Cabling Install Special Report

SPECIAL REPORT

Shielded and Unshielded Twisted-Pair Cabling: Capabilities, Options, and DeploymentChoosing between shielded and unshielded

twisted-pair cabling for high-speed applications,

like 10-Gbit/sec Ethernet and beyond, requires

consideration of several variables. The articles

in this special report provide information

on the differences between the two media

types, in terms of application support, cost,

and implementation. The report follows the

technological advancement of twisted-pair

cabling from Category 6A, supporting 10-GbE,

through under-development Category 8, which

will support 25- and 50-GbE.

REPRINTED WITH REVISIONS TO FORMAT FROM CABLING INSTALLATION & MAINTENANCE. COPYRIGHT 2015 BY PENNWELL CORPORATION

SOLUTIONS

FOR PREMISES

AND CAMPUS

COMMUNICATION

SYSTEMS

WORLDWIDE

Data center fabric - fat-tree/leaf and spine

Accessswitches

Interconnection switchesInterconnection switches(spine switches) typicallyin MDAs, but may be in IDAs

Access switches(leaf switches) in• HDAs for end/middle of row/zone• EDAs for top for rack

Servers

Active switch-to-switch connections Server connections Repeated components

40GBASE-T overcategory 8


Legend

Servers Serversin EDAs(server cabinets)

1503CIMdesignF1

Inside the numbers: 10-GbE cost comparisonsPAGE 2

The technical realities of twisted-pair beyond 10GPAGE 10

Category 8’s 30-meter reach is not a stretchPAGE 19

2 Cabling Installation & Maintenance SPECIAL REPORT

ORIGINALLY PUBLISHED MAY 2007

Inside the numbers: 10-GbE cost comparisons

by Patrick McLaughlin

This vendor roundtable discussion provides perspective on the pricing

issues associated with different 10-Gigabit Ethernet media choices.

As a technical undertaking, 10GBase-T is an accomplishment of significant proportions. The engineering efforts required to create a protocol for transmitting 10 billion bits of data per second on eight copper wires are worthy of celebration and marvel.

For professionals in the cabling industry, however, it is doubtful that those contemplating 10-Gigabit Ethernet deployment have used the word “marvelous” to describe the deliberations and considerations that have gone into selecting which flavor (10GBase-T or 10GBase-SX) to deploy. And some users who have settled on 10GBase-T have found the option of using unshielded or shielded twisted-pair cabling a source of consternation.

In the 10-GbE ecosystem, technical issues raise cost questions, which give reason for deeper consideration of the financial investments involved. Logical questions arising from cost analysis involve the long-term technical benefits of deploying 10GbE; the cycle completes itself and starts over again.



Cabling-system vendors provide full assurance that their twisted-pair solutions accommodate 10GBase-T transmission-even though the Telecommunications Industry Association’s (TIA; www.tiaonline.org) full set of Category 6A specifications is not yet finalized. With the first 10GBase-T-compliant networking products hitting the market, these cabling vendors are getting their first opportunities to prove those claims.

Meanwhile, fiber-based 10-GbE systems have been available and deployed for some time. The truism we have all heard is: even with the use of vertical-cavity surface-emitting lasers, the cost of optoelectronics equipment (i.e., fiber-based networking equipment) so far exceeds that of copper-based electronics, holding out for the introduction of copper-based systems is the most cost-effective move a user can make. And this author, for one, typically takes that statement at face value.

Just how much of a value is 10GBase-T over 10GBase-SX? And even if 10GBase-T proves to be the financially advantageous option, how should a user make the decision about whether to operate the protocol on shielded or unshielded cabling?

With those questions lingering, or put another way, fueling the 10-GbE ecosystem, Cabling Installation & Maintenance sought out three cabling-system providers, each of which offers multimode fiber, unshielded twisted-pair, and shielded twisted-pair solutions. With some vendors rather adamantly advocating one medium over the others for 10-GbE transmission, we invited ADC (www.adc.com); CommScope

The size of a Category 6A cable, which can vary significantly (as

this photo shows), is one of many considerations users must make

when choosing 10-Gigabit Ethernet media.

www.tiaonline.org

www.adc.com



(www.commscope.com), which offers the Uniprise and Systimax brands; and Tyco Electronics/AMP Netconnect (www.ampnetconnect.com) to participate in a Q&A-style discussion about the technical and, significantly, the financial considerations that users face when 10GbE is in their future.

