\begin{table}[ht!]
	\centering
    \caption{Required Communication Management messages, used for all service types except \acrfull{ud}.}
	\label{tab:required_cm_messages}
	\vspace{3mm}

     \begin{tabular}{p{2.6cm} | p{11.4cm}} 
	 \hlineB{3}
     \Tstrut
	 \textbf{CM message} & \textbf{Description}\\
	 \hhline{=|=}
	 \Tstrut
     \acrshort{req}      	& A \textit{\acrlong{req}} is used to initiate the communication establishment sequence. The node that sends this message provides the remote host with its queue pair number and its \gls{gid} and/or \gls{lid}.
	 \Bstrut\\
     \hline
	 \Tstrut
     \acrshort{mra}    		& A \textit{\acrlong{mra}} is used as a response to a \acrshort{req}, a LAP (Load Alternate Path, an optional communication message), or a \acrshort{rep}. It is used if the node which receives one of the formerly mentioned messages does not expect to be able to respond within the specified time-out. With this mechanism, unnecessary time-outs are prevented.
	 \Bstrut\\
     \hline
	 \Tstrut
         \acrshort{rej}      	& By replying with \textit{\acrlong{rej}} to a \acrshort{req}, a node indicates that it will not continue with the communication establishment sequence. The reason can be found, i.a., in the data field of the \acrshort{rej}.
	 \Bstrut\\
     \hline
	 \Tstrut
     \acrshort{rep}      	& A node sends a \textit{\acrlong{rep}} if it wants to accept a previously received \acrshort{rep} and all its parameters.
	 \Bstrut\\
     \hline
	 \Tstrut
     \acrshort{rtu}     	& A node replies with \textit{\acrlong{rtu}} after it received a \acrshort{rep} to indicate that transmission can be started.
	 \Bstrut\\
	 \hline
	 \Tstrut
     \acrshort{dreq}      & A \textit{\acrlong{dreq}} is sent if a node wants to disconnect a queue pair.
	 \Bstrut\\
     \hline
	 \Tstrut
     \acrshort{drep}      & A \textit{\acrlong{drep}} is used to acknowledge that a \acrshort{dreq} is received.
	 \Bstrut\\
	 \hlineB{3}
	\end{tabular}
\end{table}