Sisteminis tinklu planavimo metodas bei reikalavimu analizes role
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Transcript Sisteminis tinklu planavimo metodas bei reikalavimu analizes role
Infobalt’03 Seminaras
Sisteminis tinklų planavimo
metodas bei reikalavimų
analizės rolė
(nuo meno link inžinerijos)
Prof.DrTech. Algirdas Pakštas
London Metropolitan University
Department of Computing, Communications Technology and
Mathematics
[email protected],
[email protected]
Infobalt 2003, Vilnius,
2003m. spalio 23d.
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
1
Abstract:
Tutorial looks at the problem of network planning when network is
considered not as collection of separate components but as a
system. Tutorial consists of two parts. The first part of the Tutorial is
devoted to the general overview of the network analysis and design
processes. Network services and services-based networking are
discussed. Systems and network services are presented with more
details. Especial attention is devoted to characterizing of services
including discussion on service requests, service offerings, service
performance requirements, service metrics, as well as reservations
and deadline scheduling. The second part of the Tutorial is focusing
on the concepts of requirement analysis. Description of the
background for requirement analysis is followed by the discussions
on User Requirements, Application Requirements (types of
applications, reliability, capacity, delay, application groups), Host
Requirements (types of host and equipment, performance
characteristics, location information), and Network Requirements
(existing networks and migration, functional requirements, financial
requirements, enterprise requirements).
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Biography:
Prof. Algirdas Pakstas received his M.Sc. in Radiophysics and
Electronics in 1980 from the Irkutsk State University, Ph.D. in
Systems Programming in 1987 from the Institute of Control
Sciences. Currently he is with the London Metropolitan University,
Department of Computing, Communications Technology and
Mathematics where he is doing research in the area of
Communications Software Engineering and is teaching courses
"Network Planning and Management" and "Computer Systems and
Networks". He is active in the IEEE Communications Society
Technical Committees on Enterprise Networking, Communications
Software and Multimedia Communications. He has published 3
research monographs (2 authored and 1 edited) and more than 140
other publications. He is a Senior Member of the IEEE and a
Member of the ACM and the New York Academy of Sciences. He is
currently a member of the Editorial Boards of the following journals
and magazines: IEEE Communications Magazine, Cybernetics and
Systems Analysis, Journal of Information and Organizational
Sciences.
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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PART 1: OUTLINE
A Systems Approach to Network Design
Introduction - Traditional Network Design
The Analysis and Design Processes
Network Services and Services-Based
Networking
Systems and Network Services
Systems
Network Services
Characterizing Services
Service Requests
Service Offerings
Service Performance Requirements
Service Metrics
Reservations and Deadline Scheduling
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
4
Introduction - Traditional Network
Design
• A kind of art
– Evaluating and choosing network technologies
– Knowing how technologies, services and
protocols work
– Experience in what works and what does not
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Introduction - Traditional Network
Design
• As in other types of art
– Success greatly depends on the person(s) who
is/are doing it
– Designs are rarely reproducible
• Traditional network design is based on developing a
set of pragmatic rules e.g.
• “80/20 rule”
• “bridge when you can, route when you must”
• “throw bandwidth at the problem”
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Introduction - Traditional Network
Design
• It was focusing primarily on capacity planning
• Pragmatic rules worked well with limited choice of
technologies, interconnection strategies, routing
protocols
• Times have changed
– We must adapt design process to the variety of options
– Many new types of services can be offered to the users
– Additionally to the capacity planning we need to consider
optimization of the delay in the network
– Providing reliability is more than just redundant paths in the
network or resilient routing prtocols
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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The Analysis and Design
Processes
• Network analysis and design is a combination of
– Design goals
– Trade-offs
• Balance between architecture and function
• Design goals could be such as
– Minimizing network costs
– Maximizing performance
• Trade-offs
– Cost vs. performance
– Simplicity vs. function
– Many ways to achieve design goals - rarely single “right” one
• There are often many wrong ways...