Speaking for ADC is John Schmidt, senior product manager for structured cabling. Representing CommScope is Matt Brown, global data center solutions manager. Brian Davis, global product manager, represents Tyco Electronics.

Cost model lets you make your own calculationsThe TIA’s Fiber Optics LAN Section (FOLS; www.fols.org) provides on its Web site a cost model that lets users compare the costs associated with deploying the cabling infrastructure and network hardware for protocols, including Gigabit and 10-Gigabit Ethernet.

Cost-model users must register before beginning, but the registration and use of the model is free. FOLS has updated the pricing data in its cost model periodically, and the model lets users input their own numbers as well. The participants in this article-ADC, CommScope, and Tyco Electronics-are all FOLS members.

“FOLS continues to be committed to keeping our cost model current,” said Andrew Oliviero, FOLS chair, when the model was most recently updated in February. “For this update, we made changes that will make it easier for users to make accurate comparisons among architectures, essentially updating the data without making significant changes to the structure of the model.” The newest updates include new media choices, aggregate pricing reflecting current market conditions, the ability to customize port-utilization calculations, and a graphic comparison of different architectures.

www.commscope.com

www.ampnetconnect.com

www.fols.org



(Note that in providing these individuals’ answers to the questions posed, they had the option of answering or not answering any question. Also, when more than one individual answered a question the same or essentially the same, Cabling Installation & Maintenance has chosen to provide a single response.)

Q: On a “1x/1.5x/2x”-type basis, generally what are the installed-cost figures for 100-meter, 4-connector channel Category 6A UTP, Category 6A foiled/unshielded twisted-pair (F/UTP), and laser-optimized 50-µm multimode fiber cabling systems?DAVIS: Category 6A F/UTP and multimode fiber are 1x; Category 6A UTP is 1.1x.BROWN: Fiber-cable prices have remained stable during the past few years, while copper raw material prices have driven the cost of UTP and F/UTP cabling up. Based on UTP as 1x, F/UTP installed links will be 1.15x, and laser-optimized fiber links will be 1.75x.

Q: Can you provide similar information about the cost of 1-Gig network equipment (network interface cards [NICs], LAN cards), comparing 1000Base-T with 1000Base-SX?SCHMIDT: According to Intel pricing, 1000Base-T NICs are $145 while 1000Base-SX NICs are $510. And Cisco prices 1000Base-T small-form-pluggables (SFPs) at $315 while 1000Base-SX SFPs are $380. On the NIC side, 1000Base-SX will be approximately 3.5 more expensive than 1000Base-T. Keep in mind that 1000Base-T NIC ports have astronomically higher volume than 1000Base-SX. For switch ports, which have higher 1000Base-SX volume, the cost is much closer, with 1000Base-SX having only a 20% premium over 1000Base-T ports.BROWN: 1000Base-T and 1000Base-SX NICs have both fallen dramatically over the past two years. They are between 20% and 35% of their 2005 price. The price gap between -T and -SX has narrowed from 4x in 2005 to 3x today.

Q: Do you have any insight into what the market might expect, in terms of a cost difference between -T and -SX, when a full complement of 10GBase-T networking equipment is available?



BROWN: Estimates at IEEE have historically predicted 10GBase-T prices will be 40% of 10GBase-SX prices. We believe the biggest hurdle for 10GBase-T is the electronics power requirement. The most efficient NICs on the market have power consumptions of <6 watts, while fiber-based 10G NICs are readily available between 2 and 4 watts.SCHMIDT: Two NIC vendors, Tehuti Networks and Chelsio Communications, have announced product. Chelsio’s 10GBase-T NIC is priced at $1,995. Neterion’s 10GBase-CX4 NIC is $1,095, while its 10GBase-SR NIC is $1,995 and its 10GBase-LR NIC is $2,895. 10GBase-T NICs are currently about the same price as 10GBase-SR, as they have just been introduced and have low volume. It is expected that by 2009 the relative cost between 10GBase-SR and 10GBase-T will be 4x, with 10GBase-T NICs sub-$200 and 10GBase-SR around $800.

