Matthew Gingell is the business development director for MLL Telecom, and has spent over 20 years in the telecommunications industry, including at BT, Equant and data centre company Telecity. Here he looks at the neglected first mile of data centre connectivity

However, the theory and practise of data centre management in 2007 is deficient in at least one aspect – that of connectivity to the outside world. Some data centre operators have followed a systematic, well defined and complete approach to their connectivity strategy, but these are the exception. More often than not, the connectivity options available at any given data centre are a result of happenstance. This is particularly true in the private, enterprise sector, where cost and service availability considerations mean that the use of the incumbent telecommunications operator usually prevails.

The irony is that whilst the engineering and connectivity arrangements within a data centre are usually pretty sophisticated, providing back-up, performance and expansion options – and the Internet itself is inherently resilient, made up as it is of multiple IP networks – the join between these two environments is characterised by ad-hoc arrangements and vulnerability to unforeseen events.

Users of the data rarely, if ever, sit immediately above the bank of servers housed on the data centre floor beneath. They are more likely to be at least a few kilometres away, perhaps in the high-rise office of a financial district, sitting behind their laptops at home or, just as likely, on the other side of the world. It doesn’t matter that the data is still intact, secure and relevant; if the people who need to use it can not get access to it when they need it, then it is of no use at all.

Therefore we come to the key recommendation of this article, that data centre managers need to put as much effort into ensuring that the best connectivity and telecommunications back-up arrangements are in place as they do to planning contingency for the continuity of power, or the physical security of the data floor. This includes making a careful and thorough analysis of all of the fibre paths and ducts used to connect the data centre to the outside world. MLL recently advised a client who was looking to extend the connectivity of their (enormous) and mission-critical data centre housed in the docklands of London. In studying the detailed fibre maps from the two telecommunications operators who were providing connectivity to the site, it became clear that both of their fibre routes connecting the site to their networks ran over the same bridge in the heart of the docks - a single point in the architecture, the failure of which would take the data centre off the air for hours, days or even weeks.

Certainly, any user of a data centre – whether the centre is dedicated to their own use or whether they are a customer of a shared services provider – must take great care to ensure diverse fibre entry points, trunk routes and connecting to different exchanges, ideally on different carrier’s networks. Further, other connectivity media options should be examined from DSL through to satellite and, including one really important option, point-to-point microwave.

Historically, outside of the mobile cellular and broadcast industries where wireless communications lies at the heart of the business, fixed wireless access has sometimes been seen as the poor cousin to fibre and copper. Whilst benefits of mobility and speed of deployment seem obvious, these were undermined by a perception of the media as being too slow, unreliable, unsecured and potentially unsafe. Moreover, the complexities of dealing with spectrum licences, line-of-sight and property planning meant that microwave was sometimes relegated to the position of use-of-last-resort.
Within the last five years, this has changed radically, driven by technology enhancements, cost benefits versus regulated pricing and “green” issues (it’s more environmentally-friendly to install a couple of radios rather than digging up roads). There is, of course, some element of truth in some of the objections mentioned above to using fixed-wireless connections. However, each of these challenges can be completely met through proper design, planning, deployment and management. Moreover, there are compelling reasons to use microwave connectivity as an integral part of the data centre connectivity with the outside world.

Let us focus on the most obvious application; that of providing additional telecommunications resilience to the data centre. Within the centre, cabling to the frame room (or directly to a switching fabric if applicable) can become truly diverse, with the fibre connections going “down” to the entry ducts under the street, and the microwave access cabling going “up” to the antenna on the roof. Furthermore, the “A” end of a fixed wireless circuit can be chosen from a range of locations – any that can be seen “line-of-sight” from the roof or high point on the data centre infrastructure. This means that the choice for re-entry into the wired-world can be extensive, typically a radius of 25 kilometres at STM-1 speeds. Where a data centre is right out in the sticks, radio links can be daisy-chained together to cover significant distances to the most appropriate network exchange. Radio links can be deployed very quickly, usually with retrospective planning permission if a really urgent weakness needs to be protected. We have deployed STM-1 links within two working days in exceptional circumstances.

On the subject of speed, modern radio antenna equipment no longer has to resemble the Goonhilly earth station to beam signals of sufficient strength and accuracy. Dishes of only 300mm in diameter can transmit over seven kilometres at gigabit speed. Moreover, their light weight and exceptionally narrow beam means that multiple antenna can be mounted on the same pole and the signals multilinked to obtain even faster connections.
Reliability of wireless communications has sometimes been called in to question. Issues such as rain-fade, fog, damage to masts and so forth can potentially lead to degradation of service. And just because the microwave connectivity might be the third of three different connection mechanisms for any given data centre, doesn’t mean the reliability of the link is any less important than that of the fibre routes – if anything, it is even more important that it is operational when it is really needed.

Reliability comes hand in hand with two things; proper planning and proactive management. A feature of modern radio technology is that as long as monitoring and management units are deployed in the field and supported by a 24x7 Network Operations Centre, many configuration options can be used and varied in real time to ensure communication is maintained. Today’s software-defined-radios enable adjustments to be made (signal levels increased, polarity adjusted and so on) should conditions require it without requiring engineers to attend the site.

A fall-back from 1 gigabit to 155Mbps, whilst not desirable, is better than the zero which would usually be the result of a failure within a fibre network. In the end, the proof of reliability comes with the figures and the SLA which backs up connectivity commitments. MLL has customers with networks enjoying years of five and six nines up-time, many of whom use microwave as a primary with copper and fibre as a back-up. Radio networks form the heart of many police and MOD environments, for example.

This article has concentrated upon the use of microwave links in business continuity and has addressed some possible pre-conceptions about the use of wireless. One final thought on a slightly different note: Remote data centre users typically connect through one or more intermediate telecom networks or ISPs. An opportunity exists for the data centre operator to connect directly to end users located within 50km using WiMAX and pre-WiMAX technology.

With mobile and fixed WiMAX forecast to grow to 4.2 million users in Europe by 2012 (source Visiongain) and pre-WiMAX deployments already being rolled out, the role of wireless in the data centre is set to become even more critical than it is today.