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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The Analysis and Design
Processes
• Components of the Analysis and Design Processes
(listed consequently):
– The Systems Approach to Design
– Requirement Analysis
– Flow Analysis
– Logical Design
– Physical Design
– Addressing and Routing
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Network Services and
Services-Based Networking
• There has been significant effort to define and
specify “services” in the ISO/OSI model
• It is a new approach to looking at networking
from the services prospective in the IP-world
• “Services-Based Networking is the concept of
developing network designs that take into
account network services and service support”
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Network Services and
Services-Based Networking
Generations of the network services
Generation
Time Frame
Capability
First
1960s-mid-1980s Basic connectivity/
interoperability
Second
mid-1980sPerformance (IP
early/mid-1990s forwarding rates)
Third (current)
mid-to-late 1990s Network Services
(levels of network
performance and
function)
Fourth
2000-2010
Self-configuration/
administration
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
Systems
“A network system is the set of components that work
together to support or provide connectivity,
communications, and network services to users of
the system”
Generic components of a System
| User |
| User |
|Application|
|Application|
| Host |
! Host |
------------------|------(Network)-----|
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
Systems
Traditional View of a System
----------------------| Host |
| Host |
----------------------|----- (Network) ---|
Network design have focused on providing
connectivity between hosts
Systems were described as the set
(host,network)
and typically did not consider the users or applications
Thus, there is a need to define more precisely the set
(user, application, host, network)
Sometime definitions of the “host” and the “network” are not
very much obvious
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
Interfaces and Boundaries
If the components are known then thethe boundary
condition between them can be set and therefore the
interfaces
Example:
User
User
Application
Application
Host
Host
Display Parameters
User Interface
API, QoS, ToS
Drivers, Interfaces
Network
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
ATM in Network Backbone
Example: The picture below is showing the ATM
as a backbone technology
| User |
|Application |
| User |
|Application |
| Host |
| Host |
------------------\-------(x)
NETWORK
(x)--------|
\--[atmX]---[atmX] --/
Here
(x)
- Router
[atmX] - ATM Switch
Here the ATM environment is isolated from the hosts,
applications and users by the routers
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
“Native” ATM Network
Example: The picture below is showing a “native” ATM network
in which ATM is integrated into the host side
[User]
[User]
[Application]
[Application]
--------------------------------(ATM)---------------------------------
[ATM Specific API]
[ATM Specific API]
[ATM Device Driver]
[ATM Device Driver]
\ [atmX]-[atmX]-[atmX]-[atmX]/
Here
[atmX] - ATM Switch
Here the ATM is integrated into the host and will interface
directly with the applicaions
The system is best described as as the set
(user,application, ATM-specific API, ATM device driver, network)
©2003 Algirdas Pakštas
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Systems and Network Services:
Services
• According to the IETF and ATM Forum
– Network Services are sets of network capabilities
that can be configured and managed within the
network
– Network Services are defined
• as levels of performance and function that are
offered by the network, host, and/or application, to
the rest of the system,
• or as sets of requirements that are expected from
the network by the end user, application, or host
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
Services
• Levels of performance are described by the
performance characteristics, e.g.
– capacity
– delay
– reliability
• Functions include
–
–
–
–
–
security
accounting
billing
scheduling
management
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
Services
• Network services: groups of characteristics and
levels
Service Characteristics
Characteristic A \
Characteristic B
}-> Service Level
Characteristic C /
Level A \
…
/
Level B }-> Network Service
|
Level C / Description for Design
V
…
/
Characteristics used to configure services in network and as
service metrics to measure and verify services
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
Service Characteristics
Service characteristics = Individual network
performance and functional parameters
Service offering - by the network to the system
Service request - from the network by users,
applications, or hosts
Service requirements = characteristics
that are used to gauge the system’s need
for services
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
Service Characteristics
Service characteristics and requirements are
useful in the network analysis and design
processes:
In configuring services in network elements (routers,
switches, host operating systems)
In providing input into the network design
Need to be described and provisioned end-toend, at all components between end users,
applications and hosts
Service may fail if some components are not capable to
support it!