Q: Given the economics of optical networking, users may be tempted to dismiss it out of hand for channels of 100-meter distances or less. But are there circumstances under which fiber can be the best overall choice in systems ≤100 meters?DAVIS: There are several reasons to deploy fiber in horizontal links less than 100 meters, including the following seven scenarios:1. Cabling runs through or is exposed to high radio-frequency interference/

electromagnetic interference (RFI/EMI) noise areas;2. Cabling runs through or is exposed to high-voltage areas-there are no induced

voltages on all-dielectric fiber cable;3. Restricted pathway space, including but not limited to small conduits, small

bulkhead openings, and fire barriers;4. Cabling runs through or is exposed to high-temperature areas;5. 10-GbE-capable runs are needed today;6. Secure areas with concerns about transmitted/radiated signals;7. Limited termination space for highest-density connectivity.



BROWN: Fiber has its strongest play when density is a major concern, as in the storage area network (SAN) environment. This relatively short-distance application is dominated by fiber cabling due to density concerns as well as the potential for fiber to upgrade to 100-gigabit and beyond. Fiber makes sense below 100 meters when density and a clear upgrade path to next-generation speeds are major concerns.SCHMIDT: Absolutely. In particular, laser-optimized multimode fiber is an ideal medium for shorter-distance transmission for the following situations:1. Fibre Channel transmission in SANs;2. Highly secure network connections, due to fiber’s high degree of difficulty to

tap or monitor;3. Very high density network connections that require small cable diameters;4. Sub-100-meter lengths that are expected to be 100-Gigabit Ethernet

in the future.It is expected that 100-Gigabit Ethernet will have a 100-meter distance limitation on laser-optimized multimode fiber.

Q: When planning 10GBase-T-capable twisted-pair systems, end users face complicated decisions about cable types and those types’ characteristics. Assuming we are talking about a 4-connector channel in a “friendly” environment (no excessive external noise sources or extreme bends along the pathway), does your organization recommend one medium over another?SCHMIDT: Unshielded twisted-pair Augmented Category 6, for the following reasons:1. UTP Category 6A is available in the smallest diameter that will support

10GBase-T-0.275 in. versus 0.285 in. in F/UTP cables-which will improve conduit-fill ratios by allowing more cables to fit in a given-size conduit;

2. UTP Category 6A is the lowest-cost medium that will support 10GBase-T, accounting for all factors including component cost, installation cost, troubleshooting, and testing;



3. UTP Category 6A is designed to meet and exceed all the electrical requirements set forth by the IEEE, ISO, and TIA to support 10GBase-T without resorting to shielding;

4. In 2006, more than 6.2 billion feet of category-rated cable was installed in the United States; of that, less than 1.5% was F/UTP, according to market-research firm BSRIA (www.bsria.co.uk). As a result, there is very little installation, troubleshooting, and maintenance experience with F/UTP cabling in the United States-precisely why the vast majority will continue to use UTP cabling.

F/UTP and S/FTP cabling certainly has its place within the network. It will provide superior external-noise suppression for installations near high noise sources, such as radio or microwave transmitters; however, standard noise from common sources, and certainly alien crosstalk, can be more than adequately eliminated by UTP Category 6A. So, for 98.5% of installations in the United States, UTP cabling is going to be a more economical choice that does not sacrifice performance.BROWN: We recommend TIA Category 6A, ISO Class EA-compliant UTP cable. F/UTP solutions have several drawbacks beyond their 15% price premium. When using UTP cabling, the installer does not need to implement the additional bonding and grounding steps that are required with F/UTP cables. There is additional time and cost associated with terminating the shield and drain wire on F/UTP cabling. Due to the sensitivity of this operation to installer technique, between 5% and 20% of terminations need to be re-worked to properly ground them. The possibility of the foil tape folding or kinking can give F/UTP cables a larger bend radius than UTP cables. F/UTP cables typically have 2-inch bend radii (similar to coaxial cables), compared to typical UTP bend radii of one inch. Ease of cable routing and dressing are critical in today’s dense connectivity environments, such as the data center. While F/UTP cables are smaller than some UTP cables, the density advantages of F/UTP are small and do not justify the increased cost and difficulty of installation. If density is a critical concern, then fiber is preferred.

