Transcript SCTP - UMBC
SCTP Stream Control Transmission Protocol Nimish Vartak CS, UMBC SCTP - Agenda • • • • • Motivation Overview of SCTP Features of SCTP Current Implementations Comparison with other protocols Nimish Vartak SCTP – Motivation IP reference model TCP Nimish Vartak UDP 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 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 Nimish Vartak SCTP – Overview (contd …) Message Format Nimish Vartak SCTP – Key Features • • • • • Connection set-up Multi-streaming Multi-homing Selective ACKs in Data sending Connection shut-down Nimish Vartak SCTP – Features (contd …) Connection setup (SYN) INIT (SYN-ACK) INIT-ACK COOKIE-ECHO COOKIE-ACK End-Point A Nimish Vartak End-Point Z SCTP – Features (contd …) Multi-streaming Nimish Vartak SCTP – Features (contd …) Multi-homing Internet End-Point A Nimish Vartak End-Point Z SCTP – Features (contd …) SACK in Data sending Nimish Vartak SCTP – Features (contd …) Connection close SHUTDOWN SHUTDOWN-ACK SHUTDOWN-CMPL End-Point A End-Point Z No Half Closed State Nimish Vartak 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 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 SCTP – Comparison • Comparison of features with TCP and UDP Nimish Vartak * Courtesy Addison Wesley 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 Nimish Vartak 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/SCTPLWE.pdf) Nimish Vartak SCTP Thank You. Nimish Vartak