K. Salah 1

Module 1.0: Introduction

• Network overview

• What is ‘network design’?

• Network Design Lifecycle

• How it was done

• Our approach

• What is expected or unexpected

K. Salah 2

What is a Network?

•Management view

•Technical view

K. Salah 3

Management View

• 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”

K. Salah 4

Management View (cont.)

• 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?

K. Salah 5

The Technical View

• 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

K. Salah 6

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 on the problem– No consideration in delay optimisation– No guarantee of service quality

K. Salah 7

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

K. Salah 8

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

K. Salah 9

Application Bandwidths

Word Processing

File Transfers

Real-Time Imaging

100s Kbps Few Mbs

Few Mbps 10s Mbps

10s Mbps 100s Mbps

Transaction Processing 100 Bytes Few Kbps

K. Salah 10

Networking issues

• LAN, MAN and WAN

• Switching and routing

• Technologies: Ethernet, FDDI, ATM …

• Mobile networking

• Internetworking

• Applications

• Service quality

• Security concerns

K. Salah 11

Network Design: Achievable?

Response Time Cost

Business GrowthReliability

K. Salah 12

Where to begin?

WAN

CampusCampus

TrafficTrafficPatternsPatterns

Dial in Dial in UsersUsers

SecuritySecurity

WWW WWW AccessAccess

UsersUsers

NetworkNetworkManagementManagement

AddressingAddressing

K. Salah 13

A Systems Approach

Requirement Analysis

Flow Analysis

Logical Design

Physical Design

Routing & Addressing

K. Salah 14

• 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

A Systems Approach (Cont.)

K. Salah 15

Another Perspective:

• Data collection– Traffic– Costs– Constraints

• Design process

• Performance analysis

• Fine tuning

• A painstaking iterative process

K. Salah 16

One More Look

Define Objectivesand Requirements

Create InitialSolution

Define DeploymentStrategy

DevelopArchitecture

Create BuildDocumentation

Develop DetailedDesign

Review and VerifyDesign

CreateImplementation Plan

Procure Resourcesand Facilities

Stage and Install

Certify and Hand-offto Operations

Develop OperationsPolicies andCapabilities

ConfigurationManagement

FaultManagement

ChangeManagement

PerformanceManagement

Review andApprove

BusinessBusinessPlanningPlanning

OperationsOperationsImplementImplementNetworkNetwork

Network Network DesignDesign

K. Salah 17

Analysis and Design Processes

• 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

K. Salah 18

Technologies for design

• 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

K. Salah 19

Design and Study of a System

K. Salah 20

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 …

Art or Science?

K. Salah 21

• A network design project can be defined on three different levels, each with separate outcomes that must come together in the end

– Conceptual - little detail

– Logical

– Physical - most detail

Schema View of Network Design

K. Salah 22

• User level network requirements– Applications– Speed– Access to Information

• Management level network requirements– Cost and Budget Limitations– Best Value– Applications to Provide Productivity Improvements– Business Improvement

Conceptual

K. Salah 23

• Enterprise Level Requirements

– Centralized / Decentralized Email

• Area / Department Level Requirements

– High network bandwidth in medical imaging areas

– Application Oriented

Conceptual Level of Network Design

K. Salah 24

What do the users want?

– Services

What do the users need?

What don’t they know they need?

Organize and Prioritize Requirement

Conceptual Level of Network Design

K. Salah 25

Conceptual Level of Network Design

• User Requirements Performance Requirements

• Timeliness• Interactivity• Reliability• Quality• Security• Affordability• User Numbers• User Locations• User Growth

Capacity

Reliability

Delay

K. Salah 26

• 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

Logical Level Network Design

K. Salah 27

• 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

Logical Level Network Design

K. Salah 28

• Hardware level requirements

– Router performance based on bandwidth requirements

– Switches, Repeaters, etc...

• Equipment location requirements

• Physical security requirements

Physical Level Network Design

K. Salah 29

• Media selection

• Bandwidth requirements based on conceptual design

• You design answers the question- Can a network be built using the logical level requirements

Physical Level Network Design

K. Salah 30

• New network design

• Re-engineering a network design

• Network expansion design

Types of Network Design

K. Salah 31

• Actually starting from scratch

• No legacy networks to accommodate

• Major driver is the budget, no compatability issues to worry about

• Getting harder to find these situations

New Network Design

K. Salah 32

• 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

Re-engineering a Network Design

K. Salah 33

• Network designs that expand network capacity

• Technology upgrades

• Adding more users or networked equipment

Network Expansion Design

K. Salah 34

This Whole Thing is Messy

K. Salah 35

• Ambiguous Requirements

– The network will only transport IP

– The application requires Novell IPX

This Whole Thing is Messy

K. Salah 36

• Conflicting Requirements

– Keep costs down

– High performance cost money

This Whole Thing is Messy

K. Salah 37

• Lack of Design Tools

• Lack of Management Tools

• Lack of Vendor Interoperability

This Whole Thing is Messy

K. Salah 38

• Lack of Documentation

– Existing Network

– How things should be done. (I.e. wiring)

– Vendor information

This Whole Thing is Messy

K. Salah 39

• Network Management

– More management uses more bandwidth

– Every vendor has their own management tools

– Vendor tools may conflict with each other

This Whole Thing is Messy

K. Salah 40

• 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.

This Whole Thing is Messy

10Mb/s

Ethernet

10Mb/s

EthernetT1 1.5Mb/s

Firewall 200Kbs

K. Salah 41

• 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”

This Whole Thing is Messy