www.bsria.co.uk



DAVIS: For 10GBase-T-capable twisted-pair systems, Tyco Electronics recommends a Category 6A F/UTP system. From a performance perspective, shielded technology eliminates the effects of alien crosstalk-the most dominant and critical additional parameter for 10GBase-T. From an installation point of view our jack greatly simplifies installation and ensures consistent high-performance terminations. This jack is designed to handle heavier-gauge conductors and makes it easy to maintain pair twist-even with the tighter pair twist of Category 6A cables. There is no need to field-test a shielded installation for alien crosstalk, whereas an unshielded solution requires hours of additional testing for 100% coverage, or a “sampling” test procedure, which reduces the time investment by sacrificing 100% verification.

PATRICK McLAUGHLIN is chief editor of Cabling Installation & Maintenance.


ORIGINALLY PUBLISHED APRIL 2011

The technical realities of twisted-pair beyond 10G

Technology experts keep building the case for

standards groups to pick up the initiative.

by Patrick McLaughlin

Senior vice president of research at Nvidia (www.nvidia.com) Bill Dally caused quite a stir throughout the computing industry in April 2010 when in a commentary for Forbes he declared Moore’s Law dead. In that column he said central processing unit (CPU) “performance no longer doubles every 18 months.” While making the argument in his column, Dally pointed to the infrequently referenced other prediction made by Gordon Moore–that in addition to the number of transistors on an integrated circuit doubling every 18 months, “the amount of energy consumed by each unit of computing would decrease as the number of transistors increased. This enabled computing performance to scale up while the electrical power consumed remained constant. This power scaling, in addition to CPU scaling, is needed to scale CPU performance.

“But in a development that’s been largely overlooked, this power scaling has ended,” Dally wrote. The end of that power-scaling was the death knell for Moore’s Law, he argued.

Moore’s Law has been the foundation of computing-based industries for decades, and certainly the networking industry supported by structured cabling systems is among them. During a seminar produced by Cabling Installation & Maintenance and

www.nvidia.com



delivered via the Web in January 2011, Moore’s Law and power consumption were part of a dialogue about the capabilities of shielded twisted-pair cabling systems.

Standard development

Two of the speakers who participated in that seminar were David Hess, technical manager for standardization and technology with Berk-Tek, a Nexans company (www.berktek.com) and Valerie Maguire, global sales engineer with Siemon (www.siemon.com). Hess and Maguire have participated in a number of groups, some of them formal standards-making bodies and others less-formal groups made up of networking and cabling technology experts, which have explored the possibilities for shielded twisted-pair structured cabling systems to support Ethernet at transmission speeds higher than 10 Gbits/sec. Hess’s presentation focused on the standards scene and what is happening in the realm of standards activity for such high-data-rate cabling systems. Maguire’s presentation dealt with the “hows and whys” of a shielded system’s ability to support such high speeds.

In setting the landscape for current activity, Hess explained that twisted-pair Ethernet development has continued for more than 20 years. 10Base-T specified and referenced telephone inside wiring, then during the development of 100Base-TX the decision was made to articulate the cabling and formalize the reference. He then noted that, “Cabling and PHYs are essentially developed in parallel. Each new category [cabling] definition begins from an extrapolation of the last category. And co-development of cabling and PHY standards must be coordinated.”

Then Moore’s Law made its way into the conversation. Hess presented a chart that plotted the Base-T specifications developed by the Institute of Electrical and Electronics Engineers (IEEE; www.ieee.org) and the Category cabling standards developed by the Telecommunications Industry Association (TIA; www.tia.org) as well as the International Organization for Standardization (ISO; www.iso.ch), based on the years the standards were approved by their respective organizations. Also on the chart was a trend line that equated to Moore’s Law. The points representing

www.berktek.com

www.siemon.com

www.ieee.org

www.tiaonline.org

www.iso.ch



IEEE “Base-T” specs and TIA/ISO “Category” specs plotted right along the line representing Moore’s Law up to 2000, where 1000Base-T and Category 5e reside. “More recent standards have taken longer to complete,” Hess stated. The 2006 10GBase-T specification was a year behind the Moore’s-Law line that crossed the 10,000 Mbit/sec data-speed point at 2005. The Category 6A data point was even a little later than 10GBase-T.

