Outline NGN and SIGTRAN SCTP Motivation for SCTP Protocol - - PDF document

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Topics in Computer Networking Anna Brunstrom 1

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2009-0326

SCTP Stream Control Transmission Protocol

Topics in Computer Networking

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Outline

• NGN and SIGTRAN
• Motivation for SCTP
• Protocol Overview

– Packet format – Protection against SYN Flooding – Multistreaming – Multihoming

• Research Activities at Kau
• Summary
• Seminar Details

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Network Convergence

• Traditionally, telecommunication and data

communication networks have been separate entities

• Trend for voice, video, and data to converge into

single IP-based infrastructure (i.e. NGN)

• VoIP step in this direction
• Drivers of VoIP: Less costly equipment, less

regulated, better efficiency, ease of deployment, enhanced services

• Inhibitors of VoIP: immature technology, lack of

standards, QoS (reliability/availability)

• Need for seamless interoperation of VoIP with

traditional PSTN

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07 H.323/SIP

SG

Mobile Networks/ IMS

Media Gateway Network Manager

IB AAA

SS7 Switch STP

PSTN/ISDN

SS7 Switch STP

PSTN/ISDN

Media Gateway Core IP Network Gatekeeper/ Proxy Server API (PARLAY/LDAP) Application Server MGCP/Megaco/H.248 SIGTRAN SIGTRAN Н.323/ IP Network SS7 ISUP/MTP SIP/SIP-T H.323/BICC RADIUS ISUP SIP Softswitch SG Softswitch MGC SNMP

NGN

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Topics in Computer Networking Anna Brunstrom 2

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

The Telephone Network

Circuit Switched Network

Transport Layer Control Layer

Signaling System no. 7 (SS7)

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SS7 Performance Requirements

• A given route set should not be out of service for more

than 10 minutes per year (99.9998% uptime)

• No more than 1x10-7 messages should be lost
• No more than 1x10-10 messages should be delivered out of

sequence

• Numerous timing requirements must be met
• How to make sure that IP networks can support the

performance requirements of SS7?

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07 H.323/SIP

SG

Mobile Networks/ IMS

Media Gateway Network Manager

IB AAA

SS7 Switch STP

PSTN/ISDN

SS7 Switch STP

PSTN/ISDN

Media Gateway Core IP Network Gatekeeper/ Proxy Server API (PARLAY/LDAP) Application Server MGCP/Megaco/H.248 SIGTRAN SIGTRAN Н.323/ IP Network SS7 ISUP/MTP SIP/SIP-T H.323/BICC RADIUS ISUP SIP Softswitch SG Softswitch MGC SNMP

How do we solve the problem?

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SIGTRAN

Signaling Gateway Media Gateway Controller

TDM MGCP/MEGACO

PSTN

SS7

SCP SCP

Local Exchange STP STP

IP Network

SIGTRAN RTP/IP RTP/IP

Media Gateway Media Gateway Media Gateway Controller

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Topics in Computer Networking Anna Brunstrom 3

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SIGTRAN

M3UA SCTP IP ULP IP M3UA SCTP IP MTP-L3 MTP-L2 MTP-L1 NIF MTP-L3 MTP-L2 MTP-L1 ULP SS7 Signaling Gateway IPSEP SS7SEP

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP?

Applications (e.g Webbrowsers, mail clients, …) TCP UDP SCTP IP Physical

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP: Motivation

• TCP and UDP unsuitable for SS7 signaling

– Can not be used, considering the previously mentioned SS7 requirements

• SCTP:

– Like TCP, it provides reliable, full-duplex connections – Solves the following TCP issues:

• Head-of-line blocking can occur
• Application layer framing is required for messages
• Singlehomed hosts only
• Vulnerability to SYN flooding attacks
• SCTP ≈ TCP + A number of features

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP Standardization

• Stream Control Transmission Protocol (RFC 2960),

October 2000

• SCTP Partial Reliability Extension (RFC 3758), May

2004

• SCTP Padding Chunk Extension (4820), March 2007
• SCTP AUTH Extension (RFC 4895), August 2007
• SCTP DAR Extension (RFC 5061), September 2007
• Stream Control Transmission Protocol (RFC 4960),

