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Cat6A’s time has Arrived

It might have taken five years to come up with the standards, but for copper proponents the wait was worth it. The technology behind it ensures that copper-based structured cabling is good for at least 10 Gigabit Ethernet, and likely beyond.


July 1, 2008  


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At first glance, one would say that augmented Category 6 (Cat6A) cabling might have a lot of strikes against it. For one, the TIA TR 42 engineering committee had a huge technical problem to overcome in developing and ratifying a standard for a 10-Gigabit copper solution.

The technical problem centers on what electrical engineers call alien crosstalk, a coupling interference or noise that comes from adjacent cables that ultimately affects a system’s performance. Resolving such problems might greatly explains why it took five years to write the standard, now known as TIA 568 B. 2-10.

The standard for Category 6A, which the engineering committee ratified on February 8, represents the most advanced set of network cabling requirements specified up to 500 MHz. Category 6A is fully backward compatible with all the previous categories, including Category 6, Category 5e and Category 5.

“It is the most demanding stringent spec in the industry,” says Paul Kish, director of systems and standards at Belden in St Laurent, Que. and also one of the engineers who sat on TIA TR 42 committee. “It’s not just another generation of cabling. There is a lot of technology behind it.”

The specification itself is a massive 136 pages in length, replete with 32 diagrams of test configurations, 57 tables of test specs and 35 drawings of special test fixtures required to make proper measurements and conduct required tests. In addition, Cat 6A requires new test equipment, defined as a Level IIIe tester, priced between $6,500 and 8,000 plus several test adapters each at around $400.

That being the case, one would hope that there is a solid business case for companies to upgrade to Cat 6A cabling.

Much of it rests with the anticipated need for speed and reliability that the old cable categories just cannot handle. The basic drive behind Cat 6A is the desire to support 10 Gbps (informally called 10G or 10 Gig in the trade) to the desk over the standard 100 metres. Although the current Cat 6 standard will support it up to 55 metres, this is not suitable for most organizations.

One of the key questions is whether companies ought to go about installing Cat 6A cables now, or wait until prices drop, as they invariably do when supply is greater than demand. The problem being that if companies wait too long, competitors might get the edge with faster, more efficient operations.

“That’s always the dilemma, since cabling is strategic to your business needs,” says Richard Smith, Canadian region director of BICSI and manager at Bell Aliant Cabling Solutions in Moncton, N. B. “The decision ultimately comes down to the type of business that you are operating in, and where your business is headed in the short-to mid-term. Do not spend the money if you are not going to see the return on investment.”

Many analysts predict that structured cabling is ready to enter a substantial period of growth within the next five years. For example, Frank Murawski of FTM Consulting in Hummelstown, Pa., says that the worldwide market for structured cabling will grow from US $15.3 billion in 2008 at an annual compound rate of 13.7% to US $29.1 billion by 2013.

Much of the growth is expected to take place with fiber, where Murawski predicts that in 2013, fiber will account for 60.1% of the total structured cabling systems market.

If applications are the chief driving force behind Cat 6A, the main users of such high-speed copper cable are data centres and Internet server farms, most of them operating for financial-services firms.

These centres, which are often tucked away in secret secure locations, process transactions like debit, credit card and online transactions for banks, credit card companies and brokerage and insurance firms.

Given the continuing and increasing use of consumer debit and credit cards, one can easily see how a data centre can likely process billions of transactions per year.

To speed things up and shorten the time for each transaction requires both an efficient network and reliable communications between servers, while consuming less energy, which is a growing concern.

Such industry requirement easily explains the growing trend to 10 Gig in the data centre and the increased reliance on server virtualization as a means to speed up processes. “You need very quick communications between servers,” says Kish, who points out many studies show that “doing it that way increases the efficiency of the network by 80%.”

