Extensible Messaging and Presence Protocol
5. December 2012
¡ Studied 2003 – 2007 telecommunications
and computer sciences in Leipzig,
¡ In Slovakia since 2006
¡ Working for Slovak Telekom since 2007
¡ Post-grad studies at Slovak University of
Technology since 2007
¡ Worked extensively with SIP/XMPP based
presence and their possible integration
¡ This slide set is extended with content from the
presentation of Remko Tronçon et. al.: “XMPP 101”
¡ Thank you for making your talk publicly available!
¡ The book “XMPP – The Definitive Guide” is excellent
material by the authors of the XMPP standards.
¡ Yes, I bought it myself.
¡ These slides only summarize the lecture.
¡ Take notes.
¡ Some slides are placeholders for work-
ing on the white board, take care!
¡ Interrupt me any time!
Origins (RFC 2778, RFC 2779)
¡ IETF defines general model for presence and instant
¡ This model defines
¡ Presence service
¡ Instant messaging service
¡ Generic presence data model
¡ Requirements for instant messaging and presence
(IMPP) systems are also described
Presence service model, presence system
Instant Message Service
¡ Based on IETF generic IMPP RFCs, several protocols
are defined for delivering services
¡ Implementations are done by basic protocol and
particular IMPP extension
¡ Base protocol
¡ SIP (RFC 3261)
¡ XMPP Core (RFC 3920)
¡ IMPP extension
¡ SIMPLE (RFC 3265)
¡ XMPP IM (RFC 3921)
¡ To start with the relevance of the protocol, has
anyone chatted with the following services?
¡ All are based on or use XMPP to some extend*
* Some use a modification of the protocol.
XMPP, the protocol
¡ Original name: Jabber (1998, by Jeremie Miller)
¡ Purely XML based protocol (for streaming XML)
¡ Comparison: SIP is based on HTTP
¡ Information is shared using a continuous XML stream
transported over TCP
¡ SASL (Simple Authentication and Security Layer) and
TLS (Transport Layer Security) used to secure stream
¡ Based on a few RFCs and extended by many XEPs
¡ XMPP Extension Protocol
¡ Comparison: SIP extended only through RFCs
XMPP, the protocol ctd.
¡ XEPs make the protocol extensible
¡ XMPP is a decentralized, federated, asynchronous
¡ Sample messages
to=’ email@example.com' type='chat'>
<status>Giving a lecture!</status>
C2S, S2S, GW, FN/FC
Comparison to HTTP, E-mail, SIP
¡ Bare JID similar to E-mail address, identifying
responsible user and domain
¡ Full JID includes particular resource
¡ Jabber ID (JID)
¡ DNS is used for service discovery
Client Port 5222/Server Port 5269
¡ Link IP addresses with domain names
¡ Support in locating XMPP servers
¡ SRV lookup
¡ A/AAAA lookup
¡ SRV look-up indicates the domain and port the service
¡ _xmpp-server._tcp.gmail.com. 900 IN SRV 5 0 5269 xmpp-server.l.google.com.
¡ _xmpp-client._tcp.gmail.com. 900 IN SRV 5 0 5222 xmpp.l.google.com
¡ A/AAAA to find the IP address of the domain name
¡ xmpp-server.l.google.com. 300 IN A 22.214.171.124
Client vs. Server Communications
¡ XMPP uses different ports for client to server (c2s) and
server to server (s2s) communications
¡ c2s: Port 5222
¡ s2s: Port 5269
¡ Same principle for s2s as for c2s
¡ XML streams
¡ No intermediate servers for federation (unlike E-mail)
¡ Similar security mechanisms (SASL, TLS)
¡ vCards (XEP-0054, RFC 2426)
¡ Server maintains vCard of users
¡ Service Discovery (disco)
¡ Entity: disco#items
¡ Features: disco#info
¡ Server features, client capabilities, etc.
¡ Server configuration
Other aspects ctd.
¡ Server components
¡ MUC (Multi-user chat)
¡ Foreign network gateways
¡ File Transfer
¡ BOSH (Bidirectional streams over synchronous HTTP)
¡ XMPP over HTTP
¡ c2s, components
¡ Set up multi-media sessions similarly to SIP
¡ Only session setup, no media transport
¡ Negotiate content
¡ Negotiate protocol (UDP, TCP)
¡ Streaming protocol (e.g. RTP) used to transport media
¡ Similar complexity as in SIP
¡ Different protocol/ports
¡ NAT traversal
Jingle session setup
Overlap: SIP messages
¡ Powered by from Process One
¡ Thank you!
¡ Alice, Bob, Charlie, Dave
Have a look at some stanzas
Test presence, message, Jingle
Test some server components (PubSub)
XMPP vs. SIP/SIMPLE
¡ Which one is better?
¡ How have both historically developed to where they
¡ Practical application
What can one build with XMPP?
¡ Many things J - needs differentiation
¡ Obvious examples
¡ Real-time communications system
¡ Messaging bus (PubSub)
¡ Yet another…
¡ Gaming platform?
¡ Identity service? Your Ideas?!
¡ What is used these days?
¡ On the Internet
¡ By operators
¡ Can SIP and XMPP be linked/connected?
¡ Joint paper published @ ONIT 2010
¡ An alternative approach to “SIP/SIMPLE vs. XMPP”
and “Telco presence”
¡ Start point: current deployments
¡ Telephony: SIP
¡ IM/Presence: XMPP
¡ Use standard protocols (to re-use clients)
¡ Customers can keep current accounts in both worlds
SIP/XMPP consolidation ctd.
¡ Telephone state extraction can be easily added to
¡ Enhanced SIP proxy that can extract call state
¡ SIP call states must be converted to XMPP presence
¡ XMPP as main IM/P protocol
¡ A lot of open and/or free resources to follow up
¡ Programming libraries
¡ Clients, server – many open-source
¡ XMPP quite “under the radar” for now
¡ SIP gained a lot of attention w/ IMS, RCS-e, etc. in Telco
¡ Web 2.0 accelerated use of HTTP, esp. REST
¡ XMPP used, but not as “advocated”
¡ The Internet contains extensive material on XMPP
¡ This lecture was only an introduction!
¡ I hope it stimulated some ideas for future projects and
helped in understanding communications a bit better.
¡ This lecture is available at http://bit.ly/fiit-xmpp
1. RFCs 2778, 2779, 3920, 3921. Various XEPs
2. XMPP: The Definitive Guide. Peter Saint-Andre et.al.
3. XMPP 101. Remko Tronçon
4. Several own publications
5. Graphics from Google Images, Open Clipart
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