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TCP/IP Tutorial and Technical Overview - IBM Redbooks

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19.3 Presence protocols<br />

The Extensible Messaging <strong>and</strong> Presence Protocol (XMPP) is an open Extensible<br />

Markup Language (XML) protocol for near-real-time messaging, presence, <strong>and</strong><br />

request-response services <strong>and</strong> is discussed in RFC 3920 with extensions in<br />

RFC 3921.The basic syntax <strong>and</strong> semantics were developed originally in the<br />

Jabber open source community, mainly in 1999. In 2002, the XMPP WG was<br />

chartered with developing an adaptation of the Jabber protocol that would be<br />

suitable as an IETF instant messaging (IM) <strong>and</strong> presence technology. XMPP<br />

provides the basic instant messaging <strong>and</strong> presence functionality defined in RFC<br />

2779. The following discussion is based on these RFCs.<br />

Although XMPP is not wedded to any specific network architecture, to date it<br />

usually has been implemented through a client/server architecture wherein a<br />

client using XMPP accesses a server over a <strong>TCP</strong> connection, <strong>and</strong> servers also<br />

communicate with each other over <strong>TCP</strong> connections. The XMPP architecture is<br />

illustrated in Figure 19-7, where a single line (_) depicts communication through<br />

XMPP <strong>and</strong> a double line (=) depicts communication through a non-XMPP<br />

protocol.<br />

Figure 19-7 XMPP architecture<br />

We describe each of the objects in the following sections.<br />

716 <strong>TCP</strong>/<strong>IP</strong> <strong>Tutorial</strong> <strong>and</strong> <strong>Technical</strong> <strong>Overview</strong><br />

XMPP<br />

Server A<br />

Gateway<br />

Foreign Messaging<br />

Network<br />

XMPP<br />

Server B

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