Bandwidth Management

This chapter explains what Bandwidth Management is, and how to configure your Virtual Traffic Manager to control how bandwidth is used on your network.

Bandwidth Management is not available on all Virtual Traffic Manager variants. If required, it can be obtained via a software or license key upgrade.

What Is Bandwidth Management?

Bandwidth management allows the Virtual Traffic Manager to limit the number of bytes per second used by inbound or outbound traffic, for a virtual server or by the type of request.

Normally, network bandwidth is provided at the highest rate possible for all connections. This might result in uneven use of your network, possibly with too much bandwidth being used by secondary services at the expense of your most critical services. The Virtual Traffic Manager enables you to use bandwidth management to control this imbalance explicitly.

For example, consider you have a 20Mbits/s network connection that is being over-utilized for FTP downloads, and which is consequently affecting the responsiveness of the main HTTP service. You might therefore want to limit the bandwidth to the FTP virtual server to 2Mbits/s.

Bandwidth limits are automatically shared and enforced across all the Virtual Traffic Manager machines in a cluster. Individual Virtual Traffic Managers take different proportions of the total limit, depending on the load on each Virtual Traffic Manager. Unused bandwidth is equitably allocated across the cluster depending on the need of each Virtual Traffic Manager.

Bandwidth management is applicable only to traffic sent by the Virtual Traffic Manager. In other words, the Virtual Traffic Manager can control the bandwidth used when writing requests to server nodes, and when writing responses back to clients. The Virtual Traffic Manager CANNOT control how quickly clients write the requests to the Virtual Traffic Manager, or how quickly servers attempt to write responses to the Virtual Traffic Manager.

Bandwidth management applies to all data, whether sent to external addresses or just transferred internally within the Virtual Traffic Manager. Internal traffic includes, for example, where data is passed from a pool back to a virtual server using a loopback interface.