With gigabit switch sales improving, vendors are already beating the drum for the 10Gb upgrade. According to key players such as Cisco and Extreme, pre-standard products could be selling before the end of the year.
Roger Jones, technical manager for northern Europe at Lucent's Enterprise Networks Group, believes that, when they plan their next hardware upgrade, corporates would do well to think about upgrading their cabling to the new Cat 6 standard when it appears in anything up to two years' time.
This is not because gigabit ethernet won't run over Cat 5, because it does. It is just that, in Jones's opinion, making these gigabit switches is unnecessarily expensive. His point is that, while users can expect to see per-port prices for gigabit ethernet fall from the current level of $600+, as demand grows it would fall a lot faster if they could be persuaded to shift to Cat 6 cabling.
This is because up to half of the fabrication costs associated with manufacturing gigabit switches come from the vast array of special purpose application specific integrated circuits (Asics) that have to be added to the switch to compensate for the deficiencies of Cat 5 cabling. Near-end cross talk, far-end cross talk, lateral chatter - you name the evil, Cat 5 has it, and it all needs to be cleaned up if gigabit performance is going to be achieved.
Upping the ante to 10Gb magnifies the Asic issue. It's a solvable problem, but by no means free. Moving to Cat 6 hugely reduces the number of Asics required. The opportunities for price reduction, if corporates can be persuaded to move, are obvious.
A zero every five years
The same point is relevant to anyone who may be anticipating some kind of cascade towards the enterprise of the current, and coming, generations of high bandwidth carrier class and ISP dense wavelength division multiplexing (DWDM) switches.
Luc Adriaenssens, director of research and development at Lucent's Bell Laboratories, predicted that, despite the current glut in corporate Lan bandwidth technologies, corporates should expect to add a zero to their required Lan bandwidth every five years.
Taken literally, this would mean that a corporate backbone of 1Gb today will need to grow to 10Gb within five years, to 100Gb within 10 years, and to one terabit within 15 years. Adriaenssens uses this forecast to argue for a new, even cheaper, gigabit ethernet switching technology predicated on Cat 6.
Yet today, and for the next few years, it seems plain that for relatively modest per-port prices, enterprises have plenty of scope for adding bandwidth to existing Cat 5 infrastructure. The gigabit ethernet switches currently on the market will handle 1Gb scenarios well.
Corporates requiring a little more room than 1Gb in their backbone can provide aggregate 1Gb links. Cisco and other vendors have link aggregators that will allow users to bundle up to eight 1Gb ports, using trunk technology.
Bruce Tolley, Cisco's product manager who is also vice president of the 10Gb Ethernet Alliance, pointed out that the big problem with this approach at the corporate level is that it uses up expensive ports and fibre pairs. When they appear, 10Gb ports will provide a much more attractive way of moving beyond the single gigabit level.
As Jones points out, it's not just the size of the pipe that matters. Increasingly, enterprises want gigabit switches to be able to handle wire speed Quality of Service (QoS) tags as well.
Jones said: "All the vendors are gearing up for 10Gb ethernet. The standardisation process has started and a standard is probably less than two years away. However, none of the vendors today have the ability to investigate packets at wire speed."
Tolley thinks that Cisco already gets plenty of interest from customers who anticipate needing more than 1Gb in their enterprise backbone. "Once you start loading up your switches with multiple gigabit ports, a natural and obvious consequence is that you start to need more backbone. We have ISP customers who already want 10Gb pipes, but we also have corporate customers who anticipate needing this level of bandwidth soon," he said.
He pointed out that demand always starts in pockets and then spreads. "Most corporates may not need 10Gb backbones today, but we have to start now so that in two years' time, when they do have this requirement, we are ready," he said.
Cat 6 standard
Tolley also warned against Lucent's argument that the cost per port could come down dramatically if enterprises were prepared to upgrade to Cat 6 cabling. "The standard for Cat 6 cabling will not be ratified for around two years yet. This is far too long for people to wait, given the current pressure on bandwidth," he said.
