owltsim - Online in the Cloud

PROGRAM:

NAME

owltsim - one-way light time transmission delay simulator

SYNOPSIS

owltsim config_filename [-v]

DESCRIPTION

owltsim delays delivery of data between pairs of ION nodes by specified lengths of time,
simulating the signal propagation delay imposed by distance between the nodes.

Its operation is configured by delay simulation configuration lines in the file identified
by config_filename. A pair of threads is created for each line in the file: one that
receives UDP datagrams on a specified port and queues them in a linked list, and a second
that later removes queued datagrams from the linked list and sends them on to a specified
UDP port on a specified network host.

Each configuration line must be of the following form:

to from my_port# dest_host dest_port# owlt modulus

to identifies the receiving node.
This parameter is purely informational, intended to make owltsim's printed messages
more helpful to the user.

from identifies the sending node.
A value of '*' may be used to indicate "all nodes". Again, this parameter is purely
informational, intended to make owltsim's printed messages more helpful to the user.

my_port# identifies owltsim's receiving port for this traffic.
dest_host is a hostname identifying the computer to which owltsim will transmit this
traffic.
dest_port# identifies the port to which owltsim will transmit this traffic.
owlt specifies the number of seconds to wait before forwarding each received datagram.
modulus controls the artificial random data loss imposed on this traffic by owltsim.
A value of '0' specifies "no random data loss". Any other modulus value N causes
owltsim to randomly drop (i.e., not transmit upon expiration of the delay interval)
one out of every N packets.

The optional -v ("verbose") parameter causes owltsim to print a message whenever it
receives, sends, or drops (due to artificial random data loss) a datagram.

Note that error conditions may cause one delay simulation (a pair of threads) to terminate
without terminating any others.

owltsim is designed to run indefinitely. To terminate the program, just use control-C to
kill it.

EXIT STATUS

"0" Nominal termination.
"1" Termination due to an error condition, as noted in printed messages.

EXAMPLES

Here is a sample owltsim configuration file:

2 7 5502 ptl07.jpl.nasa.gov 5001 75 0
7 2 5507 ptl02.jpl.nasa.gov 5001 75 16

This file indicates that owltsim will receive on port 5502 the ION traffic from node 2
that is destined for node 7, which will receive it at port 5001 on the computer named
ptl07.jpl.nasa.gov; 75 seconds of delay (simulating a distance of 75 light seconds) will
be imposed on this transmission activity, and owltsim will not simulate any random data
loss.

In the reverse direction, owltsim will receive on port 5507 the ION traffic from node 7
that is destined for node 2, which will receive it at port 5001 on the computer named
ptl02.jpl.nasa.gov; 75 seconds of delay will again be imposed on this transmission
activity, and owltsim will randomly discard (i.e., not transmit upon expiration of the
transmission delay interval) one datagram out of every 16 received at this port.

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