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Systems and Network Services:
Service Levels
Service requirements or characteristics are
grouped together to describe service levels
Easier to configure, measure and verify service level
instead of a number of individual service characteristics
Helpful in service accounting and billing
Service levels can be described with the help of
Committed Information Rates (CIRs)
Classes of Services (CoSs)
Types of Services (ToSs)
Qualities of Services (QoSs)
Custom service levels based on groups of individual
service characteristics depending on technology,
protocol, etc.
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
22
Characterizing Services
Service Requests
Service Offerings
Service Performance Requirements
Service Metrics
Reservations and Deadline
Scheduling
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
23
Characterizing Services
Service Requests
Can be distinguished by the degree of
predictability:
Best-effort (e.g. best-effort delivery)
Specified, i.e. deterministic and
guaranteed
©2003 Algirdas Pakštas
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Characterizing Services
Service Requests
Best-effort:
No control over how network will satisfy the
service request
No guarantees are presented
Network is not obligated to do more than try
Indicates that the rest of the system
(user, application, host) will need to
adapt to the state of the network at any
given time
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
25
Characterizing Services
Service Requests
Best-effort:
Expected service for such requests is
unpredictable and variable
Such service requests
Either have no performance requirements
for the network
Or the requirements are nonspecific
Consequently service requests are not tuned to
any specific user or application (i.e. very much
universal, generally oriented)
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
26
Characterizing Services
Service Requests
Specified service requests
Are based on some knowledge of or control
over the state of the system
Have more stringent service requirements (i.e.
deterministic and guaranteed) than best-effort
To support a deterministic service request
by the network the service requirements of
the request must be measurable and
verifiable
Need for the service metrics
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Characterizing Services
Service Requests
Specified service requests
EXAMPLE:
If service request is made for capacity to be 4-10
Mb/s
Then there must be
Way to translate these service requirements into a
service offering from the network
Way to measure and/or to derive these capacity
characteristics from the network
Statistical method to control the information flow and
the network to keep this service between the targeted
4-10 Mb/s
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
28
Characterizing Services
Service Requests
Specified service requests
Service performance requirements are usually
grouped into service levels
Service levels can be the same as specified
service requests
And also can be closely related to well-known
service offerings from the network such as
ATM QoS
SMDS CoS
...
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Characterizing Services
Service Requests
Specified service requests
Mapping Service Levels to Service Offerings:
Service Request
Service Performance Requirements
Service Levels (Groups of Requirements)
|
|
|
Service Metrics -------------------------------------------------|
|
|
SMDS CoS
ATM QoS Frame Relay CIR
Service Performance Characteristics
Service Offering
SMDS CoS - Switched Multimegabit Data Service Classes of Service
ATM QoS - Asynchronous Transfer Mode Quality of Service
CIR
- Committed Information Rates
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
30
Characterizing Services
Service Offerings
Similarly to the Service Requests the
Service Offerings are also grouped as:
Best-effort
Specified
©2003 Algirdas Pakštas
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Characterizing Services
Service Offerings
Best-effort
Internet is a good example
Best-effort service offering is compatible with the
best-effort service request
EXAMPLE:
File transfer (via FTP) occurs over IP
FTP uses TCP which via sliding window flow
control mechanism adapts to the current state of
the network it is operating over
Service requirement from FTP over TCP is best-effort
Service offering from the Internet is best effort
During the FTP session the performance characteristics of
the IP network and transport method (TCP) are constantly
adapted
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
32
Characterizing Services
Service Offerings
Specified (deterministic and guaranteed)
service offerings are:
Predictable, bounded, or guaranteed
Specified refers to the network’s ability to
offer a measurable and verifiable service
Can be low- or high-performance
Specified service does not imply high performance
Similarly, ISO 900x quality assurance standards
can not guarantee you a GOOD THING but just a
SPECIFIED QUALITY whatever they mean by it!!!
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
33
Characterizing Services
Service Offerings
EXAMPLE of Specified Service :
Network to support real-time telemetry data
Design goal would be the ability to specify endto-end delay and have the network to satisfy
this delay request
For example, a service request may be for an end-toend delay of 25ms, with a delay variation of 400s
This would form the request and the service level (i.e.
