Structured cabling is an exception in the fast-moving world of information technology. While information technology managers expect to reinvest in most hardware and software every three to five years, they expect a life of up to 20 years from their installed cabling infrastructure.
To meet this requirement, new and pioneering cabling technology must be launched just as mainstream users start to recognise and reap the benefits of previous generation cabling solutions. The latest breakthrough in UTP (Unshielded Twisted Pair) technology is no exception to this rule. UTP copper cabling that supports the new 10GBASE-T standard for data speeds of 10Gbps is being introduced just as 1Gbps infrastructure begins to accelerate its deployment in LAN installations worldwide.
There are those who say such innovations run too far ahead of users' needs but, as in the past, they are likely to be proven wrong. Faster network connectivity has nearly always shown it can deliver productivity gains by speeding the flow of information through an organisation.
Users who spend less time waiting for files and applications to arrive on their PCs can do more productive work in a day. What is more, these gains are increasing as organisations install new client server, data warehousing and collaborative applications that rely on fast networking to deliver business benefits.
Gigabit network backbone and data centre links are already becoming bottlenecks as growing bandwidth demand from desktop PCs is aggregated in connections to servers and storage appliances. Most business PCs now have gigabit Ethernet interfaces and their power continues to increase with each new model. As a result, today's PCs can simultaneously run several applications, such as word processing, e-mail, Internet access, messaging and security. Often these applications initiate scanning, software updates, system monitoring, encryption, compression and proactive information organisation, all of which place unseen demands on the network.
To help IT managers deal with these and other pressures on network bandwidth, the IEEE (Institute of Electrical and Electronics Engineers) made a year-long study of the requirement for 10Gbps networking. Following this, in March 2004, it formed a task force to draft the specifications for all the key areas of the 10GBASE-T 10Gbps data transmission standard. In developing the new standard, also known as 10 Gigabit Ethernet, the taskforce focused on use of UTP cabling to provide cost-effective and easy-to-deploy connectivity. Complementing this, support for the faster data channels and longer distances are specified over fibre as well, although the electronics for fibre-optic transmission are expected to be more expensive than copper electronics.
Cost savings with UTP
For transmission over a UTP copper infrastructure, 10GBASE-T calls for transmission over 4-pair cables in which each pair operates at 2.5Gbps. Originally, the taskforce expected the new standard to include transmission over Category 5e cabling. However, it soon became clear that this cabling type could only support 10Gbps over very short distances that were not considered useful.
Category 6/Class E cabling is now accepted as the minimum cabling specification for 10GBASE-T. The IEEE objective is to support 10G transmission over Category 6/Class E up to 55m, but it remains to be determined whether this is realistic in practice, depending on installation conditions. What is certain is that for reliable communication at 10Gbps over a distance of 100m, UTP channels will have to comply with the emerging "Augmented Category 6", "New Class E" requirements. These are specified out to 500MHz, twice the bandwidth of Category 6 solutions, and include new requirements for Alien Crosstalk.
For both Category 6/Class E and Augmented Category 6/New Class E cabling, new encoding systems and electronics are required to achieve 10Gbps transmission. The signals generated utilise higher frequencies and are more sensitive to electronic noise than those in 1000BASE-T networks, which is why it is unrealistic to expect Category 6/Class E cabling to support 100m 10GBASE-T channels.
It is well known that UTP copper cabling will offer a lower cost alternative to optical fibre for 10GBASE-T channels. The electronics for 10GBASE-T may be more sophisticated than for 1000BASE-T, but they will be significantly less expensive than the electronics for 10Gbps fibre connections.
These cost savings may be especially attractive in data centres, where linking many servers, switches and SANs (storage area networks) via copper is an economic advantage. Total system costs can also be significantly lower for backbone deployments when using the new UTP cabling instead of fibre for 10Gbps connections of 100m or less.
The industry generally recognises that the capabilities in today's servers will be found in tomorrow's desktops. Therefore, although the initial target for 10GBASE-T is data centres and backbones, forward-thinking customers should recognise the benefit of deploying 10Gbps UTP cabling to the desk. As in the past, we expect greater use of existing applications combined with new, bandwidth-hungry systems will tax the capabilities of previous generations of cabling technology, and probably sooner than expected.
