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www.wellya.netTable of Contents
1. Introduction.................................................. 5
1.1 Motivation.................................................. 6
1.2 Architectural View of SCTP.................................. 6
1.3 Functional View of SCTP..................................... 7
1.3.1 Association Startup and Takedown........................ 8
1.3.2 Sequenced Delivery within Streams....................... 9
1.3.3 User Data Fragmentation................................. 9
1.3.4 Acknowledgement and Congestion Avoidance................ 9
1.3.5 Chunk Bundling ......................................... 10
1.3.6 Packet Validation....................................... 10
1.3.7 Path Management......................................... 11
1.4 Key Terms................................................... 11
1.5 Abbreviations............................................... 15
1.6 Serial Number Arithmetic.................................... 15
2. Conventions.................................................... 16
3. SCTP packet Format............................................ 16
3.1 SCTP Common Header Field Descriptions....................... 17
3.2 Chunk Field Descriptions.................................... 18
3.2.1 Optional/Variable-length Parameter Format............... 20
3.3 SCTP Chunk Definitions...................................... 21
3.3.1 Payload Data (DATA)..................................... 22
3.3.2 Initiation (INIT)....................................... 24
3.3.2.1 Optional or Variable Length Parameters.............. 26
3.3.3 Initiation Acknowledgement (INIT ACK)................... 30
3.3.3.1 Optional or Variable Length Parameters.............. 33
3.3.4 Selective Acknowledgement (SACK)........................ 33
3.3.5 Heartbeat Request (HEARTBEAT)........................... 37
3.3.6 Heartbeat Acknowledgement (HEARTBEAT ACK)............... 38
3.3.7 Abort Association (ABORT)............................... 39
3.3.8 Shutdown Association (SHUTDOWN)......................... 40
3.3.9 Shutdown Acknowledgement (SHUTDOWN ACK)................. 40
3.3.10 Operation Error (ERROR)................................ 41
3.3.10.1 Invalid Stream Identifier.......................... 42
3.3.10.2 Missing Mandatory Parameter........................ 43
3.3.10.3 Stale Cookie Error................................. 43
3.3.10.4 Out of Resource.................................... 44
3.3.10.5 Unresolvable Address............................... 44
3.3.10.6 Unrecognized Chunk Type............................ 44
3.3.10.7 Invalid Mandatory Parameter........................ 45
3.3.10.8 Unrecognized Parameters............................ 45
3.3.10.9 No User Data....................................... 46
3.3.10.10 Cookie Received While Shutting Down............... 46
3.3.11 Cookie Echo (COOKIE ECHO).............................. 46
3.3.12 Cookie Acknowledgement (COOKIE ACK).................... 47
3.3.13 Shutdown Complete (SHUTDOWN COMPLETE).................. 48
4. SCTP Association State Diagram................................. 48
Stewart, et al. Standards Track [Page 3]
RFC 2960 Stream Control Transmission Protocol October 2000
5. Association Initialization..................................... 52
5.1 Normal Establishment of an Association...................... 52
5.1.1 Handle Stream Parameters................................ 54
5.1.2 Handle Address Parameters............................... 54
5.1.3 Generating State Cookie................................. 56
5.1.4 State Cookie Processing................................. 57
5.1.5 State Cookie Authentication............................. 57
5.1.6 An Example of Normal Association Establishment.......... 58
5.2 Handle Duplicate or unexpected INIT, INIT ACK, COOKIE ECHO,
and COOKIE ACK.............................................. 60
5.2.1 Handle Duplicate INIT in COOKIE-WAIT
or COOKIE-ECHOED States................................. 60
5.2.2 Unexpected INIT in States Other than CLOSED,
COOKIE-ECHOED, COOKIE-WAIT and SHUTDOWN-ACK-SENT........ 61
5.2.3 Unexpected INIT ACK..................................... 61
5.2.4 Handle a COOKIE ECHO when a TCB exists.................. 62
5.2.4.1 An Example of a Association Restart................. 64
5.2.5 Handle Duplicate COOKIE ACK............................. 66
5.2.6 Handle Stale COOKIE Error............................... 66
5.3 Other Initialization Issues................................. 67
5.3.1 Selection of Tag Value.................................. 67
6. User Data Transfer............................................. 67