QoS level) that needs to be supported by the network
The network would then be designed to provide a
specified service offering at a QoS level of 25ms endto-end delay and 400s delay variation
The delay and delay variation would then be measured
and verified with service metrics (using tools such as
ping or tcpdump, or with custom one)
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
34
Characterizing Services
Service Offerings
Service Requests and Offerings
Service Request
|
|
Best-Effort
Deterministic/Guaranteed
|
|
| Service Performance Characteristics/Levels
|
| | |
Service Metrics -------------------------------------------------------|
| | |
| Service Performance Characteristics/Levels
|
|
Best-effort Deterministic/Guaranteed
|
|
Service Offering
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
35
Characterizing Services
Service Performance Requirements
Service Performance Requirements
Reliability, Capacity and Delay
are related to each other
Reliability:
Definition by the J.D.McCabe:
“Reliability is a measure of the system’s ability to
provide deterministic and accurate delivery of
information...”
– IT CAN BE ARGUED THAT RELIABILITY IS ONLY THE
GUARANTEE OF ACCURACY WITH NO TIME CONSTRAINTS
– DIFFERENT DEFINITION OF RELIABLITY MAY LEAD TO
BUILDING DIFFERENT CONCEPTS WHICH BETTER
REFLECT A REAL WORLD VIEW TO THE SYSTEM’S DESIGN
©2003 Algirdas Pakštas
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Characterizing Services
Service Performance Requirements
Capacity
“It is a measure of the system’s ability to transfer
information”
This term is often used intechangeably with
bandwidth, throughput and goodput
Bandwidth is sometime described as theoretical
capacity what is not strictly correct (remember
Nyquist’s and Shannon’s equations?)
Throughput is the realizable capacity of the system or
its components or elements
SONET OC-3c circuit is designed to achieve data rate
155.52 Mb/s = 3x51.84 Mb/s (i.e. 3xOC-1 circuits)
Practically achievable throughput is ~80-128 Mb/s
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Characterizing Services
Service Performance Requirements
Delay
“It is a measure of the time which is taken for the
transmission of the single unit of information (bit,
byte, cell, frame, packet) across the system”
Often used are propagation, transmission, queueing,
and processing delays
End-to-end and round-trip delays are useful
measurements
Delay represents microscopic view of network
behaviour
Latency can be defined as an overall delay caused by
the application processing and task completion times
Latency represents macroscopic view of network behaviour
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
38
Characterizing Services
Service Performance Requirements
Performance Envelops
Useful for visualizing the regions of
performance in which the network will be
expected to operate
Service performance requirements can be
mapped from the applications onto such
environments in order to show relative
performance of each application
EXAMPLES:
2-D Service Performance Envelop describing Capacity,
Data Size and End-to-end Delay
3-D Service Performance Envelop including Reliability
©2003 Algirdas Pakštas
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Characterizing Services
Service Performance Requirements
2-D Service Performance Envelop describing
Capacity, Data Size and End-to-end Delay
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
40
Characterizing Services
Service Performance Requirements
3-D Service Performance Envelop including Reliability
Note low-performance and high-performance regions!
