What is the difference between the transmission sequence and

What is the difference between the transmission sequence and the stream sequence number in SCTP? What is the purpose of having both Transmission sequence number and stream sequence numbers?

Solution

The diffrence between the transmission sequence number and the stream sequence number is its size. TSN is 32 bit and SSN is 16 bit. Transmission sequence number does not depend on stream sequence number but the stream sequence number depends on the transmission sequence number.

Both transmission sequence number and stream sequence number are required because:

Transmission sequence number is required to reconstruct a data message from its data chunks and has values from 0 to 2^32 - 1, with automatic wrap around.

Steam sequence number for the data from the stream is same for all data belonging to the same fragment where SCTP fragments data packets for transmission to match the path MTU. So both are required.