\subsection{VCHAN}
\index{vchan}

\topic{NAME}
VCHAN (Channel Virtual-Protocol)

\topic{SPECIFICATION}

\noindent 
S. O'Malley and L. Peterson.  A Dynamic Network Architecture.  {\it
ACM Transactions on Computer Systems 10}, 2 (May 1992), 110--143.

\medskip
\noindent  B. Welch. {\it The Sprite remote procedure call}. 
University of California at Berkeley, Tech Report UCB/CSD 86/302,
June 1986.

\topic{SYNOPSIS}

\noindent VCHAN is a virtual protocol that multiplexes multiple client
procedure invocations over some number of open channels. The call
blocks if there are no idle channels available.  VCHAN was originally
based on the Sprite RPC protocol.

VCHAN initially opens a default number of channels for a new session,
though this number can be increased or decreased via control
operations. 

\topic{REALM}

\noindent 
VCHAN is in the RPC realm.

\topic{PARTICIPANTS}

\noindent 
VCHAN expects an IPhost pointer on the stack of each participant.  It
will not remove this pointer before passing the address down to the
lower protocol. 


\topic{CONTROL OPERATIONS}

\begin{description}

\item[{\tt VCHAN\_INCCONCURRENCY:}]
Increase the number of active channels by the number given
({\tt xControlSessn} only).
\begin{description}
\item[{\rm Input:}] {\tt int}
\item[{\rm Output:}] none;
\end{description}

\item[{\tt VCHAN\_DECCONCURRENCY:}]
Decrease the number of active channels by the number given
({\tt xControlSessn} only).
\begin{description}
\item[{\rm Input:}] {\tt int}
\item[{\rm Output:}] none;
\end{description}

\end{description}

\topic{CONFIGURATION}

\noindent 
VCHAN expects to be configured above another RPC realm protocol.  It
expects that each xOpen on the lower protocol with the same
participants will return a new lower session.  

\topic{AUTHOR}

\noindent Ed Menze
