1. Application Software Platform Services Graphics Data Interchange
Data Management
User Interface
Software Engineering
Communication Services
Application Agent
Application Program Interface (API)
Platform (OS + Hardware)
Application process
Application process
Application Program Interface (API)
Platform (OS + Hardware)
Inter-process Communication

2. Distributed Applications = Network Applications: Client/Server
Application Software (Client Part)
Application Software (Server Part)
Client (user) Agent
Server Agent
Application Program Interface (API)
Application Program Interface (API)
System
Communication Software & Hardware
Communication Software & Hardware
Platform (OS + Hardware)
Platform (OS + Hardware)
Client Agents Examples:
Internet Explorer, Opera
MS’s Outlook, Netscape’s Messenger, Eudora
Server Agents Examples:
Internet Information Sever, Appachi
SQL query engines, …
Communication
Network

3. Layered Application Model-1
Presentation
User Interface
Business (Application Logic)
Data (Database Access)
Application Software
Application Model
Presentation: The client agent remains focused on presenting information to or receiving input from the user.
User Interface: User’s access to the application logic via client agent. It can be dynamical and configured by user. It is build on the top of the user interface control.
Dynamic User Interface:
Customizing the look (example:
Customizing the content ( examples: my.yahoo.com , )

4. Layered Application Model-2
Presentation
Presentation
User Interface
Application Interface
User Interface
User Interface Control
and Related Logic
Application Interface Control
and Related Logic
Business (Application Logic)
Business Processes
Data (Database Access)
Core Business Services
Business Rules (Application Logic)
Units of processing or algorithms that represents concept of importance to the organization using database.
Data (Database Access)
Logic to connect to database; access/manipulate data held within databases.

5. Layered Application: 3-Tier Client/Server Model
Runs by Application
Server Agent
Run by Client Agent
Business
(Application Logic)
User Interface
Presentation
user
Application Sever
Runs by Database
Server Agent
Client Workstation
(rich client)
Communication
Network
Run by Client Agent
Data
(Data Access and Storage)
User Interface
Presentation
Database
user
Mobile Client
Workstation
(thin client)
Data Server

6. “Logical Tiers vs Physical Tiers
Application Model
Logical Tiers
Presentation
User Interface
Business
Data
Physical Tiers
Client workstation
Application server
Data Base
Presentation
Client Workstation
User Interface
Business (Application Logic)
Application Server
Data
(Database Access)
Database

7. Attendant Workstations
Example: Car Rental
Router
Hub
Router
Reservation agent
workstation
Data Server
Application
Sever
Database
App.
server
WAN
Attendant
Workstations
Car Reservation Center
Router
Base Station
Car rental l& pickup
locations
App.
server
Attendant Workstations

8. Current Load Intensity
Increasing the Load
The load (transactions)
Local reservation (at car rental location)
Road assistance request
Car pickup
Phone reservation
Transaction
Current Load Intensity
CLI +5%
CLI +10%
CLI +15%
Local Res.
1.28
1.67
2.45
5.06
Road Ass.
0.64
0.87
1.37
3.20
Car Pickup
0.76
0.94
1.23
Phone Res.
0.85
1.16
1.82
4.24
Table 1.2. Response Time for Various Load
Values (sec)

9. Caching Example (1) origin Assumptions
average object size = L= 100,000 bits
avg. request rate from institution’s browser to origin serves = a= 15reqs/sec
delay from Internet router to any origin server and back to router = 2 sec
Consequences
utilization on LAN = 15%
utilization on access link=100%
total delay = Internet delay + access delay + LAN delay
= 2 secs + minutes + 20 msecs
origin
servers
public
Internet
Traffic Intensity on the access link
= 15*100,000/1.5Mbps=100%
R=1.5 Mbps
access link
institutional
network
R=10 Mbps LAN
Traffic Intensity on the LAN
= 15*100,000/10Mbps=15%

10. Link delay Traffic intensity La/R 100% 15% 60%
Average queuing delay (secs)
100%
15%
60%
20 msecs
160 msecs

11. Caching Example (2) origin servers Possible solution
public
Internet
institutional
network
10 Mbps LAN
10 Mbps
access link
Possible solution
increase bandwidth of access link to, say, 10 Mbps
Consequences
utilization on LAN = 15%
utilization on access link = 15%
total delay = Internet delay + access delay + LAN delay
= 2secs + 20msecs + 20msecs
often a costly upgrade
Traffic Intensity on the access link
= 15*100,000/10Mbps = 15%
Traffic Intensity on the LAN
= 15*100,000/10Mbps = 15%

12. Caching Example (3) Install cache origin servers Consequence
suppose hit rate is 0.4
Consequence
40% requests will be satisfied almost immediately
60% requests satisfied by origin server
utilization of access link reduced to 60%, resulting in delays (say 160 msec)
total delay = Internet delay + access delay + LAN delay
= 0.6×(2secs+160msecs+20msecs) + 0.4×20msecs = secs
origin
servers
public
Internet
institutional
network
10 Mbps LAN
1.5 Mbps
access link
cache
Traffic Intensity on the access link
= 0.6*15*100,000/1.5Mbps = 60%
Traffic Intensity on the LAN
= 15*100,000/10Mbps = 15%

13. L1=100,000bits, a1=15req/sec, h1=50%(hit rate)
در شکل زير کاربران دو LAN فايل هايی بامشخصات زير را از سرورها درخواست می نمايند. متوسط زمان دريافت يک فايل L1 بيتی را توسط کاربران LAN1 حساب کنيد. هر دو LAN از يک Cache server استفاده می کنند. (2 نمره)
L1=100,000bits, a1=15req/sec, h1=50%(hit rate)
L2=50,000bits, a2=20req/sec, h2=30%(hit rate)
Internet delay=2secs
توجه: رابطه ی تاخيربرای LAN و link عبارت است از IL/[R(1-I)] d=
L= File length (bits), I= Traffic intensity
R= Bandwidth (bps)
origin
servers
1.5 Mbps
access link1
public
Internet
2 Mbps
access link2
10 Mbps LAN1
Cache server
100 Mbps LAN2

