Software-Defined Networks (SDN) and the Cloud

This is a re-post of my article, originally published on The Ravello Blog.


The advent of the cloud has brought with it major changes in the size and nature of networks. These changes pose new challenges for network management. Software-defined networks (SDN) have the potential for helping network managers cope with their ever increasing workloads.

In the public cloud, the network could be very different from what it is in the datacenter. By enabling the automation of network configuration, Software-Defined Networks make it possible to manage network interfaces in the same way as software.

SDN presents the network administrator with the option of handing some or all aspects of network provisioning and management to a third party. The configuration of the network, which includes things such as host names, IP address and firewall rules, is an essential part of an application’s configuration. The configuration can be performed on-demand through the same interface or using an API.

This approach is particularly relevant for large-scale enterprise deployments, where large workloads necessitate automatic on-the-fly configuration, and sometimes even multiple replicas of identical networks, maintaining complete segregation.

The SDN Market

The main players in today’s SDN market are Cisco and VMware. With the acquisition of NSX, VMware is currently promoting its SDN offering as the next step in the evolution of virtualization. NSX lays down an “overlay” network on top of your existing network with the aim of saving time on configuration, improving performances, and lower costs. Cisco, on the other hand, offers a solution that combines SDN and infrastructure. It enables you to define and enforce policies through application-centric infrastructure.

Unfortunately, SDN implementation is not easy – it is not compatible with default networks, and requires a lot of work on infrastructure.

Prospects for SDN Adoption

Despite the optimism of SDN proponents, it is likely to take time before the adoption of SDNs truly catches on. When the concept of server virtualization was first introduced, it was difficult to convince the enterprise that it was reliable to virtualize their workloads – to recognize their potential and make the necessary adjustments to enable their adoption. Similarly, the spread of SDN adoption will probably be gradual. SDN faces the challenge of overcoming decision-makers’ fears of losing control. It takes time to establish trust in any new technology and changes in organization culture rarely occur overnight. Ongoing developments in network virtualization and SDNs definitely merit monitoring and consideration.