>> IP > Test Solutions > Multicast > Overview

Multicast Testing

As multicast is implemented differently on IPv4 and IPv6, testing for each will need to be performed. IPv4 uses Internet Group Management Protocol (IGMP) while IPV6 uses Multicast Listener Discovery (MLD). MLD is similar to IGMP except for its use with IPv6.

For both IGMP and MLD, a join and leave latency for group management test should be performed. Also, a scalability test which determines the number of multicast groups the device is able to support should be conducted. As most routers will be forwarding unicast traffic with multicast traffic, a throughput test using a mixture of both unicast and multicast should be executed.

As Protocol Independent Multicast (PIM) is used to route multicast over the Internet, certain aspects of PIM should be tested to determine functionality of the device. The join and prune latency of a PIM-enabled router should be tested along with validating the functionality of the PIM router's reverse path forwarding check. Finally, the last hop router and the rendezvous point scalability and throughput should be tested.

Multicast Addressing
Multicast is supported in both IPv4 and IPv6. With IPv4, multicast addresses are considered Class D address space. A Class D address will have 1110 as its first four bits in the address as documented in RFC 3171. With IPv6, the high order octet will have a hex value of 0xFF, which identifies the address as a multicast address. Any other address identifies a unicast address. In addition, IPv4 uses IGMP for multicast group management while IPv6 uses MLD for group management.