Optical/IP Networks

10-GigE Copper Heats Up

Celebrations over the ratification of CX4, a standard for 10-Gbit/s Ethernet over copper lines, might be short lived, as it appears a newer standard due in 2006 will take its place.

The 10GBase-CX4 standard, shepherded by the 802.3ak task force within the IEEE, was created as a low-cost alternative to fiber-based 10-Gbit/s Ethernet in the data center. But in the two years since CX4 got started, new advances have promised to make fiber modules cheaper. And a second copper standard, 10GBase-T, appears likely to uproot CX4 eventually.

None of this changes the fact that CX4 is available now and remains cheaper than any alternative. As a result, product announcements continue to emerge. Cisco Systems Inc. (Nasdaq: CSCO) included CX4 support in its latest raft of features for the Catalyst 6500. And Fujitsu Microelectronics America Inc. today added CX4 interfaces to its previously announced switch chip, which handles 12 ports of 10-Gbit/s Ethernet (see Cisco Beefs Up Catalyst, Fujitsu Enhances 10-GigE Switch Chip, and Fujitsu Packs in 10GigE ).

If CX4 is short lived, it will continue the streak of ill-fated copper standards for Ethernet. A similar scenario unfolded at the 1-Gbit/s generation, where a standard called 1000Base-CX was adopted, and it happened for 100-Mbit/s Ethernet as well. "You're going to see the same kind of evolution that's happened with Gigabit [Ethernet] over copper," says Steve Shalita, senior product marketing manager for Cisco's Gigabit Systems division.

The goal with CX4, which was ratified in January, was to let data centers avoid the cost of optics when dealing with short, rack-to-rack kinds of connections. "Removing the optics from 10-Gbit/s Ethernet is really a boon because you're bringing the cost down," says Asif Hazarika, product marketing manager at Fujitsu Microelectronics. In general, optical 10-Gbit/s Ethernet costs thousands of dollars per port, while copper interconnects could drop to a few hundred dollars.

But CX4 suffers on two fronts: distance and cabling.

The 802.3ak specifies distances of only 15 meters, and it's questionable whether that's enough even for connecting racks in the data center. "Nobody's really happy about this 15 meters. They'd like to have more," says Kamal Dalmia, technical marketing manager for Marvell Technology Group Ltd. (Nasdaq: MRVL).

Fujitsu's chip extends CX4 to 25 meters, and Mysticom Ltd. claims it's gotten CX4 to work at 30 meters.

But that might not be enough. The 10GBase-T standard, being developed by the 802.3an task force, calls for 50 meters and aspires to 100.

"It seems 50 to 60 meters is the maximum length for data centers," says Bruce Tolley, senior manager of emerging technologies at Cisco. "Fifteen meters doesn't get you very far in the data center."

Distance is key, but really, 10GBase-T is expected to win because it uses relatively common Category 5 copper cabling. CX4 was developed for InfiniBand cable, a more specialized variety that uses eight pairs of wire, twice as many as Cat 5. "When [10GBase-T] becomes available, there is no rationale for CX4 any more," Dalmia says.

Aside from copper concerns, CX4 faces a renewed challenge from the fiber side. In the time it's taken to finalize CX4, module vendors have created the XFP multisource agreement (MSA) for a serial 10-Gbit/s interconnect that's smaller and cheaper than previous alternatives. Separately, chip companies have banded together to create a standard for adding electronic dispersion compensation (EDC) to a 10-Gbit/s link, which would allow for the use of cheaper optics. The EDC option specifies 300-meter reaches on multimode fiber (see XFP No Longer a BFD and Vendors Still Driving LX4).

Copper is still cheaper, but these lower-priced alternatives, combined with fiber's ability to carry 10-Gbit/s signals farther, weaken the CX4 proposition, Dalmia says. "If the copper standard gets delayed too far out, it starts to lose its appeal. That's what happened to CX4."

Marvell introduced a CX4 chip in April 2003, and others -- including Broadcom Corp. (Nasdaq: BRCM) and Mysticom -- have followed suit (see Marvell Debuts 10-Gig Transceiver, Broadcom Tackles 10-Gig Copper, and Mysticom Demos 10-GigE Over Copper). Still, Marvell has no illusions about CX4's long-term future. "We're ratcheting down the emphasis on the CX4 side," Dalmia says.

