Five considerations for implementing SDN: Promise versus practicality

Citrix

#dcsarticle http://www.dcseurope.info/n/kknq

LOOKING BACK OVER THE PAST 25 YEARS, the data centre was divided into constituent parts, with the ‘useful economic life’ of individual fixed assets such as servers, storage arrays and networking components assessed. At one time these were deployed as monolithic stacks in support of specific applications or users. These ran in an ‘armed’ state regardless of actual usage, with a large part of the expense being wasted on under-utilised capacity.
Essentially, a million dollar asset was broken into smaller parts that would depreciate over a much shorter timeframe, largely because of the inflexible nature of the technology it was based upon. As demand grew, costs soared as a consequence.
The virtualised data centre
Virtualisation changed everything. The emergence of hypervisors brought the idea of ‘build once, use many times’, where
data centre workloads could be consolidated and reflect the transient demands of the business.
In recent years, cloud has further accelerated the evolution of data centres from inflexible silos into flexible service delivery platforms. It has also made the true cost of compute transparent, which means a CFO can easily see how much vCPU, Storage and Network capacity costs on the open market.
Even more evident is the speed at which data centre resources can be spun up in the cloud compared with today’s enterprise data centres. Cloud providers have built their infrastructure from scratch over the last 3-5 years, designed from the outset to be a new generation of data centre capable of serving computing power at less than the cost of on-site IT.
The virtualised network
Most enterprise data centres today are designed in two tiers:
 The central ‘Flex Tier’, where state-of-the-
art virtualisation, automation and
provisioning technology continues to add
huge value and deliver sizeable cost
savings. This approach is common,
however, in both enterprise data centres
and the service provider cloud.
 The ‘Edge Tier’, the last mile of
connectivity between the virtualised core
of the data centre and the user’s device.
This contains networking devices, security
policies, firewalls, VPNs. Until recently,
this tier was still in the data centre dark
ages, with monolithic deployment and
vast arrays of machines, cables and
blinking lights in a constant state of under-
utilisation.
Virtualisation has started to emerge in the Edge Tier as NFV (Network Function Virtualisation). Today, firewalls can be virtualised, networking hardware is becoming multi-tenant and the expensive, old-fashion Edge Tier is becoming marginalised as the power of the Flex Tier grows.
Service Providers were among the first to identify NFV’s potential to cut significant capital and operating expenses from the cost of data centre ownership.
The true strategic value lies in taking virtual networking and security workloads into the modern age – and adding the orchestration capabilities that gives the cloud its competitive edge – ultimately creating a network that is application-aware, capable of understanding who a user is, what they are trying to do and what resources are needed to deliver it.
In the future, investment is less about expanding the physical reach of networks and more about increasing network intelligence.
SDN – Promise and practicality
At a basic level, SDN is attractive because it is just good economic sense. However, this level of transformation cannot happen overnight – and it will never fully replace what went before it. Networks are better virtualised than monolithic – but a smart, informed and strategic approach is needed.
Rather than talk further about the promise of SDN, it is important to encourage businesses that are considering the SDN paradigm-shift to look at the real business drivers behind such a move - rather than taking on the technology because of its novelty. Choosing to virtualise via SDN is one option to define the future network and data centre – but it is not the only way.

A better approach is to tackle the practicalities of SDN, shedding light on what businesses can expect in terms of the impact this could have on their wider business. With that in mind, here are the top five points to consider before moving down the SDN path.
1. SDN is not the only way
Whilst SDN might be the height of fashion, there are always other means of data centre remediation. SDN is extremely valid, but by no means exclusive. Businesses should consider all options before making irreversible commitments in infrastructure. Look at not only what SDN offers, but what it lacks.
2. Understanding the need for change
What’s the business justification? Be clear about what you are set to gain. Short-term TCO returns on large-scale infrastructure investments are rare, so be prepared to take a broader view of return on investment to help build a solid business case. Anything that offers consolidation and automation tends to make good long-term financial sense, but the ease of management, improved user experience and agility offered by SDN can have a much more immediate business impact. Engage a broad range of stakeholders from across your lines of business when building up your case.
3. Impact on finance and capital expenditure
Sometimes technology moves at a faster pace than the business it supports. The idea that SDN allows you to ‘build once and use many times’ sounds appealing but doesn’t suit the way many businesses run their accounting policies. SDN requires not only a change to the data centre, but also a change in the way overheads are managed, assets are written down and departments cross-charged. A shared-service approach to data centre resources can present a challenge to the way some companies manage internal cost.
4. Impact on network utilisation and capacity planning
A move to SDN should bring with it great flexibility and resource efficiency, but do challenge suppliers to ensure their pricing and licence models are as flexible as their product. Seek out pay-as-you-grow licensing, burst packs and options for using third-party infrastructure in the cloud as availability zones. It is also important to give consideration to those offering open platforms for greater consolidation and flexibility for the future.
5. SDN ergonomics
In the past, making developmental changes to the applications being delivered out to the business was a complex cross-departmental process. Implementing a next generation network does disrupt this process and the
skill set of the workforce. Developing applications for a Software-Defined Network will become far less reliant on networking or security restrictions, so SDN will bring
with it ‘DevOps’, where development can be brought much closer to the point of consumption with rapid time-to-value for
new apps.

It’s important to task the owners of new projects with making the most of this advantage, staffing teams with the relevant skill sets. As the data centre consolidates, so will job descriptions and functional roles – so consider how data centre operatives will need cross-functional skills covering security, networking storage and related disciplines. The people responsible
The consequences of taking no action at all are significant – but equally, pay heed to the aforementioned points. The dynamic nature of cloud services requires a new level of flexibility, scalability, and programmability, which go beyond the capabilities of today’s data centre networks. It is important to consider the future of data centre and network design.

IT as a whole - the team and infrastructure - will undoubtedly face the need to evolve and become more agile, savvy and cost effective - but quite simply SDN is not the only way to achieve this. Businesses should not be afraid to make a smart, informed decision on the future network and data centre design that is right for them.