What’s the best way to lay out a local-area network? If there ever were clear answers to that question, the growth of fibre and wireless technologies and some theories on how to simplify moves, adds and changes have thrown them into doubt.
Start with zone cabling. The idea has been around for
years, but it has taken a back seat to the “”home-run”” cabling approach, in which cable from each client device runs back to a central point. That point could be a server room in a small network but is usually the wiring closet or telecommunications room for an entire floor of an office building — which is connected to a vertical backbone in a multi-storey building.
In zone cabling, network cables run from that centre to consolidation points serving workgroups or clusters of cubicles. Separate cables run from there to the desktops and other networked devices.
Zone cabling uses small enclosures, often placed in a ceiling or embedded in cubicle walls or modular furniture, where local cables are patched in to the connections back to the wiring closet.
Zone cabling costs more up front, because of the enclosures and the extra work, but the advantages become apparent in offices that get rearranged frequently. With home-run cabling, moving a desk means moving the cable that runs from that desk to the wiring closet. With zone cabling, it means moving a few metres of cable that can easily be unplugged from the zone enclosure.
Micheal Hill, product manager at zone enclosure vendor Chatsworth Products Inc. in Westlake Village, Calif., says zone cabling won’t pay off for everyone.
“”If you’ve got an office that you’re pretty much settled on a floor plan and you don’t expect high turnover,”” he says, zone cabling probably won’t be beneficial. But in “”a high-churn office environment,”” zone cabling will start paying for itself in two to three years, Hill claims.
WIRELESS HUBS CAN COVER THE LAST FEW METRES
It’s not so much shifting employees from desk to desk that makes zone cabling pay, Hill admits. In those, cases the cable can usually stay put. Zone cabling is beneficial when you re-arrange the office layout, because you need cable drops in different places.
Though the idea has been around for some time, standards are still being put in place covering some aspects of zone cabling. In particular, the Telecommunications Industry Association (TIA) has completed its 569b standard allowing for active network equipment in small, distributed enclosures. Hill expects this may help the idea gain adherents. “”I think that’s what some people — some of the consultants and designers — have been waiting for,”” he says.
Roberta Fox, president and senior partner of Fox Group Consulting in Markham, Ont., says zone cabling is still not common. But she says growing use of wireless networking is bringing about a new twist on the concept. Instead of running cable out to a zone enclosure and then running more cable from there to client devices, she says, a fair number of organizations are running the cable out to a wireless hub and then serving the workgroup wirelessly.
“”People have run out of space in the closet, so they’re sticking wireless hubs up in the ceiling.””
Brad Randall, general manager of Enersource Telecom Inc., which provides data services over an all-fibre metropolitan-area network west of Toronto, says some of his customers are looking at running fibre right to workgroup zones and then using wireless technology to cover the last few metres.
But Enersource’s construction and implementation manager, Ernie Vidovic, say some are still finding wireless performance is not as good as they would like — and security concerns about wireless networks remain a stumbling block.
The other part of the model Randall describes is the use of fibre to the zone. In fact, this is a concept optical fibre manufacturers are promoting, apparently with some success.
Zone cabling costs about 20 per cent less per end-user than running copper from the wiring closet, says David Velasquez, worldwide product line manager for premises fibre at Corning Inc. in Corning, N.Y. He adds zone cabling installations require less cable, less power and cheaper electronics in the zone enclosure.
Then there are the additional savings that operations with a lot of moves, adds and changes can realize from zone cabling.
Selling the idea can still be a challenge today, he admits. One reason is that many IT managers dislike the idea of distributing electronics — they want it centralized for better control. Velasquez points out that the electronics in zone enclosures can be remotely controlled. Standards are another issue, and here Velasquez believes the recent approval of TIA 569b should help.
Hill at Chatsworth says his company has begun in the past few months to see increased sales of active zone enclosures. These enclosures include switches, which means they function like miniature wiring closets, he says, and they make it possible to run fibre from the backbone to the zone enclosure and then use copper cabling from there.
With the combination of fibre to the zone and wireless within the workgroup, copper cabling could be eliminated from some networks without the long-talked about goal of fibre to the desktop ever being achieved.
“”I think there will certainly be buildings, situations where that will be the case,”” says Neil Osipuk, directing analyst for enterprise routers and switches at Infonetics Research Inc. in San Jose, Calif.
FIBRE TO THE DESKTOP DIFFICULT IF YOU HAVE VOICE OVER IP
Fox suggests that fibre also opens up the possibility of eliminating the wiring closet. Because fibre can handle longer distances than twisted pair, she says, it would be possible to run it directly from the zone — or the desktop — back to the data centre.
Don’t hold your breath, though.
“”This would be a total sea change for not only network design but for commercial construction design,”” says Velasquez. Moving all network electronics to the data centre might also introduce a single point of failure, he says, adding standards aren’t in place for this type of network layout.
Fox has also toyed with the idea that eliminating wiring closets, with the associated savings on electronics, might make fibre to the desktop attractive.
But she has a reservation — the rise of voice over IP (VoIP). Today’s IP telephones come with RJ-45 jacks to support twisted-pair cable, Fox says. Adapters are available to make them work with fibre, but using these introduces extra cost and complexity.
With growing interest in VoIP and the need to plan networks for possible future needs, “”if I’m building for the longer term I don’t think I could do fibre direct,”” Fox says. “”As VoIP goes up you may see fibre go down — I wouldn’t be surprised.””
That wouldn’t happen if soft phones — IP telephony software for PCs — were to catch on, but Fox is not sure that’s likely.
Doug Gourlay, director of marketing for the Catalyst 6000 product line at Cisco Systems, Inc., agrees IP phones are a stumbling block for fibre to the desktop — and not just because of their RJ-45 jacks. Many IP phones rely on electrical power delivered over the network, he notes. Power over Ethernet technology, which lets users run electrical power over the copper data cables, allows devices like IP phones to be powered over copper, but not over fibre.
This doesn’t preclude fibre to the zone, Gourlay says, because it’s not difficult to bring the power source to the zone enclosure and run Power Over Ethernet from there. But if you want fibre to the desktop, every IP phone would have to be powered locally, probably with an Uninterruptible Power Supply (UPS), to keep it working during power failures.
MOST PCs DON’T HAVE OPTICAL NETWORK INTERFACE CARDS
And it’s not only IP phones that present an obstacle to fibre to the desktop, Velasquez says. PCs also come equipped with network connections for copper. Bringing fibre direct to the PC means adding an optical network interface card or a media converter. If fibre to the desktop is to take off, he says, “”we would need to convince computer manufacturers and phone manufacturers to put on optical interfaces.””
For now, there isn’t enough interest in fibre to the desktop to make that idea attractive to the equipment vendors. So in most cases fibre will continue to stop, if not at the backbone, at least at the zone.
