Module 1.0: Introduction
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Network overview
What is ‘network design’?
Network Design Lifecycle
How it was done
Our approach
What is expected or unexpected
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What is a Network?
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Management view
Technical view
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Management View
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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
• Utilities don’t bring money into the organization
– Expense item to the Corporation
– Cannot justify Network based on “productivity Improvements”
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Management View (cont.)
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As a network designer, you need to explain to management how the
network design, even with the higher expense, can save money or
improve the companies business
– If users cannot log on to your commerce site, they will try a
competitors, 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
You need to understand how the network assists the company in
making money and play to that strength when you are developing
the network design proposal
Try to show a direct correlation between the network design project
and the companies 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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The Technical View
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A “Network” really can be thought as of three things and they all need to be considered when working on a
network design project
– Connections
– Communications
– Services
Connection
– Provided by Hardware that ties things together
 Wire/Fiber Transport Mechanisms
 Routers
 Switches/Hubs
 Computers
Communications
– 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
 SNMP
 UDP
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Traditional Network Design
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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 on the problem
– No consideration in delay optimisation
– No guarantee of service quality
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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
DS1 lines ISDN H11,
Frame Relay, ATM
MPEG-2
4~6 Mbps
DS2, DS3, ATM at DS3
rate
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Application characteristics
Applications
Message Length
Msg arrival rate
Delay need
Reliability need
Interactive terminals
Short
Low
Moderate
Very high
File transfer
Very long
Very low
Very low
Very high
Hi-resolution graphics
Very long
Low to moderate
High
Low
Packet-sized voice
Very short
Very High
High
Low
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Application Bandwidths
Transaction
Processing
100 Bytes
Few Kbps
Word Processing
100s Kbps
Few Mbs
File Transfers
Few Mbps
10s Mbps
Real-Time Imaging
10s Mbps
100s Mbps
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Networking issues
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LAN, MAN and WAN
Switching and routing
Technologies: Ethernet, FDDI, ATM …
Mobile networking
Internetworking
Applications
Service quality
Security concerns
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Network Design: Achievable?
Response Time
Cost
Business Growth
Reliability
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Where to begin?
Traffic
WWW
Addressing
Patterns
Access
Campus
Security
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Users
WAN
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Dial in
Users
Network
Management
A Systems Approach
Flow Analysis
Requirement
Analysis
Logical Design
Physical Design
Routing & Addressing
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A Systems Approach (Cont.)
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Requirement Analysis is sometimes called “Conceptual” process
Routing & Addressing
– Geographical, Functional
– Defining Autonomous Systems (AS)
– Available IP addresses assigned
– NAT usage
Flow Analysis can be part of Logical Design
Flow Analysis include:
– Flow of information from client to server –or- client to client
 For delay calculation
– Node placement (router, servers, clients)
– Network Topology (mesh, ring, bus, backbone)
– Multiplexing of Traffic
– Prioritized flow or not
 Voice
 Video Conferencing
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Another Perspective:
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Data collection
– Traffic
– Costs
– Constraints
Design process
Performance analysis
Fine tuning
A painstaking iterative process
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One More Look
Business
Planning
Network
Design
Implement
Network
Operations
Define Objectives
and Requirements
Develop
Architecture
Create
Implementation Plan
Develop Operations
Policies and
Capabilities
Create Initial
Solution
Develop Detailed
Design
Procure Resources
and Facilities
Fault
Management
Define Deployment
Strategy
Create Build
Documentation
Stage and Install
Configuration
Management
Review and
Approve
Review and Verify
Design
Certify and Hand-off
to Operations
Change
Management
Performance
Management
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Analysis and Design Processes
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Set and achieve goals
– Maximising performance
– Minimising cost
Optimisation with trade-offs
– Recognising trade-offs
– No single ‘best’ answer
Hierarchies
– Provide structure in the network
Redundancy
– Provides availability & reliability
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Design Study Approaches
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Heuristic – by using various algorithms
Exact – by working out mathematical solutions based on linear
programming etc., minimising certain cost functions
Simulation – often used when no exact analytical form exists.
