SCIENCE & ENGINEERING NEWS

San Diego, CALIF. — Logan G. Harbaugh reports that they said it couldn’t be done – running Gigabit Ethernet over standard Category 5 twisted-pair cables. Well, it has been done, and many people are excited about the possibilities of running gigabit speeds over their existing wiring. The question at hand is, at what point is it appropriate? The answer seems to be, in the server room, or when the existing cabling plant can support it.

The exciting thing about gigabit over copper is the price. Both switch ports and network interface cards (NIC) are less expensive, because they don’t need the expensive optical transceiver to convert electrical signals to optical and back. If existing wiring can be used, that also may offer substantial cost savings. However, as with many other items in the IT industry, acquisition cost does not tell the whole story. Nevertheless, interest in Gigabit Ethernet is picking up. Market watcher Dell’Oro Group ( http://www.delloro.com ) estimates that the Gigabit Ethernet segment will nearly double by this time next year, reaching about $4 billion. Not exactly chump changeand that’s only for the switches themselves.

The disappointing thing is that getting actual gigabit speeds may require re-termination, if not new cabling. Network administrators also may find they need to upgrade patch panels and wall jacks, not to mention adding new patch cords, before they can get full speeds. The good news here is that it will take an infrastructure expert (like you) to make the call.

Buying a server based on price is not the best way to goit’s a crucial part of the network and any cost savings can be quickly negated by higher administrative costs, down time, etc. Likewise, no one would buy a server and not put a good UPS on it (we hope). Anyone looking to run lots of Gigabit Ethernet should be looking at costs from the same perspective.

Running gigabit to the desktop for a normal LAN environment would be pretty silly. Even if costs were not a couple of orders of magnitude higher than for switched 100Mbps ports, the stringent requirements for the wiring would increase costs, even if just to test the wiring to ensure it’ll handle the bandwidth. When you add the fact that a normal desktop running Windows 98 will never see even 500Mbps from a gigabit adapter, the whole idea doesn’t make much sense.

So where would gigabit over copper make sense? There are several scenarios. Connecting servers to the backbone, where all wiring is contained within the server room, is one possible application, as is using the technology for high-speed uplinks to workgroup switches or remote wiring closets. Another application would be to connect specialized workstations that need higher speeds and are running operating systems that can get the higher speed out of the adapter.

Connecting servers to the backbone using gigabit over copper makes a lot of sensein a server room, Cat 5 cabling is much more durable than fiber, especially in situations where the cabling may be run temporarily across the floorstep on fiber once, and you can kill the connection. With the number of servers once again increasing dramatically as companies implement server farms for load balancing, the cost of ports also can be a great factor. Also, because the connections often will be via patch cord from the switch directly to the server, without patch panels or wall sockets, getting a high-quality connection is relatively simple and inexpensive.

On the other hand, high-speed uplinks to local workgroup switches, or links from a main server room to local wiring closets, are not an ideal application for gigabit over copper. These connections are the most likely to have high utilization, and for long periods of time. Further, the number of these connections is not likely to be large enough that a big cost savings will be realized from using copper instead of fiber. You’ll also need to consider the future. The development of 10 Gigabit Ethernet ( http://www. smartpartnermag.com/stories/issue/0,4537,2541381,00.html ) is moving right along, and it’s extremely unlikely that a 10-gigabit standard will be produced for copper.

Specialized workstations may be processing graphics, manipulating large data sets, or performing other special mathematical modeling. These systems truly need the higher bandwidth of gigabit and should have operating systems that can take advantage of it. Ifand it’s a big ifthe cabling plant is already well-suited to gigabit over copper, and runs aren’t too long, copper may be the way to go here.

However, if runs are near the limit of 100 meters, or if cabling needs to be redone to pass Cat 5 standards from end-to-end, it may turn out to be cheaper to install fiber. The real issue is that because these workstations are running critical bandwidth-intensive applications, does it make sense to save in the short run on up-front costs, but not deliver the capability promised?

Terminating the wall jack and the patch panel properly is critical for the end-to-end signal quality necessary to fully support gigabit over copper. This process often is skimped on because doing it right is physically difficult and time-consuming, so network administrators may find that their cable plant cannot pass Cat 5 certification, even though all of its parts are Cat 5 certified.

