In my previous post we've explored how SCTP packets are encoded and what protocol elements they contain. Next we will look at three SCTP procedures - association creation, user data transfer and association tear down. Each procedure requires specific message flow, which will be reviewed in separate posts.
Section 4 from RFC 4960 has a state diagram for a SCTP association. There are two main states - CLOSED and ESTABLISHED. The transfer between them contains more intermediate states (COOKIE-WAIT, COOKIE-ECHOED, etc). Two endpoints can exchange user data only when the association is in ESTABLISHED state. This is accomplished with association initialisation procedure. Once it is completed successfully the peers can exchange data by following user data transfer procedure. Finally the connection is closed with termination of association procedure. Now we will review association creation procedure.