Lehrstuhl Netzarchitekturen und Netzdienste Institut für Informatik Technische Universität München iLab2 – Introduction to SIP Daniel Raumer raumer@net.in.tum.de
Agenda SIP - What? SIP - How? Repetition Security iLab2 – Introduction to the Multicast and SIP – Daniel Raumer – 2012-11-08 2
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 3
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 4
The Protocol Application Layer Protocol Signaling Protocol for IP Networks opposed to PSTN SS7 Text based – Similarities to HTTP Uses similar status codes SIP, (RTP,…) Application • 200 OK • 3xx Moved Transport UDP TCP • 4xx Errors Internet IP (IPv4, IPv6) RFC 3261 defines the Framework Network … Ethernet Header fields Access 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… iLab2 – Introduction to the Multicast and SIP – Daniel Raumer – 2012-11-08 5
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 6
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 7
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 8
Reinvitation sip:bob@someplace Sorry Bob is not here – Try mobile sip:bobmobile@someplace iLab2 – Introduction to the Multicast and SIP – Daniel Raumer – 2012-11-08 9
SIP Based VoIP Call Furni.er Jamai.ca iLab2 – Introduction to the Multicast and SIP – Daniel Raumer – 2012-11-08 10
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 11
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 12
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 13
The End iLab2 – Introduction to the Multicast and SIP – Daniel Raumer – 2012-11-08 14
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