We believe upgrading to 10Gbps connections will ensure user productivity is not affected while waiting for transmission of files containing complex documents, high-resolution images or video presentations. In addition, faster connections will significantly improve the quality for real-time voice and video for IP telephony, conferencing and remote learning.
High-speed connections to the desktop also open the way to emerging new technologies such as grid computing. This is a key emerging technology connecting large numbers of standard PCs to harness their idle processing resources to achieve the computing power of a super computer. But, realising the full potential of PC grids for simulations, complex modelling and analyses demands very fast interconnections between the PCs.
Cabling design
Delivering new communication channels that are 10 times faster than today's Gigabit Ethernet connections presented cabling designers with some significant challenges. Achieving reliable 10Gbps throughputs means these channels must support multilevel signal encoding and modulation frequencies up to 500MHz. Both these features make the signal more sensitive to small electrical disturbances (noise) that have no effect on lower speed systems.
Clever design of network electronics can help cancel out many unwanted electrical interactions that cause noise within the cabling channels. The techniques electronics designers use include digital signal processing (DSP), adaptive equalisation, echo cancellation and other sophisticated methods to cancel some of the noise. However, there are effects within and between cables that cannot be dealt with by electronics alone. The best way to manage these effects is in the cabling design.
The 10GBASE-T networking specification recognises the importance of connectivity by specifying additional cabling parameters not included in earlier standards. Most important of these is Alien Crosstalk, which is the unwanted noise affecting a cable caused by emanations from other cables that surround it.
The challenge for the cabling industry is to produce end-to-end solutions that meet all the new specifications, even under worst-case conditions. This is difficult because there are as many as 256 interactions between the pairs within a 4-pair cable that can have a significant effect on performance. Alien Crosstalk, caused by adjacent cables, complicates matters even more, increasing the number of interactions to 1 024.
To manage all these interactions in the design of new cabling solutions, engineers (at SYSTIMAX Labs1) have developed computer-based modelling tools. These immediately show the effects of cable, connector and patch cord combinations, so designers can quickly arrive at system and component designs that provide the best end-to-end throughput.
Alien effects
When developing solutions to meet the emerging Augmented Category 6/New Class E standard, designers applied their unique modelling tools to the complete 100m, 4-connector channel.
It became apparent early in the development that to reach the required breakthrough end-to-end performance, including Alien Crosstalk requirements, it would not be sufficient to design a new generation of UTP cable. Particular attention had to be paid to the design and tuning of new connectors, outlets, cords and patching hardware to ensure these had compatible characteristics when combined to deliver a complete channel.
As well as advanced modelling techniques, new testing methods were also needed to determine whether Augmented Category 6 cabling would meet enhanced specifications. One of the most demanding of these new methods is the '6-around-1' test (developed by SYSTIMAX Labs) in which the channel under test is surrounded by six others. This 6-around-1 configuration was determined to be representative of the performance of large cable bundles. To ensure the channel will perform to specifications even under worst-case installation conditions, signals are injected into the six surrounding channels and the Alien Crosstalk is computed to confirm that the specifications in the standard are achieved.
Leading manufacturers now use the '6-around-1' test on complete channels, including connectors, outlets and cords. Testing components individually is of limited value since the interactions between components cause many of the worst noise effects. In the same way, testing complete channels without surrounding cables producing Alien Crosstalk does not tell engineers how cabling will perform in real networks.
In the real world, many data cables are bundled together in channels and trays. Added to this, there may be nearby power cables, lift motors, lighting systems and other sources of electromagnetic emanations. Good cabling design can prevent this potential interference from disrupting the sensitive, multilevel encoded signals in a 10GBASE-T network.
Among potential early adopters of 10GBASE-T, data centre managers are likely to be the first to decide whether the new copper cabling solution can meet their needs. Attractive savings over 10Gbps fibre links over distances up to 100m should make investment in the new technology easy for them to justify.
For desktop connections, 10GBASE-T will meet the needs of collaborative, multimedia systems now being introduced. As such network-centric applications emerge, most users will see a payback on an investment in Augmented Category 6 cabling earlier than they might think. With information technology managers expecting their cabling infrastructure to last from 15 to 20 years, the choice of 10Gbps over 1Gbps cabling could subsequently pay for itself several times over.
For more information, please contact James Preston, Sales Director Sub-Saharan Africa at jamespreston@systimax.com.
Share
