Книга: Iptables Tutorial 1.2.2

SCTP COOKIE ECHO chunk

SCTP COOKIE ECHO chunk

The COOKIE ECHO chunk is used during the initialization of the SCTP connection by the initiating party to reply to the cookie sent by the responding party in the State cookie field in the INIT ACK packet. It may be sent together with DATA chunks in the same packet, but must precede the DATA chunks in such case.

Type - bit 0-7. The chunk type is always set to 10 for this chunk.

Chunk flags - bit 8-15. This field is not used today. The RFC specifies that the flags should always be set to 0, but this might cause trouble as can be seen in the SCTP Common and generic headers section above, specifically the Chunk flags explanation.

Length - bit 16-31. Specifies the length of the chunk, including type, chunk flags, length and cookie fields in bytes.

Cookie - bit 32-n. This field contains the cookie as sent in the previous INIT ACK chunk. It must be the exact same as the cookie sent by the responding party for the other end to actually open the connection. The RFC 2960 - Stream Control Transmission Protocol specifies that the cookie should be as small as possible to insure interoperability, which is very vague and doesn't say much.

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