Timothy
Parker Consulting Incorporated
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Finishing it off In the last issue of this column, we configured the UNIX systems to work on our peer-to-peer network. With that dealt with, our peer-to-peer network is complete, supporting Windows 3.X, DOS, Windows 95 and NT, and UNIX systems all on a simple 10Base-T network. A few last items dealing with this type of simple network round out our look at this issue. We chose twisted pair 10Base-T cables (those with RJ45 connectors on them) for this network because it tends to be easier to install than 10Base-2 systems. The latter look like television coaxial cables, and must run in a contiguous chain from one machine to another, covering the entire network. 10Base-T network cards are cheaper than 10Base-2 cards, and the cabling is much more flexible and all runs terminate at a hub. For small networks, unintelligent hubs are fine as well as inexpensive. However, 10Base-T cannot be used on all devices, so you may find yourself dealing with coaxial cables instead of or as well as 10Base-T. Some network peripherals like printer network interfaces, HP’s JetDirect EX Plus 3 printer distribution panel, network remote access server units, and other devices come only with BNC coax connectors. You can buy a converter that will plug into the BNC connector and allow use of a twisted pair cable instead, but these tend to be expensive and are often awkward to install. Some UNIX workstations are shipped without RJ45 connectors, too, forcing converters or 10Base-2 cables. Using 10Base-2 is not a hassle, and in many ways it can be easier than 10Base-T. (There’s also an issue of speed differences. In the labs, 10Base-2 consistently offers a higher throughput than 10Base-T under the same loads. The difference is not significant for most networks, though.) To string coax cables, each device needs a T-connector on its BNC port, and a coax cable running from that T to another. The system is set up as one long chain, with devices connected through Ts at each machine. At the two ends, one side of the T has a terminating resistor. The primary problem with 10Base-2 networks is that a disconnected device or failure of one network interface card along the chain may cause a complete network failure, although this is very rare. Coax cable is still flexible enough to be stapled along baseboards or snaked through ceilings and walls, but it is much more expensive than twisted pair cabling. A special crimping tool is needed to add your own connectors to the cable, too, due to the amount of force required. You can run both coax and twisted pair quite easily together, as long as your 10Base-T hub has a BNC connector (most do). In my network, I have a few BNC-specific devices chained together with coax, which terminates at the unintelligent hub. From the 8-port hub, twisted pair cables snake to each Windows machine. The hub handles the routing from twisted pair to coax and vice versa for you, and there are no noticeably delays in transmission across the two networks. It’s a nice way to blend together the two types of devices, and provide more flexibility for your network peripherals. If you are installing more than eight network devices into a hub, and you expect heavy network usage, you may want to consider upgrading to an intelligent hub. (Having said that, I know many installations that run 16 or 32 network devices to unintelligent hubs, but their network use is only a fraction of capacity.) An intelligent hub, as the name implies, has some smarts built in to handle routing tasks and to generally increase speed on the network. Many intelligent hubs are available in a variety of configurations with differing numbers of network ports, modem ports, and speeds. If you want to go to 100Mbps Ethernet, you need a hub that can support it, as well as network cards that can do the same. The older 10Mbps Ethernet is fine for most small networks, but since the price different is minimal today, it may make sense to go for the faster hubs and cards. Intelligent hubs are usually managed from a Windows 95 or Windows NT machine. These run software specific to the intelligent hub, and allow remote configuration and monitoring of the hub. You can change hub behavior on the fly, which is often handy for optimizing throughput. Intelligent hubs cost a heck of a lot more than their dumb siblings, though. A typical dumb hub is less than $200, while the low-priced intelligent hubs start at $1,000. Other than remote management, what do you get for your money? Speed. A recent test in my lab for a US magazine showed that on a 10Mbps Ethernet network, an intelligent hub provided 28% faster throughput than its unintelligent version. Do you need to spend the money for an intelligent hub? The decision really depends on the network. If you find it running slow, or you have to support a lot of ports at once, then the price of an intelligent hub may pay off. For small networks of 32 devices or less with a low network usage (less than 30% capacity), forget the hub and buy something else instead. |
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