The next point made by Hess, which Maguire later reinforced and explained in detail, bears a striking similarity to the sentiments Nvidia’s Dally expressed in his Moore’s Law death declaration. “Two dates are given for 10GBase-T,” Hess said. “2006 for 802.3an, the primary PHY approval, and 2010 for 802.3az, Energy Efficient Ethernet PHY approval.” Energy Efficient Ethernet enables lower-cost 10GBase-T operation, he explained.

Power in focus

Dally said the reason Moore’s Law is dead is because it is no longer true that each computing unit consumes less power as the number of transistors on an integrated circuit increases. It would be far from conclusive to point to the delayed development of Base-T Ethernet and Category cabling specs since 2000 as proof that Dally has it right. However, Maguire voiced the opinion during the January seminar that power consumption will be a significant consideration for those setting their sights on twisted-pair-based applications at speeds beyond 10 Gbits/sec.

Interestingly, the cause-and-effect sequence that eventually leads to an examination of power consumption begins with a reference to Moore’s Law. “In the data center, server-cluster storage rates are increasing faster than Moore’s Law predicts,” Maguire said. “They are doubling every year as opposed to every 18 months. This tells us that the need for high-speed throughput in the data center is growing at a faster rate than for high-speed twisted pair applications for Ethernet in the LAN. We can predict that in three to five years we are going to have a need to support 40-Gbit/sec Ethernet in the data center.”



In corporate LAN environments, she explained, growth is being driven by video applications and high-performance computing. Transmission-rate increases are not as rapid in the corporate LAN as they are in the data center. Maguire said she expects LANs to begin having a need for 40-Gbit/sec Ethernet in five to ten years.

As for data centers’ three- to five-year timeframe, “We need to start planning for that application now,” she said, and that is why companies such as Siemon and Nexans have shared ideas and participated in industry activities to further investigate the practicalities of higher-than-10G over twisted-pair.

“Data center experts are telling us they’re very concerned about two issues: cooling and power. We need to take this consideration into account when we plan for the capability of the beyond-10GBase-T application. We need to make sure that powering is not an issue, and heat generation is not an issue. We need to take into consideration this feedback from data center experts, and ensure the technology we use to support greater-than-10GBase-T isn’t power-hungry and that it supports the optimum throughput capability of the media.”

As of January 2011 there was no official Project Call for Interest within IEEE for a greater-than-10G application over twisted-pair. Without such a call, no one can make application-support claims. Maguire explained why. “There are a whole range of considerations that would affect the capability of a 40-Gbit/sec application over twisted-pair. These include the level of encoding, the level of cancellation and strategies to alleviate power consumption.” With no call for interest there are no agreed-upon models for considerations such as these. “We can generate our own capacity models,” Maguire explained. “We can look at channel-length histograms for data center environments. And we can share our expertise among companies that are interested in pursuing this initiative to come up with our best guess of what the media and the topology to support a greater-than-10-Gbit/sec application would look like.”



While no official activity is taking place within the IEEE, Berk-Tek’s Hess noted, “The trend toward parallel development is continuing. And interest is forming among 10GBase-T solution providers.”

The crystal ball

Maguire engaged in some crystal-ball gazing, offering her own vision of what the realm of beyond-10G-over-twisted-pair will look like. “My belief,” she said, “is that we’re going to break this project up and look at the immediate need of the data center, and reserve research into the needs of the LAN environment for later in the project or in a future project.

“I think it’s going to be extremely desirable not to significantly increase the equipment complexity beyond existing 10GBase-T levels. This means, if anything, we want to reduce cancellation. We want to reduce power consumption. We do not want a more-sophisticated or more power-hungry chip technology.”

The cancellation of noise might be viewed as a central issue that ties together several elements discussed so far in this article: Moore’s Law, power consumption, increasing data rates for Base-T Ethernet, and shielded cabling systems as a potential solution. As Base-T standards have gone from 10 to 100 to 1000 to 10,000 Mbits/sec, the frequency range over which data signals are carried has also increased. 10Base-T uses the frequency range up to 20 MHz, whereas 100Base-TX uses the frequency range up to 31.25 MHz, 1000Base-T uses twice that frequency range, up to 62.5 MHz. For 10GBase-T, there is a substantial increase to 413 MHz, but the increase is still not 10x. Efficiency is also being increased for each new generation.

