2001: First release of Linphone, for GNU/Linux, with minimalist GTK+-1.2 interface - GPLv2 License - Basic audio calls

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Camron Gilmore
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1 May 2018

2 A bit of history 2001: First release of Linphone, for GNU/Linux, with minimalist GTK+-1.2 interface - GPLv2 License - Basic audio calls 2006: Video calls added, ported to Windows 2010: Creation of Belledonne Communications SARL, the company developing Linphone - Dual licensing - Support - Specific developments / customisation 2011: Linphone is ported to ios and Android with video 2012: Launch of sip.linphone.org free SIP service, based on our Flexisip SIP proxy server : Improved UI, Instant Messaging with delivery notifications, security features 2017: Launch of Linphone 4 for desktop, with a brand-new UI based on QT framework 2018: Android & ios releases incorporating group chat features

3 Group chat requirements Ø Create sessions with multiple participants Ø Administrators (the creator is admin by default) Ø Participants can be added or removed Ø Undefined lifetime Ø Message store & forward Ø Delivery notifications Ø File transfer Ø Optionnaly: end to end data protection

4 SIP vs XMPP XMMP - Extensible Messaging and Presence Protocol SIP Session Initiation Protocol Pros: Is IETF RFC6120, added with XEP extensions Several mature open-source client and server implementations do exist Is established in IM and group IM since a long time (first RFC in 2004) Pros: Signaling protocol for initiating general purpose «sessions» Is IETF RFC3261 Is well-established for audio/video calls Has very modular design on server side Cons: Has monolitic design on server side Has evolved lately to audio/video (Jingle evolved from experimental to draft in 2009) Cons: Has evolved lately to Instant Messaging Confusing approaches for IM (MESSAGE, MSRP) Until now, not very commonly used for IM

5 Why did we use SIP for goup chat? Given Belledonne Communications s background, moving out of SIP was not an option Keeping SIP for audio/video while adding XMMP for IM would lead to major drawbacks: Ø An increased amount of code to be embedded into Linphone, in order to implement the two protocol stacks Ø The duplication of TLS connections - authentication procedure and username/password management - server infrastructure - Engineering expertise Published IETF RFCs and GSMA RCS specifications offer solutions for group chat We already have a working and robust client & server implementation of one-to-one messaging on top of SIP It brings the possibility to extend from group chat to audio/video conference, with the same architecture

6 Group chat according to IETF and GSMA/RCS specifications Session establishment SIP methods: INVITE, REFER, BYE between clients and a conference server SIP Call Control - Conferencing for User Agents RFC4579 Conference Establishment Using Request-Contained Lists in SIP RFC5366 Obtaining and Using Globally Routable User Agent URIs (GRUUs) in SIP RFC5627 : working with multiple devices Event notification to clients (someone joined or left the group etc.) SIP SUBSCRIBE/NOTIFY - RFC6665 SIP Event Package for Conference State - RFC4575 Message transport Message Session Relay Protocol RFC4975 recommended for text and files SIP MESSAGE request - RFC3428 is considered as obsolete File transfer also possible via HTTP POST/GET - RCS vnd.gsma.rcs-ft-http+xml Message format and auxiliary messages Common Presence and Instant Messaging (CPIM): Message Format RFC3862 defines content and associated metadata format Instant Message Disposition Notification RFC5438 Indication of Message Composition for Instant Messaging RFC3994

Linphone s group chat implementation Session establishment SIP methods: INVITE, REFER, BYE between clients and a conference server SIP Call Control - Conferencing for User Agents RFC4579 Conference

7 Linphone s group chat implementation Session establishment SIP methods: INVITE, REFER, BYE between clients and a conference server SIP Call Control - Conferencing for User Agents RFC4579 Conference Establishment Using Request-Contained Lists in SIP RFC5366 Obtaining and Using Globally Routable User Agent URIs (GRUUs) in SIP RFC5627 : working with multiple devices Event notification to clients (someone joined or left the group etc.) SIP SUBSCRIBE/NOTIFY - RFC6665 SIP Event Package for Conference State - RFC state id Message transport Message Session Relay Protocol RFC4975 recommended for text and files SIP MESSAGE request - RFC3428 is considered as obsolete File transfer also possible via HTTP POST/GET - RCS vnd.gsma.rcs-ft-http+xml Message format and auxiliary messages Common Presence and Instant Messaging (CPIM): Message Format RFC3862 defines content and associated metadata format Instant Message Disposition Notification RFC5438 Indication of Message Composition for Instant Messaging RFC3994

8 MSRP vs SIP MESSAGE for transport of IM data? MSRP advantages: Ø Simple Ø Built-in store and forward capability Ø Allows direct file transfer Ø Separates signaling path from message delivery path BUT: Ø Yet another protocol to implement Ø Yet another connection the client has to initiate Ø Integration with push services to be done Ø Our Flexisip proxy already does store & forward and push notification for SIP MESSAGE We chose the SIP MESSAGE solution as a first step However, the path for transitioning in the future from SIP MESSAGE to MSRP is non-disruptive.

9 Overall architecture Registrar database (redis) Mariadb (groups and events storage) ios/android push service Flexisip proxy server SIP Flexisip conference server private (secured) network SIP/TLS Bob Alice John User authentication DoS attacks protection Registrar Push services SIP routing (calls, messages)

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Department of Computer Science. Burapha University 6 SIP (I)

Burapha University ก Department of Computer Science 6 SIP (I) Functionalities of SIP Network elements that might be used in the SIP network Structure of Request and Response SIP messages Other important