SCTP (Stream Control Transmission Protocol) Chanmin Park ( 박 찬 민 ) CARES lab.

Contents  Introduction  SCTP Architecture  Packet  Association/Shutdown States  Data Transmission  API  SCTP Characteristics  Conclusion  References

Introduction  SCTP (Stream Control Transmission Protocol)  Reliable message-based & connection-oriented transport protocol  Standardization  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

SCTP concept

SCTP – Packet  Common Header (12 bytes)  Source/destination port : same as TCP  Verification Tag : 32 bit session ID  Checksum : 32 bit (TCP : 16bit)  Chunks  Type : distinguish control and data chunks  Flag : ordered/unordered bit  Length : length is variable  TSN (Transport Sequence Number), Stream ID, SSN (Stream Sequence Number)  Protocol ID : 132 (TCP – 17, UDP – 6)

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

SCTP Association/Shutdown TCP SCTP

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

SCTP API  ULP to SCTP  Initialize, Associate, Shutdown, Abort, Send, Set Primary, Receive, Status, Change Heartbeat, Request Heartbeat,  SCTP to ULP (Asynchronous notifications)  DATA ARRIVE, SEND FAILURE, NETWORK STATUS CHANGE, COMMUNICATION UP, COMMUNICATION LOST, COMMUNICATION ERROR, RESTART

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

Multi-Streaming

Multi-Homing

Features comparison

Conclusion  Applications  Reliable transmission (authentication, authorization system, etc.)  Mobile IP  Real-time internet multimedia (http, etc.)  Security (SCTP based TLS)  Other Issues  PR-SCTP (Partial Reliable SCTP) for real-time apps.  ADD-IP for MSCTP (Mobile SCTP)  Congestion control for each stream  Adaptive fail-over mechanism  Future & Vision  Substitute ?  Coexist ?  Killer application ?

References  Signaling Transport over IP (SIGTRAN)   SCTP for Beginners   An introduction to the SCTP (RFC 3286)   Standards Track (RFC 2960)   Linux Kernel SCTP   SCTP 표준기술 분석 및 전망, 전자통신동향분석 제 18 권 제 3 호 2003 년 6 월. 고석주 외.  Naver 지식인

Q & A