Jabber

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Jabber is an open system primarily built to provide instant messaging service and presence information (aka buddy lists). The protocol is built to be extensible and other features such as Voice over IP and file transfers have been added.

Unlike most instant messaging protocols, Jabber is based on open standards. Like e-mail, it is an open system where anyone who has a domain name and a suitable internet connection can run their own Jabber server and talk to users on other servers. The standard server implementations and many clients are also free/open source software.

Jabber-based software is deployed on thousands of servers across the Internet and by 2003 was used by over ten million people worldwide, according to the XMPP Standards Foundation.^[1]

Popular commercial servers are run by Google Talk and the Gizmo Project. Popular client software include the freeware clients offered by Google and the Gizmo Project, multi-protocol instant messengers such as iChat and Pidgin (formerly Gaim), and free dedicated clients such as Psi.

Contents 1 History 2 Features 3 Decentralisation and addressing 4 Message delivery process 5 Connecting to other protocols 6 Jabber and HTTP 7 Uptake and clients 8 References 9 See also 10 External links

[edit] History

Jeremie Miller began the project in 1998. Its first major public release occurred in May 2000. The project's main product was jabberd, a Jabber server.

This early Jabber protocol formed the basis for the IETF standards-track protocol named XMPP, published as RFC 3920. It has often been regarded as being in competition with SIMPLE, based on the SIP protocol, as the standard protocol for instant messaging and presence notification;^{[citation needed]} however, the design of XMPP is intended to provide a more general-purpose XML-based inter-application middleware facility.^{[citation needed]}

As of 2005, about half a dozen XMPP server software implementations written in different programming languages and targeting different use cases existed.^{[citation needed]}

In August 2005, Google introduced Google Talk, a combination VoIP and IM system which uses Jabber/XMPP for its instant messaging function. The initial launch did not include server-to-server communications, but as of January 17, 2006, it has server-to-server communications enabled.

[edit] Features

Decentralization 

The architecture of the Jabber network is similar to email; anyone can run their own Jabber server and there is no central master server.

Open standards 

The Internet Engineering Task Force has formalized Jabber's core XML streaming protocols as an approved instant messaging and presence technology under the name of XMPP, and the XMPP specifications have been published as RFC 3920 and RFC 3921. No royalties are required to implement support of these specifications and their development is not tied to a single vendor.

History 

Jabber technologies have been in use since 1998. Multiple implementations of Jabber's standards exist for clients, servers, components, and code libraries, with the backing of large companies such as Sun Microsystems and Google.

Security 

Jabber servers may be isolated from the public Jabber network (e.g., on a company intranet), and robust security (via SASL and TLS) has been built into the core XMPP specifications. To encourage use of channel encryption, the XMPP Standards Foundation also runs an intermediate certification authority at xmpp.net offering free digital certificates to Jabber/XMPP server administrators under the auspices of the StartCom Certification Authority (which is the root CA for the intermediate CA).

Flexibility 

Custom functionality can be built on top of Jabber's core protocols; to maintain interoperability, common extensions are managed by the XMPP Software Foundation. Jabber applications beyond IM include network management, content syndication, collaboration tools, file sharing, gaming, and remote systems monitoring.

[edit] Decentralisation and addressing

The Jabber network is server-based (i.e. clients do not talk directly to one another) but decentralized; by design there is no central authoritative server, as there is with services such as AOL Instant Messenger or MSN Messenger. Some confusion often arises on this point as there is a public Jabber server being run at "Jabber.org", to which a large number of users subscribe. However, anyone may run their own Jabber server on their own domain.

Every user on the network has a unique Jabber ID (usually abbreviated as JID). To avoid the need for a central server with a list of IDs, the JID is structured like an e-mail address with a username and a DNS address for the server where that user resides separated by an at sign (@), such as username@domain.com.

Since a user may wish to log in from multiple locations, the server allows the client to specify a further string known as a resource, which identifies which of the user's clients it is (for example home, work and mobile). This may then be included in the JID by adding a forward slash followed by the name of the resource. For example the full JID of a user's mobile account would be username@domain.com/mobile. Messages that are simply sent to username@domain.com will go to all the user's clients, but those sent to username@domain.com/mobile will only go to the mobile client.

JIDs without a username part are also valid and may be used (with or without a resource part) for system messages and control of special features on the server.

[edit] Message delivery process

Suppose juliet@capulet.com wants to chat with romeo@montague.net. Juliet and Romeo each respectively have accounts on the capulet.com and montague.net servers. When Juliet types in and sends her message, a sequence of events is set in action:

1. Juliet's Jabber client sends her message to the capulet.com Jabber server
   • If montague.net is blocked on capulet.com the message is dropped.
2. The capulet.com Jabber server opens a connection to the montague.net Jabber server.
3. The montague.net Jabber server delivers the message to Romeo
   • If capulet.com is blocked on montague.net, the message is dropped.
   • If Romeo is not currently connected, the message is stored for later delivery.

Juliet

↔

capulet.com

→

montague.net

↔

Romeo

[edit] Connecting to other protocols

Another useful feature of the Jabber system is that of transports, also known as gateways, which allow users to access networks using other protocols. This can be other instant messaging protocols, but also protocols such as SMS or E-mail. Unlike multi-protocol clients, Jabber provides this access at the server level by communicating via special gateway services running on a remote computer. Any Jabber user can "register" with one of these gateways by providing the information needed to log on to that network, and can then communicate with users of that network as though they were Jabber users. This means that any client which fully supports the Jabber protocol can be used to access any network to which a gateway exists, without the need for any extra code in the client and without the need for the client to have direct access to the internet. This may violate terms of service on the protocol used; however, such terms of service are not legally enforceable in several countries.

[edit] Jabber and HTTP

Another interesting aspect of the Jabber protocol and server is the HTTP binding for users behind restricted firewalls. Jabber can use HTTP in two ways: polling^[2] and binding.^[3] HTTP polling essentially implies messages stored on a server-side database being fetched (and posted) regularly by a Jabber client by way of HTTP 'GET' and 'POST' requests. With binding, the client uses longer-lived HTTP connections to receive messages as soon as they are sent. This push-model of notification is more efficient than polling, where many of the polls return no new data.

Because the client uses HTTP, most firewalls would allow the client to fetch and post messages without any hindrance. Thus, in scenarios where the TCP port used by Jabber is blocked, a server can listen on the normal HTTP port and the traffic should pass without problems. There also are various websites which allow people to sign in to Jabber via their browser.

[edit] Uptake and clients

[edit] References

[edit] See also

• Comparison of instant messaging clients
• Comparison of instant messaging protocols
• XMPP specifications
• List of Jabber client software
• List of Jabber component software
• List of Jabber server software
• Secure communication

[edit] External links

• Jabber User Guide - End user introduction to Jabber.
• XMPP Standards Foundation
• List of Jabber servers by country or domain