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SCTP
(Stream Control Transmission Protocol)
2005. 10. 19.
Chanmin Park (박 찬 민)
CARES lab.
([email protected])
Contents
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Introduction
SCTP Characteristics
SCTP Architecture
Packet
 Association
 Data Transmission
 API
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SCTP Applications
Conclusion
References
Introduction
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SCTP (Stream Control Transmission Protocol)
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Message-based, connection-oriented transport protocol
Standardization
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2000. 10. RFC 2960 by SIGTRAN WG
PSTN (Public Switched Telephone Network)
 IP Network
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support real-time multimedia applications
Characteristics
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Transport layer protocol above IP : TCP + UDP
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Overcoming the drawbacks of TCP, UDP
Reliability, Flexibility, Security
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Multi-streaming, multi-homing
SCTP concept
SCTP Characteristics
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Multi-Streaming
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Multi-stream per association
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Avoid HOL (Head of Line) Blocking of TCP
Ordered/Unordered transport
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Reliable data transmission
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U flag of Data Chunk
Each stream has Stream Sequence Number (SSN)
Multi-Homing
Multiple (Ethernet) IPs per association
 If primary path fail occurs, reconnect secondary
path
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Reliable data transmission
SCTP – Packet
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Common Header (12 bytes)
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Source/destination port : same as TCP
Verification Tag : 32 bit
Checksum : 32 bit (TCP : 16bit)
Chunks
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Type : distinguish control and data chunks
Flag : ordered/unordered bit
Length : length is variable
Chunks – Type (13)
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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)
SCTP Association Startup/Takedown
SCTP
Host B
Host A
SYN
SYN
Host B
Host A
FIN
K
, AC
AC K
N
of FI
FIN
AC K
AC K o f
FIN
TCP
SCTP Data Transmission
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Flow Control
Congestion Control / Slow-start
Selective Acknowledgement
Ordered and Unordered Delivery
Fragmentation and Reassembly
Bundling
Path MTU Discovery
Multi-Streaming
Multi-Homing
SCTP API
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ULP to SCTP
SCTP to ULP (Asynchronous)
Features comparison
SCTP Applications
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Applications
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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
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SCTP  all-IP network
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Sun Microsystems : SCTP for 4G IP wireless communication
SoftNetworks : SCTP for Voice over Mobile IP (VoMo)
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Improving Multimedia performance over lossy networks
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Robust SCTP
Multi-homing for hand-off processing
Conclusion
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SCTP Characteristics (주요기능)
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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
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Congestion control
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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
References
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Signaling Transport over IP (SIGTRAN)
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SCTP for Beginners
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http://www.ietf.org/rfc/rfc2960.txt
Linux Kernel SCTP
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http://www.ietf.org/rfc/rfc3286.txt
Standards Track (RFC 2960)
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http://tdrwww.exp-math.uni-essen.de/inhalt/forschung/sctp_fb/
An introduction to the SCTP (RFC 3286)
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http://www.sctp.de/
http://sourceforge.net/projects/lksctp/
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