VEPA

A virtual switch is a software component of a virtual server, providing network connectivity to virtual machines (VMs). The challenge with virtual switches is integrating them into the rest of the network in order to maintain visibility and control.

The diagram shows how the emerging VEPA (Virtual Ethernet Port Aggregator) standard addresses this challenge by ensuring that packets from the virtual machines connected to the virtual switch (shown in green) also pass through an adjacent hardware switch (Bridge). In a blade server, the adjacent hardware switch would be the blade switch. If stand-alone servers are used, then the adjacent hardware switch would be the top of rack switch.

Passing traffic through the hardware switch offloads tasks such as rate limiting and access control lists (ACLs), simplifying the virtual switch and freeing CPU cycles that can be used by the virtual machines.

The sFlow standard is widely supported by switch vendors. Selecting blade switches and top of rack switches with sFlow and VEPA support will offer visibility and control of the network edge.

Virtual servers

Convergence blurs the traditional line between the servers and the network. In order to maintain visibility and control, it is important to identify and monitor all the switches in the converged network. Previously, the importance of maintaining visibility while migrating to blade servers was discussed. Maintaining visibility while virtualizing servers creates similar challenges.

The diagram shows the migration of multiple stand-alone servers connected to a stand-alone switch to a single server running multiple virtual machines. In this transition, where did the switch go? Popular virtual server systems such as VMWare® and Xen® make use of software "virtual switches" to connect virtual machines together and to the network. Using sFlow to monitor the virtual switches ensures that the benefits of virtualization can be realized without losing the visibility into network traffic that is essential for network troubleshooting, traffic accounting and security.

Currently, software probes are required to monitor virtual switches. However, the approach of using software probes has similar limitations to using probes to monitor physical switches: probes have limited performance and the installation and configuration of probes adds complexity to the task of managing the network. To provide a truly scalable solution, visibility must be an integral part of every switch, physical or virtual. The need for visibility is evident to virtualization vendors and virtual switches will soon be available with built-in sFlow support.

Multi-vendor support for sFlow ensures that all the layers in the network, from virtual switches, blade switches, top of rack switches and core switches can be monitored using a single technology. Convergence to high speed switched Ethernet unifies LAN and SAN connectivity and convergence to sFlow for traffic monitoring provides the network-wide visibility needed manage and control the unified network.

Blade servers

The need for network visibility in the data center and the challenge posed by converged networking and networked storage can be managed if all the switches in the data center include the sFlow monitoring standard that most vendors support.

The diagram shows the migration from stand-alone servers connected to a stand-alone switch to a blade server (collapsing the discrete servers into blades within a common chassis). In this transition, where did the switch go? Typically a blade server also encloses a blade switch that provides network connectivity to each of the blades, connecting them to each other and to the rest of the data center. The management of the blade switch may be integrated into the blade server manager and the blade switch may not be described as a switch, but it serves the function of a switch (providing connectivity by directing Ethernet packets).

Convergence blurs the traditional line between the servers and the network and it is important to identify and monitor all the switches in order to maintain visibility and control of the network. In the case of a blade server, select a blade switch with sFlow in order to manage the growing demand for bandwidth that comes with data center consolidation. Ask your blade server vendor about sFlow and select a networking solution that provides the performance, visibility and control needed to successfully operate a converged data center.