How Bandwidth Management and Flow Control Works

Searchnetworking.com defines bandwidth as “the amount of data that can be carried from one point to another in a given time period (usually a second).” Bandwidth management enables you to assign a portion of the available bandwidth of a physical NIC to a consumer, such as an application or customer. You can control bandwidth on a per- application, per-port, per-protocol, and per-address basis. Bandwidth management assures efficient use of the large amount of bandwidth available from the new GLDv3 network interfaces.

Resource control features enable you implement a series of controls on an interface's available bandwidth. For example, you can set a guarantee of an interface's bandwidth to a particular consumer. That guarantee is the minimum amount of assured bandwidth allocated to the application or enterprise The allocated portion of bandwidth is known as a share. By setting up guarantees, you can allocate enough bandwidth for applications that cannot function properly without a certain amount of bandwidth. For example, streaming media and Voice over IP consume a great deal of bandwidth. You can use the resource control features to guarantee that these two applications have enough bandwidth to successfully run.

You can also set a limit on the share. The limit is the maximum allocation of bandwidth the share can consume. Using limits, you can contain non-critical services from taking away bandwidth from critical services.

Finally, you can prioritize among the various shares allotted to consumers. You can give highest priority to critical traffic, such as heartbeat packets for a cluster, and lower priority for less critical applications.

For example, application service providers (ASPs) can offer customers fee-based levels of service that are based on the bandwidth share that the customer purchases. As part of the service level agreement (SLA), each share is then guaranteed an amount of bandwidth, to not exceed the purchased limit. (For more information on service level agreements, see Implementing Service-Level Agreements in System Administration Guide: IP Services. Priority controls might be based on different tiers of the SLA, or different prices paid by the SLA customer.

Bandwidth usage is controlled through management of flows. A flow is a stream of packets that all have certain characteristics, such as the port number or destination address. These flows are managed by transport, service, or virtual machine, including zones. Flows cannot exceed the amount of bandwidth that is guaranteed to the application or to the customer's purchased share.

When a VNIC or flow is assigned a guarantee, the VNIC is assured its designated bandwidth even if other flows or VNICs also use the interface. However, assigned guarantees are workable only if they do not exceed the maximum bandwidth of the physical interface.