Others agree on the power of virtualization. “Virtualization for data centres is one of the driving forces for 10-Gigabit Ethernet,” says George Zimmerman, chief technology officer for Solareflare Communications in Irvine, Calif., a silicon vendor of Ethernet products that enable the adoption of 10 Gigabit for data centres and enterprise networks. “Virtualization and storage are driving 10G. The virtualization application makes companies run at 70% or 80% capacity in data centres. It allows a virtual data centres to operate more efficiently. And since many of these data centres have been using copper solutions, they will likely stick with copper.” For one, copper allows ad-hoc upgrades, when needed, something that cannot easily be done with a fiber solution.

Thus, with Cat 6A, Storage over Ethernet links can now replace fiber channel over Ethernet.

Future of Cat 7 & Cat7A

The Cat 7 standard had been created to allow 10- Gigabit Ethernet over 100 metres of copper. The cable contains four twisted copper wire pairs, just like the earlier standards.

Cat 7 can be terminated in RJ-45 compatible GG45 electrical connectors, which incorporate the RJ-45 standard, and a new type of connection to enable a smoother migration to the new standard.

When combined with GG-45 connectors, Cat 7 is rated for transmission frequencies of up to 600 MHz, which is greater than Cat 6A.

While there might not be any significant current uses for such bandwidth in the typical office, it will likely become more important if trends toward the use of high-speed and highbandwidth video take place.

In short, convergence will (finally) be a reality. Two video applications, in particular, come to mind as very real possibilities: video-phones and video on demand at the desktop. Such high-speed and high-bandwidth applications might drive the need for a Cat 7 or Cat 7A solution for businesses.

One anticipated area of growth is employee training, where trainers would deliver lectures and training material via video straight to the desktop (see sidebar, Beyond Cat 6A).

To be sure, things are moving forward for a 100-Gig copper solution. A test at Penn State University last year showed that it was possible to transport 100 Gigabits per second over 70 metres of Cat 7 cable (ISO/IEC11801: 2002 category 7/class F). They are looking to extend the range to 100 metres using a cable manufactured by Nexans. “We have examined the possibility of sending digital data at a rate of 100 Gigabits per second over 100 meters of Category-7 copper cable,” said Mohsen Kavehrad, the W. L. Weiss endowed chair professor of electrical engineering. “These are the current, new generation of Ethernet cables.” This technology may be available in early 2013.

Yet, not everyone agrees that there is a need for a 10-Gig copper solution, let alone a 40-or 100-Gig copper pipe. “There is no real business case for Cat 6A,” says Jim Hayes, founder of the Structured Cabling Association in Fallbrook, Calif.

“LAN backbones have already become a fiber-optic stronghold and upgrades to 10G Ethernet can be done by just swapping out the electronics at most companies. New cabling systems are using laser-optimized OM3 fiber, the perfect media for 10G Ethernet and perhaps even 40G and 100G when they become available.”

That reasoning, Hayes says, essentially leaves server connections as the only available market for Cat 6A, and even then, that could well be served 10Gbase-CX4, which although limited to 15 m, is adequate for most server
connections.

Other concerns relate to the cable’s size. The diameter of a Cat 6A is 0.31-inches versus 0.22 inches for Cat 6, a 40% increase. That is a significant difference in bulk, particularly when you are running hundreds or even thousands of feet of cable for an installation.

As well, optical makers such as Corning Cable Systems point out the following: A typical plenum Cat 6A UTP cable weighs 46 lbs per 1,000 ft of cable. The accumulated weight of Cat 6A cabling alone to serve a 108-circuit, 200-ft length, 10G installation will be about 1,000 lbs, compared to 40 lbs for the same length of a 216-fiberoptical cable.

The 25-times greater weight of Cat 6A cables, the company argues, “will require additional hardware costs to support the load, and may contribute to cable strain relief issues in hardware, as well as compression issues in trays and conduits.” Corning does not mention, however, the greater cost of optical fiber over copper — up to four times more in some cases. As well, fiber is still trickier to handle and install than copper.

Even so, Hayes focuses less on large data centres and server farms and more on everyday business users, typically those who operate small to medium sized businesses. For Hayes and other like-minded individuals, it is all about mobility and convenience and wireless fits that need exceptionally well.

