First Packet Forwarding For Lossless Multicast; Multicast Policies; Ipv4 Multicast Policies - Dell Force10 Z9000 Configuration Manual

First Packet Forwarding for Lossless Multicast

All initial multicast packets are forwarded to receivers to achieve lossless multicast.
In previous versions, when the Dell Networking system is an RP, all initial packets are dropped until PIM creates an (S,G) entry. When
the system is an RP and a Source DR, these initial packet drops represent a loss of native data, and when the system is an RP only,
the initial packets drops represent a loss of register packets.
Both scenarios might be unacceptable depending on the multicast application. When the Dell Networking system is the RP, and has
receivers for a group G, it forwards all initial multicast packets for the group based on the (*,G) entry rather than discarding them
until the (S,G) entry is created, making Dell Networking systems suitable for applications sensitive to multicast packet loss.
NOTE: When a source begins sending traffic, the Source DR forwards the initial packets to the RP as encapsulated
registered packets. These packets are forwarded via the soft path at a maximum rate of 70 packets/second. Incoming
packets beyond this rate are dropped.

Multicast Policies

Dell Networking OS offers parallel multicast features for IPv4.
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IPv4 Multicast Policies

IPv4 Multicast Policies
The following sections describe IPv4 multicast policies.
• Limiting the Number of Multicast Routes
• Preventing a Host from Joining a Group
• Preventing a PIM Router from Forming an Adjacency
• Preventing a Source from Registering with the RP
• Preventing a PIM Router from Processing a Join
Limiting the Number of Multicast Routes
When the total number of multicast routes on a system limit is reached, Dell Networking OS does not process any IGMP or multicast
listener discovery protocol (MLD) joins to PIM — though it still processes leave messages — until the number of entries decreases
below 95% of the limit.
When the limit falls below 95% after hitting the maximum, the system begins relearning route entries through IGMP, MLD, and
MSDP.
• If the limit is increased after it is reached, join subsequent join requests are accepted. In this case, increase the limit by at least
10% for IGMP and MLD to resume.
• If the limit is decreased after it is reached, Dell Networking OS does not clear the existing sessions. Entries are cleared after a
timeout (you may also clear entries using clear ip mroute).
NOTE: Dell Networking OS waits at least 30 seconds between stopping and starting IGMP join processing. You may
experience this delay when manipulating the limit after it is reached.
When the multicast route limit is reached, Dell Networking OS displays the following:
3w1d13h: %RPM0-P:RP2 %PIM-3-PIM_TIB_LIMIT: PIM TIB limit reached. No new routes will
be learnt until TIB level falls below low watermark.
3w1d13h: %RPM0-P:RP2 %PIM-3-PIM_TIB_LIMIT: PIM TIB below low watermark. Route learning
will begin.
To limit the number of multicast routes, use the following command.
• Limit the total number of multicast routes on the system.
CONFIGURATION mode
ip multicast-limit
467
Multicast Features