Hess pointed out that while speeds increased by a factor of 10 with each successive specification set, “the most outstanding measure of progress is evidenced in the efficiency, that is, the bits-per-second-per-hertz.” By that measure, computing efficiency went from 0.5 bits/sec/Hz with 10Base-T, to 3.2 with 100Base-TX, to 16 with 1000Base-T, and to 24.2 with 10GBase-T. Hess added, “There is significant



further study needed to consider how far 10GBase-T complexity might be surpassed for the next generation.”

Quieting the noise

Even with such advancements in efficiency, it remains true that as transmission-frequency increases, more noise is encountered and therefore, noise cancellation has become a more-complicated and more-challenging task for creators of Base-T standards. And once noise-cancellation is defined, its very existence in a transmission specification has side effects. Maguire explained, “The 10GBase-T application uses quite a bit of digital signal processing [DSP] to provide crosstalk cancellation. A result of this DSP is an increase in latency. And latency can be very critical for applications.”

In addition to developing ways of cancelling noise, effort goes into strengthening a signal’s transmission to begin with. The efforts are complementary methods of ensuring a receiver can discern between the transmitted signal and the noise. Signal-strengthening has its consequences in the realm of chip design. Maguire described a wish list for the design of a chip for greater-than-10G on twisted-pair, with attention on reducing power consumption and latency: “I’d like to reduce a couple items in chip design. One is line-driver power. I’d also like to reduce the number of chokes and transformers in my system. If I consume less power I’ll have a solution that requires less tooling. If I’m doing less digital signal processing I’ll have a solution that has better latency performance. That will satisfy the needs of my customers.”

The complexities of chip design, power consumption, digital-signal processing, noise cancellation and other electro engineering issues are what lead Hess, Maguire and others in the industry to consider shielded cabling systems as the medium best suited for the next-generation Base-T specification, if and when one is created. On the reduction of line-driver power, Maguire noted, “That can be done in a couple ways. One is to use a media type that has improved insertion-loss performance, such as Category 7A. I can also accomplish it by deploying over a shorter channel length.



The optimum performance will be realized by doing both.” Reducing the number of chokes and transformers can be accommodated “by using a shielded cable that has superior electromagnetic immunity performance,” she added.

But it’s not as if a Base-T solution is the only option for Ethernet transmission at speeds greater than 10 Gbits/sec. Optical and twinaxial versions of 40-Gbit/sec Ethernet already exist. Why would or should a standards body go through the effort to produce another option? “It’s related to some shortcomings with the existing twinax and optical-fiber solutions, as well as one of the features of a Base-T application,” Maguire opined. “The high-speed twinax solution supports short-length topologies, less than seven meters,” she said. “This means the configuration is ideally suited for top-of-rack and possibly some middle-of-row deployments. But it does not support a structured cabling topology, which is required by the TIA-942 and pending TIA-942-A standards.”

The multimode-fiber versions of 40- and 100-Gbit Ethernet “require serial transmission that uses 8- and 20-fiber links,” Maguire explained. “The effect is the user may be losing some density because, in order to support these 8- and 20-fiber links, you need to use MPO-style cassettes, which do not have the density to this point of LC connectors.”

She then pointed out a characteristic that distinguishes Base-T applications from others. “These are the only applications that support autonegotiation, which means it can match speeds between servers and switches. This is very important because deploying Base-T-type applications means when it’s time for a network upgrade, you do not have to upgrade your servers and switches at the same time. So there is a real need for a twisted-pair beyond-10GBase-T application.

Even with no formal activity taking place within the IEEE, Maguire made known her own perspective on how things could and may play out. “I believe the next application speed is going to be 40-Gbit/sec, and I believe that would be agreed



upon by most industry experts. The longest support or reach of a 40-Gbit over twisted-pair application would be over Category 7A cabling. That doesn’t preclude the use of Category 6A, but Category 7A will support the longest reach and most flexibility in the data center. I also think that for the initial, data center 40-Gbit/sec solution we might be looking at a reduced-length topology.” As mentioned earlier, Maguire foresees a data-center-focused specification being developed first, followed by a specification more geared toward a corporate LAN environment.

