iLab2 Introduction to SIP Daniel Raumer raumer@net.in.tum.de - - PowerPoint PPT Presentation

Lehrstuhl Netzarchitekturen und Netzdienste

Institut für Informatik Technische Universität München

iLab2 – Introduction to SIP

Daniel Raumer raumer@net.in.tum.de

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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Agenda

 SIP - What?  SIP - How?  Repetition Security

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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SIP – What?

 RFC 2543 – Session Initiation Protocol  Definition: “SIP – An application layer signalling protocol that defines

initiation modification and termination of interactive, multimedia communication sessions between users!“

 Current RFC 3261  Today used for

• VoIP (mainly)
• Instant Messaging (MSN)
• Messaging systems often use SIMPLE  Simplified version of SIP
• Online Games
• Signalling Protocol for Next Generation Networks
• All IP Networks (IP Multimedia Subsystem - IMS)

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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SIP – What?

 RFC 2543 – Session Initiation Protocol  Definition: “SIP – An application layer signalling protocol that defines

initiation modification and termination of interactive, multimedia communication sessions between users!“

 Current RFC 3261

1996: First technology concept drafts 1999: RFC 2543 2000: SIP became signaling protocol in the 3GPP and element in IMS 2002: official IETF Standard …increase of application & a lot of extensions

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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The Protocol

 Application Layer Protocol

• Signaling Protocol for IP Networks opposed to PSTN SS7

 Text based – Similarities to HTTP

• Uses similar status codes
• 200  OK
• 3xx  Moved
• 4xx  Errors

 RFC 3261 defines the Framework

• Header fields
• Protocol
• What to do when
• Which messages are sent at which point of the session
• …
• Additional RFCs complement this basic framework
• Privacy (RFC 3323)
• Compression (RFC 3320)
• Body Content, Media Description…

Application SIP, (RTP,…) Transport UDP TCP Internet IP (IPv4, IPv6) Network Access Ethernet …

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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What does it do?

 Session Initiation  Localization of users

• Using SIP URIs: ilab2@net.in.tum.de

 Presence indication  Negotiation of Parameters

• Codecs to be used, Security Parameters

 Setup of the session

• Media targets

 Management and maintenance of the session

• Forwarding or cancelation of a session
• Invite, re-Invites, …

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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What it does NOT

 SIP is not a ready-for-use application

• It is not Instant messaging, VoIP, or Video on demand.

 SIP does not transport media

• but does work with Session Description Protocol (SDP)

 SIP does not provide QoS

• but can work with Resource Reservation Protocol (RSVP) and Real-Time

Transport Protocol (RTP)

 SIP does not provide Authentication

• but works with RADIUS and LDAP

 “SIP needs alphabet soup to stay healthy!”

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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SIP Based VoIP Call

sip:bob@someplace Protocol / Negotiation Call Protocol / End Call

RTP Session

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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Reinvitation

Sorry Bob is not here – Try mobile sip:bob@someplace sip:bobmobile@someplace

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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SIP Based VoIP Call

Jamai.ca Furni.er

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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Repetition Security

 Security Objectives:

• Integrity,
• Authenticity,
• Confidentiality,
• Availability,
• Accountability

 Some attack types (not distinct)

• Replay Attack
• Relay Attack
• Monitoring/Snooping
• (Identity-)Spoofing
• DoS (e.g. BYE message injecting)
• …

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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SIP Security “Alphabet Soup”

 SRTP (Secure Real-Time Transport Protocol) RFC 3711  SDES (Session Description Protocol Security Descriptions) RFC 4568

• Key exchange for RTP – but requires a secure channel (TLS or S/MIME)

 ZRTP (Zimmermann Real-Time Transport Protocol) RFC 6189

• Diffie-Hellman for the RTP
• Man in the middle?

 …but SIPS is usually realized over TLS hop by hop

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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Content of the Lab

 Much short lab  So fun  Such less coding

WOW

iLab2 – Introduction to the Multicast and SIP – Daniel Raumer– 2012-11-08

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The End