Assisted Replication of Broadcast, Unknown Unicast, and Multicast Traffic

Starting with Contrail Networking Release 1907, you can configure assisted replication on datacenter devices and assign the AR-Replicator and AR-Client roles to them.

Assisted replication or assisted ingress replication is a method to transport ingress broadcast, unknown unicast, and multicast (BUM) traffic in a more efficient way. In assisted replication, you configure a datacenter device as a dedicated replicator, which receives BUM traffic from the network virtualization edge (NVE) devices or provider edge (PE) devices.

An AR-Replicator is a network virtualization overlay (NVO) device or a provider edge device that replicates BUM traffic received through an overlay tunnel to other overlay tunnels and local attachment circuits. An AR-Client is a device that supports assisted replication and sends BUM traffic only to AR-Replicator.

You can designate powerful spines in the datacenter as replicators, which can receive the BUM traffic from ToRs and replicate them to the PEs in the network. To enable assisted replication, you can configure the AR-Client role to MX Series, QFX10000 and QFX5000 devices as spine or leaf, and the AR-Replicator role to QFX10000 devices as spine or leaf.

Assisted replication feature optimizes replication of ingress BUM traffic received from the CE interfaces by directing the BUM traffic towards a single EVPN core Replicator PE (a QFX10000 device) rather than sending it to all the PE devices for replication. Configuring a dedicated replicator for BUM traffic reduces the load on the PEs and improves the performance and efficiency of the network in transporting BUM traffic. This in turn leads to better utilization of the bandwidth.

Figure 1 shows how Leaf 1 node sends traffic received from a multicast source to the assisted replicator through a VXLAN tunnel and how the assisted replicator replicates traffic to the leaf nodes. Here, the task of replicating BUM traffic to other PEs is shifted from the leaf to the spine, which functions as a dedicated replicator. Leaf 1, which receives the multicast traffic from the multicast source, replicates it to the spine as well as to the Leaf 2 through a VXLAN tunnel. The assisted replicator (spine) does not send the multicast traffic back to the leaf which the multicast source is connected to.

Figure 1: Traffic Path in Assisted Replication

Assisted replication is similar to conventional network segmentation. While the segments in conventional network segmentation could be in different regions, the segments in assisted replication exist in the same region.

You can configure assisted replication and assign roles to devices in a datacenter from the Infrastructure > Fabrics > Create Fabric page in Contrail Command. See Assign a Role to a Device for step-by-step procedure to assign roles to a device.