Telco data center operators have recently begun to consider how to bring the benefits of virtualization to the networking domain. OpenStack has been rapidly gaining traction, but concerns remain that it lacks some of the functionality required to support highly available and highly scalable networks. Numerous vendors have taken up the challenge of filling that gap.
In my recently published report, "Overlays for Data Center Networking: Drivers & Challenges," I explore some of the expected benefits and perceived challenges surrounding overlay networking. It highlights and analyzes the potential impact overlay networking will have on the telco data center networking domain, including the various drivers that support its deployment. It also provides analysis of some of the main challenges that overlay networking can introduce into the environment. It also analyzes the strategies of ten key overlay networking technology suppliers.
Overlays have been proposed as a way to provide the connectivity needed to support the networking needs within the data center. They abstract the details of the physical network, making it much faster to connect virtual machines (VMs) and other devices. Rather than provision paths on physical devices, overlays encapsulate traffic using protocols such as VXLAN and NVGRE to tunnel across the physical network. These newer protocols allow operators to move beyond the limitations of VLANs, which only support 4,096 virtual networks, so they can better support multi-tenant cloud services.
Another driver, which is not as clearly understood, is the emergence of network functions virtualization (NFV). In NFV, functions that had previously resided on purpose-built, proprietary platforms will be supported on general-purpose servers in the form of virtualized network functions (VNFs). How these workloads will behave in terms of elasticity and mobility is still being determined, but overlays are seen as an effective approach to providing the flexibility they will need to manage VNFs. Overlay networks also make it easier to move workloads between and across data centers. By mapping VXLAN to MPLS paths, virtual private networks can be extended beyond the data center across the WAN.
Despite these potential benefits, overlays are often seen as introducing more complexity into the data center environment. Opinions vary as to how significant this issue is: Some argue that in the end, operational expense will decline, because less time will be spent managing the physical network; others contend that managing service performance will become more complicated from having two domains to consider. Even when overlays are present, the physical network will remain critical for ensuring service quality. Discussions with operators suggest that the benefits will ultimately outweigh these concerns, although it will take time for operations to get comfortable with the new approach.
— Roz Roseboro, Senior Analyst, Heavy Reading