14. Communication-Processing Delay
S2SLAN
W1Scpu
S1Scpu
W2SLAN
W1Sio
S1Ccpu
S2Ccpu
S1Sio
time
Client (C)
Server (S)
LAN
B[bps]
Figure 3.1. Communication-Processing
delay diagram for 2-tier C/S system. Rr
[r,m1]
[r,m2]
[rth request, m1 bytes]
[rth response, m2 bytes]

15. The Times Service Time during jth visit: Sji
Waiting Time during jth visit: Wji
Residence Time during jth visit: R’i
Resource i
Sji
Wji
R’i
Rr = R’Ccpu + R’Scpu + R’Sio + R’LAN
Rr = response time of a request r
R’Ccpu = residence times at the client cpu
R’Scpu = residence times at the server cpu
R’Sio = residence times at the server io
R’LAN = residence times at the LAN
(3.2.5)
3-15

16. Residence Time
Service Demand (sum of all service time for a request at source i): Di
Di = Σj Sji (3.2.2)
Queuing Time (sum of all waiting time for a request at source i): Qi
Qi = Σj Wji (3.2.3)
R’i = Di + Qi (3.2.4)
Rr = Σi R’i (3.2.5)
Service demand at server’s cpu
DScpu = S1Scpu + S2Scpu
DLAN = 8(m1 + m2 )/B
m1 = request length [B]
m2 = reply length [B]
QScpu = W1Scpu + W2Scpu
Queuing time at server’s cpu
3-16

17. Example 3.1 S1Ccpu = 5ms, S1Scpu = 10ms AvgSeek = 9ms (Server’s Disk)
AvgLatency = 4.17msec (Server’s Disk)
TransferRate = 20 MB/s (Server’s Disk)
DataReads = 10×2048 Byte
Sd = /20M = 13.3 ms
(Disk Average Service Time)
Dd = 10×Sd = 133 ms
(Service Demand at Server’s Disk)
m1 = 1,518, m2 = 7×1,518 Bytes
DLAN = 8(m1 +m2 )/10Mbps= 9.7ms
Rt > DCcpu+ DScpu+ Dd+ DLAN=158 ms
The minimum value for response time
to transaction t; all waiting times are ignored.
S2Scpu
W1Scpu
W2Scpu
W1Sio
S1Ccpu
S2Ccpu
S1Sio
time
Client (C)
Server (S)
LAN
B[bps] Rr
[r,m1]
[r,m2]
3-17

18. Three-Tier WAN Figure 3.3. Three-tier C/S system. LAN2 LAN1 Client
B2[bps]
WAN
Client
LAN1
B1[bps]
Database Sever
(Data Access Tier)
Application Sever
(Business Tier)
Figure 3.3. Three-tier C/S system.
3-18

19. 3-Tier Delay diagram
Client
LAN1
Application
Server
LAN2
WAN
Database
[r,m1]
[r,m2] ●
Scpu
Wnet
Qcpu
Dcpu
Qnet
Ddisk
Qdisk Rr
Figure 3.4. Communications-processing delay diagram for a 3-tier C/S system.
3-19

20. Validating Workload Models2
Calibration NO
Actual
Workload
C/S System
measured response times,
throughputs, utilizations, etc.
Synthetic
Workload
C/S System
measured response times,
throughputs, utilizations, etc.
acceptable?
YES
Figure 5.8. Workload model validation

21. A Methodology for CP in C/S Environment2
Understanding the Environment
Cost Model
Cost Prediction
Development of
a Cost Model
Workload Characterization
Workload Model Validation
& Calibration
Workload Forecasting
Workload
Model
Cost/Performance Analysis
Configuration Plan
Personnel Plan
Performance Model
Development
Performance Model Validation
& Calibration
Performance Prediction
Performance
Model
Investment Plan
Figure 5.2. A methodology for capacity planning

22. Figure 5. 5. Space for workload characterization (no
Figure 5.5. Space for workload characterization (no. of I/Os, CPU time)
No. I/Os
200
180
160
140
120
100 80 60 40 20
CPU Time (msec)
Cluster 2
average over
all points
Cluster 3
Cluster 1 19
4.5

23. Chapter3-Outlines Service Times and service demands Introduction
Communication-Processing Delay Diagrams
Service Times and service demands
Service Times at Single Disks and Disk Arrays
Service Times in Networks
Service Time in Routers
Queues and Contention
Some Basic Performance Results
Utilization Law
Forced Flow Law
Service Demand Law
Little’s Law
Summary of Basic Results
Performance Metrics in C/S System
Concluding Remarks
References

24. Figure 5.3. Example C/S System for Capacity Planning Methodology.
16 Mbps Token Ring-LAN4
File
Server
SQL
100 NT
Clients
FDDI ring
100 Mbps
LAN 5
10 Mbps
Ethernet
LAN1
120 NT
LAN3
ftp proxy server,
telnet proxy server,
Web proxy server,
server.
50 Unix
Workstations
RISC-type
File Server
512 Gbytes
RAID-5s
Internet
LAN2

25. Figures 5.10/11. High-level/Detailed QN of LAN 3
FDDI
Internet
Web server
100 Windows
Clients
LAN 3
Web server
FDDI
Internet
100 Windows
Clients
LAN 3
disks
CPUs