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INSTITUT FÜRNACHRICHTENVERMITTLUNG
UND DATENVERARBEITUNGProf. Dr.-Ing. Dr. h. c. mult. P. J. Kühn
Universität StuttgartINSTITUT FÜR
KOMMUNIKATIONSNETZEUND RECHNERSYSTEME
Prof. Dr.-Ing. Dr. h. c. mult. P. J. Kühn
Universität Stuttgart
Modeling and Performance Evaluationof a Manual Logon System
for Electronic Fee Collection
VDE/ITG-Workshop: Communication Applications for Logistics: Maut, Telematics & More
VDE/ITG FA 5.2., Bremen, January 26th., 2006
Joerg Sommer, Hanna Zündel, Christoph GaugerUniversity of Stuttgart, Institut für Kommunikationsnetze und Rechnersysteme
Steffen TackeDaimlerChrysler AG, Research and Technology
Institute of Communication Networks and Computer Engineering University of Stuttgart
Contents
❑ TollCollect’s logon processand system architecture
❑ Modeling aspects
❑ Performance evaluation
❑ Backoff Algorithm
Institute of Communication Networks and Computer Engineering University of Stuttgart
• 2005, Germany introduced an Electronic Fee Collection System (EFC)
• Global navigation satellite system and cellular network (GNSS/CN)
• Currently > 700,000 registered usersBy 2012, might grow to over 9 million in Europe
• Three approaches for payment
Automatic Logon Manual Logon
• > 460,000(July 2005)
• approx. 3600 terminals
• approx. 80%revenue
• marginal anddeclining
• approx. 400 frequently usedterminals
• approx. 400 rarely usedterminals
On-boardunit
Internet andCall Centre
Toll-StationTerminal
German Toll Collection System "TollCollect"
Institute of Communication Networks and Computer Engineering University of Stuttgart
TollCollect’s Manual Logon Process for EFC
Institute of Communication Networks and Computer Engineering University of Stuttgart
• Billing data records have to be transferred quickly for enforcement
➥ System behavior after failure or outage is critical
TollCollect’s Manual Logon Process for EFC
Institute of Communication Networks and Computer Engineering University of Stuttgart
Challenging Scenarios• System failure or breakdown of key components
• Billing and Data Centre
• Remote Access Server (RAS)
• Overload situation• Breakdown of the automatic GNSS/CN EFC system
• Specific and unexpected peaks
➥ Financial losses and negative standing for the operator
Aim of this work• Model and evaluate the overall manual logon process
regarding performance and scalability
• Optimize the algorithm and parameters for transmissionof billing data records after system outage
Manual Logon Process
Institute of Communication Networks and Computer Engineering University of Stuttgart
Terminal-based EFC system architecture
Institute of Communication Networks and Computer Engineering University of Stuttgart
Failure-free billing data records (BDR) delivering
TServerTimeout35 s.
TST RAS BDMUser/Driver
Timer abort
Tfollowup45 s.
Top
Connectionrequest
ACK
BDR
BDR
ACK
ACK
Connectiontermination
Tconnect~10 s.
Normal operational mode
Institute of Communication Networks and Computer Engineering University of Stuttgart
Erroneous connection establishment
TServerTimeout35 s.
TST RAS BDMUser/Driver
Top
Connectionrequest
ACK
BDR
BDR
Connectiontermination
Tconnect~10 s.
Enterautonomous
mode
Autonomous mode
Institute of Communication Networks and Computer Engineering University of Stuttgart
Billing data records (BDR) delivering
...
Parameters
• AutoReconnectIntervalARI
• AutoSendIntervalASI
• Number of deliveredBDRs n
• Time to transfer oneBDR tBDR
Relations
n
1 ASI t BDR<
ASIt BDR----------- ASI t BDR≥
⎩⎪⎨⎪⎧
=
RAS BDM
Connectionrequest
BDR
ACK
Connectiontermination
ACK
BDR
ACK
BDR
ACK
BDR
ACK
... ...
ARI
1 BDR
n BDR
Tfollowup45 s.
TST
ARI
Autonomous mode
Institute of Communication Networks and Computer Engineering University of Stuttgart
Open queueing network
• Frontend comprises the terminals and the RAS
• Backend represents the BDM as a M/D/k-Multi-Server-Delay-System
THport...
FIFO...
FIFO
notification
Toll-StationTerminals
λIRS
λ1
λ2
λm
BDMRAS
IRS
Top
λBDM
λRASrp2
rps
rp1
...
D
D
D
...
M/D/kMulti-Server-Delay-System
2
k
1
Modeling the terminal-based EFC system
Institute of Communication Networks and Computer Engineering University of Stuttgart
Scenario
Term
inal
que
ues
t
BDR arrivals
Normaloperation mode Autonomous mode
1 h outage Trecovery
Performance evaluation
Institute of Communication Networks and Computer Engineering University of Stuttgart
Scenario
...
