such as hard disks, CD-ROM drives, and printers. It usually does not include modems or other forms of connection to the Internet. Since my work often requires using the Internet for accessing support sites, or working on remote client host machines via TelNet or FTP, I sometime have a problem when my use of the resource conflicts with that my son, who wants to check his e-mail or look something up on the Web for his homework. The conflict happens just often enough to be a nuisance but not enough to warrant yet another telephone line into the house/office. Now, however, with the use of gateway/router software, shared resources can also mean simultaneous usage of a single Internet connection between the machines on the network. The connection to the network might be via a dial-up connection--the Dial-Up Networking Adapter, as typically used for connecting to an Internet Service Provider (ISP), an ISDN line, an ADSL line, or a cable modem. THERE ARE SEVERAL ways of enabling the sharing, such as installing and configuring software on a machine running Windows NT. However, there are now software packages that have simplified the installation and do not require a Windows NT platform. These will run quite nicely on a Windows 95 or Windows 98 platform. SyGate Server 3.1 happens to be the package that I tried. You can download an evaluation copy from Sygate's Web site (www.sygate.com). The software provides several functions: a) it acts as a DHCP server; b) it acts as a NAT (Network Address Translation) router, c) it acts as a firewall, and d) it provides black-list and white-list services. Let's take a look at each of these functionsDHCP. When you connect to the Internet, each machine must have a unique address, of the form nnn.nnn.nnn.nnn, where each of the 'nnn's represents a number from 0 to 255. Originally, when you signed up with an ISP, you were given a specific number, say 209.123.162.12. Typically, the left-most digits (209.123) or (209.123.162) denote the "network number" associated with the ISP, and the right most digits (162.12) or (12) denote the machine within the ISP's network, i.e. your machine. Unfortunately, this numbering scheme ran the risk of running out of numbers available, so the mechanism of dynamic address assignment was invented. With dynamic address assignment, an address is "leased" to your machine for the duration of the call, once the call is terminated, the address is returned to the available pool and made available to the next caller. The DHCP protocol is used by a client machine (your PC) to request a DHCP server (the ISP) or in the case of SyGate Server and similar to provide an IP address for the duration of the call. In addition to DHCP, the Internet standards committee reserved a block of addresses (192.168.0.0 through 192.168.255.255 is one of them) for use by "intranets." In this context, an intranet is a local area network under the control of the enterprise; in our case it is your network of a few (up to 255) machines. The standards are such that messages with addresses in the range of 192.168 will not be allowed to leave the local network, thus reducing the traffic through the Internet. NAT. Network Address Translation is a service provided by a router that substitutes a valid and routable IP address for a non-routable address. Thus, if your machine has the address of 192.168.0.3 assigned to it by the local DHCP server, and you ask for a web page at 209.1.2.3, the NAT function obtains an IP address from the ISP's DHCP server, and substitutes that "return address" for you local non-routable address. When a message is delivered with from the Internet with the routable IP address in the packet, the NAT substitutes the local address and delivers it to your machine. It performs the necessary adjustments to the packet for such things as check sum, and even makes adjustment to special-purpose packets as used by some Internet functions. With NAT, if each machine on your local network has a unique IP address, as it will because of DHCP, NAT can keep track that machine A requested a page from www.nick.com, machine B requested a page from www.e-Bay.com, and machine C is checking the mail system. Firewall. The simplified explanation, because the "real" address of your machine is never visible to the outside world, is that it is not possible for an intruder to obtain access to the contents of your machine. Black-list/White-List. Putting an IP address in the black list on the gateway prevents a client machine from communicating with any computer or application at that site. Assigning a white list to a client machine restricts the client machine to being able to access IP addresses only on the "approved" list. SyGate Server specificsA client of mine had recently installed a cable modem and wanted to let the other machines in his home office have access to the Internet. I did some searching on the Internet and came up with about 40 possible software or hardware candidates. Most of them were targeted at the corporate market, but a few also had pricing that made it reasonable for the small office/home office market. After comparing product features, I decided to download the trial version of SyGate Server 3.1 with a 3 concurrent user license, SG31.EXE - 2.3MB.
