CSE 550 Computer Network Design Dr. Mohammed H. Sqalli COE, KFUPM Spring 2012 (Term 112)

CSE 550Computer Network Design

Dr. Mohammed H. SqalliCOE, KFUPM

Spring 2012 (Term 112)

CSE-550-T112 Lecture Notes - 1 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?


What is a Network?

Management view

Technical view


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



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



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?


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

Connections Provided by Hardware that ties things together

Wire/Fiber/Wireless Transport Mechanisms Routers Switches/Hubs Computers


The Technical View (2/2)

Communications/Protocols 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


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


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 Very low Very high

Hi-resolution graphics

Very long Low to moderate

High Low

Packetized voice

Very short Very high High Low


Application Bandwidths

Word Processing

File Transfers

Real-Time Imaging

100s Kbps Few Mbps

Few Mbps 10s Mbps

10s Mbps 100s Mbps

Transaction Processing 100 Bytes Few Kbps


A Look on Multimedia NetworkingVideo standard Bandwidth per

userWAN 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


Some Networking Issues

LAN, MAN and WAN Switching and routing Technologies: Ethernet, FDDI, ATM … Wireless/Mobile networking Internetworking Applications Service quality Security concerns


Network Design: Achievable?

Response Time Cost

Business GrowthReliability


Where to begin?

WAN

CampusCampus

TrafficTrafficPatternsPatterns

Dial in Dial in UsersUsers

SecuritySecurity

WWW WWW AccessAccess

UsersUsers

NetworkNetworkManagementManagement

AddressingAddressing


Traditional Network Design Methodology

Many network design tools and methodologies that have been used 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


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


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


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


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


Network Development Life Cycle

Management

Analysis

Design

Simulation/Prototyping

Implementation

Monitoring


Network Design and Implementation Cycle


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



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



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


Another Perspective

Data collection Traffic Costs Constraints

Design process Performance analysis Fine tuning A painstaking iterative process


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



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



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


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


Information Flows between Network Analysis, Architecture, and Design


Requirements (business, application, and data) definition is required prior to network design activities

Expected compliance with requirements in a Request For Proposal (RFP) by both in-house personnel and outside consultants

Activities from various stages often take place simultaneously and backtrack to previous activities is sometimes needed

This methodology is an overall guideline to the network development process rather than “cookbook” instructions

Network Analysis and Design Methodology- Overall Characteristics -


Network Analysis and Design Methodology- Critical Success Factors of the NDLC (1/3) -

Identification of all potential customers and constituencies All groups must be consulted

Political awareness: Corporate culture: hierarchical, distributed, or open Backroom politics can play a role in systems design Find ways to ensure objectivity of the analysis and design

process (e.g., measurable goals) Buy-in:

Reach consensus on the acceptability of results of each stage Approved results of one stage become the foundation or

starting point for the next stage Makes the final presentation smoother



Communication: With all groups Write memos, communicate with key people in person,

etc. Detailed project documentation:

Prepare agendas Take meeting minutes Action items Use a project binder for all the above


Process/Product awareness: Stay focused: what is the process/product at each

stage? Keep meeting on track: no off-subject discussions

Be honest with yourself: Be your own harshest critic (no one else knows the

potential weaknesses or areas for improvement in your proposal better than you)

Use peer reviews Not all weaknesses can be corrected (e.g., financial or

time constraints)



Network Analysis and Design Methodology - Overall Guidelines -

Start with a clearly defined problem: Identify affected parties and representatives Held brainstorming sessions to define problems and

requirements of a solution Understand strategic business objectives defined by

senior management Collect baseline data from customer groups about

the current status of the system and network This is used to measure eventual impact of the

installed network Perform a feasibility study: problem definition and

associated alternative recommendations for further study


Customer’s Requirements- Understanding the Customer -

A good network design must recognize the customer’s requirements - need to make sure your design meets THEIR needs and not just YOURS!

The “Customer” may be your own firm, the “who” you are designing the network for

Need an overview of a customer’s requirements The best designed network will fail miserably without

the support of people


What do the users want? Services

What do the users need? What don’t they know but they need? Organize and Prioritize Requirement

Customer’s Requirements- Users’ Needs -


Customer’s Requirements- How they are used -

User Requirements Performance Requirements

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

Capacity

Reliability

Delay


Analysis and Design Processes

Set and achieve goals Maximizing performance Minimizing cost

Optimization with trade-offs Recognizing trade-offs No single ‘best’ answer

Hierarchies Provide structure in the network

Redundancy Provides availability & reliability


Approaches Used for Design

Heuristic – by using various algorithms Exact – by working out mathematical

solutions based on linear programming, etc., minimizing certain cost functions

Simulation – often used when no exact analytical form exists. Experiments are conducted on simplified models to see the performance of a network


Design and Study of a System


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?


New network design

Re-engineering a network design

Network expansion design

Types of Network Design


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

New Network Design


Modifications to an existing network to compensate for original design problems

Sometimes required when network users change existing applications or functionality

More of the type of problems seen today

Re-engineering a Network Design


Network designs that expand network capacity

Technology upgrades

Adding more users or networked equipment

Network Expansion Design

This Whole Thing is Messy


Ambiguous Requirements

The network will only transport IP

The application requires Novell IPX



Conflicting Requirements

Keep costs down

High performance costs money



Lack of Design Tools

Lack of Management Tools

Lack of Vendor Interoperability



Lack of Documentation

Existing network

How things should be done (e.g., wiring)

Vendor information



Network Management

More management uses more bandwidth

Every vendor has their own management tools

Vendor tools may conflict with each other



Security What is enough security? What is too much security?

Security and management can not be dealt with as ‘afterthoughts’. It is not an add-on feature, it has to be integrated within.


10Mb/s

Ethernet

10Mb/s

EthernetT1 1.5Mb/s

Firewall 200Kbs


Evolving Network Technologies Everything is a moving target Products are put onto the market before

standards are approved Everyone is a computer “expert”



OAM&POperations, Administration, Maintenance, Provisioning

NetworkManagement

NetworkProvisioning

Network Operations

NetworkMaintenance

Planning

Design

Fault Management

Trouble Ticket

Administration

Network Installation

Network Repairs

Facilities Installation

& Maintenance

Routine Network

Tests

Fault Management / Service Restoration

Configuration Management

Performance Management / Traffic Management

Security Management

Accounting Management

Reports Management

Inventory Management

Data Gathering & Analyses

Figure 1.21 Network Management Functional Groupings


Functional Flow Chart

Engineering Group

- Network Planning &Design

Operations GroupNOC

- Network Operations

I & M Group

-Network Installation &Maintenance

Fault TT

Configuration Data

TT RestorationPerformance & Traffic Data

Installation

Figure 1.22. Network Management Functional Flow Chart

NewTechnology

Network

Users

ManagementDecision


References

Dr. Khalid Salah (ICS, KFUPM), CSE 550 Lecture Slides, Term 032

Dr. Marwan Abu-Amara (COE, KFUPM), CSE 550 Lecture Slides, Term 052

P. Oppenheimer, “Top-Down Network Design,” Cisco Press, 3rd edition, 2010

J. McCabe, “Network Analysis, Architecture, and Design” Morgan Kaufmann Publishers, Inc., 3rd edition, 2007

J. E. Goldman, “Applied Data Communications - A Business-Oriented Approach”, 1998

Mani Subramanian, “Network Management – Principles and Practice” by, Pearson, Second Edition, 2010.

Documents

CSE 550 Computer Network Design Dr. Mohammed H. Sqalli COE, KFUPM Spring 2012 (Term 112)