D-Link DES-3828 Product Manual - Page 386

xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch CLI Manual Assert Messages At times on the PIM-SM enabled network, parallel paths are created from source to receiver, meaning some receivers will receive the same multicast packets twice. To improve this situation, Assert messages are sent from the receiving device to both multicast sources to determine which single router will send the receiver the necessary multicast data. The source with the shortest metric (hop count) will be elected as the primary multicast source. This metric value is included within the Assert message. PIM-DM The Protocol Independent Multicast - Dense Mode (PIM-DM) protocol should be used in networks with a low delay (low latency) and high bandwidth as PIM-DM is optimized to guarantee delivery of multicast packets, not to reduce overhead. The PIM-DM multicast routing protocol is assumes that all downstream routers want to receive multicast messages and relies upon explicit prune messages from downstream routers to remove branches from the multicast delivery tree that do not contain multicast group members. PIM-DM has no explicit 'join' messages. It relies upon periodic flooding of multicast messages to all interfaces and then either waiting for a timer to expire (the Join/Prune Interval) or for the downstream routers to transmit explicit 'prune' messages indicating that there are no multicast members on their respective branches. PIM-DM then removes these branches ('prunes' them) from the multicast delivery tree. Because a member of a pruned branch of a multicast delivery tree may want to join a multicast delivery group (at some point in the future), the protocol periodically removes the 'prune' information from its database and floods multicast messages to all interfaces on that branch. The interval for removing 'prune' information is the Join/Prune Interval. The PIM commands in the Command Line Interface(CLI) are listed below, along with their appropriate parameters, in the following table. Command enable pim Parameters disable pim config pim config pim register_probe_time config pim register_suppression_time create pim crp group delete pim crp group config pim crp create pim static_rp group delete pim static_rp group show pim static_rp config pim rp_spt_threshold config pim last_hop_spt_threshold show pim rpset show pim crp config pim cbsr show pim cbsr show pim [[ipif | all] {hello | jp_interval | state [enable | disable] | mode [dm | sm] | dr_priority } rp {holdtime | priority | wildcard_prefix_cnt [0 | 1]} rp [ | infinity] [ | infinity] [ipif {priority [-1 | ]} | hash_masklen | bootstrap_period ] {ipif } {ipif } 382