How is Multistreaming in SCTP different from opening Multiple Connections in TCP?

Question

How does Multiple streams in SCTP reside in a single association while in TCP we have to have multiple ports involved.Is SCTP, does multistreaming also involves ports in any way. RFC 6525 says that only 65k+ streams are possible which seems equal to number of ports possible.

Answer 1

The use of multiple streams does not require the use of multiple ports, an SCTP association has a single port (or one local port and one remote port) but may use many streams.

The intent of using multiple streams is that messages which don't require in sequence delivery may be sent on different streams and thus avoid unnecessary head of line blocking. If you are using SCTP for telecoms signaling then messages for independent telephone calls can be sent on different streams. All messages for a particular call will be delivered in sequence but retransmission of a message for one call need not delay delivery of messages for another call.

The use of streams allows this to be achieved without the creation of new associations which would typically require considerable system resources for tx and rx buffers in addition to association establishment costs.

The choice of which stream to send a message on is made by the SCTP User and communicated to SCTP across the SCTP API.