1. CSE 550 Computer Network Design
Dr. Mohammed H. Sqalli
COE, KFUPM
Spring 2008 (Term 072)

2. Introduction What is a Network? What is “Network Design”?
Top-Down Network Design
Network Development Life Cycle (NDLC)
Network Analysis and Design Methodology
Types of Network Design
And Then What?
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3. What is a Network? Management view Technical view CSE-550-T072
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4. The Management View (1/3)
A network is a utility
Computers and their users are customers of the network utility
The network must accommodate the needs of customers
As computer usage increases so does the requirements of the network utility
Resources will be used to manage the network
The Network Utility is NOT free!
Someone must pay the cost of installing and maintaining the network
Manpower is required to support the network utility
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5. The Management View (2/3)
Utilities don’t bring money into the organization
Expense item to the Corporation
Cannot justify Network based on “Productivity Improvements”
As a network designer, you need to explain to management how the network design, even with the high expense, can save money or improve the company’s business
If users cannot log on to your commerce site, they will try your competitor, and you have lost sales
If you cannot get the information your customers are asking about due to a network that is down, they may go to your competitor
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6. The Management View (3/3)
You need to understand how the network assists the company in making money and play on that strength when you are developing the network design proposal
Try to show a direct correlation between the network design project and the company’s business
“Because you want a faster network” is not good enough, the question that management sends back is WHY DO I NEED A FASTER ONE?
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7. The Technical View (1/2)
A “Network” really can be thought of as three parts and they all need to be considered when working on a network design project:
Connections
Communications/Protocols
Services
Provided by Hardware that ties things together
Wire/Fiber/Wireless Transport Mechanisms
Routers
Switches/Hubs
Computers
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8. The Technical View (2/2) Communications/Protocols Services
Provided by Software
A common language for 2 systems to communicate with each other
TCP/IP (Internet/Windows NT)
IPX / SPX (Novell Netware 4)
AppleTalk
Other Network OS
Services
The Heart of Networking
Cooperation between 2 or more systems to perform some function - Applications
telnet
FTP
HTTP
SMTP
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9. Traditional Network Design
Based on a set of general rules
“80/20”
“Bridge when you can, route when you must”
Can’t deal with scalability & complexity
Focused on capacity planning
Throw more bandwidth at the problem
No consideration to delay optimization
No guarantee of service quality
Less importance given to network RMA (Reliability, Maintainability, and Availability) compared to throughput
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10. Application Characteristics
Applications
Message Length
Message arrival rate
Delay need
Reliability need
Interactive terminals
Short
Low
Moderate
Very high
File transfer
Very long
Very low
Hi-resolution graphics
Low to moderate
High
Packetized voice
Very short
Networks must be work independent of the fine details of applications, e.g., message arrival scheme.
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11. Application Bandwidths
Transaction Processing
100 Bytes Few Kbps
Word Processing
100s Kbps Few Mbps
File Transfers
Few Mbps s Mbps
Real-Time Imaging
10s Mbps s Mbps
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12. A Look on Multimedia Networking
Video standard
Bandwidth per user
WAN services
Digital video interactive
1.2 Mbps
DS1 lines ISDN H11, Frame Relay, ATM
Motion JPEG
10 to 240 Mbps
ATM 155 or 622 Mbps
MPEG-1
1.5 Mbps
MPEG-2
4~6 Mbps
DS2, DS3, ATM at DS3 rate
This table provides a bandwidth-based choice.
The ability to add or subtract bandwidth on demand is a key requirement. Video conferencing.
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13. Some Networking Issues
LAN, MAN and WAN
Switching and routing
Technologies: Ethernet, FDDI, ATM …
Wireless/Mobile networking
Internetworking
Applications
Service quality
Security concerns
There are still more to come, if we look into deeper networking layers.
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14. Generations of Networking
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15. Network Design: Achievable?
Response Time
Cost
Reliability
Business Growth
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16. Where to begin? Addressing Traffic Patterns WWW Access Campus Users
Dial in Users
A puzzle.
Network Management
Security
WAN
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17. Traditional Network Design Methodology
Many network design tools and methodologies in use today resemble the “connect-the-dots” game
These tools let you place internetworking devices on a palette and connect them with LAN or WAN media
Problem with this methodology:
It skips the steps of analyzing a customer's requirements, and selecting devices and media based on those requirements
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18. Top-Down Network Design Methodology (1/2)
Good network design
Recognizes that a customer’s requirements embody many business and technical goals
May specify a required level of network performance, i.e., service level
Includes difficult network design choices and tradeoffs that must be made when designing the logical network before any physical devices or media are selected
When a customer expects a quick response to a network design request
A bottom-up (connect-the-dots) network design methodology can be used, if the customer’s applications and goals are well known
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19. Top-Down Network Design Methodology (2/2)
Network designers often think they understand a customer’s applications and requirements.
However, after the network installation, they may discover that:
They did not capture the customer's most important needs
Unexpected scalability and performance problems appear as the number of network users increases
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20. Top-Down Network Design Process (1/2)
Begins at the upper layers of the OSI reference model before moving to the lower layers
Focuses on applications, sessions, and data transport before the selection of routers, switches, and media that operate at the lower layers
Explores divisional structures to find the people:
For whom the network will provide services, and
From whom to get valuable information to make the design succeed
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21. Top-Down Network Design Process (2/2)
It is an iterative process:
It is important to first get an overall view of a customer's requirements
More detail can be gathered later on protocol behavior, scalability requirements, technology preferences, etc.
