SCTP: State of the art in Research, Products, and Technical Challenges

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SCTP State of the art in Research, Products, and
Technical Challenges

• Mohammed AtiquzzamanSchool of Computer
  ScienceUniversity of Oklahoma.
• Email atiq_at_ieee.orgWeb www.cs.ou.edu/atiq
• Co-Author Shaojian Fu

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Introduction

• Stream Control Transmission Protocol (SCTP)
• proposed by IETF in October 2000 to accomplish
  SS7 signaling transport.
• SCTP should be useful in a wider range of
  applications instead of just the signaling
  transport area.
• SCTP has received much attention from the
  research community due to its attractive new
  features
• multi-streaming
• multi-homing.

Objectives Update readers with recent research
activities related to SCTP, products, and open
problems
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Outline

• Main features of SCTP
• Comparison of SCTP and TCP
• State-of-the-art in SCTP research activities
• SCTP research tools
• Commercial SCTP products
• Open issues and research challenges

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• Stream Control Transmission Protocol

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Stream Control Transmission Protocol

• SCTP (RFC 2960) is being developed by IETF as the
  next generation transport protocol.
• Reliable retransmission of lost packets, ack of
  packets.
• In-order delivery re-sequencing at the
  destination.
• Transport layer protocol which operates on top of
  an unreliable connectionless network layer such
  as IP.
• Transparent to IPv4 or IPv6
• Key unique features
• Multistreaming Support for multiple logical
  streams to improve data transmission throughput
• Multihoming Support for multiple network
  interfaces to achieve high availability
• .

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SCTP in the Internet Protocol suite
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Multi-streaming and Multihoming
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Illustration of SCTP multihoming
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SCTP Multi-streaming
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Web page transfer with multi-streaming
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Differences between TCP and SCTP
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• State-of-the-art in
• SCTP RESEARCH

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Congestion Control

• Can SCTP co-exist fairly with TCP in a shared
  network?

• Study 1 SCTP and TCP share a WAN link
  Jungmaier2000
• SCTP and TCP shared the bandwidth fairly.
• TCP faced no adverse effect due to the presence
  of SCTP.

• Study 2 SCTP and TCP share Satellite link
  Alamgir, et.al. 2002
• TCP and SCTP shared the satellite link fairly
• TCP achieved slightly higher throughput because
  of its advanced retransmission policy

Both studies demonstrated that SCTP can coexist
with TCP
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Multi-homing

• Fast failure recovery for high-availability,
  seamless switchover at transport layer vs.
  switchover at user-layer Jungmaier2002.

• Transport layer switchover based on multi-homing
• User layer switchover using two associations

Transport layer switchover resulted in smoother
transition by having a lower average segment
delay.
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Multi-streaming

• Transport multimedia traffic over lossy network
  Caro2001,Atiquzzaman2002
• Eliminate HOL effect by utilizing inter-stream
  independence.
• Sensitivity of transport layer throughput to
  network loss decreased compared with TCP.
• User satisfaction on the picture quality
  increased.
• Reduced receiver buffer requirements.

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Application in Wireless/Mobile Environment

• Make SCTP well suited for wireless channel
  characteristics and mobility issues arising from
  3G and beyond wireless networks.
• Delay spikes are common in wireless network. Like
  TCP, SCTP also suffers Spurious Timeout after the
  delay spike, but SACK can be used to make SCTP
  free of Spurious Fast Retransmissions Fu2002.
• SCTP in Mobile-IP networks (as a dumb transport
  protocol) can achieve a better performance than
  TCP-SACK by exploiting SCTP's support of large
  number of GapACK blocks in its SACK Fu2003.
• SCTP multi-homing can be used to reduce the
  network load caused by triangular routing after a
  Mobile handover Noonan2002.
• SCTP over ad-hoc networks, e.g. IEEE 802.11
  network.

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• SCTP Products

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Free Software

• Reference Implementation
• Kernel module for BSD/OS 4.3, FreeBSD 4.7,
  NetBSD 1.6, and OpenBSD 3.2 available. Work on
  Solaris discontinued.
• SCTP patch for the ns-2 simulator
• provides the core SCTP features (as specified in
  RFC 2960) including multi-streaming,
  multi-homing, congestion-control, chunk bundling,
  etc.
• Linux Kernel SCTP (LKSCTP)
• An open source implementation under GNU GPL
  (General Public License) to provide an SCTP
  module in Linux kernel 2.6.0-test4.

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Commercial Products

• Geared towards providing a SS7 signaling
  transport solution.

• Cisco ITP in IOS 12.2.
• Adax APS-SCTP/T
• Ulticom SignalWare
• Dataconnection DC-SCTP

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• Future SCTP Research

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Issues and Challenges

• Meeting the Reliability Requirements of the SS7
  Standard
• The time needed to switch to another link when
  link failure occurs should be less than 800ms
• The availability of communication service between
  two signaling points should be at least 99.998.
• No more than one in 107 messages may be lost at
  Message Transfer Part (MTP) layer
• Performance in wireless networks
• SCTP is designed with wire-line environments in
  mind wireless mobile networks encounter higher
  Bit Error Rates (BER) and more frequent delay
  spikes which will cause SCTPs poor performance
• Dynamic Address Reconfiguration
• Useful in mission-critical applications or mobile
  environments by supporting service
  reconfiguration without interrupting on-going
  data transfers.

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• Acknowledgements
• National Aeronautics and Space Administration
  (NASA)
• William Ivancic, NASA.
• Further Information
• Dr. Mohammed Atiquzzaman
• atiq_at_ou.edu, [phone]
• These slides are available at
• www.cs.ou.edu/atiq
  

Thank you