Telescope 2007

Cabling: 10G on tap

10 Gbps over fibre has been around for a long time in the backbone. Now, as 10 Gigabit Ethernet over copper (10GbE) emerges into the sunshine, it is proving to be a viable alternative to expensive fibre optic cable. The cost differential is on account of the fact that 10G on fibre uses active components that cost eight times as much as passive ones making fibre too expensive for large-scale implementations of 10Gbps Ethernet. That’s why a copper solution was sought. 10GBASE-T is being touted as that solution. By Faiz Askari

As the density of devices in enterprise networks and data centres rises, there is an emerging need for low-cost, 10GbE over twisted-pair cabling. 10GbE copper cabling system has been verified to comply with the newly-ratified Institute of Electronics and Electrical Engineers (IEEE) 802.3an 10GBASE-T standard for 10GbE transmissions over a copper cabling system. The 10GbE over copper system was the first UTP (unshielded twisted pair) augmented Category 6 cabling system to fully comply with the IEEE 10GBASE-T standard. A 10GBASE-T standard that is in the works will support 10GbE over new wiring at distances of up to 330 feet and existing wiring at distances of up to 182 feet.

10GBASE-T doubles the bandwidth offering a 500 MHz ‘channel’ (end-to-end) and it can work up to 330 feet offering fibre-equivalent throughput of 10 Gbps. In comparison, Cat 6 offers 250 MHz over 10 metres topping out at 1Gbps. The ratification of the IEEE standard is an important milestone as it removes specification uncertainties for the manufacturers of 10GBASE-T switches and will lead to the commercial availability of electronics within the year. For customers, the promise of near-term 10GbE electronics is critical in their selection of 10G Ethernet cabling system over lower performance cabling alternatives.

The 10 Gigabit Ethernet Standard is an extension of the basic IEEE 802.3 standard protocols to a wire speed of 10 Gbps. As an extension, 10G is still fully Ethernet compatible and retains the key Ethernet architecture, including the Media Access Control protocol, the Ethernet frame format, and the minimum and maximum frame size. Just as Gigabit Ethernet followed the standard Ethernet model, 10G continues the evolution in speed while using virtually the same architecture that’s been used in other Ethernet specifications. 10G can be deployed with existing network equipment retaining the existing principles of network operation and management.

Rajesh Shenoy

There are specific cases—for e.g. data centres, SAN—where there are genuine requirements for such transmission rates. As of now, though, penetration is low. Rajesh R Shenoy, Business Head, Building Network Group, Belden explains, “Today customers are waiting for a switch manufacturer to come out with a robust 10Gbase-T switch. People are waiting to hear from switch vendors. Cisco and Foundry seem to be ready for a launch in the coming months. With this the market may move forward. This segment has good prospects in the near future.”

Gaurav Sharma, Senior Consultant, WAN specialist, Network Solutions comments, “10GbE over copper’s popularity is definitely picking up in India. A lot of interest has been generated for this in the last year or so. As modern day applications are bandwidth-hungry and require lower latency, enterprises and financial institutions including banks are evaluating 10GbE as a solution for their data centres or Storage Area Networks (SANs) as it merges with the existing Ethernet infrastructures.”

Although, at this point of time, 10Gbps over copper has found few takers in India, once support over active devices, especially switches, becomes available, the technology should take off.

Eliminating external noise

Milind Tamhane

10GBASE-T solves an important issue with Cat6. As transmission rates climb and signals extend into higher frequencies, other noise sources come into play; external noise source and alien crosstalk (ANEXT) that’s caused by signal coupling between adjacent cabling channels. Although the magnitude of alien crosstalk is usually less than crosstalk (NEXT) within the cable, its effect on channel capacity is greater because it is more difficult to suppress ANEXT through digital signal processing techniques commonly used in today’s equipment.

Says Milind Tamhane, Vice-president, Manufacturing, D-Link India: “These are more robust cables, predominantly shielded varieties though there are solutions with UTP, that are popular in India. More systematic cable dressings to avoid alien crosstalk, superior jacks and plugs are required.”

Higher bandwidth and ‘future proofing’

LAN backbones are expected to adopt this technology at the earliest. 10GbE will encompass all IP networks across the enterprise. It is the preferred LAN backbone connectivity option today. With 100 Mbps Ethernet to each desktop and 10GbE connecting the wiring closet switches to the backbone, 10 GbE provides a scalable interconnection between the LAN backbone switches. Most enterprises are already migrating to 10GbE on the desktop. It is the preferred interconnect for most enterprises and is expected to be deployed for applications such as video streaming to the desktop, aggregations between server farm and service provider data centres, data centre communication from LAN switches to storage networks, and grid computing. It is consequently being adopted in desktop and server farms, on campuses.

