D-Link DGS-3308FG Product Manual - Page 108
Hello Interval, Join/Prune Interval, Join/Prune Interval, Join/Prune Interval., State:<, Layer 2
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8-port Gigabit Ethernet Switch User's Guide Note: 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. • Hello Interval:[30 ] - This field allows an entry of between 1 and 18,724 seconds and determines the interval between sending Hello packets to other routers on the network. The Hello messages are used by the router to determine if it is the root router on the delivery tree or not. If the router does not receive a Hello message within the Hello Interval, it will begin transmitting Hello messages to advertise its availability to become the root router. The default is 30 seconds. • Join/Prune Interval:[60 ] - This field allows an entry of between 1 and 18,724 seconds and determines the interval between transmitting (flooding to all interfaces) multicast messages to downstream routers, and automatically 'pruning' a branch from the multicast delivery tree. This interval also determines the time interval the router uses to automatically remove prune information from a branch of a multicast delivery tree and begin to flood multicast messages to all branches of that delivery tree. These two actions are equivalent. The default is 60 seconds. Note: 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. Note: 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. Note: 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. • State: - Toggle between Enabled and Disabled using the space bar to enable or disable PIM-DM for the IP interface. The default is Disabled. Static Router Port Note: There is no difference between the setup of a 'router port' in Layer 2 Only mode and in IP Routing mode. Note: A router port allows UDP multicast and IGMP packets to be forwarded to a designated port regardless of VLAN configuration. Note: A router port functions within layer 2 of the OSI model. This section is repeated in the Layer 2 Multicasting section of this manual above because of the possible confusion caused by the term 'router port' when compared to a traditional router. A static router port is a port that has a router attached to it. Generally, this router would have a connection to a WAN or to the Internet. Establishing a router port will allow multicast packets coming from the router to be propagated through the network, as well as allowing multicast messages coming from the network to be propagated to the router. The purpose of a router port is to enable UDP multicast packets, and IGMP multicast group membership messages, to reach multiple ports of a multicast-enabled router. Routers do not implement IGMP snooping or transmit/forward IGMP report packets. Thus, forwarding all IP UDP multicast packets to a static router port on the DGS-3308 guarantees that all ports of a multicast-enabled router - attached to the DGS-3308 - can reach all multicast group members through the attached router's other ports. To setup a static router port: 98