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% Copyright (c) 1996,1993,1991,1990  Arizona Board of Regents
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% Revision 1.2  1996/02/02 00:04:22  slm
% Updated copyright and version.
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% Revision 1.1  1995/07/28  21:22:13  slm
% Initial revision
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% Revision 1.1.1.3.1.1  1994/10/21  00:00:56  hkaram
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% Revision 1.1.1.3  1994/08/02  23:55:43  davidm
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% Revision 1.1.1.2  1994/07/05  00:42:34  ho
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% Revision 1.1.1.1  1994/04/25  19:39:48  menze
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\subsection{VDROP}
\index{vdrop}

\topic{NAME}
VDROP (Virtual Drop Protocol)

\topic{SPECIFICATION}

\noindent 
Throws away occasional incoming packets.  Used to exercise the
recovery mechanisms of other protocols.

\topic{SYNOPSIS}

\noindent 
VDROP sessions throw away incoming packets at regular intervals.  By
default, this interval is set in a somewhat random fashion at session
creation time, though it can be set explicitly on a per-protocol basis
via a ROM option (see CONFIGURATION below) or on a per-session basis
via a control operation.

VDROP has no effect on outgoing packets.

VDROP should probably
allow sessions to have more interesting distributions of drop
intervals than ``once every N packets.''

 
\topic{REALM}

\noindent 
VDROP is in the ASYNC realm.

\topic{PARTICIPANTS}

\noindent 
VDROP passes participants to the lower protocols without manipulating
them. 

\topic{CONTROL OPERATIONS}

\begin{description}

\item[{\tt VDROP\_SETINTERVAL:}]
Sets the drop interval for this session.  An interval of 1 drops every
packet, an interval of 2 drops every other packet, etc.  An interval
of zero indicates that VDROP is disabled for that session.  (session only)
\begin{description}
\item[{\rm Input:}] {\tt int interval}
\item[{\rm Output:}] none
\end{description}


\item[{\tt VDROP\_GETINTERVAL:}]
Returns the current drop interval for this session.
(session only)
\begin{description}
\item[{\rm Input:}] none
\item[{\rm Output:}] {\tt int interval}
\end{description}

\end{description}


\topic{CONFIGURATION}

\noindent 
VDROP recognizes the following ROM options:

\smallskip

{\tt vdrop/xxx interval N}: Instantiation {\em xxx} of VDROP
will use N as the drop interval for all of its sessions.


\topic{AUTHOR}

\noindent Ed Menze
