First Packet Forwarding For Lossless Multicast - Dell Force10 C150 Configuration Manual

FTOS supports PIM-SM graceful restart based on the GenID. Per RFC 4601, hello messages should
contain a Generation_Identifier option, which contains a randomly generated value (GenID) that is
regenerated each time PIM forwarding is started or restarted on the interface, including when the router
restarts. When a router receives from a neighbor a hello message with a new GenID, any old hello
information about that neighbor should be discarded and superseded by the information from the new hello
message.
FTOS supports graceful restart based on the GenID. A Dell Force10 PIM router announces its graceful
restart capability to its neighbors up front as an option in its hello messages.
If a graceful-restart capable router recognizes that a graceful-restart capable neighbor has restarted, it
preserves the state from the neighbor and continues forwarding multicast traffic while the neighbor
restarts.
• The router holds on to the entries learned from the neighbor for the graceful restart interval. If it does
not receive a hello from the neighbor within this time, it purges all state associated with the neighbor.
• If the neighbor restarts and sends a hello with a new GenID before this interval expires, the router
sends a join message towards the neighbor for the relevant entries.
If a graceful-restart capable router restarts, the router preserves all multicast entries in hardware until it
receives and consolidates joins from its graceful-restart capable neighbors. The router is not taken off the
forwarding path during restart.
Enable PIM-SM graceful restart (non-stop forwarding capability) using the command
graceful-restart nsf
restart-time
•
stale-entry-time
•
restarting neighbor. The default value is 60 seconds.
In helper-only mode, the system preserves the PIM states of a neighboring router while the neighbor
gracefully restarts, but the Dell Force10 system allows itself to be taken off the forwarding path if it
restarts. Enable this mode using the command
precedence over any graceful restart configuration.

First Packet Forwarding for Lossless Multicast

When the Dell Force10 system is the RP, packets arriving before an (S,G) entry is created are soft
forwarded using the (*,G) entry. This provides for zero multicast packet loss on FTOS with two
exceptions:
1. These packets can be soft (slow path) forwarded to receivers at a maximum rate of 70 packets/second.
Incoming packets beyond this rate are dropped.
2. When the system is both the source-DR and the RP, in some cases, packet loss, packet reordering, or
duplicate packets might occur.
from CONFIGURATION mode. There are two options with this command:
is the time required by the Dell Force10 system to restart. The default value is 180 seconds.
is the maximum amount of time that the Dell Force10 system preserves entries from a
ip pim graceful-restart helper-only
ip pim
. This mode takes
PIM Sparse-Mode | 765