SCTP

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SCTP
Stream Control Transmission Protocol

• Nimish Vartak
• CS, UMBC

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SCTP - Agenda

• Motivation
• Overview of SCTP
• Features of SCTP
• Current Implementations
• Comparison with other protocols

Nimish Vartak
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SCTP Motivation

• IP reference model

TCP UDP
Nimish Vartak
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SCTP Motivation (contd )

• New applications
• Migration from PSTN to Packet based Internet
• Telephony signaling messages
• Shortcomings of existing protocols
• TCP
• head-of-line blocking
• Byte-oriented, not message-oriented
• Multi-homing support not built in
• DoS attack prone
• UDP
• No Reliability
• Absence of congestion control
• Absence of flow control

Nimish Vartak
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SCTP Overview

• SCTP is a reliable transport protocol operating
  on top of a connectionless packet network such as
  IP. RFC 2960
• Has built-in support for multi-homed hosts
• Is message-based conserves the message
  boundaries.
• Classifies messages as
• sequenced delivery of user messages within
  multiple streams
• with an option for un-ordered delivery of
  individual user messages
• Additional security mechanisms

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SCTP Overview (contd )

• Message Format

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SCTP Key Features

• Connection set-up
• Multi-streaming
• Multi-homing
• Selective ACKs in Data sending
• Connection shut-down

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SCTP Features (contd )

• Connection setup

(SYN) INIT
(SYN-ACK) INIT-ACK
COOKIE-ECHO
COOKIE-ACK
End-Point A
End-Point Z
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SCTP Features (contd )

• Multi-streaming

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SCTP Features (contd )

• Multi-homing

Internet
End-Point A
End-Point Z
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SCTP Features (contd )

• SACK in Data sending

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SCTP Features (contd )

• Connection close

SHUTDOWN
SHUTDOWN-ACK
SHUTDOWN-CMPL
End-Point A
End-Point Z
No Half Closed State
Nimish Vartak
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SCTP Special Features

• Heartbeat keep-alive mechanism
• Selective acknowledgments
• Security perspective
• Connection based
• DoS attack prevention
• Data based
• IPSec under SCTP
• TLS over SCTP

Nimish Vartak
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SCTP Implementations

• Implementation
• Kernel Level - Highly scalable
• Platforms Linux, Solaris, FreeBSD, Unix,
• Several Implementations in progress in the
• The Linux Kernel SCTP
• User Level - Easy maintenance
• Randall Stewart's reference implementation
• http//www.sctp.org/
• Ported to many platforms - Linux, Solaris,
• FreeBSD, AIX, Tru64(Compaq), Windows, etc.

Nimish Vartak
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SCTP Comparison

• Comparison of features with TCP and UDP

Nimish Vartak
Courtesy Addison Wesley
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SCTP Summary
Well suited for Multimedia

• Like TCP
• Provides connection establishment
• Ensures Reliability
• Provisions for ordered and un-ordered data
• Provides Congestion Control
• In addition to TCP features
• Provides multi-homing
• Provides multi-streaming
• Has security features

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SCTP References

• Computer.org
• (http//www.computer.org/internet/v5n6/w6wire.htm
  )
• IETF RFC 2960
• (http//www.ietf.org/rfc/rfc2960.txt)
• Stream Control Transmission Protocol (SCTP) A
  Reference Guide, R. Stewart and Q. Xie, Addison
  Wesley
• IBM.com
• (http//oss.software.ibm.com/linux/presentations/
  lwce2002/Chats/SCTP/SCTP-LWE.pdf)

Nimish Vartak
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SCTP

• Thank You.

Nimish Vartak