Well, with all this doom and gloom, why support CX4 at all? For one, it's been completed as a standard, while 10GBase-T isn't expected to complete the IEEE ratification process until 2006. The 802.3an task force is still in its early stages; last week, the group heard technology proposals from companies including startups KeyEye Communications Inc., SolarFlare Communications Inc., and Teranetics Inc. SolarFlare, for one, expects to be shipping chips "by the end of the year," says Ron Cates, vice president of marketing.

Still, CX4 is in the driver's seat temporarily. "Since it's substantially cheaper than any of the other interconnects, and since data centers are the primary operation for 10-Gbit/s Ethernet today, we expect CX4 to be successful," Tolley says.

In Marvell's eyes, CX4 was a stage-setter, proving that 10-Gbit/s Ethernet could work on copper lines and -- more important -- putting pressure on optical vendors to bring prices down.

"If we didn't do CX4, the cost of optics would still be very high," Dalmia says. "CX4 has served its purpose from that perspective. It got the XFP group to move and got the EDC guys to move."

— Craig Matsumoto, Senior Editor, Light Reading
jayja 12/5/2012 | 2:10:50 AM
re: 10-GigE Copper Heats Up You can call a goat a horse, but it is still a goat.
bwoodruff 12/5/2012 | 2:10:48 AM
re: 10-GigE Copper Heats Up Hey, in a contest where you're the only one there, you can look great!

It's the lowest cost way to do a XENPAK type module for 10GE, if you're in neighboring rack.

It may not be the long term ideal, but it is real and shipping.

Xile 12/5/2012 | 2:10:24 AM
re: 10-GigE Copper Heats Up Bill, good to hear you again.

Beatles fan (yeh, yeh): CX4 fills the same need in today's data center than 1000BASE-CX filled until 1000BASE-T arrived. The Si vendors are doing the same thing they did in 1GbE days to try to differentiate - brag about distance. But the market for this is all short distance(sub 15m). So in typical Ethernet fashion - lots of vendors, all meeting spec - the result will be cheap, cheap cheap connections. It ain't sexy and it won't make your IPO but it will fill a necessary gap.

- Xile
DanDove 12/5/2012 | 2:10:20 AM
re: 10-GigE Copper Heats Up I understand that "Light Reading" is aligned with the optical networking business, but I don't understand why they chose to attack CX4 with false statements when in fact, CX4 is their FRIEND.

The standard did not start "two years ago". It technically started in Spring of 03 when it was given task-force status. Before that, it was a discussion. It was one of the fastest 802,3 standard efforts ever done in my recollection.

The issue of reach is valid, however, as understated in the article, clustering, aggregating, and stacking of Gigabit switches does not require long lengths.

Here is the kicker. Here is the reason Light Reading should be HAPPY that CX4 has been approved and is rapidly becoming available... As customers move to Gigabit in their desktop switches, and they use 10GBASE-CX4 to aggregate those switches, how are they going to interconnect their wiring closets? How are they going to interconnect their buildings? How are they going to expand the overall network bandwidth for Ethernet??? FIBER!!

Don't you get it? CX4 will do more for the growth of 10G Fiber products than anything else done in the last 4 years. Be grateful! Don't diss this technology, embrace it.

Dan Dove
Former Chair, P802.3ak
maximuscomehome 12/5/2012 | 2:10:17 AM
re: 10-GigE Copper Heats Up Dan Dove..." Don't you get it? CX4 will do more for the growth of 10G Fiber products than anything else done in the last 4 years. Be grateful! Don't diss this technology, embrace it."

Yes, and we should also be grateful for the OTHER technologie visions from this very talented group of people:

1 Mbits Ethernet Starlan
10 Mbits ethernet on coax
100 Mbps VG (The 100 Mbps AnyLAN aka 802.12)
1Gbps Ethernet 1000BASE-CX over copper cable
and now
** the obvious solution to the fiber problem **
10Gbps ethernet (CX-4)

wait! You mean you never heard of the other technologies? Well damn! you ARE an idiot.

