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10-Gigabit Ethernet Backbone Interface Options: Which One Should I Choose?

This week’s question comes to us from Chris in New York:
We plan to upgrade our network backbone to 10-Gigabit Ethernet.
What interconnect platform should we use? 



Thanks Chris for your question.  This topic comes up quite frequently for a number of reasons.  Not too long ago, only medium to large enterprises could viably afford to make the leap to 10-Gigabit Ethernet on their networks.  That is simply no longer the case today.  Not only are there hundreds of 10GbE-ready switch manufacturers on the market today, but there are also multiple interconnect platforms available that support the 10-Gigabit Ethernet protocol.  As you can see by the timeline above, 10-Gigabit Ethernet has already surpassed the point of being a widespread and mature technology; ensuring low implementation costs.

Because this is a lengthy topic, I will need to divide it up into two segments.  The first segment will focus on the most obvious interconnect platform for 10-Gigabit Ethernet applications: 10GBASE-T. 10GBASE-T, also referred to as IEEE 802.3an-2006, is essentially 10-Gigabit Ethernet over standard twisted pair (UTP or STP) copper wire, such as Category-6 (CAT6) Cables and Category-6a (CAT6a) Cables.  A great number of networks have featured a 1000BASE-T (Gigabit) backbone using CAT6/CAT6a. Transmitting data at 1.0 Gbps speeds over this cable type is fairly easy from a hardware perspective and was therefore a highly implemented option for network administrators.


 Pictured: Typical Gigabit Ethernet (1000BASE-T) Network 


However, the entire equation changes dramatically when you have to increase the data throughput by a factor of ten from 1.0 Gbps up to 10.0 Gbps.  At this high 10-Gigabit speed, a whole bunch of negative performance ramifications come into play that were simply ignored or non-existent in the case of Gigabit Ethernet.  Some of these factors include:

Bandwidth:  To transfer data at 10-Gigabit speeds, the required cabling must be designed to support a substantial amount of bandwidth.  To operate effectively over a sizable distance (up to 100 meters or 330 feet), Category-6a Cabling must be used thanks to its inherent support of up to 500 MHz of bandwidth.  To compare, regular Gigabit Ethernet (1000BASE-T) can operate with plenty of headroom using a 100 MHz bandwidth capable Category-5e (CAT5e) Patch Cable.  To increase bandwidth, you have to operate at extremely high frequencies.  High frequencies behave quite differently from lower frequencies, thus demanding a more capable interconnect design.

Bandwidth can be visualized as a pipe (see below).  A high-bandwidth capable interface, like 10-GbE, requires a thicker data pipeline (backbone) so that all of the high-speed data can stream through it without resistance. If you try and force high-bandwidth data through a low-bandwidth pipe, you will witness a massive slowdown in data throughput. Sometimes, like in real life, the pipe will burst and the interface will shut down.  This is why maintaining high bandwidth is so critical.    

(Pictured: Bandwidth Conceptualized via a Pipe) 


Alien Crosstalk:  Alien Crosstalk, also known as ANEXT, is when signals from outside sources, such as other patch cables in close proximity or other localized sources of electromagnetic interference (EMI/RFI) like lighting, power transformers, wireless access points, etc., interfere with the 10-Gigabit Ethernet signal that travels down the cable.  Regular Category-6 (CAT6) Cables do not address the issue of ANEXT directly and as a consequence can only support 10-Gigabit Ethernet at distances up to 50 meters (166 feet).

(Pictured: Cables Affected by Alien Cross-Talk)



To mitigate the problems associated with bandwidth and ANEXT, Category-6a Cables utilize three principles:  Pair Separation, Shielding and Tight Tolerance.  Pair separation involves placing a plastic x-shaped insulator in the middle of the cable itself.  This keeps a designated amount of spacing between the wire pairs, thus assisting with Near-End Cross-Talk (NEXT) and maintaining proper cable impedance.  Shielding involves shrouding the entire cable in a concentric ring of Aluminum foil.  This prevents outside EMI/RFI interference and related Alien Cross-Talk (ANEXT) from wrecking the signal.  Tight tolerance simply means that Category-6a (CAT6a) Cabling is designed and assembled with minimal tolerance for out-of-specification characteristics such as maintaining a perfect number of cable twists-per-inch. 

Now that the technical specifics are out of the way, how do we reach a determination as to whether 10GBASE-T (10-Gigabit Ethernet over Twisted Pair) is the right choice for your network upgrade?  I like to look at three critical cost factors.  The more dollar signs shown, the more expensive the cost.


Critical Factor #1:  Switch Cost 




In all likelihood, your largest upgrade expense is going to come from the cost of updating all of your switches to 10-Gigabit Ethernet compliant models.  Unfortunately, this is where 10GBASE-T fairs the absolute worst.  Development was significantly delayed on 10GBASE-T hardware, specifically the silicon chipsets that power the switches.  10GBASE-T proved far easier to develop on paper than it did in the real world.  As a consequence, while 10GBASE-T products are just barely trickling out to the market from a select few manufacturers, other 10-Gigabit Ethernet interface standards, such as SFP+ Direct Attach and 10GBASE-CX4 have taken hold.


Critical Factor #2:  Cable Cost




This is where the 10GBASE-T interface dominates hands-down.  Cables for 10GBASE-T are the absolute cheapest option because all you need to purchase are Category-6a (CAT6a) Patch Cables.  At Amphenol Cables on Demand (http://www.CablesOnDemand.com), we stock a variety of Category-6a (CAT6a) Patch Cords in your choice of length and color at prices starting at only $3.16 (even less when on sale).  This is perhaps 90-95% cheaper than the other aforementioned interface options!


Critical Factor #3:  Power Consumption




Power Consumption is the Achilles Heel of 10GBASE-T.  The fact is, the engineers who came up with the Ethernet standard decades ago never imagined that inexpensive twisted pair communications cable would support the blazing fast speeds of today.  As such, engineers have had to squeeze 10-pounds of bandwidth into a 1-pound bandwidth bag.  This comes at a price.  To make up for the cable’s inherent deficiencies, the switch has to do the heavy lifting by using extra power to sort through all of the signal errors and lost packets that will naturally occur over twisted pair cabling.  As such, 10GBASE-T switches are both power hungry and heavy in terms of heat dissipation, posing a major issue from an environmental management perspective.  There’s no such thing as a “Free Lunch” as they say; in this case the free lunch being cables that cost 90-95% less than other options!      



While 10GBASE-T, 10-Gigabit Ethernet over Twisted Pair, has been hyped for years as the inevitable de-facto solution for 10-Gigabit networks, reality simply eliminates this possibility.  Delayed development, cost overruns, limited suppliers; combined with high switch and power consumption costs makes 10GBASE-T an unattractive option. The only upside to 10-Gigabit Ethernet over CAT6/6a  is the fact that CAT6/6a Cables are so inexpensive.  I can’t in good conscience recommend 10GBASE-T for your network upgrade under these circumstances.  


Recommended?  NO


Stay tuned for the follow-up blog to this question in which we will discuss two other 10-Gigabit Ethernet interface choices: CX4 and SFP+.


The Cable Guy

Amphenol Cables on Demand


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