New fiber connector technologiessuch as 3M’s Volition and the MT-RJ standardmake the termination of fiber not only much easier than with the old ST and SC connectors, but also arguably easier than proper termination of Cat 5e copper cabling.

If running new cabling is relatively straightforward, the costs of installing fiber may not be much higher than redoing the copper cabling plant. If the plant has not yet been installed, or if the installed twisted-pair cabling cannot be upgraded to Cat 5 (for instance, if the wiring is the older Cat 3 standard), fiber may be the way to go.

The benefits include more than a cabling plant that easily can handle gigabit, because fiber is immune to electromagnetic interference (EMI). Fiber technology also provides the added benefit of having an upgrade path toyep, you guessed it10 Gigabit Ethernet.

Alternatives There is yet another option for workstations that need high bandwidth. This choice can provide a solution even with operating systems that may only get 150Mbps to 250Mbps of throughput with Gigabit Ethernet. If there are multiple Cat 5 jacks in each location, or if wiring has not yet been installed, multiport 10/100 adapters may be the solution. They provide two or four 10/100 ports on a single NIC, which can be concatenated together to provide a single, 400Mbps connection.

That can provide higher throughput than a gigabit NIC, and at substantially lower system overhead, as well. The total cost also may be less, even counting the multiple cables necessary, because switched 10/100 ports are much less expensive than gigabit ports.

While that action may solve immediate needs, it’s becoming clearer and clearer that to go a lot faster, almost every installation will need to move to a fiber-based environment. While your clients can “do it now” or “do it later,” there’s an opportunity for you at this point in time to become an expert in this new wiring infrastructure paradigm.

The Gigabit Ethernet Alliance recommends that potential users of 1000Base-T test their Cat 5 cabling for return loss and Equal Level Far-End Crosstalk (ELFEXT). Return loss is a measure of reflected energy from impedances in the cabling, while ELFEXT measures the noise from signal leakage at the receiving end of a connection. The alliance warns that these two dynamics may have little effect at the 10Base-T threshold of operation, but that higher speedsboth 100Base-T and 1000Base-Tare prone to performance degradation.

Test suites are available from a number of vendors, including Datacom/Textron, Fluke Corp., HP, Microtest and Wavetek Wandel Goltermann. If, after testing, IT managers find that the Cat 5 links fail, the alliance recommends three kinds of corrective measures: switching to high-performance patch cables; reducing the number of connectors in the link; and reconfiguring some or all of the connectors. Fun!

What is Category 5 cable? It’s not necessarily cabling of a predefined sizeit’s cabling that passes a set of tests to verify minimum data-transmission standards. Cat 5 is based on the ANSI/EIA/TIA 568 Commercial Building Telecommunications Wiring Standard developed by the Electronics Industries Association as requested by the Computer Communications Industry Association in 1985. Category 5 enhanced, (Cat 5e) Cat 6 and Cat 7 also are based on their ability to pass data. While Cat 5e cable is an enhanced version of Cat 5 that can be used anywhere Cat 5 can be used, the same cannot be said of Cat 6 and Cat 7.

It’s unfortunate that there is no standard for connectors, cabling or anything else that ensures interoperability between one Cat 6 cable and another Cat 6 jack. Currently, a number of vendors are working on, or trying to promote, Cat 6 and Cat 7 standards, but there is no accepted industry standard. Sounds to us like the various types of Unix.

As with the various categories of twisted-pair cabling, there are a number of different fiber standards, although in the case of fiber, the only difference is the connectors. The actual fiber is the same for all. The most prevalent connectors are the ST and SC connectors, which comprise most of the existing switch and NIC interfaces. 3M’s Volition, MT-RJ, Lucent’s LC and Panduit’s Opti-Jack are all connectors designed to improve the process of terminating fiber connections.

As an example, a standard ST connector may take an experienced technician between five and 10 minutes to terminate. A Volition connector can be terminated in a minute or so by even an inexperienced staffer, and the quality of the connection is less subject to the ability of the technician, as well.

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