The document describes a simulation of a telephone system to track processed, completed, blocked and busy calls. It shows the system state at various time steps as calls arrive and are connected or finished. When lines are all in use, arriving calls are delayed rather than lost. The simulation runs by scanning for the next event, selecting the activity that causes it, updating records to reflect the event's effects, and gathering statistics.

1. •Lost-Call System
•Objective of simulation will be to process
given number of call to determine
processed, completed, blocked and busy
call.
Simulation of Telephone System

2. 1
2
3
4
5
6
7
8
0
1
0
1
1
0
1
0
LINES
MAX No.
IN USE
3
2
LINK
S
102
7
CLOCK
1 7 20
FRO
M
TO LENGT
H
1057
ARRIVAL TIME
NEX
T
CALL
4 7 1075
2 5 1053
FRO
M
TO END
CALLS IN
PROGRESS
131 98 5 28
PROCESS
ED
COMPLETE
D
BLOCKED BUSY
CALL COUNTERS
Fig (a) : - System State - 1

3.  Fig (a), records the state of the system at time
1027
 There are two activities causing events:
 New calls can arrive
 Existing calls can finish

4.  As shown in fig(a), there are 3 future events:
 The call between lines 2 and 5 is due to finish at
time 1053
 The call between lines 4 and 7 is due to finish at
time 1075
 New call is due to arrive at time 1057

5.  First step= scan the next potential event
 In this case, the next potential event is 1053. The
clock is updated.
 Second step= Select the Activity that is to cause
event
 In this case, the activity is to disconnect the call.
 Third step= Test whether the potential event can
be executed
 Fourth step= Change records to reflect the effects
of the event
 The call is shown to be disconnected by setting 0
for lines 2 and 5, reducing the number of links in
use by 1, and removing the finished call from the
call-in-progress table

6.  Fifth and final step= Gather statistics of simulation
output
 Counters are set aside to record the number of
processed, completed, blocked and busy calls.
 With the disconnection of a call processed and
completed call counts are increased by 1
 The state of the system then appears as shown in
fig(b)

7. 1
2
3
4
5
6
7
8
0
0
0
1
0
0
1
0
LINES
MAX No.
IN USE
3
1
LINK
S
105
3
CLOCK
1 7 20
FRO
M
TO LENGT
H
1057
ARRIVAL TIME
NEX
T
CALL
4 7 1075
FRO
M
TO END
CALLS IN
PROGRESS
132 99 5 28
PROCESS
ED
COMPLETE
D
BLOCKED BUSY
CALL COUNTERS
Fig (b) : - System State - 2

8. 1
2
3
4
5
6
7
8
0
0
0
1
0
0
1
0
LINES
MAX No.
IN USE
3
1
LINK
S
105
7
CLOCK
3 6 98
FRO
M
TO LENGT
H
1063
ARRIVAL TIME
NEX
T
CALL
4 7 1075
FRO
M
TO END
CALLS IN
PROGRESS
133 99 5 29
PROCESS
ED
COMPLETE
D
BLOCKED BUSY
CALL COUNTERS
Fig (c) : - System State - 3

9. 1
2
3
4
5
6
7
8
0
0
1
1
0
1
1
0
LINES
MAX No.
IN USE
3
2
LINK
S
106
3
CLOCK
1 5 132
FRO
M
TO LENGT
H
1082
ARRIVAL TIME
NEX
T
CALL
3 6 1161
4 7 1075
FRO
M
TO END
CALLS IN
PROGRESS
133 99 5 29
PROCESS
ED
COMPLETE
D
BLOCKED BUSY
CALL COUNTERS
Fig (d) : - System State - 4

10.  Typically, the simulation will run until a given
number of calls has been processed or certain
time has elapsed

11. Delayed Calls
 Telephone system modified so that call which is
not connected are not lost
 Instead they wait until they are connected
 Happens to messages in switching system that
has store and forward capability

12. 1
2
3
4
5
6
7
8
0
0
0
1
0
0
1
0
LINES
MAX No.
IN USE
3
1
LINK
S
105
7
CLOCK
3 6 98
FRO
M
TO LENGT
H
1063
ARRIVAL TIME
NEX
T
CALL
4 7 1075
FRO
M
TO END
CALLS IN
PROGRESS
132 99 5 29
PROCESS
ED
COMPLETE
D
BLOCKED BUSY
CALL COUNTERS
Fig (e) : - System State – 3A
1 7 20
FRO
M
TO LENGT
H
DELAYED CALLS

13.  System moves through the first 2 states exactly
as before
 State of the system at time 1057, when the call
from line 1 has arrived, now appears as shown in
fig(e), which is labelled as system state-3A
 Same as state 3, shown in fig(c), except that it
now shows the delayed call
 When a call is completed, it is necessary to check
the delayed call list to see if a waiting call can be
connected
 The next event, however is arrival of call from line
3 at time 1063 which is going to line 6. The

14. 1
2
3
4
5
6
7
8
0
0
1
1
0
1
1
0
LINES
MAX No.
IN USE
3
2
LINK
S
106
3
CLOCK
1 5 132
FRO
M
TO LENGT
H
1082
ARRIVAL TIME
NEX
T
CALL
3 6 1161
4 7 1075
FRO
M
TO END
CALLS IN
PROGRESS
132 99 5 29
PROCESS
ED
COMPLETE
D
BLOCKED BUSY
CALL COUNTERS
Fig (f) : - System State – 4A
1 7 20
FRO
M
TO LENGT
H
DELAYED CALLS

15. 1
2
3
4
5
6
7
8
1
0
1
0
0
1
1
0
LINES
MAX No.
IN USE
3
2
LINK
S
107
5
CLOCK
1 5 132
FRO
M
TO LENGT
H
1082
ARRIVAL TIME
NEX
T
CALL
3 6 1161
1 7 1097
FRO
M
TO END
CALLS IN
PROGRESS
133 100 5 29
PROCESS
ED
COMPLETE
D
BLOCKED BUSY
CALL COUNTERS
Fig (g) : - System State – 5A
FRO
M
TO LENGT
H
DELAYED CALLS

16.  Thankyou!