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NT Enterprise
The Bandwidth Bottleneck
Plan accordingly, or your new intranet and multimedia applications will bring your network to its knees.

-- by Tom Henderson

It's been a full year now that I've been writing about enterprise issues in WINDOWS Magazine, and what a blistering year it's been. During my tour of duty on these pages, businesses have flocked to the Internet, deployed intranets at a dizzying rate and pushed out massive multimedia applications to desktop users.

Amid this flurry of activity, many businesses failed to anticipate the network congestion these new applications can cause. Indeed, networks are increasingly clogged by Internet feeds from PointCast and CNET, not to mention rich (translation: fatter) document types. Add imaging, video or groupware documents to the mix, and network response times can slow to a crawl.

Infrastructure overhaul

You could throw CPU and memory upgrades at the problem, but a wiser move is to check your network's infrastructure. Cabling and distribution methods that were once lucid may now bear a stronger resemblance to clogged arteries. So, be a good network cardiologist and attack the disease before the problem becomes serious or even fatal. The solution is often wider arteries-as provided by technologies such as Fast Ethernet and Asynchronous Transfer Mode (ATM)-which can carry data 10 or more times faster than conventional 10Mb-per-second Ethernet networks.

Fast Ethernet has two flavors: IEEE 802.3u 100BaseTX and 100BaseT4. Cabling for 100BaseTX has to be wired according to a specification called EIA (Electronic Industries Association)/TIA (Telecommunications Industry Association)-568 (A or B). Specifically, the cabling and all the connecting components, such as wall plates and punch blocks, must be graded to TIA Category 5. Each cable segment can be 90 meters long, with another 10 meters as the cable link to a node.

The other Fast Ethernet version, 100BaseT4, can run on a lesser grade cable called Category 3, often referred to as Cat 3. This cable is commonly used in older Ethernet 10BaseT networks, and for many slow (4Mbps) Token Ring networks. Although 100BaseT4 looks like a perfect retrofit for Ethernet 10BaseT networks, many organizations that choose this option are surprised to find that all four Cat 3 wire pairs in their Ethernet 10BaseT cable weren't connected at installation.

Why not? Ethernet 10BaseT and Ethernet 100BaseTX use just two pairs of wire within the four-pair Cat 3 cable. As there was no industrial specification mandating the connection of the remaining two pairs of wires, many installers either didn't connect them (why do more work?) or used the remaining pairs for something else.

A pair of problems

The problem is that 100BaseT4 requires all four Cat 3 wire pairs. It's estimated that about a third of organizations with Ethernet 10BaseT wiring can't run Ethernet 100BaseT4 because of the frustrating two pair/four pair wiring issue.

The lost pairs problem also affects another high-speed alternative: Hewlett-Packard's 100VG/AnyLAN, which also runs over all four pairs of Category 3 cabling.

The IEEE standards body had a working group that covered 100VG called the 802.12. The 100VG system looked promising because it supported inexpensive cable and could use either Ethernet or Token Ring frame types. Better yet, 100VG has an integrated Quality of Service capability that can prioritize bandwidth-intensive multimedia transmissions between machines. But alas, 100VG appears relegated to niche status because only selected smart hub and router vendors support it.

Regardless of which high-speed networking technology you choose, the safest bet is installing Category 5 cable, which supports Ethernet 10BaseT, 100BaseTX, 100BaseT4, ATM (running from 25Mbps to 155Mbps) and all current versions of Token Ring. Also, during the installation, ensure that all four pairs of Cat 5 are reserved for the network.

The ultimate fat pipe, Gigabit Ethernet, is maturing rapidly, with standardization expected as early as this spring. At least for the short term, running Gigabit Ethernet will likely require more costly fiber optic connections. But since the most expensive part of a wire installation is the cable pulling-rather than buying the actual cable-fiber may be something you want to consider for new network installations. Some administrators question whether Gigabit Ethernet on fiber is really needed, but they're probably the same folks who questioned the need for Fast Ethernet a few years back.

Aerobic networking

Several other variables can hinder network performance. For instance, response times usually slow as more users are added to a network segment-hence the use of routers and switches to reduce the user-to-segment ratio.

Sometimes the performance bottleneck is on the server. One of the silliest things I've seen repeatedly is a hefty NT applications server choked by a single conventional Ethernet connection.

Novell has had a handle on the server bandwidth problem for years. Put several network cards into a NetWare server and you can add the bandwidth of the cards together in many designs. In other words, the server can concurrently communicate with numerous networked clients. But first, a problem had to be overcome with the IPX protocol once favored by Novell (the company is finally-albeit slowly-embracing native TCP/IP)

In an IPX enterprise, each NetWare server network card must have a unique IPX Network Number. The problem is that IPX clients favor binding to the server card with the lowest Network Number, meaning there's little or no load balancing between multiple cards on a NetWare server.

Novell has released IPXRTR.NLM for NetWare 4.x. This allows several network cards to share the load. It also offers a transparent failover from one network card to another, should a card failure or network problem arise.

Microsoft's NT Server-which can run TCP/IP or IPX-can support several network cards. However, a multicard NT server running IPX suffers the same load-balancing problem that NetWare used to have. To see the bottleneck for yourself, link a multicard NT Server (version 3.5x or 4.x) to an Ethernet switch. The result is one card flooded with traffic, and there's no way around the problem.

Once you've mastered load balancing, as well as network wiring and segmenting, your network ought to be breathing easier. After all, a modern EIA/TIA-568 cabling infrastructure was designed to give companies a solid foundation for today's leading signaling methods. With luck, you'll get a few years of life from it-until Petabit Ethernet arrives.

Moving on to other subjects, you've probably read the early reports on Microsoft Office 97. I have a few pointers to add for administrators. First, test it like crazy, especially if you have Office-enabled applications. I've had some difficulty with VBA-enabled applications that surrounded OLE object transfers. If you have the Office SDK, look through the libraries for appropriate fixes.

A positive Outlook

Despite the problems, Office 97 feels more integrated than prior versions. One component, Outlook 97, will likely be a popular replacement for Microsoft's Exchange client, but

beware. Like Exchange, Outlook appears to freeze if a desired transport to the Exchange server isn't available and the option to ask the user for the transport method isn't checked. You can't change the properties for Exchange services by right-clicking on the Outlook desktop shortcut, or even the Outlook icon. Instead, change the properties of the Exchange icon to change or make new user Profiles.

Outlook also makes a nice replacement for Symantec's ACT (it can import ACT files) and Microsoft's Schedule+, but there's a catch. A wizard will guide you through the process of importing Schedule+ files if it detects your existing Schedule+ installation. If, however, Office 97 is installed without replacing an older Office version (for example, if Office 97 and 16-bit Office reside in different directories), then you'll need the passwords to your old Office and Schedule+ files. The upshot is that calendars and contacts can be either replaced or duplicated, meaning you could have redundant files on your hard drive.

Contributing Editor Tom Henderson is vice president of engineering for Indianapolis-based Unitel. Contact Tom in the "Enterprise Administrator" topic of WINDOWS Magazine's areas on America Online and CompuServe, or care of the editor at the e-mail addresses here.

Copyright (c) 1997 CMP Media Inc.

Windows Magazine, March 1997, page NT37.

[ Go to March 1997 Table of Contents ]