prof. dr.-ing. dr. h. c. mult. p. j. kühn modeling and performance...
TRANSCRIPT
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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
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Institute of Communication Networks and Computer Engineering University of Stuttgart
Contents
❑ TollCollect’s logon processand system architecture
❑ Modeling aspects
❑ Performance evaluation
❑ Backoff Algorithm
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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"
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Institute of Communication Networks and Computer Engineering University of Stuttgart
TollCollect’s Manual Logon Process for EFC
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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
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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
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Institute of Communication Networks and Computer Engineering University of Stuttgart
Terminal-based EFC system architecture
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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)
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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)
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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
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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