per-prefix-label

Syntax

Hierarchy Level

Description

Allocate a unique label for each prefix. The per-prefix-label statement helps minimize packet loss in most deployments.

Although allocating a label for each prefix is not generally ideal for scaling, it is assumed that a small number of labels are used for BGP labeled-unicast. When labeled BGP is used to set up transport label-switched paths (LSPs), the common case is that each prefix has a unique next hop. Thus, the use of per-prefix labels does not have an adverse scaling impact. On the contrary, the use of per-prefix labels reduces churn in the network when multipath load balancing is enabled for IPv4 labeled-unicast, and a subset of the paths are withdrawn for some reason.

The advantage of per-prefix labeling is that the advertised upstream label is more stable during network changes. That is, if the downstream label changes, the advertised upstream label remains the same under most scenarios. This way, the upstream router is isolated from the downstream network change, and the overall network is more stable. The greater stability of the advertised upstream label helps to reduce traffic loss during many different network change scenarios.

Default

By default, label allocation is per next-hop router.

Required Privilege Level

routing—To view this statement in the configuration.

routing-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Release 12.1x48.