Device service clustering, or DSC, is an underlying architecture within BIG-IP Traffic Management Operation System (TMOS). DSC provides synchronization and failover of BIG-IP configuration data at user-defined levels of granularity, among multiple BIG-IP devices on a network. More specifically, you can configure a BIG-IP device on a network to:

• Synchronize some or all of its configuration data among several BIG-IP devices
• Fail over to one of many available devices
• Mirror connections to a peer device to prevent interruption in service during failover

If you have two BIG-IP devices only, you can create either an active-standby or an active-active configuration. With more than two devices, you can create a configuration in which multiple devices are active and can fail over to one of many, if necessary.

By setting up DSC, you ensure that BIG-IP configuration objects are synchronized and can fail over at useful levels of granularity to the most-available BIG-IP devices on the network. You also ensure that failover from one device to another, when enabled, occurs seamlessly, with minimal to no interruption in application delivery.

The BIG-IP system supports either homogeneous or heterogeneous hardware platforms within a device group.

Device service clustering (DSC) is based on a few key components.

Devices

A device is a physical or virtual BIG-IP system, as well as a member of a local trust domain and a device group. Each device member has a set of unique identification properties that the BIG-IP system generates.

Device groups

A device group is a collection of BIG-IP devices that trust each other and can synchronize, and sometimes fail over, their BIG-IP configuration data. You can create two types of devices groups: A Sync-Failover device group contains devices that synchronize configuration data and support traffic groups for failover purposes when a device becomes unavailable. A Sync-Only device group contains devices that synchronize configuration data, such as policy data, but do not synchronize failover objects.

Traffic groups

A traffic group is a collection of related configuration objects (such as a virtual IP address and a self IP address) that run on a BIG-IP device and process a particular type of application traffic. When a BIG-IP device becomes unavailable, a traffic group can float to another device in a device group to ensure that application traffic continues to be processed with little to no interruption in service.

Device trust and trust domains

Underlying the success of device groups and traffic groups is a feature known as device trust. Device trust establishes trust relationships between BIG-IP devices on the network, through mutual certificate-based authentication. A trust domain is a collection of BIG-IP devices that trust one another and can therefore synchronize and fail over their BIG-IP configuration data, as well as exchange status and failover messages on a regular basis. A local trust domain is a trust domain that includes the local device, that is, the device you are currently logged in to.

Folders

Folders are containers for the configuration objects on a BIG-IP device. For every administrative partition on the BIG-IP system, there is a high-level folder. At the highest level of the folder hierarchy is a folder named root. The BIG-IP system uses folders to affect the level of granularity to which it synchronizes configuration data to other devices in the device group.