Multicast in an LWAPP Deployment
Understanding multicast within an LWAPP deployment is necessary to deploy the Vocera broadcast function. This document later covers the essential steps to enable multicast within the controller−based solution. There are currently two delivery methods that the LWAPP controller uses to deliver multicast to the clients:
∙Unicast−Multicast
∙Multicast−Multicast
Unicast−Multicast Delivery Method
The unicast−multicast delivery method creates a copy of every multicast packet and forwards it to every access−point. When a client sends a multicast join to the wireless LAN, the access point forwards this join through the LWAPP tunnel to the controller. The controller bridges this multicast join onto it's directly connected local area network connection that is the default VLAN for the associated WLAN of the client. When an IP multicast packet arrives from the network to the controller, the controller replicates this packet with an LWAPP header for each access point that has a client within the wireless domain who has joined this specific group. When the source of the multicast is also a receiver within the wireless domain, this packet is also duplicated and forwarded back to the same client who sent this packet. For Vocera badges, this is not the preferred method of multicast delivery within the LWAPP controller solution. The unicast delivery method works with small deployments. However, due to the considerable overhead on the Wireless LAN Controller (WLC), this is never the recommended multicast delivery method.