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How switching technologies transform data centres

Posted: 11 May 2012     Print Version  Bookmark and Share

Keywords:network virtualisation  switching  VM-aware 

Over the past years, network virtualisation technologies have evolved rapidly, illustrating dramatic potential for evolution in longstanding network infrastructures. Combine this evolving technology with the growth of cloud computing, and the result is a surprisingly creative approach to improving data centre performance and agility. Even enterprise networks firmly rooted in operational efficiencies are taking a fresh look at their data centres as a source for growth, competitive advantage and return on IT investment.

The potential for transformation starts with the basic historical structure of a network—with physical servers once tiered for north-south data flow from access, distribution, and core layers to the wide area network and back again. Today that network is moving more and more traffic patterns that are east-west in nature, inherent to modern distributed systems and applications with data that moves across racks and pods. The result is swift adoption of fast, fat, and flat network topologies and network virtualisation—creating deployments that rely on sophisticated switching technologies to deliver maximum scale and performance.

Network transformation with VM-aware switching
Network usage models are indeed shifting rapidly, and network infrastructure designers must pay close attention to switching and virtualisation requirements as part of this market's evolution. Global data traffic is increasing exponentially, anticipated to reach 26 times today's level within the next three years, and millions of minutes of video are expected to cross the network every second. Connected devices are at the heart of this growth, and projections place the number of devices expanding to two times the global population by 2015. The highly scalable, virtualized network deployments that manage these transactions must rely on sophisticated switching technologies, enabling the full potential of applications that are sensitive to network performance.

Virtual machine (VM) aware switching is essential in these environments, which increasingly require native OS-based server level performance, without performance penalties incurred by virtualized servers running multiple VMs. Several standards-based switching technologies such as SR-IOV (Single Root I/O Virtualisation by PCI Special Interest Group) and VEPA/EVB (Virtual Ethernet Port Aggregator/Edge Virtual Bridging by IEEE 802.1) have emerged to address this consideration, and ensure improved performance and scalability of applications that run in VMs.

Effective VM switching means access layer switches in the data centre network (e.g., top–of-rack switches, blade switches, or end-of-row switches) must support a large number of virtual switch ports (VSPs). In turn, VSPs in access layer switches must also support features including link aggregation, load balancing, traffic mirroring, and statistics counters similar to what is available for physical switch ports. Such features are essential to enabling VMs with the same level of reliability, performance, and monitoring as physical servers.

VM-aware switches are engineered specifically to meet current feature and scale requirements of private and public cloud networks, a new essential in virtualized networks. Deployments can now feature virtual switch ports supporting high-level functionality, such as link aggregation, queuing, access control list (ACL), statistics, and mirroring services, that embodies many of the same services readily available in physical ports.

Smarter, more flexible deployments
Optimal switch solutions support live VM migration as part of the more prevalent east-west traffic pattern, allowing layer 2 (L2) networks to scale across pods, sites within the data centre, or even across data centres. Live VM migration improves disaster recovery and is a fundamental consideration for increasing server utilisation, in turn meeting the overall IT goal of implementing a dynamic data centre infrastructure.

Achieving live VM migration across servers, racks, or pods requires that they reside in the same L2 network segments, often referred to as a flat network. L2oL3 overlay technologies further extend the benefits of these fast, fat, and flat architectures; this provides an essential means of combining L2 and L3 topologies and enabling network virtualisation at cloud-scale. Consider the mega-scale or Internet-scale data centre which commonly incorporates inexpensive L3 technologies for physical network infrastructure. This historical approach follows the success and scalability of the Internet, built on IP and incorporating a scalable hierarchical addressing scheme as opposed to flat L2 addressing. When L2oL3 technologies are implemented, L3 networks have a natural mechanism to create a flat L2 network. This readily manages VM migration within and across data centres, and further enables scale and multi-tenancy.

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