“The network of the future is certainly not recabling every couple of years with another UTP upgrade. If 10G needs to be delivered to the desk, it’s probably going to be on fiber,” Hayes predicts, “not just for the bandwidth, but also for the lower power consumption. But I’m betting on more mobile applications, with a backbone of fiber connecting wireless access points.”

Zimmerman of Solareflare could not disagree more. “I see wired and wireless networks co-existing,” he says. “In terms of reliability and security, the wired network is the main infrastructure and the wireless network is more of a convenience network.” That being said, it might well be that there is room for both copper and fiber in today’s business environment. Kish of Belden makes his strongest point on the staying power of structured copper cables like Cat 6A.

For the newer applications that will require higher bandwidth and greater speeds, whether that is VoIP, video on demand or video-phones, companies will have to seriously consider the merits of Cat 6A cabling solutions as they either expand or upgrade their networks and look at the whole issue of convergence.

“If you consider some of the technology that’s built in, “it’s quite impressive,” Belden’s Kish says. “It’s the most reliable cabling system that you can put in.”

Fair enough. Copper has many advantages, says Steven Foster, marketing manager at The Siemon Company, a maker of network cabling in Watertown, Conn: “Copper cabling is straightforward, reliable and almost universal,” he says. “It’s flexible and can be laid rapidly, effective for nearly all applications. It comes in several varieties, designated by their performance category rating. The sheer functionality and cost-effectiveness of copper cabling mean it will be the system of choice for a long time to come.”

That being the case, it looks as if Cat 6A will be a winner, leading the way to future improvements in structured cabling, when, one day in the future, 100G installations become the industry norm.

Simply put, one should be cautious about predicting copper’s demise. Copper is here to stay.

Perry Greenbaum is a Montreal-based freelance writer. He can be reached at pjgreenbaum@gmail.com.

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Alien Cross-talk

Alien cross-talk (AXT) is cable-to-cable noise that becomes more pronounced at higher frequencies and more problematic in unshielded (UTP) systems. The noise coupling occurs on like pairs (for instance bluewhite to blue-white), since they will have roughly the same twist lay. This is not a concern with screened or shielded systems, because the shield prevents alien cross-talk from affecting adjacent cables.

Alien cross-talk between cables reduces the operational bandwidth of a cabling channel, because an increased level of cross-talk noise decreases the overall signal-to-noise ratio. For higher bandwidth applications like 10GBASE-T, its effects are much more severe than for lower-speed network applications.

Because of this, managing alien cross-talk has become very critical in the deployment of 10GBASET. Accordingly, there has been increased amount of research and development in technologies to address this problem.

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The Cat6A specification itself is a massive 136 pages in length, replete with 32 diagrams of test configurations, 57 tables of test specs and 35 drawings of special test fixtures required to make proper measurements and conduct required tests.

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One of the key questions is whether companies ought to go about installing Cat 6A cables now, or wait until prices drop, as they invariably do when supply is greater than demand. The problem being that if companies wait too long, competitors might get the edge with faster, more efficient operations.

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Beyond Cat 6A

Here is a look at some of the structured cabling solutions beyond Cat 6A. Some will become more popular within the next few years.

Category 7: Considered by many cabling professionals as a Germany-only solution, Cat 7 is now considered by some data centre . and network managers to be a superior option to Cat 6A, says Steven Foster, marketing manager at Siemon. “With 600 MHz components it offers better headroom and, because each pair in the cable and connectors is shielded from every other pair, it offers a number of technical advantages.”

These include the elimination of alien cross-talk, the biggest hurdle in the development of Cat 6A. Cat 7 is fully backward compatible with Cat 5e, 6 and 6A.

Category 7A: This standard is currently in development by the cabling standards bodies, and is expected to run at 1000 MHz — double that of Cat 6A. With more than double the Shannon capacity of Cat 6A, it will process full bandwidth 800/900 MHz HD digital video, and possibly the next advance in Ethernet after 10G. (The Shannon limit or Shannon capacity of a communications channel is, for a particular noise level, the theoretical maximum information transfer rate of the channel.) OM3 Fiber:. OM3 allows 10-Gigabit/s transmission at up to 300 metres, yet can still be used to connect legacy Gigabit optical interfaces.