6.5.6 DTLS and SCTP

Although DTLS can run under any reliable or unreliable layer, there are special requirements for SCTP according to [RFC6083]. We summarize the most important below, however for a full treatment we refer to [RFC6083].

• The MTU set via gnutls_dtls_set_mtu must be 2^14.
• Replay detection must be disabled; use the flag GNUTLS_NO_REPLAY_PROTECTION with gnutls_init.
• Retransmission of messages must be disabled; use gnutls_dtls_set_timeouts with a retransmission timeout larger than the total.
• Handshake, Alert and ChangeCipherSpec messages must be sent over stream 0 with unlimited reliability and with the ordered delivery feature.
• During a rehandshake, the caching of messages with unknown epoch is not handled by GnuTLS; this must be implemented in a special pull function.