1 files changed, 54 insertions, 4 deletions
diff --git a/lib/diameter/doc/src/diameter_intro.xml b/lib/diameter/doc/src/diameter_intro.xml
index 0009b2b77d..ef08002a8b 100644
--- a/lib/diameter/doc/src/diameter_intro.xml
+++ b/lib/diameter/doc/src/diameter_intro.xml
@@ -36,10 +36,60 @@ under the License.
 <p>
 The diameter application is an implementation of the Diameter protocol
 as defined by RFC 3588.
-It supports arbitrary Diameter applications by allowing a client to
-specify the commands and AVP's to be supported and has support for
-implementing all roles defined in the RFC: client, server and agent.
-</p>
+It supports arbitrary Diameter applications by way of a
+<em>dictionary</em> interface that allows messages and AVP's to be
+defined and input into diameter as configuration.
+It has support for all roles defined in the RFC: client, server and
+agent.
+This chapter provides a short overview of the application.</p>
+
+<p>
+A Diameter peer is implemented by configuring a <em>service</em> and
+one or more <em>transports</em> using the interface module
+<seealso marker="diameter">diameter</seealso>.
+The service configuration defines the Diameter applications to be
+supported by the peer and, typically, the capabilities that it should
+send to remote peers at capabilities exchange upon the establishment
+of transport connections.
+A transport is configured on a service and provides protocol-specific
+send/receive functionality by way of a transport interface defined by
+diameter and implemented by a transport module.
+The diameter application provides two transport modules: <seealso
+marker="diameter_tcp">diameter_tcp</seealso> and <seealso
+marker="diameter_sctp">diameter_sctp</seealso> for transport over TCP
+(using <c>gen_tcp</c>) and SCTP (using <c>gen_sctp</c>) respectively.
+Other transports can be provided by any module that implements
+diameter's <seealso marker="diameter_transport">transport
+interface</seealso>.</p>
+
+<p>
+While a service typically implements a single Diameter peer (as
+identified by an Origin-Host AVP), transports can themselves be
+associated with capabilities AVP's so that a single service be used to
+implement more than one Diameter peer.</p>
+
+<p>
+Each Diameter application defined on a service is configured with a
+callback module that implements the <seealso
+marker="diameter_app">application interface</seealso> through which
+diameter communicates the connectivity of remote peers, requests peer
+selection for outgoing requests, and communicates the reception of
+incoming Diameter request and answer messages.
+An application using diameter implements these application callback
+modules to provide the functionality of the Diameter peer(s) it
+implements.</p>
+
+<p>
+Each Diameter application is also configured with one or more
+dictionary modules
+that provide encode/decode functionality for outgoing/incoming
+Diameter messages.
+A module is generated from a <seealso
+marker="diameter_dict">specification file</seealso> using the <seealso
+marker="diameterc">diameterc</seealso> utility.
+Dictionaries for the RFC 3588 Diameter Common Messages, Base
+Accounting and Relay applications are provided by the diameter
+application.</p>
 
 </chapter>