Virtualization of Data Centers: New Options in the Control and Data Planes (Part III)

Raghu Kondapalli is director of technology focused on Strategic Planning and Solution Architecture for the Networking Components Division of LSI Corporation. He brings a rich experience and deep knowledge of the cloud-based, service provider and enterprise networking business, specifically in packet processing, switching and SoC architectures.

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This Industry Perspectives article is the third and final in a series of three that analyzes the network-related issues being caused by the Data Deluge in virtualized data centers, and how these are having an effect on both cloud service providers and the enterprise. The focus of the first article was on the overall effect server virtualization is having on storage virtualization and traffic flows in the data center network, while the second article dove a bit deeper into the network management complexities and control plane requirements needed to address those challenges. This article examines two ways of scaling the control plane to accommodate these additional requirements in virtualized data centers.

The control plane can scale in two directions: out or up. In the scale-out approach, the control plane functions are separated and distributed across physical or virtual servers.  In the scale-up approach, the server’s processing power is augmented by adding extra compute resources, such as x86 processors. In both the scale-out and scale-up architectures, performance can be further enhanced by providing function-specific hardware acceleration.

Control Plane Scale-out Architecture

In the scale-out architecture, the basic platform is implemented with generic processors augmented by separate communications processors with specialized hardware accelerators that can offload control plane functions. The control plane tasks are divided into sub-tasks, such as discovery, dissemination, and recovery, and are then distributed across the data center. Because the various tasks can execute on any server in the network or in the cloud, the scale-out architecture lends itself well to Software Defined Networking (SDN). Owing to its distributed arrangement, the architecture requires robust communications between the control plane and the data planes using APIs for the network protocol, such as OpenFlow.

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Depending on the network size and configuration, hardware acceleration of these networking functions may be necessary to achieve satisfactory performance.  Protocol-aware communications processors are designed to handle specific control plane tasks and/or network management functions, including packet analysis and routing, security, ARP offload, OAM offload, IGMP messages, networking statistics, application-aware firewalling, QoS, etc.

Control Plane Scale-up Architecture

In the scale-up architecture, the existing network control platforms are supplemented by additional and/or more powerful compute engines to help execute the network control stack. These supplemental resources free up server CPU cycles for other tasks, and result in an overall improvement in the network performance.  Because general-purpose processors are not optimized for packet processing functions, however, they are not an ideal solution for the scale-up architecture.  As with the scale-out architecture, performance can be improved dramatically using function-specific, protocol-aware communications processors.

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