I suspect if we ever have 40G ethernet - we know who will try to push it on coax.

Thanks, O Dan Dove! For this brilliant solution!

-- Massimo
DanDove 12/5/2012 | 2:10:10 AM
re: 10-GigE Copper Heats Up I suggest that if you want to quote my post, you look at the one arguing for the increased overall network bandwidth that CX4 will create and its value to the fiberoptic market.

I am not anti-fiber by any means. I am recommending to my high performance customers that if they anticipate a need for higher than 1G to the desktop they consider running 10u fiber along side their CAT6e shielded cable or CAT7.

That said, for wiring closet interconnects, aggregation, and clustering, CX4 is going to support a much lower cost point which will enable broader migration to Gigabit to the desktop.

If the demand for reach exceeds 15m, fiber is a great solution at a higher price.

Thanks for your intelligent and persuasive post.

maximuscomehome 12/5/2012 | 2:10:04 AM
re: 10-GigE Copper Heats Up Mr. Dove:

My apologies if my "persuasive points" failed with you.

The technologies I mentioned all started off with good intention - to provide yet another solution for wiring connectivity or for inferior grade (cheaper) cable etc.

Perhaps 802.3 should have waited a bit to see how fiber prices stabilise - before specifying a stop-gap standard that will only create confusion in the market (no doubt good for vendors).

Especially after the dismal record of 1000BASE-CX.

I did compare the cost for (<15m) connectivity between fiber and CX-4. When you take into account the cost of the systems (routers/switches/servers), the stocking cost, sparing and support (also known as TCO) - where are the savings with CX-4?

I did have this discussion with my HP salesman years ago about 1000BASE-CX - and ended up brain-washed and bought 1000BASE-CX.

I shouldn't have. It was on odd piece of gear - and at the end we retired it as soon as budget allowed. The switch was fine - it worked as advertised - the CX interface was a bum.

So I am the user that you so heavy-handedly profess to help (well at least one of them :-)
And from my past experience with your previous concoctions - may I suggest you become just a tad less high-browed about "how obvious" CX-4 is and how people should just "get it"?

I recently looked at the Cisco 10G (fiber) gear -it's pretty darn good, compatible with the other products in the line and they assure me they will have 10G-T when it's solid. In the meantime - the price is fine.

-- Massimo

---Didn't you guys invent the LX4 stuff in the first place and were going around telling us how this VCSEL-based plastic CWDM part will be cheaper than anything? What happened to that?
DanDove 12/5/2012 | 2:10:02 AM
re: 10-GigE Copper Heats Up Maximus,

You create so many points to address... where is the time?

1) The 10G standard has been done for over two years. How long were we supposed to wait for prices on optics to "stabilize"? The IEEE uses a model of 10X the performance for 2-3X the cost.

Right now, 10G optics are close to 20X the cost of gigabit. The IEEE used good judgement in this case. Many companies supported its development and now deployment is in progress. At the minimum, CX4 will spur the reduction in optics cost we all desire.

2) 1000BASE-CX failed for a few good reasons. It had EMI problems due to the unscrambled IDLE, and by the time it was properly deployed, 1000BASE-T was available and supporting existing cabling for longer distances. I support the 10GBASE-T effort, but it will be a while till its done. Yes, CX4 is a stopgap solution. The question is, how long will the gap exist? (Hint: 10GBASE-T deploys in volume or optics drop to comparable prices..take your pick)

3) My apologies if I came off heavy handed, but you have to understand that while you are a user, there are others who might just disagree with you. We can't please all the people all the time... some people are never pleased.

I recently spoke to a few end users who are really excited about CX4 and how it is going to lower the cost of their networks. These people were extremely intelligent network engineers and not likely to be "brainwashed". They can see the value CX4 offers and if they don't, we will be happy to offer them a fiber alternative.

4) LX4 was promoted by Agilent. Different company.

I would love to have a point-by-point debate with you for the next week or two, but I really don't have time and what would be the objective?

If you don't like CX4, I recommend you use one of the alternative 10G technologies. Please don't take offense, none is intended.

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