Whether we’re talking with the press or with analysts, the acronym SDN comes up again and again, combined with questions regarding PRTG Network Monitor and Paessler’s position on the topic. Even our clients are continuously confronted with the matter and ask us what SDN actually is, whether they need it and if PRTG supports it. It’s time to shed some light on SDN and do a little explaining.
What Is SDN?
Simply put, SDN is network virtualization. SDN stands for Software Defined Networking and indicates decoupling of the so-called control plane, or control level, from the data plane—the level on which data is moved around and on which hardware (switches, routers, etc.) is located, in addition to raw data. The control plane communicates with the data plane via OpenFlow protocol, for example, which is managed by the trade organization Open Networking Foundation. The application plane is a level above the control plane and is where applications run.
Why SDN?
The following are reasons for—and advantages of—introducing SDN:
- Networks are more complex than ever. Configuring network devices requires a lot of effort—and usually has to be done by the administrator, by hand. SDN claims to be able to reduce this effort dramatically.
- Virtualization, Big Data, Internet of Things, Cloud Computing, BYOD: almost all big IT topics that arose in the past few years increase data traffic significantly and pose new challenges and requirements regarding planning and coordinating data streams in a network. SDN boasts of having the solution to this as well.
- Another aspect that is attributed to SDN is a kind of birds-eye perspective on the network. The idea behind it is a central 'intelligence' that is capable of seeing the big picture and is thus able to control and optimize data streams better and more efficiently.
- Thanks to the separation of the control function and the data level, single devices can be better optimized for their individual tasks. This means few, high performance servers for control and slim, 'dumb' switches on data level. This is supposed to enable significant savings on energy and hardware costs.
Where Is SDN Implemented Today?
According to a Gartner survey from December 2014, SDN was implemented on a significant level in 7% of the surveyed companies. Taking Gartner's focus on large corporations into consideration, as well as the fact that SDN is currently only plausibly affordable and advantageous for large companies, implementation in small and medium sized companies is probably much lower. According to Gartner, 10,000 companies will have implemented SDN by the end of 2016. This number seems high at first glance, but is quickly put into perspective when one realizes that in Germany alone, there are more than 3.5 million companies, 330,000 of which have more than 10 employees.
What Is Delaying the Spread of SDN?
Three main factors stand in the way of SDN expanding more quickly:
- Lacking market consolidation
Currently, many manufacturers with sometimes contradicting concepts are trying to establish their position in the SDN market. Cisco is a big player in network hardware and is pushing its own standard "Open Network Environment" (ONE) with a tight coupling of the control plane and the underlying (Cisco) hardware. By contrast, virtualization specialist VMware argues that SDN is already part of a comprehensive (VMware) virtualization package. Most companies are wisely waiting to see which concept and which manufacturers will prevail and can offer long term perspective before taking the jump and making such a serious change to their IT. - 'Old' hardware
Hardware on the data plane can be 'dumber' (and cheaper) than current network hardware, but it has to support OpenFlow (or the manufacturer's equivalent)—which usually isn't the case for current hardware. Most companies would have to replace their entire network hardware before implementing SDN, which is an enormous cost factor. - Implementation cost and effort
Implementing SDN means completely restructuring the existing IT infrastructure. Personnel have to be trained, hardware must be updated (see #2) and a project of this amplitude will cause massive interference with regular business processes. What large corporations can afford with their own teams and external consultants is hardly feasible for smaller companies.
Is it Possible to Monitor SDN?
As a manufacturer of a monitoring solution that offers unified monitoring for small and midsized companies, Paessler is often asked about supporting SDN-controlled networks. Even software-controlled networks need functioning hardware. The control plane can maybe compensate for failure of single devices so that no direct damage occurs, but the overall network performance is still influenced by failures and disturbances. Proactive and complete monitoring of the data plane is absolutely essential even for SDN controlled networks. On the other hand, applications have to be docked to the control plane via interfaces in order to send and receive data. The interfaces and the applications have to be operating and available at all times and should be included in comprehensive network monitoring.
Current monitoring solutions, however, generally aren't yet able to monitor the control plane. Consistent standards and interfaces need to be established before manufacturers of monitoring tools can take action. Assuming that each SDN provider also provides standards with which the solutions can calculate and make available the corresponding control plane performance data, conventional monitoring software providers can jump in, pick up this data and integrate it in a central, comprehensive overview of the entire IT.
Established manufacturers of virtualization software like VMware, Citrix and Microsoft are good examples of this. Most monitoring solutions are now proficient in handling their standards comprehensively and integrating the virtual environment in overall monitoring. However, several years of hypes and drawbacks passed before virtualization was able to establish itself on the market. As virtualization really started to spread, well-known monitoring solutions were prepared. SDN will be similar: it will take years for administrators of midsized companies to think seriously about implementing SDN and how to maintain control of the control plane. If they have established, comprehensive monitoring solutions implemented in their networks, they can assume that they will be prepared for SDN by then, too.
