Transcript QoS for NGI

SCTP: State of the art in Research,
Products, and Technical Challenges
Mohammed Atiquzzaman
School of Computer Science
University of Oklahoma.
Email: [email protected]
Web: www.cs.ou.edu/~atiq
Co-Author: Shaojian Fu
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
1
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
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
2
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
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
3
Stream Control Transmission Protocol
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
4
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;
.
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
5
SCTP in the Internet Protocol suite
Upper layer applications
TCP, UDP, SCTP
IP
Link Layer
Physical Layer
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
6
Multi-streaming and Multihoming
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
7
Illustration of SCTP multihoming
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
8
SCTP Multi-streaming
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
9
Web page transfer with multi-streaming
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
10
Differences between TCP and SCTP
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
11
State-of-the-art in
SCTP RESEARCH
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
12
Congestion Control
 Can SCTP co-exist fairly with TCP in a shared
network?
• Study 1: SCTP and TCP share a WAN
link [Jungmaier:2000]
• 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
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
13
Multi-homing
 Fast failure recovery for high-availability, seamless
switchover at transport layer vs. switchover at userlayer [Jungmaier:2002].
• 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.
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
14
Multi-streaming
 Transport multimedia traffic over lossy network
[Caro:2001,Atiquzzaman:2002]
 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.
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
15
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 [Fu:2002].
 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
[Fu:2003].
 SCTP multi-homing can be used to reduce the network load
caused by triangular routing after a Mobile handover
[Noonan:2002].
 SCTP over ad-hoc networks, e.g. IEEE 802.11 network.
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
16
SCTP Products
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
17
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.
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
18
Commercial Products
 Geared towards providing a SS7 signaling transport
solution.
•Cisco ITP in
IOS 12.2.
•Adax APSSCTP/T
•Ulticom
SignalWare
•Dataconnection
DC-SCTP
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
19
Future SCTP Research
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
20
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 SCTP’s poor performance
 Dynamic Address Reconfiguration:
 Useful in mission-critical applications or mobile environments by
supporting service reconfiguration without interrupting on-going
data transfers.
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
21
 Acknowledgements
 National Aeronautics and Space Administration (NASA)
 William Ivancic, NASA.
 Further Information
Dr. Mohammed Atiquzzaman
[email protected], (405) 325 8077
 These slides are available at
www.cs.ou.edu/~atiq
Atiquzzaman, “SCTP: State of the art”
Oct 2003.
22