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+\subsection{Extensions to the DNS protocol}
+
+\subsubsection{Multicast DNS}
+\term{Multicast DNS}~\cite{rfc6762} (mDNS) describes an extension of the Domain Name
+System that allows DNS resource records to be distributed on multiple hosts in a
+network, therefore avoiding the need of a central server.
+
+Software that supports resolution of mDNS records listens on the reserved
+link-local multicast address \code{224.0.0.251} (for IPv4 queries) or
+\code{FF02::FB} (for IPv6 queries) on UDP port 5353 for incoming queries.
+Queries sent to those multicast address and port are standard DNS queries, and
+if a host receiving a query knows about the queried resource, it responds to the
+querying host with a standard DNS response. The querying host can then simply
+finish and use the result, or wait until other hosts respond to its query. The
+latter is typically the case when querying for \code{SRV} records to obtain a
+list of services which are present in the network.
+
+Another feature of Multicast DNS is the reduction of traffic through
+\term{Known-Answer Suppression}. It allows a querying host to specify already
+known resources in its query when querying resources that could exist on more
+than one host (e.~g., SRV records). The hosts matching those resources then do
+not generate a response.
+
+Finally, hosts may also send unsolicited responses. This can be used to notify
+the network of new services available on the host.
+
+\pages{1}
+
+\subsubsection{DNS-Based Service Discovery}
+\todo
+\term{DNS-based Service Discovery} \cite{rfc6763}
+\begin{itemize}
+	\item allows flexible mapping of available services to ports
+	\item utilization of SRV \cite{rfc2782}, TXT and PTR records 
+	\item case study for IoT in \cite{Klauck:2012:BCC:2352852.2352881}
+\end{itemize}
+
+\pages{1}
+% vim: set ft=tex et ts=2 sw=2 :