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
41
Characterizing Services
Service Metrics
Service metrics are intended to be
measurable
Can be used to establish reference levels
(a combination of service metrics for
reliability, capacity and delay) for service
performance
3 types of reference levels:
Service thresholds
Service boundaries
Service guarantees
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
42
Characterizing Services
Service Metrics
Service thresholds - discriminators used on
applications to distinguish between highperformance and low-performance service
Service boundaries - combinations of lowand/or high-performance levels used to
predict a service level for an application
Service guarantees - strict performance
levels. If they are not met it may cause some
type of action from the system (such as
policing)
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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Characterizing Services
Service Metrics
Reference levels are described in terms of
service metrics for the system
EXAMPLE: System using SNMP has MIB
variables for each network element
We may choose:
A reference level of the amount of the capacity
being utilized
A service metric of the number of bytes in or out of
each interface of the network elements
MIB variables of ifInOctets and ifOutOctets
©2003 Algirdas Pakštas
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Characterizing Services
Service Metrics
Example of Reference Levels-Service Thresholds
Threshold
|
App3 App6
|
App5
App2
App1
|
App4
--------------------|--------------->
Service
Low Capacity
|
High Capacity
Threshold
Expected/Predicted Application Capacities
©2003 Algirdas Pakštas
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Characterizing Services
Service Metrics
Example of Reference Levels Boundaries and Guarantees
©2003 Algirdas Pakštas
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46
Characterizing Services
Reservations and Deadline
Scheduling
Some applications may be operating in
real-time
Session may be not active until time T
Resources for this application are not
required until time T and can be used for
something else
Application may have a deadline when all
tasks must be completed
May need prioritizing of the use of network
resources for this application
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
47
Conclusions for PART 1
It is very important to take a system’s
approach to network design
System = (user, application, host, network)
System is offering services to the end
users/customers
In order to implement services and and
achieve their characteristics we need to
quantify requirements
Requirements Analysis is the next step
in the network analysis process:
To gather, analyze, and understand the
requirements from the system
©2003 Algirdas Pakštas
Sisteminis tinklų planavimo metodas bei reikalavimų analizės rolė (nuo meno link inžinerijos)
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PART 2: OUTLINE
Requirements Analysis: Concepts
Background for Requirement Analysis
User Requirements
Application Requirements
Types of Applications
Reliability
Capacity
Delay
Application Groups
Host Requirements
Types of Host and Equipment
Performance Characteristics
Location Information
Network Requirements
Existing Networks and Migration
Functional Requirements
Financial Requirements
Enterprise Requirements
©2003 Algirdas Pakštas
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Background for Requirement
Analysis
Requirement Analysis helps to understand
design environment
Consists of
Identifying, gathering, and understanding system
requirements and their characteristics
Developing thresholds for performance to
distinguish between low- and high-performance
services
Determining specified services for the network
Requirement Analysis is fundamental to the
network design process but is often
overlooked or ignored
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Background for Requirement
Analysis
Gathering requirements means talking to
users and network personnel and
interpreting the results
Each user has its own set of requirements
Network personnel are often distanced from the
users and do not have clear idea of what users
want or need
Thus it is a difficult part of the design process
Not doing it may lead to the solutions which
are not those which the users and
applications may need
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Background for Requirement
Analysis
EXAMPLES:
Design is based on a particular technology,
typically on the most comfortable for the
designer
Design is based on a particular vendor…
This happens due to the budget constraints and
deadlines which are forcing to use familiar, easy
to apply technologies
Problem is that such designs are not objective
Familiar technologies, protocols or vendors may
be poor choices for that particular environment
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Background for Requirement
Analysis
The results of the Requirement Analysis are
Requirements Specification
Application Map
Requirements Specification is a series of
worksheets that list the requirements
gathered for the design
Application Map shows the location
dependencies between applications
Will be used for Flow Analysis
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User Requirements
The user component of the generic system
and the interface:
[ User ]
[ User ] /Timeliness
---------------------------------------< Interactivity
[Application]
[Application] \Reliability
[ Host ]
[ Host ]
------------------\----(Network)-----/
Quality
Adaptability
Security
Affordability
User Numbers
User Locations
Expected Growth
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User Requirements
Timeliness
“Timeliness is a requirement that the user is
able to access, transfer, or modify
information within a tolerable time frame”
What is “tolerable” depends on the user’s
perception of the delay in the system
EXAMPLES-delays that network will need to
provide:
User wants to download files from a server and
complete each transfer in 10 minutes
User wants to receive video frames every 30ms
End-to-end or round-trip delay is important
measurement
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User Requirements
Interactivity
Similar to “timeliness” but focuses on a
response time from the system or network
Interactivity is to be looked as an indication
of the response time which are on the order
of the human response times
“Interactivity is a measure of the response
time of the system when it is required to
actively interact with a human”
The round-trip delay is a measure of the
interactivity
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User Requirements
Reliability
From the user prospective it is a requirement
for constantly available service
Possibility to have access to system resources a
very high percentage of time
Consistent level of service to the user in terms of
network performance
Thus, reliability as requirement is closely related
to the performance characteristic reliability where
delay and capacity are also important
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User Requirements
Quality
Refers to the quality of the presentation to
the user
Perception of audio, video and/or data displays
EXAMPLE: Providing videoconferencing,
videofeeds and telephony
It is possible to do it on the Internet!