I followed the instructions and configured my machine to let SyGate Server 3.1 manage my dial-up networking connections and to provide DHCP server capabilities. As part of the install, you manually connect to the Internet by double-clicking on your dial-up networking connection. SyGate Server 3.1 then finds the connection and completes its configuration. I then went to another machine on my network and configured it to look for the SyGate Server. after that I checked as instructed: I first used 'ping' to make sure that I could see the server. I then 'ping'ed a site out on the Net (SyGate suggested trying www.intel.com). I was quite pleased to hear the server running on the machine in the other room grab the modem, get the dial tone, and dial my ISP. In a few seconds ping responded with messages from www.intel.com. I immediately started my browser on the second client machine and was able to "surf". I started a download and then went to the server machine and checked my e-mail. It worked. The download completed on the client machine, and I put my son to work surfing. I then did some simultaneous surfing from my primary machine. We did not interfere with each other, and both of us had acceptable response time. Deciding to "go for broke," I connected my notebook computer, and it, too, was able to surf--three machines connected to the Internet via one 56K dial-up modem connection on one telephone line! After an hour or so of test playing with it, I was sold on SyGate Server 3.1. I logged onto the company's Web site and followed the instructions for purchasing/registering, and using a secure site. Within an hour I received a "key" via e-mail with simple instructions for entering, and my server was registered. The trial download permits use for 30 days and has a 100MB download cap. Quite enough for evaluation. A few days later I downloaded and registered a copy for my client. His connection is somewhat different. A cable modem requires two network cards in the "server" machine. The first one is connected to the cable modem and is often included in the cable modem lease. The second one is connected to the hub, which connects the elements of the local area network. SyGate Server 3.1 then "owns" the network card associated with the cable modem and interposes itself as a router/gateway/firewall between the two network cards. Other than having to identify during installation which card is connected to the cable modem versus which network card is connected to the local area network's hub, installation is the same. ISDN and ADSL connections are handled in the same manner as a cable modem. There are a few well-chosen options available for configuring SyGate Server 3.1. For a dial-up connection, you may specify whether a client machine can cause the server to initiate a dial-up connection, and you may specify how much inactivity on the dial-up connection to allow before causing a disconnect. You may specify whether it is to start when the machine boots. You may control whether DHCP services are to be provided. (On a corporate LAN, you may have already assigned IP addresses, so you wouldn't want DHCP.) You may control whether a log of activity is to be maintained. Here is a sample from the log. The log file is continuous: When it reaches a certain size, older entries are removed from the top. Sun Aug 29 20:23:23 1999 DNS 192.168.0.3:1037--->192.168.0.1:53
www.microsoft.com The server normally runs as a mini-icon in the system tray, next to the clock. You may open it up to run various diagnostic functions, see which machines are currently attached, control file and printer sharing, etc. Figure 1 shows the server screen expanded. In the left frame I have highlighted "Status" and the status of the server is displayed in the right frame. I then clicked on Tools/Configuration to get the property page shown--most of these settings are the defaults. The server will run on Windows 95/98/NT. When run on an NT machine, it runs as a service. Clients that make use of the server may run 95/98/NT and even Windows 3.11. All in all, I am very satisfied by the program. Oh yes, the price: the three-user license is $39.95. Visit their site, read the reviews there, download and read the manual, then download the software and give it a try. Lastly, some legal comments: Check your agreement with your service provider about restrictions limiting or prohibiting you from connecting their service to a local area network. Because configuration of a proxy server or gateway has previously been difficult to support, many of them do not support networked connections. They will only assist with problems on a non-networked machine. SyGate Server makes support a non-issue. |
| Bruce Preston is president of West Mountain Systems, a consultancy in Ridgefield, CT, specializing in database applications. A DACS director and moderator of the Random Access sessions at general meetings, Bruce also leads the Access SIG. |
With a three-concurrent-user license you
may have more than three machines connected to the Internet via
the server, but at any given instant, only three may be actively
sending or receiving data. The server software needs to be installed
on only one machine--the one that has the physical connection
to the Internet, be it via dial-up networking, ISDN, ADSL, or
cable modem. It is not necessary to install any software on the
client machines. Since everything you need is provided by the
operating system, you need only to configure the machines to
make use of DHCP to get an IP address; the default configuration
in Windows 95/98/NT is that the machine will find the DHCP server
on its own. Download the file SYGATE.PDF - 176KB for very complete
and easy-to-follow instructions.