SCTP cookie echo data block format

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Network protocol message format

SCTP cookie echo data block format[size=13.3333px]
Format of status cookie (cookie echo) data block

This data block is only used when coupling is started. It is sent to the opposite end by the initiator of coupling to complete the starting process. This data block must be sent before the data block sent on the coupling, but it can be bundled into the same SCTP packet with other data blocks.

Figure 1 SCTP cookie echo data block format

Chunk flags (8bit): all zeros are set at the sender and ignored at the receiver.Length: (16 bit unsigned integer): the number of bytes set to the length of the data block, including the length of 4-byte data block header and cookie.Cookie (variable length): this field must contain the accurate cookie received from the state cookie parameter of the previous init ack data block. When using cookie, it should be as small as possible to ensure interoperability.

Message example
Reference standard
standard