Question

An SCTP association is in the COOKIE-WAIT state. It receives an INIT chunk; what does it need to do?

Answer 1

When in COOKIE-WAIT state, an SCTP association needs to send a COOKIE-ECHO chunk in response to an INIT chunk.

Step-by-step explanation:

When an SCTP association is in the COOKIE-WAIT state and it receives an INIT chunk, it needs to do the following:

1. Send a COOKIE-ECHO chunk in response to the INIT chunk.
2. Generate a Cookie Parameter containing the state of the association, the source and destination IP addresses, and the verification tag of the INIT chunk.
3. Add the generated Cookie Parameter to the COOKIE-ECHO chunk.

The COOKIE-ECHO chunk is then sent back to the peer, which will eventually lead to the association transitioning out of the COOKIE-WAIT state.

When an SCTP (Stream Control Transmission Protocol) association is in the COOKIE-WAIT state and it receives an INIT chunk, the endpoint should resend the INIT-ACK with the State Cookie it had previously transmitted. According to the SCTP protocol specification (RFC 4960), in the COOKIE-WAIT state, the endpoint is waiting for a COOKIE ECHO chunk in response to the INIT-ACK it has sent after receiving the initial INIT chunk from its peer.

If it receives another INIT instead, this typically indicates that the INIT-ACK may have been lost or the peer did not receive it; therefore, the endpoint should retransmit the INIT-ACK including the cookie. This ensures the robustness of the SCTP handshake process and helps to establish the association reliably.