"You can buy pre-standard Cat 6 cabling from a variety of vendors today, but different versions of Cat 6 tend not to interoperate well. If you mix and match Cat 6 cabling from various vendors you stand a good chance of not ending up with Cat 6 performance." As for switches that capitalise on pure Cat 6, that technology is still in the lab, he said.
Cisco's own 1000 Base-T gigabit switches, the Catalyst 4000 and 6500 range, will both run on Cat 5 and should also run on vendor-labelled Cat 6 cabling, Tolley said. The 4006 series has 12 1000 Base-T ports and two GBIC (gigabit interface connector) ports. The Catalyst 6500 series offers a 16-port module. Although the distance limit on Cat 5 is 100 metres, it should prove more than adequate for buildings. As Tolley pointed out, the way the Building Standard for structured wiring is written, people should not be pulling cable runs longer than this anyway.
Tolley also said that Cisco plans to ship a pre-standard 10Gbps module for the Catalyst 6500 series later this year. It will come with short-reach optics for data centre applications, medium reach for campus topologies and longer reach optics for Metro class applications that should run to 40 or 50 kilometres.
The module, when it appears, will offer full duplex 10Gbps, "not some cobbled together TDM (time division multiplexing) solution as demonstrated by some vendors", he said.
Linking to optical networks
Cisco plans to offer the optics separately from the line card, giving customers a broad choice of how they link into optical networks. Coarse or wide DWDM products (a coarse-grained wave division technique with 10 to 20 nanometres between frequency channels) that can map 10Gb onto DWDM equipment are available from vendors such as Adulent and Spectralan.
"There is a requirement in the IEEE standard to match the OC192 9.58Gbps, and we expect to see a range of equipment that will interface to map 10Gb ethernet into an optic link. The rate adaptation between 10Gbps ethernet and the OC192 9.58Gbps speed will be taken care of at the physical layer," Tolley said.
Tony Lee, director of product marketing at Extreme Networks, and chairman of the 10Gb Ethernet Alliance, pointed out that one of the drivers pushing corporates towards 10Gbps instead of just a single gigabit pipe is the current trend to deploy 1Gb links between server farms and the core enterprise backbone.
"As these server farms grow, they start to need a lot more bandwidth to aggregate traffic on the Lan. They also need more bandwidth to pull traffic down off the enterprise link to the local metropolitan area network (Man)," he said.
"If we see - as seems likely - a big uptake in the use of corporate portals as the central depository of all relevant information, we are going to see huge increases in traffic in the Lan and over the Wan. Employees, partners and clients will be logging on from locations all over the place to access information. If you add streaming media to the depository, with online product catalogues with media clips, traffic will grow exponentially," he added.
Lee argued that already, in the Man, "new age" IP over DWDM service providers were very interested in deploying 10Gb ethernet technologies. Extreme already has around 20 Mans built on ethernet/IP around the world, including some internet exchanges providing peering services for their ISP members, such as the London Internet Exchange site in London Docklands.
"Dataquest did a report at the end of December which showed that an ethernet Man solution will work out at around a fifth to a tenth of the cost of a SONET or SDH-based option. In the enterprise, the cost per port for gigabit ethernet switches is now below USD625 for a 32-port 100/1000 switch, delivering 1.488 million packets a second for each gigabit port," he said.
Lee thinks that we are going to see the Man extending right into the corporate wiring closet. When this happens there is going to be even more corporate traffic to aggregate on to the Man link aggregators at 1Gb ethernet, and they are not going to be able to compete in cost terms with 10Gb link aggregators when those arrive, he said.
According to Lee, Extreme is already talking to a number of corporate customers who have plans to deploy 100/1000 Base-T autosensing Nics in corporate power user desktops. At between $400 and $600 per card, this is more of a server option today, but Lee expects to see the rollout to power users happening shortly.
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