But other technologies can provide much better
presentation quality
It is often not sufficient to provide just a capability
over a network
Measures of quality should include all the
performance characteristics
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User Requirements
Adaptability
“It is ability of the system to adapt to the
user’s changing needs”
EXAMPLES:
Distance-independence
Relying on the network
Coupling to the logical servers and decoupling from
the physical - it does not matter where the servers
are as long as users can get services
As a result user may lose a part of his rights - the
ability to know where the job was executed
Mobility
Mobile computing, access to the services and
resources from any location via portable computers
and ad-hoc access to the network
Adaptability must be reflected in the system
design
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User Requirements
Security
It is a requirement to guarantee
Integrity (accuracy and authenticity) of the user’s
information and physical resources
Access to the user’s and system resources
Security is probably closest to the
performance characteristic reliability
It impacts capacity and delay
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User Requirements
Affordability
It is the last general user requirement
“We would like to have it but how much does it
cost?”
Not technical but will impact the network design!
We have to look at the user/customer
budget
Are design costs too expensive to implement?
How cost and funding are tied to users or groups
of users?
Funding should be discussed as a system-wide
requirement from the overall budget perspective
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Application Requirements
We will look at
Types of Applications
Reliability
Capacity
Delay
Application Groups
[ User ]
[ User ]
[Application]
[Application]
[ Host ]
[ Host ]
------------------\----(Network)-----/
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Application Requirements
Types of Applications
Service and service performance
requirements of the applications can be
characterized as:
Mission-critical applications
Deterministic and/or guaranteed reliability
Controlled-rate applications
Specified capacity
Real-time/interactive applications
Specified delay
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Application Requirements
Types of Applications
User Service and Performance Requirements
Timeliness \_________________ / DELAY
Interactivity /
\
Reliability \
/
Quality
\__________________/ RELIABILITY
Adaptability /
\
Security
/
\
Affordability
\
/
User Numbers
\_____________/ CAPACITY
User Locations
/
\
Expected Growth /
\
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Application Requirements
Reliability
Reliability can be subjective but some
applications must maintain high reliability in
order to function
Loss of reliability can result in
Loss of revenue or customers
Typical application: transaction/money dependant,
investment banking or airline reservation system
Unrecoverable information or situation
Telemetry processing and teleconferencing applications
Loss of sensitive data
Customer ID/billing and intelligence-gathering
applications
Loss of life
Transportation or health-care monitoring applications
QUESTION: Can the Best-Effort System be at all suitable
for the mission-critical applications?
