HP ProCurve 6200yl Multicast And Routing Manual page 66

PIM-DM (Dense Mode)
Configuring PIM-DM
3-16
For example, if multiple routers are connected to the same
VLAN and the routing switch requests multicast traffic, all
routers on the VLAN receive that traffic. (Those which have
pruned the traffic will drop it when they receive it.) If the
upstream router loses contact with the routing switch
receiving the multicast traffic (that is, fails to receive a Hello
packet when expected), then the shorter Hello Interval causes
it to stop transmitting multicast traffic onto the VLAN
sooner, resulting in less unnecessary bandwidth usage.
Not used with the no form of the ip pim-dense command.
Syntax: ip pim-dense [ hello-delay < 0 - 5 >]
vlan < vid > ip pim-dense [ hello-delay < 0 - 5 >]
Changes the maximum time in seconds before the routing
switch actually transmits the initial PIM Hello message on
the current VLAN. In cases where a new VLAN activates with
connections to multiple routers, if all of the connected
routers sent Hello packets at the same time, then the
receiving router could become momentarily overloaded. This
value randomizes the transmission delay to a time between
0 and the hello delay setting. Using "0" means no delay. After
the routing switch sends the initial Hello Packet to a newly
detected VLAN interface, it sends subsequent Hello packets
according to the current Hello Interval setting. Not used with
the no form of the ip pim-dense command. Default: 5 seconds.
Syntax: ip pim-dense [ graft-retry-interval < 1-10 >]
vlan < vid > ip pim-dense [ graft-retry-interval < 1-10 >]
Graft packets result when a downstream router transmits a
request to join a flow. The upstream router responds with a
graft acknowledgment packet. If the Graft Ack is not received
within the time period of the graft-retry-interval, it resends
the graft packet. This command changes the interval (in
seconds) the routing switch waits for the Graft Ack
(acknowledgement) from another router before resending
the Graft request. Not used with the no form of the ip pim­
dense command. (Default: 3 seconds.)