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Ch61-I044963.fm Page 303 Thursday, July 27, 2006 9:04 AM
Thursday, July 27, 2006
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Ch61-I044963.fm
9:04 AM
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received jpeg pictures decreases strongly as a function of increased delay with and without VPN. FTP
tolerates long delays up to eight times the reference level but after that the connection is lost. It can be
seen that data packaging (-25%) is carried out in VPN. Download time increases linearly as a function
of delay. If VPN is not used connection tolerates delays twice as long.

Transferred data vs. Delay
Transfer Time vs. Delay
bytes Transferred data vs. Delay minutes Transfer Time vs. Delay
6.0
120000
MCRS_VPN
FTP
FTP MCRS_VPN
5.0
100000
FTP_V \ 4.0
FTP_VPN \
80000 FTP_VPN FTP
FTP
\ IE
IE
60000 \ \ 3.0
IE_VPN /cR^y(
IE_VPN
MCRS_VPN
_ V P N MCRS_VPN MCRS \
2.0
40000
, — - MCRS r IE IE *•, \
20000 1.0
IE_VPN
IE_VPN
ms ms
0 ^ " • • - ~ 0.0
0 5000 10000 15000 20000 0 5000 10000 15000 20000
15000
20000
5000
10000
Figure 1: Transferred data and transfer times as a function of delay
Jitter effect. Figure 2 shows how jitter affects applications. MCRS tolerates large variations of delay
well. VPN increases the amount of transferred data by 30 to 40 %. Access time to the MGS increases
again linearly as a function of jitter but nevertheless jitters up to 5 seconds are tolerated. VPN does not
significantly affect access time. IE tolerates very long jitters and the connection holds up but the
received jpeg pictures decreases as a function of increased jitter. The effect of VPN on the application
can be seen as a 10 to 50 % decrease in the amount received jpeg pictures when jitter increases. The
download time remains fairly constant. FTP with and without the VPN handles well even 5-second
jitter variations. VPN does not significantly affect the operation.
bytes minutes Transfer time vs. Jitter
minutes
bytes Transferred data vs. Jitter r Transfer time vs. Jitter
Transferred data vs. Jitte
120000 2,50
120000
2,50
FTP
100000
100000
2,00
2,00
FTP_VPN
MCRS
80000 FTP_VPN
80000
IE 1,50
1,50
FTP
60000
60000
MCRS_VPN
IE_VPN
1,00
1,00
40000
40000 IE_VPN
MCRS_VPN
IE
20000 0,50
20000
0,50
MCRS
0 0 ms 0,00 ms
0,00
5000
2000
3000
4000
0 1000 2000 3000 4000 5000 0 1000 2000 3000 4000 5000
1000
3000
5000
4000
2000
1000
Figure 2: Transferred data transfer times and as a function of jitter
Packet loss effect. Figure 3 shows packet loss effect (3 to 12%). MCRS tolerates 6 % packet loss well
and the system without VPN behaves well even with packet loss up to 12 % though the access time
doubles from the 6 % case. VPN increases the amount of transferred data about 20 % when packet loss
is doubled. In the IE case doubling the packet loss to 6 % decreases the received jpeg pictures from the
full 79 to on average of 59 without VPN. With VPN the decrease is from 79 to 24 jpeg pictures. The
downloading time in the 6 % packet loss situation is 30 % longer with VPN and in the 12 % packet
loss situation the downloading time is 70 % longer. In FTP the 6 % packet loss halves the data transfer
rate with and without the VPN, and there is no significant difference in data transfer time either. The
packet loss of 12 % makes the operation of FTP impossible in both cases.