Cloud computing services have experienced rapid growth over the past few years because they can keep costs down by allowing multiple tenants to share system resources. One requirement of making this multiple tenancy possible is to provide each tenant with network isolation. Segmenting the traffic using VLAN is a typical solution to this problem. However, service providers also need to keep up with customer demand by being able to move workloads to those servers that have spare resources.
To do so, network traffic needs to be encapsulated so that the workload is not tied to the underlying hardware. This can be a problem because the networking architecture ties the workloads to the underlying hardware, which restricts the movements of these workloads and limits where these workloads can be placed. In addition, segmenting the physical LAN using VLANs does not scale beyond a certain limit.
Virtual extensible LAN (VXLAN) is a network encapsulation mechanism that enables virtual machines to be deployed on any physical host, regardless of the host’s network configuration. It solves the problems of mobility and scalability in two ways:
- It uses MAC in UDP encapsulation, which allows the virtual machine to communicate using an overlay network that spans across multiple physical networks. It decouples the virtual machine from the underlying network thereby allowing the virtual machine to move across the network without reconfiguring the network.
- VXLAN uses a 24-bit identifier, which means that a single network can support up to 16 million LAN segments. This number is much higher than the 4,094 limit imposed by the IEEE 802.1Q VLAN specification.
Since VXLAN is an additional encapsulation mechanism introduced at the hypervisor layer, there are certain performance implications. This paper demonstrates that the performance of VXLAN on vSphere 5.1 is very close to a configuration without VXLAN, and vSphere 5.1 with VXLAN configured can meet the demands of today’s network-intensive applications.
VMware has used industry-standard benchmarks to conduct our experiments that demonstrate:
- A virtual machine configured with VXLAN achieved similar networking performance to a virtual machine without VXLAN configured, both in terms of throughput and CPU cost.
- vSphere 5.1 scales well as we add more virtual machines on the VXLAN network.