Recognizes that the logical model and the physical design may change as more information is gathered
A top-down approach lets a network designer get “the big picture” first and then spiral downward into detailed technical requirements and specifications
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22. Structured Network Design Process - A Systems Approach (1/2) -
The system is designed in a top-down sequence
Several techniques and models can be used to characterize the existing system, new user requirements, and a structure for the future system
A focus is placed on understanding:
Data flow, data types, and processes that access or change the data
The location and needs of user communities that access or change data and processes
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23. Structured Network Design Process - A Systems Approach (2/2) -
A logical model is developed before the physical model
The logical model represents the basic building blocks, divided by function, and the structure of the system
The physical model represents devices and specific technologies and implementations
For large network design projects, modularity is essential
The design should be split functionally to make the project more manageable
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24. Network Development Life Cycle
Analysis
Management
Design
Simulation/
Prototyping
Monitoring
80 percent of the traffic on a given network segment should be local (destined for a target in the same workgroup), and not more than 20 percent of the network traffic should need to move across a backbone (the spine that connects various segments or "subnetworks"). Backbone congestion can indicate that traffic patterns are not meeting the 80/20 rule. In this case, rather than adding switches or upgrading hubs, it may be easier to improve network performance by doing one of the following:
Move resources to contain traffic locally within a workgroup.
Move users (logically, if not physically) so that the workgroups more closely reflect the actual traffic patterns
Add servers so that users can access them locally without having to cross the backbone.
After you have ensured proper network design and resource location, the next step is to determine the optimal technology to meet your growing needs.
Implementation
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25. Network Design and Implementation Cycle
80 percent of the traffic on a given network segment should be local (destined for a target in the same workgroup), and not more than 20 percent of the network traffic should need to move across a backbone (the spine that connects various segments or "subnetworks"). Backbone congestion can indicate that traffic patterns are not meeting the 80/20 rule. In this case, rather than adding switches or upgrading hubs, it may be easier to improve network performance by doing one of the following:
Move resources to contain traffic locally within a workgroup.
Move users (logically, if not physically) so that the workgroups more closely reflect the actual traffic patterns
Add servers so that users can access them locally without having to cross the backbone.
After you have ensured proper network design and resource location, the next step is to determine the optimal technology to meet your growing needs.
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26. Network Design and Implementation Cycle (1/3)
Analyze requirements:
Interviews with users and technical personnel
Understand business and technical goals for a new or enhanced system
Characterize the existing network: logical and physical topology, and network performance
Analyze current and future network traffic, including traffic flow and load, protocol behavior, and QoS requirements
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27. Network Design and Implementation Cycle (2/3)
Develop the logical design:
Deals with a logical topology for the new or enhanced network
Network layer addressing and naming
Switching and routing protocols
Security planning
Network management design
Initial investigation into which service providers can meet WAN and remote access requirements
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28. Network Design and Implementation Cycle (3/3)
Develop the physical design:
Specific technologies and products to realize the logical design are selected
The investigation into service providers must be completed during this phase
Test, optimize, and document the design:
Write and implement a test plan
Build a prototype or pilot
Optimize the network design
Document your work with a network design proposal
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29. Another Perspective Data collection Design process
Traffic
Costs
Constraints
Design process
Performance analysis
Fine tuning
A painstaking iterative process
This can be basically an iterative process and a painstaking one!
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30. PDIOO Network Life Cycle (1/3) (Cisco)
Plan:
Network requirements are identified in this phase
Analysis of areas where the network will be installed
Identification of users who will require network services
Design:
Accomplish the logical and physical design, according to requirements gathered during the Plan phase
Implement:
Network is built according to the Design specifications
Implementation also serves to verify the design
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31. PDIOO Network Life Cycle (2/3) (Cisco)
Operate:
Operation is the final test of the effectiveness of the design
The network is monitored during this phase for performance problems and any faults, to provide input into the Optimize phase
Optimize:
Based on proactive network management which identifies and resolves problems before network disruptions arise
The optimize phase may lead to a network redesign
if too many problems arise due to design errors, or
as network performance degrades over time as actual use and capabilities diverge
Redesign may also be required when requirements change significantly
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32. PDIOO Network Life Cycle (3/3) (Cisco)
Retire:
When the network, or a part of the network, is out-of-date, it may be taken out of production
Although Retire is not incorporated into the name of the life cycle (PDIOO), it is nonetheless an important phase
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33. One More Look Business Planning Network Design Implement Network
Operations
Develop Operations Policies and Capabilities
Define Objectives and Requirements
Develop Architecture
Create Implementation Plan
Create Initial Solution
Develop Detailed Design
Procure Resources and Facilities
Fault Management
Define Deployment Strategy
Create Build Documentation
Configuration Management
Stage and Install
Review and Approve
Review and Verify Design
Certify and Hand-off to Operations
Change Management
Performance Management
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34. Information Flows between Network Analysis, Architecture, and Design
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