# Interface-Level Admission Bandwidth Limits for IPv6 Overview

Interface-level multicast admission control is performed when an outgoing interface (OIF) on the interface is added to the mroute for a given (S,G) multicast data stream and the multicast bandwidth map contains a set admission-bandwidth action for that (S,G). When enabled, the admission-bandwidth for a particular (S,G) is read from the multicast bandwidth map and recorded in the mroute when the (S,G) mroute is created.

| Caution: Before you can limit interface-level admission bandwidth, you must first create a bandwidth map. See Example: Configuring an IPv6 Multicast Bandwidth Map for details.

When an OIF is subsequently added to the mroute, the OIF is blocked from forwarding data if the additional bandwidth contributed by the (S,G) exceeds the admission-bandwidth limit for the interface. In JunosE releases earlier than Release 12.0.x, in an OIF mapping scenario where the digital subscriber line access multiplexer (DSLAM) does not perform per-subscriber multicast admission control, the router disregards the multicast admission bandwidth limit configured on the join interface. If the limit configured on the mapped interface exceeds the admission-bandwidth limit for the interface, the router blocks the mapped interface from forwarding data.

Now, in an OIF mapping scenario where the DSLAM performs per-subscriber multicast admission control, the router checks the bandwidth limit configured on the join interface. If the multicast stream is forwarded over the mapped interface, the router admits the multicast stream and forwards the stream to the join interfaces whose bandwidth does not exceed the configured bandwidth limit. The router also performs QoS Adjust for the multicast stream on the unblocked (forwarding) subscriber interfaces. The router does not replicate the stream to the subscriber interfaces whose bandwidth exceeds the configured bandwidth limit and it does not perform QoS Adjust for the multicast stream on the blocked subscriber interfaces.

If the multicast stream is not forwarded over the mapped interface, the router blocks the multicast stream and does not forward the stream. The router also does not perform QoS Adjust for the multicast stream on the blocked subscriber interface.

#### Related Documentation

- Enabling Interface-Level Admission Bandwidth Limitation for IPv6
- OIF Interface Reevaluation for IPv6
- set admission-bandwidth