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Application Requirements
Capacity
Could be required by the applications having
well understood amount of capacity
EXAMPLE: Controlled-rate applications
Voice, non-buffered video, some teleservice
applications
May require to define:
Thresholds
Bounds
Guarantees on minimum capacity
Peak capacity
Sustained capacity
Can be tied to the end-to-end delay of the
network
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Application Requirements
Delay
Optimizing the total (end-to-end and roundtrip) delay is the most important for the
application service
Need for “better than the best-effort”
services
Applications with delay requirements are
migrating to the Internet or IP intranets
Applications previously dedicated to a single
user/host are used via Internet/intranet
Term “real-time” describes the need for strict
delay tolerance
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Application Requirements
Delay
Real-time applications
Have the most strict timing relationship
between source and destination
Timers are set for the receipt of information
If information is received after the timers expire it is
considered worthless and is dropped
Does not mean that information has to be
transferred within predefined time, rather
Delay boundaries (and, hopefully, consequences)
are understood by source and destination
Destination does not wait beyond this boundary
EXAMPLE: Video playback - delay beyond the
playback timer can cause blank parts in frames
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Application Requirements
Delay
Non-real-time applications
Various end-to-end delay requirements
Destination will wait until the information is
received (defined by the timers in
applications and hosts)
Majority of the applications are non-real-time
Can be
Interactive
Asynchronous
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Application Requirements
Delay
Interactive applications
Assume timing relationship between source
and destination
Typical applications: telnet, FTP, Web
Asynchronous applications
Intensive to time
Assumes no timing relationship
EXAMPLE: E-mail
Can be
Burst
Bulk
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Application Requirements
Delay
Application Delay Types
Real Time|
Non-Real-Time
|
/
\
|Interactive |Asynchronous
|
/ \
|
|Burst | Bulk |Time-Intensive
-------------------------------------Telemetry|Telnet| FTP |E-mail
Processing
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Application Requirements
Application Groups
It is useful to group together the
applications with similar performance
characteristics
Helps in mapping performance characteristics
Helps in gathering requirements
Groups may have some overlap…
EXAMPLES of the groups are discussed
below
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Application Requirements
Application Groups
Command and control/telemetry applications
Information is transmitted between remote objects
Characterized as having high-performance delay and
reliability
Possibly mission-critical and/or real-time applications
Visualization applications
Viewing and manipulation of 2-D, 3-D and VR objects
Characterized as having high-performance capacity and
delay
Possibly real-time and/or controlled-rate applications
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Application Requirements
Application Groups
Distributed computing applications
Different variants of the processor coupling
Share the same local bus
Co-located at the same LAN (computing cluster)
Distributed across LAN, MAN, and WAN boundaries
Degree of distribution/parallelism is also
determined by the granularity of the task
Characterized as having high performance delay
Possibly being interactive applications
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Application Requirements
Application Groups
Applications for Web access, development and
use
Involves accessing remote host and
downloading/uploading information
Web-sessions are
Interactive
Amounts of information are small
Characterized as being delay-sensitive but NOT highperformance
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Application Requirements
Application Groups
Bulk data transport
Typically file transfer (FTP)
Optimization of the data transfer rate at the
expense of interactivity
Characterized as being not high-performance
Tele-service applications
Teleconferencing, telemedicine, teleseminars,…
Simultaneous delivering of mixture of the data, voice,
and video to the groups of people at various locations
EXAMPLE: Multicast backbone (mbone) on the Internet
Characterized as having high-performance
capacity, delay, and/or reliability, depending on
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application
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Application Requirements
Application Groups
Operations, administration, and maintenance
(OAM) applications
Needed for proper functioning and operation of
the network
Domain name service (DNS)
Mail service/SMTP
News services/NNTP
Address resolution service (ARP)
Network monitoring and management
Network security
Systems accounting
Generally requires high reliability
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Application Requirements
Application Groups
Application Component Interface to System
[ User ]
[ User ]
/Application
|
|
/ Group
[Application] [Application] / Application
-----------------------------------------< Type
[ Host ]
[ Host ]
| Application
------------------| Performance
\----(Network)-----/
| Characteristics
|Application
| Locations
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Host Requirements
Host Component of the Generic System
[ User ]
[ User ]
|
|
[Application]
[Application]
|
|
[ Host ]
[ Host ]
------------------\----(Network)-----/
We will look at
Types of Host and Equipment
Performance Characteristics
Location Information
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Host Requirements
Types of Host and Equipment
Generic computing devices
Dos-, Windows-based PCs, Macs, Unix workstations,
etc.
Form access points into the network for [single] user
Important from end-to-end perspective
Tend to be overlooked
Creates “last foot” problem in systems performance
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Host Requirements
Types of Host and Equipment
Servers
More powerful
Computing servers, storage servers, application
servers, etc.
Also have requirements for “last foot” performance
Requirements specific to the server’s role
Specialized Equipment
Supercomputers, mainframes, parallel or
distributed computing systems, sensors, data
acquisition devices, etc.
