<Li> Jump up ^ Counted as follows: 12 bytes SCTP header + 16 bytes DATA chunk header or 20 bytes I - DATA chunk header + 16 + bytes SACK chunk . Additional non-data chunks (e.g. AUTH) and / or headers for additional data chunks, which might easily increase the overhead with 50 bytes or more, not counted . </Li> <P> ISO / IEC 8073 / ITU - T Recommendation X. 224, "Information Technology - Open Systems Interconnection - Protocol for providing the connection - mode transport service", defines five classes of connection - mode transport protocols designated class 0 (TP0) to class 4 (TP4). Class 0 contains no error recovery, and was designed for use on network layers that provide error - free connections . Class 4 is closest to TCP, although TCP contains functions, such as the graceful close, which OSI assigns to the session layer . All OSI connection - mode protocol classes provide expedited data and preservation of record boundaries . Detailed characteristics of the classes are shown in the following table: </P> <Table> <Tr> <Th> Service </Th> <Th> TP0 </Th> <Th> TP1 </Th> <Th> TP2 </Th> <Th> TP3 </Th> <Th> TP4 </Th> </Tr> <Tr> <Td> Connection - oriented network </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> </Tr> <Tr> <Td> Connectionless network </Td> <Td> No </Td> <Td> No </Td> <Td> No </Td> <Td> No </Td> <Td> Yes </Td> </Tr> <Tr> <Td> Concatenation and separation </Td> <Td> No </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> </Tr> <Tr> <Td> Segmentation and reassembly </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> </Tr> <Tr> <Td> Error recovery </Td> <Td> No </Td> <Td> Yes </Td> <Td> No </Td> <Td> Yes </Td> <Td> Yes </Td> </Tr> <Tr> <Td> Reinitiate connection (if an excessive number of PDUs are unacknowledged) </Td> <Td> No </Td> <Td> Yes </Td> <Td> No </Td> <Td> Yes </Td> <Td> No </Td> </Tr> <Tr> <Td> Multiplexing and demultiplexing over a single virtual circuit </Td> <Td> No </Td> <Td> No </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> </Tr> <Tr> <Td> Explicit flow control </Td> <Td> No </Td> <Td> No </Td> <Td> Yes </Td> <Td> Yes </Td> <Td> Yes </Td> </Tr> <Tr> <Td> Retransmission on timeout </Td> <Td> No </Td> <Td> No </Td> <Td> No </Td> <Td> No </Td> <Td> Yes </Td> </Tr> <Tr> <Td> Reliable Transport Service </Td> <Td> No </Td> <Td> Yes </Td> <Td> No </Td> <Td> Yes </Td> <Td> Yes </Td> </Tr> </Table> <Tr> <Th> Service </Th> <Th> TP0 </Th> <Th> TP1 </Th> <Th> TP2 </Th> <Th> TP3 </Th> <Th> TP4 </Th> </Tr>

Protocols used in transport layer of osi model