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Chapter 13

Chapter 13. Stream Control Transmission Protocol. Objectives. Upon completion you will be able to:. Be able to name and understand the services offered by SCTP Understand SCTP’s flow and error control and congestion control Be familiar with the fields in a SCTP segment

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Chapter 13

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  1. Chapter 13 Stream ControlTransmission Protocol Objectives Upon completion you will be able to: • Be able to name and understand the services offered by SCTP • Understand SCTP’s flow and error control and congestion control • Be familiar with the fields in a SCTP segment • Understand the phases in an SCTP association • Understand the SCTP state transition diagram TCP/IP Protocol Suite

  2. Figure 13.1TCP/IP protocol suite TCP/IP Protocol Suite

  3. Note: SCTP is a message-oriented, reliable protocol that combines the good features of UDP and TCP. TCP/IP Protocol Suite

  4. 13.1 SCTP SERVICES We explain the services offered by SCTP to the application layer processes. The topics discussed in this section include: Process-to-Process Communication Multiple Streams Multihoming Full-Duplex Communication Connection-Oriented Service Reliable Service TCP/IP Protocol Suite

  5. Table 13.1 Some SCTP applications TCP/IP Protocol Suite

  6. Figure 13.2Multiple-stream concept TCP/IP Protocol Suite

  7. Note: An association in SCTP can involve multiple streams. TCP/IP Protocol Suite

  8. Figure 13.3Multihoming concept TCP/IP Protocol Suite

  9. Note: SCTP association allows multiple IP addresses for each end. TCP/IP Protocol Suite

  10. 13.2 SCTP FEATURES We discuss the general features of SCTP and then compare them with those of TCP. The topics discussed in this section include: Transmission Sequence Number (TSN) Stream Identifier (SI) Stream Sequence Number (SSN) Packets Acknowledgment Number Flow Control Error Control Congestion Control TCP/IP Protocol Suite

  11. Note: In SCTP, a data chunk is numbered using a TSN. TCP/IP Protocol Suite

  12. Note: To distinguish between different streams, SCTP uses an SI. TCP/IP Protocol Suite

  13. Note: To distinguish between different data chunks belonging to the same stream, SCTP uses SSNs. TCP/IP Protocol Suite

  14. Figure 13.4Comparison between a TCP segment and an SCTP packet TCP/IP Protocol Suite

  15. Note: TCP has segments; SCTP has packets. TCP/IP Protocol Suite

  16. Note: In SCTP, control information and data information are carried in separate chunks. TCP/IP Protocol Suite

  17. Figure 13.5Packet, data chunks, and streams TCP/IP Protocol Suite

  18. Note: Data chunks are identified by three identifiers: TSN, SI, and SSN. TSN is a cumulative number identifying the association; SI defines the stream; SSN defines the chunk in a stream. TCP/IP Protocol Suite

  19. Note: In SCTP, acknowledgment numbers are used to acknowledge only data chunks; control chunks are acknowledged by other control chunks if necessary. TCP/IP Protocol Suite

  20. 13.3 PACKET FORMAT We show the format of a packet and different types of chunks. An SCTP packet has a mandatory general header and a set of blocks called chunks. There are two types of chunks: control chunks and data chunks. The topics discussed in this section include: General Header Chunks TCP/IP Protocol Suite

  21. Figure 13.6SCTP packet format TCP/IP Protocol Suite

  22. Note: In an SCTP packet, control chunks come before data chunks. TCP/IP Protocol Suite

  23. Figure 13.7General header TCP/IP Protocol Suite

  24. Figure 13.8Common layout of a chunk TCP/IP Protocol Suite

  25. Note: Chunks need to terminate on a 32-bit (4 byte) boundary. TCP/IP Protocol Suite

  26. Table 13.2 Chunks TCP/IP Protocol Suite

  27. Note: The number of padding bytes are not included in the value of the length field. TCP/IP Protocol Suite

  28. Figure 13.9DATA chunk TCP/IP Protocol Suite

  29. Note: A DATA chunk cannot carry data belonging to more than one message, but a message can be split into several chunks.The data field of the DATA chunk must carry at least one byte of data, which means the value of length field cannot be less than 17. TCP/IP Protocol Suite

  30. Figure 13.10INIT chunk TCP/IP Protocol Suite

  31. Format for variable length parameters 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Parameter Type | Parameter Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ -+ \ \ / one or more Parameter Value / \ \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ TCP/IP Protocol Suite

  32. Parameter Type The Parameter Types are encoded such that the highest-order two bits specify the action that must be taken if the processing endpoint does not recognize the Parameter Type. 00 - Stop processing this SCTP packet and discard it, do not process any further chunks within it. 01 - Stop processing this SCTP packet and discard it, do not process any further chunks within it, and report the unrecognized parameter in an 'Unrecognized Parameter Type' (in either an ERROR or in the INIT ACK). 10 - Skip this parameter and continue processing. 11 - Skip this parameter and continue processing but report the unrecognized parameter in an 'Unrecognized Parameter Type' (in either an ERROR or in the INIT ACK). TCP/IP Protocol Suite

  33. Note: No other chunk can be carried in a packet that carries an INIT chunk. TCP/IP Protocol Suite

  34. Figure 13.11INIT ACK chunk TCP/IP Protocol Suite

  35. Note: No other chunk can be carried in a packet that carries an INIT ACK chunk. TCP/IP Protocol Suite

  36. Figure 13.12COOKIE ECHO chunk TCP/IP Protocol Suite

  37. Figure 13.13COOKIE ACK TCP/IP Protocol Suite

  38. Figure 13.14SACK chunk TCP/IP Protocol Suite

  39. Figure 13.15HEARTBEAT and HEARTBEAT ACK chunks TCP/IP Protocol Suite

  40. Figure 13.16SHUTDOWN, SHUTDOWN ACK, and SHUTDOWN COMPLETE chunks The T bit is set to 0 if the sender had a TCB that it destroyed. If the sender did not have a TCB it should set this bit to 1. TCP/IP Protocol Suite

  41. Figure 13.17ERROR chunk 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cause Code | Cause Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cause-specific Information | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ TCP/IP Protocol Suite

  42. Table 13.3 Errors TCP/IP Protocol Suite

  43. Figure 13.18ABORT chunk T The T bit is set to 0 if the sender had a TCB that it destroyed. If the sender did not have a TCB it should set this bit to 1. TCP/IP Protocol Suite

  44. 13.4 AN SCTP ASSOCIATION SCTP, like TCP, is a connection-oriented protocol. However, a connection in SCTP is called an association to emphasize multihoming The topics discussed in this section include: Association Establishment Data Transfer Association Termination Association Abortion TCP/IP Protocol Suite

  45. Note: A connection in SCTP is called an association. TCP/IP Protocol Suite

  46. Figure 13.19Four-way handshaking TCP/IP Protocol Suite

  47. Note: No other chunk is allowed in a packet carrying an INIT or INIT ACK chunk. A COOKIE ECHO or a COOKIE ACK chunk can carry DATA chunks. TCP/IP Protocol Suite

  48. Note: In SCTP, only DATA chunks consume TSNs; DATA chunks are the only chunks that are acknowledged. TCP/IP Protocol Suite

  49. Figure 13.20Simple data transfer TCP/IP Protocol Suite

  50. Note: The acknowledgment in SCTP defines the cumulative TSN, the TSN of the last DATA chunk received in order. TCP/IP Protocol Suite

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