SpaceTeam · raffael0 · Mar 24, 2026 · Mar 21, 2026 · Mar 21, 2026
diff --git a/LiquidCAN.pdf b/LiquidCAN.pdf
diff --git a/LiquidCAN.tex b/LiquidCAN.tex
@@ -89,7 +89,7 @@
 
 \vspace{1cm}
 
-{\large Version 1.4}
+{\large Version 1.5}
 
 \vspace{0.5cm}
 
@@ -116,6 +116,7 @@ \section*{Version History}
 1.2 & 2026-02-09 & Fixed inconsistant field value lengths \& typos & Raffael Rott\\
 1.3 & 2026-02-28 & Added a status field to field access responses& Raffael Rott\\
 1.4 & 2026-03-05 & Variable-length frame serialization; updated payload sizes & Michael Debertol\\
+1.5 & 2026-03-21 & Defined reserved Node IDs & Michael Debertol\\
 % Make sure to change the version on the first page
 \bottomrule
 \end{longtable}

diff --git a/liquidcan_rust/src/lib.rs b/liquidcan_rust/src/lib.rs
@@ -5,4 +5,4 @@ pub mod payloads;
 pub mod raw_can_message;
 
 pub use can_message::CanMessage;
-pub use raw_can_message::CanMessageId;
+pub use raw_can_message::{CanMessageId, NODE_ID_BROADCAST, NODE_ID_INVALID, NODE_ID_SERVER};
diff --git a/liquidcan_rust/src/raw_can_message.rs b/liquidcan_rust/src/raw_can_message.rs
@@ -7,6 +7,11 @@ pub enum CanMessagePriority {
     High = 1,
 }
 
+/// Reserved Node IDs with special meaning.
+pub const NODE_ID_INVALID: u8 = 0;
+pub const NODE_ID_SERVER: u8 = 1;
+pub const NODE_ID_BROADCAST: u8 = 31;
+
 #[bitfield]
 #[derive(Debug, Copy, Clone, PartialEq)]
 #[repr(u16)]

diff --git a/sections/02_can_id_scheme.tex b/sections/02_can_id_scheme.tex
@@ -1,5 +1,5 @@
 \section{CAN Identifier Scheme \& NodeID}\label{sec:can-id-scheme}
-Each device on the bus has its own unique Node ID. The Server is assigned the Node ID 0.
+Each device on the bus has its own unique Node ID. Node IDs are 5 bits wide, giving a range of 0--31.
 The CAN ID is composed of 11 bits. It contains the sender and receiver Node IDs and a priority bit.
 
 \paragraph{}
@@ -22,4 +22,18 @@ \section{CAN Identifier Scheme \& NodeID}\label{sec:can-id-scheme}
 
 \end{center}
 
-% TODO: Describe ID allocation strategy and priority rules
+\subsection{Reserved Node IDs}\label{sec:reserved-node-ids}
+Certain Node ID values carry special meaning and must not be assigned to regular client nodes:
+
+\begin{center}
+\begin{tabular}{c l p{8cm}}
+\toprule
+\textbf{Node ID} & \textbf{Name} & \textbf{Description} \\
+\midrule
+0  & Invalid   & Reserved as an invalid/unassigned address. No node may use this ID. \\
+1  & Server    & The central server node. \\
+31 & Broadcast & Broadcast address. Messages sent with this receiver ID are received by all nodes on the bus. \\
+\bottomrule
+\end{tabular}
+\end{center}
+
diff --git a/sections/04_node_registration.tex b/sections/04_node_registration.tex
@@ -1,5 +1,5 @@
 \section{Node Registration}\label{sec:node-registration}
-As soon as a node comes online (or when it receives a \texttt{node\_info\_req}), it enters the registration phase. See Figure \ref{fig:node-registration-flow} for a graphical representation the whole registration procedure. Here it sends out a \texttt{node\_info\_announcement}.
+As soon as a node comes online (or when it receives a \texttt{node\_info\_req}), it enters the registration phase. A \texttt{node\_info\_req} is broadcast (\ref{sec:reserved-node-ids}) by the server when \textit{it} comes online. See Figure \ref{fig:node-registration-flow} for a graphical representation the whole registration procedure. Here it sends out a \texttt{node\_info\_announcement}.
 This announces the node to the bus and includes its name, number of telemetryValues and parameters, and its firmware version through
 the firmware and LiquidCan hashes (see \ref{struct:NodeInfoRes}). The central server registers the new node and waits for \texttt{field\_registration} messages. From this point on the 
 node is able to send/receive messages on the bus.