Post on 18-Nov-2014
description
SCTP introduction
Richard Xiong2013/2/8
Motivations
• Provide reliable transfer without sequence maintenance.
• The stream-oriented nature of TCP is often an inconvenience. SCTP provides message based transfer.
• TCP is relatively vulnerable to denial-of-service attacks, such as SYN attacks.
• …
History• First implementation on 1991• submitted to IETF on 1998. RFC 4960 defines t
he protocol. RFC 3286 provides an introduction. (RFC2960 and RFC3309 are obsoleted).
• Designed for telecom signaling transfer at first, and used on other applications
• supported by Cisco, Linux, HP, Solaris, Alcatel-Lucent,…
» refrence
Network layers
Upper layer applications
TCP UDP SCTP
IP
Link Layer
Physical Layer
Features
• Message-based• Multi-homing• Multi-stream• Reliable transfer• Robust and safety ( four way
handshake ,heartbeat, three way shutdown )
Multi-homing
End-pointA
SW1
SW2
HUB1
HUB2
End-pointZ
10.0.0.1
10.0.0.65
10.0.0.3
10.0.0.68
Primary path
Alternate Path
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm1SSN 2
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm2SSN 3
Strm1SSN 3
SSN: Stream Sequence Number
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm1SSN 2
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm2SSN 3
Strm1SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1Strm1
SSN 2
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm2SSN 3
Strm1SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm1SSN 2
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm2SSN 3
Strm1SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm1SSN 3
Strm1SSN 2
Strm2SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm2SSN 2
Strm3SSN 2Strm3
SSN 3Strm1SSN 3
Strm1SSN 2
Strm2SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm1SSN 3
Strm1SSN 2
Strm2SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm1SSN 3
Strm1SSN 2
Strm2SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm1SSN 3
Strm1SSN 2
Strm2SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm1SSN 3
Strm1SSN 2
Strm2SSN 3
Multi-stream
End-pointA
End-pointZ
Strm1SSN 1
Strm2SSN 1
Strm3SSN 1
Strm2SSN 2
Strm3SSN 2
Strm3SSN 3
Strm1SSN 3
Strm1SSN 2
Strm2SSN 3
Status of AssociationCLOSED COOKIE_WAIT
COOKIE_ECHOED
ESTABLISHED
SHUTDOWN-PENDING
SHUTDOWN-ACK-SENT
SHUTDOWN-SENT
SHUTDOWN-RECIEVED
SCTP messages
• Data -- SACK• INIT -- INIT ACK -- COOKIE ECHO -- C
OOKIE ACK• Heartbeat -- Heartbeat ACK• Shutdown – Shutdown ACK -- SHUTDO
WN COMPLETE• Abort
Setting Up Endpoint A Endpoint Z
INIT
INIT-ACK
COOKIE-ECHO
COOKIE-ACK
*
*
* -- User data can be attached
COOKIE-WAIT
COOKIE-ECHOED
CLOSED CLOSED
ESTABLISHED ESTABLISHED
1
2
Transfer data
Close
Shutdown from application
Endpoint A Endpoint Z
SHUTDOWN SHUTDOWN-SENT
SHUTDOWN-PENDING
Transfer remaining data
SHUTDOWN-RECEIVED
SHUTDOWN ACK
SHUTDOWN-ACK-SENT
SHUTDOWN COMPLETE CLOSED CLOSED
Chunk structure--DATA chunk
Chunk structure--SACK chunk
Fault management
• Primary/alternate Path detection• Resend mechanism• Congestion control (RFC2581)
Installation on Linux (lksctp)
• Check if SCTP is installed– grep SCTP /proc/net/protocols – checksctp
• Download code from http://lksctp.sourceforge.net/
SCTP socket API• One-to-many style and one-to-one style are supported.• Please read the API standard before programming, there
are lots of different features comparing to TCP socket.• One-to-many server
– socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP)– bind(sock, (struct sockaddr*)&addr, sizeof(struct sockaddr))– setsockopt(m_fds[i].fd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on));– listen(sock, 2);– sctp_recvmsg(sock, buffer, BUFFER_SIZE, NULL, 0, NULL, &flags)– close(sock)
• One-to-many client– socket(PF_INET, SOCK_SEQPACKET, IPPROTO_SCTP))– connect(sock, (struct sockaddr*)&addr, sizeof(struct sockaddr)– send(sock, buffer, MSG_SIZE, 0)– close(sock)
» Refer SCTP API
Others
• shortages– http://datatag.web.cern.ch/datatag/WP3/sctp/t
ests.htm
• New research– Concurrent multipath transfer
Reference• http://en.wikipedia.org/wiki/Stream_Control_Transmissio
n_Protocol• RFC4960• RFC 2581• http://www.youtube.com/watch?v=dIPwN-z6lVA• http://www.sctp.org/• http://www.sourceforge.net/projects/lksctp• http://linux.die.net/man/7/sctp• http://www.ibm.com/developerworks/library/l-sctp/• http://www.linuxjournal.com/article/9784
Q&A