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+\section{Introduction}
+\label{sec:intro}
+
+The Named-data Link State Routing protocol (NLSR) is an intra-domain routing protocol for Named Data Networking (NDN).
+It is an application level protocol similar to many IP routing protocols, but NLSR uses NDN's Interest/Data packets to disseminate routing updates.
+Although NLSR is designed in the context of a single domain, its design patterns may offer a useful reference for future development of inter-domain routing protocols.
+
+NLSR supports name-based routing in NDN, computes routing ranks for all policy-compliant next-hops which provides a name-based multi-path routing table for NDN's forwarding strategy,
+and ensures that routers can originate only their own routing updates using a hierarchical trust model.
+
+\subsection{NLSR Modules and Data Structures}
+\label{sec:modules}
+NLSR contains multiple modules that each contribute to the total realization of the protocol.
+Many of the modules interact with one another to trigger some behavior or to modify information in data structures.
+NLSR uses the following modules:
+\begin{itemize}
+\item \textbf{Hello Protocol} (Section~\ref{sec:hello-protocol}) - determines the status of neighboring routers using periodic Hello Interests and notifies other modules when neighbors' statuses change.
+\item \textbf{NSync} - provides LSDB synchronization by extending the ChronoSync protocol~\cite{chronosync}.
+\item \textbf{Sync Logic Handler} (Section~\ref{sec:sync-logic}) - handles sync update notifications from NSync by retrieving updated LSAs.
+\item \textbf{LSAs} (Section~\ref{sec:lsas}) - represent routing information published by the router.
+\item \textbf{LSDB} (Section~\ref{sec:lsdb}) - stores the LSA information distributed by other routers in the network.
+\item \textbf{Routing Table} (Section~\ref{sec:routing-table}) - calculates and maintains a list of next hops for each router in the network.
+\item \textbf{Name Prefix Table} (Section~\ref{sec:npt}) - stores all advertised name prefixes and their next hops.
+\item \textbf{FIB} (Section~\ref{sec:fib}) - maintains a shadow FIB which represents the intended state of NFD's FIB~\cite{NFD}.
+\item \textbf{Prefix Update Processor} - listens for dynamic prefix announcements to advertise or withdraw name prefixes.
+\end{itemize}
+
+\subsection{Protocol Overview}
+\label{sec:protocol-overview}
+
+NLSR is designed to accomplish three main tasks: (1) discover adjacent neighbors; (2) disseminate and synchronize topology, name prefix, and hyperbolic routing information; and (3) calculate a consistent routing table and populate NFD's FIB.
+The entire protocol is described in detail in the NLSR paper~\cite{NlsrTr}.
+
+\subsubsection{Discovering Neighbors}
+
+NLSR determines the adjacency status of neighboring routers using the Hello Protocol module (Section~\ref{sec:hello-protocol}).
+When the Hello Protocol detects a status change for a neighbor, it will ask the LSDB module (Section~\ref{sec:lsdb}) to update the router's advertised adjacency information.
+
+\subsubsection{Disseminating Routing Information}
+
+When one of a router's LSAs (Section~\ref{sec:lsas}) changes, the information of this change should be distributed to every other router in the network.
+The Sync Logic Handler module (Section~\ref{sec:sync-logic}) is used to notify the synchronization protocol of changes to the router's own LSAs as well as to learn of LSA changes from other routers in the network;
+the Sync Logic Handler module interfaces with NSync to perform the two tasks.
+
+When the Sync Logic Handler module learns of a new LSA, it will inform the LSDB module.
+The LSDB module will attempt to fetch the new LSA and will store it in the LSDB module's database if it can be retrieved.
+If the newly fetched LSA informs the router of previously unknown routing information, the LSDB module will inform other modules depending on the type of routing information:
+\begin{itemize}
+\item \textbf{Change in network topology} - the LSDB module will inform the Routing Table module (Section~\ref{sec:routing-table}), so the Routing Table module can calculate an up-to-date routing table.
+\item \textbf{Change in name prefix advertisement} - the LSDB module will inform the Name Prefix Table module (Section~\ref{sec:npt}), which will in turn notify the FIB module (Section~\ref{sec:fib}) in order to add or remove the changed name prefixes.
+\item \textbf{Change in hyperbolic coordinates} - the LSDB module will inform the Routing Table module (Section~\ref{sec:routing-table}), so the Routing Table module can calculate an up-to-date routing table.
+\end{itemize}
+
+\subsubsection{Calculating the Routing Table and Populating NFD's FIB}
+
+When the routing table is calculated by the Routing Table module, the computed next hops are passed to the Name Prefix Table module.
+The Name Prefix Table module will then further pass the next hops to the FIB module to update NLSR's expected state of NFD's FIB.
+The FIB module will then perform the registrations or unregistrations with NFD's FIB.\\
+
+A simplified diagram of NLSR's actions when receiving new routing information is shown in Figure~\ref{fig:system-interaction}.
+The remainder of this documentation will describe the purpose of and interaction between each module in more detail.
+
+\begin{figure}
+\center
+\includegraphics[width=\linewidth]{figures/system-interaction}
+\caption{Simplified Diagram of the Actions of NLSR's Modules}
+\label{fig:system-interaction}
+\end{figure}
+