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Pragmatic General Multicast (PGM)

Pragmatic General Multicast (PGM) provides reliable, duplicate-free delivery of data packets while reducing network congestion. PGM guarantees that receivers either receive all data packets from transmissions and retransmissions, or can detect unrecoverable data packet loss. PGM is particularly well suited to `push' applications with relatively small information transfers such as stock and news updates. For more information about PGM concepts and terminology, refer to Configuring IP Multicast Routing Protocols.

The 8000 Series switches implement the network element portion of PGM. They support the following PGM options:

• NAK list
• FEC (forwarding error correction)

The 8000 Series switch cannot act as a DLR, which requires a large amount of buffering.

• Configuration prerequisites
• Enabling PGM globally
• Enabling PGM on an interface
• Configuring VLANs with PGM
• Viewing and editing PGM interface parameters
• Graphing SPM and RDATA statistics for an interface
• Graphing NAK, NNAK, and NCF statistics for an interface
• Viewing PGM session parameters
• Graphing SPM statistics for a session
• Graphing NAK statistics for a session
• Viewing the Retransmit parameters