λIRS = 160 s-1
Class 1
λBDM...
...
Class 2
Class 3
Class 4
1920 RAS portsconnection requests 24 s-1
3600 terminals
k = 50h = 2 s
Term
inal
que
ues
t
BDR arrivals
Autonomous mode
1 h outage TrecoveryNormaloperation mode
Performance evaluation
Institute of Communication Networks and Computer Engineering University of Stuttgart
Scenario
...
λIRS = 160 s-1
λBDM...
...
HomogeneousscenarioIAT = 180 s
1920 RAS portsconnection requests 24 s-1
3600 terminals
k = 50h = 2 s
Term
inal
que
ues
t
BDR arrivals
Autonomous mode
1 h outage TrecoveryNormaloperation mode
Performance evaluation
Institute of Communication Networks and Computer Engineering University of Stuttgart
CDF of the queue processing (n = 1)
• With default configuration (ARI = 150 s) approximately Trecovery = 2.5 h
3000 4000 5000 6000 7000 8000 90000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
t [s]
Dis
trib
utio
n of
term
inal
s do
ne
ARI = 150(default)
Performance evaluation
Institute of Communication Networks and Computer Engineering University of Stuttgart
CDF of the queue processing (n = 1)
➥ Decreasing ARI values reduce Trecovery
3000 4000 5000 6000 7000 8000 90000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
t [s]
Dis
trib
utio
n of
term
inal
s do
ne
ARI = 150(default)
ARI decreases
ARI = 100
ARI = 80
ARI = 60
Performance evaluation
Institute of Communication Networks and Computer Engineering University of Stuttgart
BDM utilization (n = 1)
• ARI = 150 s can not utilize the BDM continuously
0 1000 2000 3000 4000 5000 6000 7000 80000
5
10
15
20
25
t [s]
Req
uest
s [1
/s]
24 s−1 RAS limit
ARI =150
Performance evaluation
Institute of Communication Networks and Computer Engineering University of Stuttgart
BDM utilization (n = 1)
➥ Smaller ARI values are feasible due to RAS boundary
0 1000 2000 3000 4000 5000 6000 7000 80000
5
10
15
20
25
t [s]
Req
uest
s [1
/s]
24 s−1 RAS limit
ARI = 150
ARI = 100
ARI = 80
ARI = 60
Performance evaluation
Institute of Communication Networks and Computer Engineering University of Stuttgart
So far, deterministic approach• ARI and n are constant values for all terminals
• Periodic system behavior → possible instability• Default of the recovery algorithm is too restrictive
➥ The parameters after an outage are not optimal
➥ Challenge: improvement and optimization of the algorithm and parameters
➥ Aim: minimization of the recovery duration with controlled BDM load
Backoff Algorithm (1)
Institute of Communication Networks and Computer Engineering University of Stuttgart
New approach for the backoff algorithm
Initial configuration in the autonomous mode ARI0=150 s, n0=2
Failure-free case Connection to RAS could be established successfully
Failure case Connection to RAS could not be established
ARIi+1 ARI0ARIi
2-----------+= n i+1
n i 2⋅ if 2n q l≤
q l else⎩⎨⎧
=
ARIi+1ARIi
ARIi2
-----------– if ARIiARIi
2-----------–⎝ ⎠
⎛ ⎞ ARI0≥
ARI0 else⎩⎪⎨⎪⎧
=
n i+1
n i2---- if
ni2---- n0≥
n0 else⎩⎪⎨⎪⎧
=
Backoff Algorithm (2)
Institute of Communication Networks and Computer Engineering University of Stuttgart
• Modeled the manual logon process (users and system)
• Evaluated the recovery process in the autonomous mode
• Introduced a new approach for the backoff resolution
➥ Default manual logon process works stable,but is restrictive after an outage
• System behaviour depending on different downtime scenarios
• Optimization of the Backoff Algorithm to minimize RAS and BDMutilization
• Make the Backoff Algorithm dependant on state of
- terminal queue
- BDM
• Evaluate heterogeneous scenarios
Conclusion and outlook
INSTITUT FÜRNACHRICHTENVERMITTLUNG
UND DATENVERARBEITUNGProf. Dr.-Ing. Dr. h. c. mult. P. J. Kühn
Universität StuttgartINSTITUT FÜR
KOMMUNIKATIONSNETZEUND RECHNERSYSTEME
Prof. Dr.-Ing. Dr. h. c. mult. P. J. Kühn
Universität Stuttgart
Modeling and Performance Evaluationof a Manual Logon System
for Electronic Fee Collection
VDE/ITG-Workshop: Communication Applications for Logistics: Maut, Telematics & More
VDE/ITG FA 5.2., Bremen, January 26th., 2006
Joerg Sommer, Hanna Zündel, Christoph GaugerUniversity of Stuttgart, Institut für Kommunikationsnetze und Rechnersysteme
Steffen TackeDaimlerChrysler AG, Research and Technology