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.\"
.IX Title "LTPMETER 1"
.TH LTPMETER 1 "2016-07-07" "perl v5.24.1" "LTP executables"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
ltpmeter \- LTP daemon task for aggregating and segmenting transmission blocks
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
\&\fBltpmeter\fR \fIremote_engine_nbr\fR
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
\&\fBltpmeter\fR is a background \*(L"daemon\*(R" task that manages the presentation of
\&\s-1LTP\s0 segments to link service output tasks.  Each \*(L"span\*(R" of \s-1LTP\s0 data interchange
between the local \s-1LTP\s0 engine and a neighboring \s-1LTP\s0 engine requires its own
\&\fBltpmeter\fR task.  All \fBltpmeter\fR tasks are spawned automatically by
\&\fBltpadmin\fR in response to the 's' command that starts operation of the
\&\s-1LTP\s0 protocol, and they are all terminated by \fBltpadmin\fR in response to an
\&'x' (\s-1STOP\s0) command.
.PP
\&\fBltpmeter\fR waits until its span's current transmission block (the data
to be transmitted during the transmission session that is currently being
constructed) is ready for transmission, then divides the data in the
span's block buffer into segments and enqueues the segments for transmission
by the span's link service output task (giving the segments semaphore to
unblock the link service output task as necessary), then reinitializes the
span's block buffer and starts another session (giving the \*(L"buffer empty\*(R"
semaphore to unblock the client service task \*(-- nominally \fBltpclo\fR, the
\&\s-1LTP\s0 convergence layer output task for Bundle Protocol \*(-- as necessary).
.PP
\&\fBltpmeter\fR determines that the current transmission block is ready for
transmission by waiting until either (a) the aggregate size of all service
data units in the block's buffer exceeds the aggregation size limit for
this span or (b) the length of time that the first service data unit in
the block's buffer has been awaiting transmission exceeds the aggregation
time limit for this span.  The \*(L"buffer full\*(R" semaphore is given when \s-1ION
\&\s0(either the \fIltp_send()\fR function or the \fBltpclock\fR daemon) determines
that one of these conditions is true; \fBltpmeter\fR simply waits for this
semaphore to be given.
.PP
The initiation of a new session may also be blocked: the total number of
transmission sessions that the local \s-1LTP\s0 engine may have open at a single
time is limited (this is \s-1LTP\s0 flow control), and while the engine is at this
limit no new sessions can be started.  Availability of a session from the
session pool is signaled by the \*(L"session\*(R" semaphore, which is given whenever
a session is completed or canceled.
.SH "EXIT STATUS"
.IX Header "EXIT STATUS"
.ie n .IP """0""" 4
.el .IP "``0''" 4
.IX Item "0"
\&\fBltpmeter\fR terminated normally, for reasons noted in the \fBion.log\fR file.  If
this termination was not commanded, investigate and solve the problem identified
in the log file and use \fBltpadmin\fR to restart \fBltpmeter\fR.
.ie n .IP """1""" 4
.el .IP "``1''" 4
.IX Item "1"
\&\fBltpmeter\fR terminated abnormally, for reasons noted in the \fBion.log\fR file.
Investigate and solve the problem identified in the log file, then use
\&\fBltpadmin\fR to restart \fBltpmeter\fR.
.SH "FILES"
.IX Header "FILES"
No configuration files are needed.
.SH "ENVIRONMENT"
.IX Header "ENVIRONMENT"
No environment variables apply.
.SH "DIAGNOSTICS"
.IX Header "DIAGNOSTICS"
The following diagnostics may be issued to the \fBion.log\fR log file:
.IP "ltpmeter can't initialize \s-1LTP.\s0" 4
.IX Item "ltpmeter can't initialize LTP."
\&\fBltpadmin\fR has not yet initialized \s-1LTP\s0 protocol operations.
.IP "No such engine in database." 4
.IX Item "No such engine in database."
\&\fIremote_engine_nbr\fR is invalid, or the applicable span has not yet
been added to the \s-1LTP\s0 database by \fBltpadmin\fR.
.IP "ltpmeter task is already started for this engine." 4
.IX Item "ltpmeter task is already started for this engine."
Redundant initiation of \fBltpmeter\fR.
.IP "ltpmeter can't start new session." 4
.IX Item "ltpmeter can't start new session."
An unrecoverable database error was encountered.  \fBltpmeter\fR terminates.
.IP "Can't take bufClosedSemaphore." 4
.IX Item "Can't take bufClosedSemaphore."
An unrecoverable database error was encountered.  \fBltpmeter\fR terminates.
.IP "Can't create extents list." 4
.IX Item "Can't create extents list."
An unrecoverable database error was encountered.  \fBltpmeter\fR terminates.
.IP "Can't post ExportSessionStart notice." 4
.IX Item "Can't post ExportSessionStart notice."
An unrecoverable database error was encountered.  \fBltpmeter\fR terminates.
.IP "Can't finish session." 4
.IX Item "Can't finish session."
An unrecoverable database error was encountered.  \fBltpmeter\fR terminates.
.SH "BUGS"
.IX Header "BUGS"
Report bugs to <ion\-bugs@korgano.eecs.ohiou.edu>
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIltpadmin\fR\|(1), \fIltpclock\fR\|(1)