She was up front about the fact that advocacy of Category 7A is not in keeping with the way the IEEE has approached Base-T standards to this point. “This is going to require a change in thinking among IEEE experts who develop Ethernet standards,” she said. “Historically IEEE has targeted cabling that has the largest installed base. But in this case, we have to question whether that choice makes sense–if we choose the highest-performing grade of cabling versus the most widely installed Category of cabling. We also need to look at the topology. Traditionally we have targeted the 100-meter, 4-connector topology. But in this case if we are looking for an application that is targeted to the data center, doesn’t it make sense to look at a topology that matches the needs of the data center?”

She then pointed out that end-user organizations can benefit from using the highest grade of cabling. “The benefit is extreme and is realized in the form of cost savings,” she said. In a typical IT market expenditure, 17 percent is represented by IT hardware, which includes cabling. Other expenditures including software (18 percent), salary and benefits (36 percent), IT services (13 percent) research-and-development (5 percent), and others (11 percent).

“What’s interesting is if I further break down the hardware into more detail, cabling is typically 2 to 3 percent of the total hardware spend,” she noted. “So I have two options. I can install a higher grade of cabling that doesn’t represent most of the installed base but represents an additional 2 or 3 percent of the IT spend. Or I can develop equipment that has very high power needs, perhaps increased latency,



and costs significantly more, potentially increasing the overall percentage of the hardware to be significantly beyond 17 percent. The benefits of specifying a superior media type is cost savings in terms of the network electronics we’re going to deploy to support 40GBase-T and beyond.”

Hess and Maguire made a compelling case to A) move forward with 40GBase-T, and B) recognize shielded twisted-pair cabling as the preferred medium for 10GBase-T. How compelling it is to other industry experts who would participate in such specification creation will be interesting to track. We will continue to cover this topic, and plan to provide you with information on any related standards activities that take place..

PATRICK McLAUGHLIN is chief editor of Cabling Installation & Maintenance.


ORIGINALLY PUBLISHED MARCH 2015

Category 8’s 30-meter reach is not a stretch

By Patrick McLaughlin, Chief Editor

The hand-in-glove relationship between Category 8 and

40GBase-T will have multiple applications in the data center.

THE SPECIFICATIONS UNDER development by the Telecommunications Industry Association (TIA; www.tiaonline.org) for Category 8 cabling systems-ANSI/TIA-568-C.2-1-are breaking the proverbial mold for TIA twisted-pair cabling specs in that the channel distance specified within the standard will be 30 meters, not the 100-meter distance specified in its predecessor standards and to which the industry has become accustomed. The reasoning behind a 30-meter channel is fairly straightforward, and the implications of that distance hold promise for the timeframe in which Category 8 cabling may be deployed and put to use in networks.

Category 8 cabling will be a hand-in-glove fit (that’s this author’s characterization only) with the also-in-development 40GBase-T Ethernet specification of the Institute of Electrical and Electronics Engineers (IEEE; www.ieee.org). As such, Category 8 will be installed in data centers for server-to-switch connections, including top-of-rack (ToR) and end-of-row (EoR) architectures for which 30 meters is sufficient distance.

This image shows in red the potential application of 40GBase-T over Category 8 cabling in a fat-tree/leaf-spine switching architecture in a data center. The original illustration is from ANSI/TIA-942-A-1. The notation in red was added when this graphic was presented to IEEE P 802.3bq in July 2014. That presentation

www.tiaonline.org

www.ieee.org



included several similar illustrations, all of which highlighted the use of 40GBase-T over Category 8 cabling for server-to-switch connections in various data center architectures.

In a Panduit Connections blog post titled “Reaching for 40GBase-T,” Panduit’s solutions marketing manager for high-speed data transport solutions Tom Kovanic addressed the 30-meter issue. He explained, in part, “When developing a new networking standard, several attributes need to be balanced to optimize its implementation. To optimize the implementation of 40GBase-T, the IEEE P802.3bq appears to have settled on a reach of 30 meters. This is a tradeoff between power dissipation of the silicon physical layer (PHY) integrated circuit driving the cable, the complexity of the PHY which would impact cost, the implementation of the channel, and the reach of the link.” The full post, which can be found at panduitblog.com, asks whether or not 30 meters is long enough-then provides detailed reasons why the answer is yes.

