4.9. PIM Packet Formats

PIM messages are encapsulated in IP packets with protocol number 103.

Common PIM Header:

• Version (4 bits): PIM version, currently 2
• Type (4 bits): Message type
• Reserved (8 bits)
• Checksum (16 bits): Covers entire PIM message

Message Types:

• Type 0: Hello
• Type 1: Register
• Type 2: Register-Stop
• Type 3: Join/Prune
• Type 4: Bootstrap
• Type 5: Assert
• Type 6: Graft (PIM-DM)
• Type 7: Graft-Ack (PIM-DM)
• Type 8: Candidate-RP-Advertisement

Encoded Address Format: PIM uses a common encoded address format with:

• Address Family (8 bits)
• Encoding Type (8 bits)
• Address (variable length)

Group and Source Encodings: Include additional fields for wildcards, sparse/dense flags, and RPT bits.

note

For complete packet format specifications, field definitions, and encoding details, see Section 4.9 of RFC 7761.