Use Case for PIM Join Load Balancing

Large-scale service providers often have to meet the dynamic requirements of rapidly growing, worldwide virtual private network (VPN) markets. Service providers use the VPN infrastructure to deliver sophisticated services, such as video and voice conferencing, over highly secure, resilient networks. These services are usually loss-sensitive or delay-sensitive, and their data packets need to be delivered over a large-scale IP network in real time. The use of IP Multicast bandwidth-conserving technology has enabled service providers to exceed the most stringent service-level agreements (SLAs) and resiliency requirements.

IP multicast enables service providers to optimize network utilization while offering new revenue-generating value-added services, such as voice, video, and collaboration-based applications. IP multicast applications are becoming increasingly popular among enterprises, and as new applications start using multicast to deploy high-bandwidth and mission-critical services, it raises a new set of challenges for deploying IP multicast in the network.

IP multicast applications act as an essential communication protocol to effectively manage bandwidth and to reduce application server load by replicating the traffic on the network when the need arises. IP Protocol Independent Multicast (PIM) is the most important IP multicast routing protocol that is used to communicate between the multicast routers, and is the industry standard for building multicast distribution trees of receiving hosts. The multipath PIM join load-balancing feature in a multicast VPN provides bandwidth efficiency by utilizing unequal paths toward a destination, improves scalability for large service providers, and minimizes service disruption.

The large-scale demands of service providers for IP access require Layer 3 VPN composite next hops along with external and internal BGP (EIBGP) VPN load balancing. The multipath PIM join load-balancing feature meets the large-scale requirements of enterprises by enabling l3vpn-composite-nh to be turned on along with EIBGP load balancing.

When the service provider network does not have the multipath PIM join load-balancing feature enabled on the provider edge (PE) routers, a hash-based algorithm is used to determine the best route to transmit multicast datagrams throughout the network. With hash-based join load balancing, adding new PE routers to the candidate upstream toward the destination results in PIM join messages being redistributed to new upstream paths. If the number of join messages is large, network performance is impacted because join messages are being sent to the new reverse path forwarding (RPF) neighbor and prune messages are being sent to the old RPF neighbor. In next-generation multicast virtual private network (MVPN), this results in multicast data messages being withdrawn from old upstream paths and advertised on new upstream paths, impacting network performance.