Software-defined networking

Software-defined networking

Why there is no getting around software-defined networking


The next step after the virtualisation of processing power and storage: software-defined networking brings agility to networks, removes the need for expensive hardware and is easy to configure.


Text: Florian Waelfler/Urs Binder,




Every day, gigantic quantities of data run through today’s networks. Companies and public authorities are also experiencing an explosion in data traffic. This increase in data is placing ever greater demands on network infrastructure – thus increasing the costs and the complexity. Software-defined networking (SDN) offers relief. And virtualisation fever has also reached the network sector. According to IDC, the SDN market worldwide is expected to grow to eight billion US dollars by 2018. But what is SDN and what purpose does it serve?


Fully thought-out virtualisation

The term software-defined networking goes back to a Stanford article about network operating systems published in 2005. Its authors describe how complex networks are and how complicated they are to manage. Unlike modern operating systems, which are simpler to handle due to an abstraction layer, within a network everything is maintained at the lowest configuration level in individual components. So why not virtualise the network too? Three years later, the first companies, including Google, Yahoo and Verizon, founded the “Open Networking Foundation”, which dedicated itself to adapting SDN.


Cloud forces a rethink

IT today makes wide use of flexibilisation and virtualisation. Within the data networks, however, a lot of things have stayed the same. This is because existing networks represent considerable investment in expensive hardware such as Cisco, Juniper etc. In combination with this hardware, network providers and users have gathered a lot of specific know-how – making it difficult to throw all of this overboard and implement network functionality virtually via software.


However, there is no getting around the virtualisation of all network aspects, particularly in large cloud environments. A quick look at the daily work of a network administrator makes clear: within the virtual machines (VMs) of the cloud environment, virtual network interfaces (NICs) that can be configured using software are responsible for the connection to the outside world. However, the cloud provider must take care of all network aspects outside of the VMs: in typical installations, every cloud customer has an assigned virtual Local Area Network (VLAN) into which the virtual NICs need to be integrated. For the administrator, this is a nightmare of maintenance and scaling – every time a new VM needs to be integrated, difficult manual work is required.


Within cloud environments at the latest – whether the cloud of a provider or a Private Cloud within a company’s data centre – manually maintained networks are hitting their limits. This is because a cloud means agility: customers want to set up and start virtual machines, including a network connection, in just a few seconds via self service.


Decoupled and agile

In the case of SDN, the lower function levels of the network are abstracted from the hardware in the form of virtual services. Customers use a dashboard to access all relevant functions, have a complete end-to-end view of all communication services at the same time, can monitor the network’s behaviour in real time and receive information about compliance with the Service Level Agreement.


Services can be booked or cancelled online, bandwidths can be adapted within minutes, and functionalities such as firewalls can be implemented in no time – just as one is used to doing within the cloud for the management of computing and storage resources. Activating a firewall, for example, used to take up to six weeks. With SDN it happens at the touch of a button. Services such as TV, PWLAN, mobiles or telephony can be integrated within minutes, depending on the provider, and can be combined on request.


And the users are not the only ones to benefit from SDN. Administrators can also breathe a sigh of relief: the new paradigm of the software-controlled network offers security and stability. The working day is made so much easier. Administrators can smoothly adapt the network to requirements without complicated hardware configuration changes, even if there are sudden, significant fluctuations. And the cloud providers not only benefit from the increased productivity of network administrators. An SDN-based network can be set up with open network operating systems and cost-effective “open networking” hardware instead of expensive proprietary switches.


Without SDN, nothing will work in future

“Software is eating the world,” announced Netscape founder Marc Andreessen as early as 2011. In the network of the future, software defines all network services. Control is being emancipated from hardware. A standard piece of hardware can become a firewall, a switch or a modem – all thanks to virtualisation.


Until now, there was a close link between the data and control channels for technical reasons; they were both processed directly within the network hardware. Virtualisation is breaking down this link, which slows down the network during scaling and extension. In the future, there will be no getting around software-defined networking. Within record time, SDN will be on the agenda of all IT managers who are planning or already using scalable virtual environments. Only with SDN can the network finally become a service – technology is taking a back seat.







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