sync: xmpp communication primitives, dns-sd, outline for comparison. mock images...

[skm-ma-ws1314.git] / xmpp.tex

diff --git a/xmpp.tex b/xmpp.tex
index b4dc98a..44f16b0 100644 (file)
--- a/xmpp.tex
+++ b/xmpp.tex
@@ -22,6 +22,7 @@ the resource is only needed for routing between client and server.
 \subsubsection{Architecture}
 \begin{wrapfigure}{r}{0.4\textwidth}
 %\begin{figure}[htop]
+  \label{fig:xmpparch}
   \centering
   \includegraphics[width=0.4\textwidth]{xmpp-architecture-mock.jpg}
   \caption{XMPP architecture}
@@ -29,11 +30,11 @@ the resource is only needed for routing between client and server.
 \end{wrapfigure}
 
 The original architecture underlying XMPP strongly leans on the established
-design of Internet Mail. The distributed network is formed by \term{XMPP
-servers} on one hand, which make up the always available backbone of the network
-and manage user accounts and statuses, and \term{XMPP clients} on the other
-hand, which represent a single logged-in user and make up the interface for
-communication with other users.
+design of Internet Mail, and an example is depicted in Fig.~\ref{fig:xmpparch}.
+The distributed network is formed by \term{XMPP servers} on one hand, which make
+up the always-on backbone of the network used for routing message, and manage
+user accounts and statuses. On the other hand, \term{XMPP clients} represent a
+single logged-in user and are the interface for communication with other users.
 
 Every client communicates only with the server that manages the respective user
 account which is configured in the client, as given in the user's JID. The
@@ -43,34 +44,44 @@ sends the message to a client where the receiving JID is logged in. If the user
 is not logged in at the time the message is sent, the server can store it for
 the user and deliver it on the next login.
 
-\todo{use of DNS-SD?}
+XMPP strongly relies on DNS Service Discovery (see Section~\ref{sec:dnssd}) to
+determine the server being in charge of a domain. For example, the server who
+manages the users for the domain \code{example.org} is given by the SRV record
+\code{\_xmpp-server.\_tcp.example.org}.
 
 \subsubsection{Communication primitives}
 
+All communication over XMPP is based on XML. To minimize communication overhead,
+only fragments of XML, called \term{stanzas}, are sent between hosts. A stanza
+is always well-formed as a whole; it consist of a root element, which also
+includes routing attributes (\code{to} and \code{from}), and its optional child
+elements.
+
+On top of that, living connections between hosts are represented by \term{XML
+streams}. The client initiates a connection by sending an XML declaration
+followed by an opening \code{<stream>} tag. The server then responds also with
+an opening \code{<stream>} tag. The client then performs SASL authentication and
+binds its stream to a resource for proper addressing. If this process succeeded,
+both client and server can send an unlimited number of stanzas, until the
+connection is closed by one side by sending an closing \code{</stream>} tag. The
+other side then has the chance to send all outstanding stanzas and likewise
+closes its stream. If both streams are closed, the underlying TCP connection is
+terminated.
+
+\todo{Example stream}
+
 \subsubsection{Multi-User Chats}
 
 \cite{xep-0045}
 
 \subsubsection{Publish/Subscribe and the Roster}
 
-is this really needed?
-
 \cite{xep-0060}
 
 \subsubsection{Presence}
 
 
 \cite{rfc6120}
-\begin{itemize}
-       \item architecture: client-server, use of DNS-SD
-       \item addressing: JIDs, resources
-       \item XML-based communication primitives, stanzas and streams
-       \item presence
-       \item publish/subscribe \cite{xep-0060}, roster
-       \item multi-user chats \cite{xep-0045}
-\end{itemize}
-
-
 
 \subsubsection{XMPP Serverless Messaging}
 \todo