At a meeting of the IEEE P802.3bq 40GBase-T Task Force in July 2014, Anixter’s vice president of technology, Andy Jimenez, presented on the advantages and use cases of 40GBase-T. A portion of that presentation addressed the goals of the Category 8 standard, which include the support of EoR and ToR deployments in

Data center fabric - fat-tree/leaf and spine

Accessswitches

Interconnection switchesInterconnection switches(spine switches) typicallyin MDAs, but may be in IDAs

Access switches(leaf switches) in• HDAs for end/middle of row/zone• EDAs for top for rack

Servers

Active switch-to-switch connections Server connections Repeated components



Legend

Servers Serversin EDAs(server cabinets)

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the data center. One slide in particular within that presentation (which is available for viewing and download through the IEEE website) states, “40GBase-T will work anywhere in a data center where 30-meter connections will reach. This includes: anywhere in the classic three-level hierarchy [access switch/aggregation switch/core switch]; for the fat-tree/leaf-and-spine/interconnected fat-tree fabric architecture; for full-mesh, interconnected meshes, and centralized switch; for virtual switch.” Diagrams within that presentation indicate that 40GBase-T over Category 8 cabling can serve in each of those setups/fabrics as connection points between the servers and the first-level switches. The illustration in this article is taken from that presentation.

Jimenez’s presentation indicates that CommScope’s Masood Shariff and Panduit’s Frank Straka also were contributors to it. Jimenez and Straka have co-chaired the effort within TIA’s TR-42.7 Subcommittee to produce the near-complete TIA document Telecommunications Systems Bulletin TSB-5019 High Performance Structured Cabling (HPSC) Applications. The document will provide usage details for deploying Category 8 structured cabling in data centers-likely including the connections just described.

The reach of 40GBase-T to 30 meters might be regarded as the manifestation of lessons learned from the IEEE’s development of 10GBase-T. David Chalupsky, who chairs the Ethernet Alliance Base-T Subcommittee and the IEEE P802.3bq 40GBase-T Task Force, has pointed out, “With server-to-switch connections as the target use for 40GBase-T, 30-meter reach was seen as sufficient for installations using middle-of-row or end-of-row placement for switching equipment.”

Additionally, in 2013 Anixter produced a one-page technology brief that explained how the lessons learned from the development of 10GBase-T were likely to be applied to 40G. It says that both 40GBase-T and Category 8 “build on the lessons learned from the existing IEEE 802.1an 10GBase-T standard: reasonable power consumption and physical form factor. Both were mitigating factors in the broad



approval of 10GBase-T technology in the market because increased heat dissipation on the higher powered chipsets and reduced port count on the networking switches made 10GBase-T less attractive than alternatives such as SFP+ and optical interfaces from a price-versus-performance point of view.

“In order to address these issues, the IEEE, TIA and ISO committees have gained consensus to reduce the maximum supported cabling channel length to 30 meters to make sure that the power footprint for 40GBase-T chipsets are minimized,” Anixter’s document continues. “Surveys by both the TIA and IEEE organizations have shown that 30 meters will support the majority of data center architectures when using twisted-pair cabling.”

As David Chalupsky pointed out in last month’s issue, , in an article titled “IEEE to study new Base-T data rates for data centers and enterprise applications,” there’s also a likelihood that 25GBase-T specifications will ride along with the 40GBase-T standard, using Category 8 as a supporting infrastructure. Chalupsky stated, “Although first defined for 40GBase-T, Category 8 is also anticipated to be the target channel for 25GBase-T, which raises some interesting points. Analysis to date of 25GBase-T on Category 8 has shown that it is generally an easier problem to solve than running 10 Gbits/sec on 100 meters of Category 6A. This means that the cost per bit, and power per bit, of 25GBase-T products could decline quickly to rather economic levels.”

From several angles, the hard lessons learned during the development and market entrance of 10GBase-T appear to hold promise for Category 8 and the applications it will support.

PATRICK McLAUGHLIN is our chief editor.

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