Tends to be location-dependent
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Host Requirements
Types of Host and Equipment
Specialized Equipment Tends to be Location-Dependent
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Host Requirements
Performance Characteristics
Performance of the components impacts the
overall performance of the server/host
Operating
System
Processing
Memory
System Bus
Network
Interface
Disk Drive
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Other
Peripherals
83
Host Requirements
Performance Characteristics
Performance of the components end-to-end in
the host is important
Storage performance
Disk-drive seek time
Tape performance
Processor (CPU) performance
Memory performance
Access time
System bus performance
Capacity and arbitration mechanisms
Effectiveness of Software
Driver
OS (effectiveness of the protocol stack)
Number of memory copies in the protocol stack
Cost of execution of a given OS
API
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Host Requirements
Location Information
Helps to determine
Relationships between components
Flow characteristics
Particularly important
In the outsourcing of system components or
functions
In the consolidation of organizations,
components or functions
In the relocation of system components or
functions within an organization
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Host Requirements
System Components can have Location Dependencies
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Host Requirements
Summary of the Host/Network
Interface
Host Component Interface to System
[ User ]
[ User ]
/Types of
|
|
/ Hosts and
[Application]
[Application] / Equipment
|
|
/
[ Host ]
[ Host ] / Location
------------------- / Information
---------|----------------------|------<
\----(Network)----/
\ Host/Equipment
\
\
Performance
Characteristics
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Network Requirements
Existing Networks and Migration
Functional Requirements
Financial Requirements
Enterprise Requirements
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Network Requirements
Existing Networks and Migration
Network Component Interface to System
[ User ]
[ User ]
/-Scaling
|
|
/
[Application]
[Application] / -Interoperability
|
|
/
[ Host ]
[ Host ]
/ -Location Information
------------------/
|
|
/
-Network Services
(
Network
)--<
:…....(<Existing Network> )...: \
-Support Services
:
/
: \
:...<Existing Network>…....:
\ -Network Performance
\ Characteristics
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Network Requirements
Functional Requirements
Requirements for Network Management and
Security
Categories of network management tasks
Monitoring (automatic?)
For event notification (frequent snapshot of the system)
For metrics and planning (large archives)
Actions (manual?)
Network configuration
Troubleshooting
Monitoring:
Obtaining values for network management parameters
from network elements
Processing the data
Visualization
Archiving the data
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Network Requirements
Functional Requirements
General Network Management Requirements
Monitoring methods
Instrumentation methods
Protocols (SNMP, SNMPv2/v3, CMIP, RMON)
Parameter lists (MIBs)
Monitoring tools
Direct access
The characteristics sets for monitoring
In-band vs. out-of-band monitoring
Centralized vs. distributed monitoring
Performance requirements
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Network Requirements
Functional Requirements
Developing a security plan for the network:
User requirements
Security policies
Risk analysis
User Requirements for Security
Government specified requirements: MoD/DoD/DoE...
Organization-specified security requirements
End-user-specified security requirements
May be applied to
Users/User groups
Projects
Specific types of data (also how data are generated,
transferred, processed and stored)
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Network Requirements
Financial Requirements
Level of funding for implementing network
design is system-wide requirement
Funding is associated with
Overall cost limit
Recurring components
Expected to occur or be replaced/upgraded periodically
Operations, administrations and maintenance, costs
from service providers, provisions for network
modification
Non-recurring components - building of the
network
Network design
Network deployment
Hardware/Software components
Initial installation or establishment of any services from
service providers
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Network Requirements
Enterprise Requirements
Enterprises need transfer of
Phone/voice
FAX
Video
Enterprise environment presumes integration
of such services into a common transmission
infrastructure
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Requirement Analysis
Conclusions
The Process Model for Requirement Analysis
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Bibliography
• James D. McCabe: “Practical Computer
Network Analysis and Design”, Morgan
Kaufmann Publishers, San Francisco, USA,
1998. ISBN 1-55860-498-7
• Algirdas Pakštas: Raspredelennye
programmnye konfiguracii: Analiz i razrabotka
(“Distributed Software Configurations: Analysis
and Development”), Mokslas, Vilnius, 1989.
ISBN 5-420-00637-5
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