Experiments are conducted on simplified models to see the
performance of network
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Design and Study of a System
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Art or Science?
The Art of Network Design
• Technology choices
• Relations to business goals
The Science of Network Design
Understanding of network technologies
Analysis of capacity, redundancy, delay …
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Schema View of Network Design
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A network design project can be defined on three different levels,
each with separate outcomes that must come together in the end
– Conceptual - little details
– Logical
– Physical - most details
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Conceptual
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User level network requirements
– Applications
– Speed
– Access to Information
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Management level network requirements
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Cost and Budget Limitations
Best Value
Applications to Provide Productivity Improvements
Business Improvement
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Conceptual Level of Network Design
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Enterprise Level Requirements
– Centralized / Decentralized Email
Area / Department Level Requirements
– High network bandwidth in medical imaging areas
– Application Oriented
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Conceptual Level of Network Design
 What do the users want?
– Services
 What do the users need?
 What don’t they know they need?
 Organize and Prioritize Requirement
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Conceptual Level of Network Design
• User Requirements 
Performance Requirements
• Timeliness
• Interactivity
• Reliability
• Quality
• Security
• Affordability
• User Numbers
• User Locations
• User Growth
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Delay
Reliability
Capacity
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Logical Level Network Design
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Network level requirements based on the conceptual design (the
big picture)
– what kind of network will meet the conceptual design based
on the information gathered
– Start to get from idea’s to networking items from a design
choice standpoint
– Still not at the specific detail level yet
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Logical Level Network Design
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Network Protocol selection
– IP addressing issues
– Other protocol addressing issues
– How to make all these protocols work together
Need for sub-netting (breaking the network into segments)
Network Topology to use
Simple block diagram type design
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Physical Level Network Design
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Hardware level requirements
– Router performance based on bandwidth requirements
– Switches, Repeaters, etc...
Equipment location requirements
Physical security requirements
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Physical Level Network Design
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Media selection
Bandwidth requirements based on conceptual design
You design answers the question- Can a network be built using
the logical level requirements
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Types of Network Design
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New network design
Re-engineering a network design
Network expansion design
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New Network Design
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Actually starting from scratch
No legacy networks to accommodate
Major driver is the budget, no compatibility issues to worry about
Getting harder to find these situations
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Re-engineering a Network Design
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Modifications to an existing network to compensate for original
design problems
Sometimes required when networks users change existing
applications or functionality
More of the type of problem seen today
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Network Expansion Design
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Network designs that expand network capacity
Technology upgrades
Adding more users or networked equipment
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This Whole Thing is Messy
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This Whole Thing is Messy
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Ambiguous Requirements
– The network will only transport IP
– The application requires Novell IPX
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This Whole Thing is Messy
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Conflicting Requirements
– Keep costs down
– High performance cost money
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This Whole Thing is Messy
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Lack of Design Tools
Lack of Management Tools
Lack of Vendor Interoperability
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This Whole Thing is Messy
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Lack of Documentation
– Existing Network
– How things should be done. (I.e. wiring)
– Vendor information
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This Whole Thing is Messy
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Network Management
– More management uses more bandwidth
– Every vendor has their own management tools
– Vendor tools may conflict with each other
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This Whole Thing is Messy
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Security
– What is enough security?
– What is too much security?
– security and management can not be dealt as
‘afterthoughts’. It is not an add-on feature, it has to be
integrated within.
Firewall
200Kbs
10Mb/s
Ethernet
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T1 1.5Mb/s
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10Mb/s
Ethernet
This Whole Thing is Messy
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Evolving Network Technologies
– Everything is a moving target
– Products are put onto the market before standards are
approved
– Whiz Bang Theory
– Everyone is a computer “expert”
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