September 2007

• Sockets API Extensions for SCTP, (internet-draft), latest

version from March 2010

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Topics in Computer Networking Anna Brunstrom 4

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP: Services and Features

• Services/Features

SCTP TCP UDP

• Full-duplex data transmission

yes yes yes

• Connection-oriented

yes yes no

• Reliable data transfer

yes yes no

• Partially reliable data transfer

yes no no

• Ordered data delivery

yes yes no

• Flow and Congestion Control

yes yes no

• Selective acks

yes yes no

• PMTUD

yes yes no

• Application data fragmentation

yes yes no

• Preservation of message boundaries

yes no yes

• Protection agains SYN flooding attacks

yes no n/a

• Unordered data delivery

yes no yes

• Multistreaming

yes no no

• Multihoming

yes no no

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Why Messages?

• TCP applications often transmit large byte

streams (bulk transfers)

• SCTP signaling applications transmit small

independent units of data

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Packet Formats

TCP SCTP

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Chunk Type Length Value Flags

N 2 1 1

SCTP Chunks

• Type

– Used to distinguish data chunks and different types of control chunks

• Flags

– Usage depends on Chunk type

• Length

– Required because chunks have a variable length

• Value

– Payload field

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Topics in Computer Networking Anna Brunstrom 5

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Payload Data 1 Initiation 2 Initiation Acknowledgement 3 Selective Acknowledgement 4 Heartbeat Request 5 Heartbeat Acknowledgement 6 Abort 7 Shutdown 8 Shutdown Acknowledgement 9 Operation Error 10 State Cookie 11 Cookie Acknowledgement 12 Reserved for Explicit Congestion Notification Echo 13 Reserved for Congestion Window Reduced 14 Shutdown Complete 15 Authentication chunk 128 Address Configuration Change Acknowledgement 132 SCTP packet padding 192 Forward Cumulative TSN 193 Address Configuration Change

Chunk Types

Chunk Type Length Value Flags

N 2 1 1

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP Data Chunk

Type = 0 Reserv. Stream Sequence Number N Length Transmission Sequence Number (TSN) User Data (seq. n of Stream S) Payload Protocol Identifier Stream Identifier S U B E

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP: Services and Features

• Services/Features

SCTP TCP UDP

• Full-duplex data transmission

yes yes yes

• Connection-oriented

yes yes no

• Reliable data transfer

yes yes no

• Partially reliable data transfer

yes no no

• Ordered data delivery

yes yes no

• Flow and Congestion Control

yes yes no

• Selective acks

yes yes no

• PMTUD

yes yes no

• Application data fragmentation

yes yes no

• Preservation of message boundaries

yes no yes

• Protection against SYN flooding attack

yes no n/a

• Unordered data delivery

yes no yes

• Multistreaming

yes no no

• Multihoming

yes no no

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SYN Flooding?

client server

SYN SYN, ACK ACK Resource Allocation

SLIDE 6

Topics in Computer Networking Anna Brunstrom 6

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP Association Establishment

client server

INIT COOKIE-ACK COOKIE-ECHO INIT-ACK Resource Allocation

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP: Services and Features

• Services/Features

SCTP TCP UDP

• Full-duplex data transmission

yes yes yes

• Connection-oriented

yes yes no

• Reliable data transfer

yes yes no

• Partially reliable data transfer

yes no no

• Ordered data delivery

yes yes no

• Flow and Congestion Control

yes yes no

• Selective acks

yes yes no

• PMTUD

yes yes no

• Application data fragmentation

yes yes no

• Preservation of message boundaries

yes no yes

• Protection agains SYN flooding attack

yes no n/a

• Multistreaming

yes no no

• Unordered data delivery

yes no yes

• Multihoming

yes no no

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Why Streams and Unordered Delivery?

