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1991-11-21
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131 lines
A B M D E M O
-------------
INTRODUCTION
ABMDEMO is a program written to demonstrate the operation of the
Asynchronous Balanced Mode (ABM) version of the HDLC communications
protocol. ABM is the mode of HDLC that is used in many areas
of communications. It is the basis for LAP-B in X.25, IS8802 in
LANs, LAP-D in ISDN, etc.
ABMDEMO simulates the two ends of the HDLC link and produces a
display showing the transmission taking place, the identities of
the frames, and the key state variables at each end of the link.
It has been used at Monash University to aid in the teaching of
communications protocols.
The program runs under MSDOS 3.3 or later, and does not use a graphics card.
DISTRIBUTION
This distribution contains the executable, plus some sample control
files and some batch files to demonstrate their use.
OPERATION
To run ABMDEMO, the invocation is:
abmdemo [-ccontrolfile] [-llogfile]
where controlfile is a file of parameters for the simulation, and
logfile is the name of a file in which a copy of the screen
output is stored for later perusal. If either is missing, the
user is prompted for the file names, if any. If there is no
control file the run details are requested in a series of prompts.
The following are the run parameters:
For each of the 'A' and 'B' DTEs in turn:
(a) "f" if there are to be a fixed number of I frames in the
simulation, or "c" if it is to be a continuous random
generation of I frames
(b) if the above was "f", the number of I frames to send. If it
was "c", the % of time the link is to be busy.
(c) "f" if the frames are to be of a fixed length (in "clock ticks")
or "r" if the frames are to be of a random length.
(d) the frame length in clock ticks (4 <= L <= 15). In the "r" case
it is the average length.
(e) the probability of an I frame encountering an error
during transmission
Finally, specify the number of clock ticks in the run.
Here is a sample controlfile:
f 2 f 5 40
f 0 f 4 0
60
This file would result in a run of 60 clock ticks. DTE A would have
2 I frames, each of length 5 ticks, and there would be a 40% chance of
an I frame being received in error. DTE B has no frames.
The result of this simulation run would be:
A B M D E M O HDLC SIMULATOR
D T E A D T E B
R V V F N N C T F N N V V R
T S R R S R L I R S R S R T
C A O C A C
M C K M
E K E
1 1 0 I 0 0 P/F=0 ooo 0 0 0 0
1 1 0 OOO 1 0 0 0
1 1 0 OOO 2 0 0 0
1 1 0 OOO 3 0 0 0
1 1 0 OOO 4 0 0 0
2 2 0 I 1 0 P/F=0 ooo 5 ooo RR 1 P/F=0 0 1 0
2 2 0 XXX 6 OOO 0 1 0
2 2 0 XXX 7 OOO 0 1 0
2 2 0 XXX 8 OOO 0 1 0
1 2 0 XXX 9 0 1 0
1 2 0 10 0 1 0
[At this point frame 0 has been acknowledged, but frame 1 was corrupted
so DTE B ignores it. In this example, DTE A's "ack timer" runs out and
triggers a recover sequence. Look for the RR P/F = 1.]
1 2 0 11 0 1 0
1 2 0 12 0 1 0
1 2 0 13 0 1 0
[some clock ticks deleted to save space]
1 2 0 37 0 1 0
1 2 0 RR 0 P/F=1 ooo 38 0 1 0
1 2 0 OOO 39 0 1 0
1 2 0 OOO 40 0 1 0
1 2 0 OOO 41 0 1 0
1 2 0 42 ooo RR 1 P/F=1 0 1 0
1 2 0 43 OOO 0 1 0
1 2 0 44 OOO 0 1 0
1 2 0 45 OOO 0 1 0
1 2 0 I 1 0 P/F=0 ooo 46 0 1 0
1 2 0 OOO 47 0 1 0
1 2 0 OOO 48 0 1 0
1 2 0 OOO 49 0 1 0
1 2 0 OOO 50 0 1 0
1 2 0 51 ooo RR 2 P/F=0 0 2 0
1 2 0 52 OOO 0 2 0
1 2 0 53 OOO 0 2 0
1 2 0 54 OOO 0 2 0
0 2 0 55 0 2 0
AUTHOR
Jim Breen
Department of Robotics & Digital Technology
Monash University
Melbourne, Australia
jwb@capek.rdt.monash.edu.au