SCTP (Stream Control Transmission Protocol)

1. SCTP(Stream Control Transmission Protocol) 2005. 10. 19. Chanmin Park (박 찬 민) CARES lab. (cmpark@davinci.snu.ac.kr)

2. Contents • Introduction • SCTP Characteristics • SCTP Architecture • Packet • Association • Data Transmission • API • SCTP Applications • Conclusion • References

3. Introduction • SCTP (Stream Control Transmission Protocol) • Message-based, connection-oriented transport protocol • Standardization • 2000. 10. RFC 2960 by SIGTRAN WG • PSTN (Public Switched Telephone Network)  IP Network • support real-time multimedia applications • Characteristics • Transport layer protocol above IP : TCP + UDP • Overcoming the drawbacks of TCP, UDP • Reliability, Flexibility, Security • Multi-streaming, multi-homing

4. SCTP concept

5. SCTP Characteristics • Multi-Streaming • Multi-stream per association • Avoid HOL (Head of Line) Blocking of TCP • Ordered/Unordered transport • U flag of Data Chunk • Reliable data transmission • Each stream has Stream Sequence Number (SSN) • Multi-Homing • Multiple (Ethernet) IPs per association • If primary path fail occurs, reconnect secondary path • Reliable data transmission

6. SCTP – Packet • Common Header (12 bytes) • Source/destination port : same as TCP • Verification Tag : 32 bit • Checksum : 32 bit (TCP : 16bit) • Chunks • Type : distinguish control and data chunks • Flag : ordered/unordered bit • Length : length is variable

7. Chunks – Type (13) • Payload Data (0) • Initiation (INIT) (1) • Initiation Acknowledgement (INIT ACK) (2) • Selective Acknowledgement (SACK) (3) • Heartbeat Request (HEARTBEAT) (4) • Heartbeat Acknowledgement (HEARTBEAT ACK) (5) • Abort Association (ABORT) (6) • Shutdown Association (SHUTDOWN) (7) • Shutdown Acknowledgement (SHUTDOWN ACK) (8) • Operation Error (ERROR) (9) • Cookie Echo (COOKIE ECHO) (10) • Cookie Acknowledgement (COOKIE ACK) (11) • Shutdown Complete (SHUTDOWN COMPLETE) (14)

8. SCTP Association Startup/Takedown SCTP TCP

9. SCTP Data Transmission • Flow Control • Congestion Control / Slow-start • Selective Acknowledgement • Ordered and Unordered Delivery • Fragmentation and Reassembly • Bundling • Path MTU Discovery

10. Multi-Streaming

11. Multi-Homing

12. SCTP API • ULP to SCTP • SCTP to ULP (Asynchronous)

13. Features comparison

14. SCTP Applications • Applications • Reliable transmission (authentication, authorization system, etc.) • Mobile IP • Real-time internet multimedia (http, etc.) • Security (SCTP based TLS) • Research Trends • Transport layer protocol for future wireless all-IP networks • SCTP  all-IP network • Sun Microsystems : SCTP for 4G IP wireless communication • SoftNetworks :SCTP for Voice over Mobile IP (VoMo) • Improving Multimedia performance over lossy networks • Robust SCTP • Multi-homing for hand-off processing

15. Conclusion • SCTP Characteristics (주요기능) • 4 way handshaking association • Check validity of packet • Monitoring data transmission path and idle path • Ordered and Unordered Data Transmission • Chunk Bundling • Multi-Streaming • Multi-Homing • Congestion Control • Fragmentation and Reassembly • Other Issues • Congestion control • 여러 stream 별 공평성 유지 (stream들을 하나 또는 다른 app 가 사용시) • Adaptive failover mechanism • PR-SCTP (Partial Reliable SCTP) • MSCTP (Mobile SCTP) • Future & Vision

16. References • Signaling Transport over IP (SIGTRAN) • http://www.sctp.de/ • SCTP for Beginners • http://tdrwww.exp-math.uni-essen.de/inhalt/forschung/sctp_fb/ • An introduction to the SCTP (RFC 3286) • http://www.ietf.org/rfc/rfc3286.txt • Standards Track (RFC 2960) • http://www.ietf.org/rfc/rfc2960.txt • Linux Kernel SCTP • http://sourceforge.net/projects/lksctp/ • Naver 지식인

17. Q & A