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Multistreaming

• Stream: unidirectional data flow within an

SCTP association

– Within streams: Stream Sequence Number (SSN) – Between streams no data order preserved Multistreaming

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Topics in Computer Networking Anna Brunstrom 7

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Unordered Delivery

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP: Services and Features

• Services/Features

SCTP TCP UDP

• Full-duplex data transmission

yes yes yes

• Connection-oriented

yes yes no

• Reliable data transfer

yes yes no

• Partially reliable data transfer

yes no no

• Ordered data delivery

yes yes no

• Flow and Congestion Control

yes yes no

• Selective acks

yes yes no

• PMTUD

yes yes no

• Application data fragmentation

yes yes no

• Preservation of message boundaries

yes no yes

• Protection agains SYN flooding attack

yes no n/a

• Unordered data delivery

yes no yes

• Multistreaming

yes no no

• Multihoming

yes no no

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Why Multihoming?

• Allows use of multiple IP addresses at

each endpoint for a single association

• Originally for redundancy purposes only
• Primary path

Alternate/backup path

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Redundancy through Multihoming

• Primary destination address

– Normally used for the transmission of new packets

• Secondary destination address

– considered as a “backup” destination – periodically monitored with the transmission of probe packets (heartbeats)

• Secondary destination address used to

– retransmit lost packets – transmit new packets if the primary interface fails

• number of consecutive timeouts exceeds an

established threshold

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Topics in Computer Networking Anna Brunstrom 8

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Multihoming/Failover

• Timeout!!

Timeout!!

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Dynamic Address Reconfiguration

• Adding or deleting IP

addresses from the existing SCTP association

• Changing primary IP

address for SCTP association

• Intended for hot

pluggable interfaces and renumbering

• Can also be used for

transport layer mobility

• !

" #

• "

# !$ $

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

SCTP Research at KaU

• SCTP multihoming

– Failover performance: protocol tuning, SIGTRAN vs. SS7 – Relaxed timer backoff proposed to improve performance – Using SCTP for transport layer mobility – Improved start-up on alternate path

• SCTP performance for single-homed associations

– Impact of head-of-line blocking – Timely loss recovery – Use of partially reliable service for syslog traffic

• SCTP as a basis for secure applications

– Dynamic encryption service – Data protection based on physical separation – E2E security in SCTP: S²SCTP

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Summary

• SCTP is a, relatively new, transport protocol
• Motivated by the need for IP-based telephony

signaling transport

• It differs from TCP in that it is capable of:

– Avoiding head-of-line blocking – Transfer messages – Multihoming – Surviving SYN flooding attacks

• SCTP is quite flexible, partly due to the packet

structure, and can therefore be modified for

• ther purposes

– e.g. load-balancing, mobility

SLIDE 9

Topics in Computer Networking Anna Brunstrom 9

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Seminar

• Wednesday 100414, 09:15 (21E 309)

– Answer a quiz about SCTP – Discussion about SCTP – Related independent study topics

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Seminar

• Mandatory reading

– SCTP: state of the art in research, products, and technical challenges Shaojian Fu; Atiquzzaman, M.;Communications Magazine, IEEE, Volume: 42, Issue: 4, Apr 2004, Pages: 64-76 – Evaluation of transport protocols for the session initiation protocol Camarillo, G.; Kantola, R.; Schulzrinne, H.;Network, IEEE, Volume: 17, Issue: 5, Sept.-Oct. 2003, Pages:40-46 – On the use of SCTP in failover-scenarios Jungmaier, A.; Rathgeb, E. P.; Tüxen, M., In Proc. of the 6th World Multiconference on Systemics, Cybernetics and Informatics, Jul. 14-18, 2002, Orlando, Florida

• Study questions at the course website

– http://www.cs.kau.se/cs/education/courses/dvad02/p2/

Anna Brunstrom Karlstad University Department of Computer Science

Topics in Computer Networking 2010-04-07

Further Reading

• SCTP for Beginners (Recommended)

– http://tdrwww.exp-math.uni-essen.de/inhalt/forschung/sctp_fb/index.html

• Introduction to SCTP

– http://tools.ietf.org/html/rfc3286

• The SCTP RFC (4960)

– http://www.ietf.org/rfc/rfc4960.txt

• SCTP Multihoming

– Material at the course website