Dabinder Singh, Head, IT, Greenply Industries says, “10GbE copper technology is perfect for load balancing and we are also evaluating the technology for last mile connectivity at selected locations. The technology is helpful where zero delay is required for resource-intensive applications such as ERP, CRM or SCM.”

Daya Prakash, Senior Manager, IT, LG CNS Global adds, “10GbE over copper will help speed up throughput and in case the Internet Service Provider uses this technology it will help provide optimum reliability to users. This technology can be a boon for mission-critical applications such as ERP and for messaging and collaboration. It is also beneficial for video streaming.”

In the Indian scenario, 10GbE is already being used within buildings for LAN uplinks. For example, 10GbE uplinks from the switches to the core are expected to happen in six to eight months. In the case of inter-switch links, situations where two large Ethernet switches have to communicate, 10GbE is a must. On the server side NICs will be 10GbE. In green-field set-ups large businesses will consider 10GbE on copper to ‘future-proof’ their network because it is difficult to replace cabling inside walls and in ducts under floors. The rationale behind this is that cabling will last for at least eight to 10 years and will support four to five generations of equipment during that time.

10GbE over copper is expected to bring in change in IP SANs that will move towards 10GbE as it offers a simplified and cost-effective interconnect mechanism when compared to other technologies that are available. Cabling vendors are of the opinion that the adoption of 10GbE over copper will make high-speed IP SANs a viable option.

An alternative to fibre?

In terms of capability and uniqueness, in the 10Gbps network, transmission protocols like 1000Base-T need only 65 MHz of the available 200 MHz (in Cat6). This makes a Cat6 cabling solution quite stable at 1 Gbps. On the contrary the 10GBase-T will need the full 500MHz of a Cat6a-augmented solution. This means that a bad Cat 6a solution will fail faster. It also makes it riskier for customers who are going in for a Cat 6a solution, that does not provide greater headroom.

With regard to 10 GbE networks being considered a substitute for optic fibre, Shenoy states, “I disagree from the standpoint that says that fibre will be replaced by 10 GbE in the near future. I think both fibre and copper will co-exist. They have different uses and capabilities.”

Tamhane has a similar view, “10GbE transmission includes all types of fibres 10GBase SR addresses multimode fibre at short wavelength (850nm), 10GBase LR is using both multimode as well as single mode at 1310 nm wavelength and 10GBase ER is the extended range of beyond 40 km using single mode fibre at 1550 nm.”

As to whether 10GBASE-T will be an alternative to fibre optics, the answer is a clear ‘no,’ because both the media have their specific applications. The environment where one expects reasonable low electronic noise, shorter distances, less MAC (moves, adds & changes) and cheaper solutions may move to 10 GbE.

Copper vs FTTD

The idea of fibre to the desktop (FTTD) has been around for quite some time. Early proponents of FTTD cited problems with UTP systems and limited distances as reasons for their recommendations. There are 10GBASE-X fibre applications, and in fact, those needing 10G bandwidth have had fibre options for some time now. In evaluating copper versus FTTD, it is important to include overall network costs (including electronics), not just cabling costs.

Fibre components for 10G are expected to settle at a cost that is roughly 10x the cost of a gigabit port. On the copper side, however, the cost will be about 3x the cost of a gigabit port or roughly one third the cost of a 10G fibre port. All PCs shipping today come with 10/100/1000 Mbps copper network interfaces. In order to use FTTD, that investment will go to waste and a new fibre card will need to be procured. The same cost differential applies. It is also noteworthy that the 10GBASE-T copper chips will auto-negotiate from 10 Mbps up to 10 Gbps. This means that one chip will be used for all network connections. It is far less expensive to mass produce one chip than several varieties. As 10GBASE-T chips begin mass production, they will begin to surface in server NICs, switch ports etc.

Challenges ahead

In any growing market, identifying initial challenges and how to deal with them is a decisive factor in a technology’s future. 10GbE networks are gaining ground but some challenges remain to be tackled.

Highlighting key elements that need to be worked upon, Shenoy says, “Customer awareness is low as to what a real 10GbE solution is. Customers take a call on the basis of market perception rather than the technical reality. This could hamper adoption of this technology in the long run. 10GbE vendors should show the path by telling the customer what the pros and cons of going for a Cat6a solution are as the technology hasn’t been ratified yet.”

Sharma states, “The future of 10GbE market is definitely bright in India. To quote the data from a survey done in India, it was quite evident that nearly 50 percent of organisations understood the importance of upgrading their networks and considered future-proofing their backbone cabling infrastructure using the latest 10G Ethernet equipment.”