6.1 Transmission of DATA Chunks................................. 69
6.2 Acknowledgement on Reception of DATA Chunks................. 70
6.2.1 Tracking Peer’s Receive Buffer Space.................... 73
6.3 Management Retransmission Timer............................. 75
6.3.1 RTO Calculation......................................... 75
6.3.2 Retransmission Timer Rules.............................. 76
6.3.3 Handle T3-rtx Expiration................................ 77
6.4 Multi-homed SCTP Endpoints.................................. 78
6.4.1 Failover from Inactive Destination Address.............. 79
6.5 Stream Identifier and Stream Sequence Number................ 80
6.6 Ordered and Unordered Delivery.............................. 80
6.7 Report Gaps in Received DATA TSNs........................... 81
6.8 Adler-32 Checksum Calculation............................... 82
6.9 Fragmentation............................................... 83
6.10 Bundling .................................................. 84
7. Congestion Control .......................................... 85
7.1 SCTP Differences from TCP Congestion Control................ 85
7.2 SCTP Slow-Start and Congestion Avoidance.................... 87
7.2.1 Slow-Start.............................................. 87
7.2.2 Congestion Avoidance.................................... 89
7.2.3 Congestion Control...................................... 89
7.2.4 Fast Retransmit on Gap Reports.......................... 90
7.3 Path MTU Discovery.......................................... 91
8. Fault Management.............................................. 92
8.1 Endpoint Failure Detection.................................. 92
8.2 Path Failure Detection...................................... 92
Stewart, et al. Standards Track [Page 4]
RFC 2960 Stream Control Transmission Protocol October 2000
8.3 Path Heartbeat.............................................. 93
8.4 Handle "Out of the blue" Packets............................ 95
8.5 Verification Tag............................................ 96
8.5.1 Exceptions in Verification Tag Rules.................... 97
9. Termination of Association..................................... 98
9.1 Abort of an Association..................................... 98
9.2 Shutdown of an Association.................................. 98
10. Interface with Upper Layer....................................101
10.1 ULP-to-SCTP................................................101
10.2 SCTP-to-ULP................................................111
11. Security Considerations.......................................114
11.1 Security Objectives........................................114
11.2 SCTP Responses To Potential Threats........................115
11.2.1 Countering Insider Attacks.............................115
11.2.2 Protecting against Data Corruption in the Network......115
11.2.3 Protecting Confidentiality.............................115
11.2.4 Protecting against Blind Denial of Service Attacks.....116
11.2.4.1 Flooding...........................................116
11.2.4.2 Blind Masquerade...................................118
11.2.4.3 Improper Monopolization of Services................118
11.3 Protection against Fraud and Repudiation...................119
12. Recommended Transmission Control Block (TCB) Parameters.......120
12.1 Parameters necessary for the SCTP instance.................120
12.2 Parameters necessary per association (i.e. the TCB)........120
12.3 Per Transport Address Data.................................122
12.4 General Parameters Needed..................................123
13. IANA Considerations...........................................123
13.1 IETF-defined Chunk Extension...............................123
13.2 IETF-defined Chunk Parameter Extension.....................124
13.3 IETF-defined Additional Error Causes.......................124
13.4 Payload Protocol Identifiers...............................125
14. Suggested SCTP Protocol Parameter Values......................125
15. Acknowledgements..............................................126
16. Authors’ Addresses............................................126
17. References....................................................128
18. Bibliography..................................................129
Appendix A .......................................................131
Appendix B .......................................................132
Full Copyright Statement .........................................134
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