Planeamentoe Gestãode Redes Análise de Requisitos

Planeamento 1

Planeamento e Gestão de Redes

Análise de Requisitos

Manuel P. Ricardo

Faculdade de Engenharia da Universidade do Porto

Planeamento 2

♦ Book

Top-Down Network Design, Second Edition

Priscilla Oppenheimer

Cisco Press

♦ Chapters 1 to 4

♦ Credits

These slides are based on the material made available by

Priscilla Oppenheimer

on the book’s site http://www.topdownbook.com

Planeamento 3

Structured Network Design

• Set of best practices

• Layer 7 first

• Identification of

– Business/technical goals

– Groups of users/their locations

– Applications

usage, generated traffic

Application

Presentation

Session

Transport

Network

Data Link

PhysicalLayer 1

Layer 7

Layer 6

Layer 5

Layer 4

Layer 3

Layer 2

Planeamento 4

Analyze

requirements

Develop

logical

design

Develop

physical

design

Test, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network

Top-Down Network Design Process

Planeamento 5Phase 1 –

Analyze Requirements

♦ Analyze company business goals

♦ Analyze network technical goals

♦ Characterize the existing network

♦ Characterize network traffic

♦ The steps addressed in this set of slides

Analyze

requirement

s

Develop

logical

design

Develop

physical

design

Test, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network


Logical Network Design

♦ Design a network topology

♦ Design models for addressing and naming

♦ Select switching and routing protocols

♦ Develop network security strategies

♦ Develop network management strategies Analyze

requirements

Develop

logical

design

Develop

physical

design

Test, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network


Physical Network Design

♦ Select technologies and devices for the networks

Analyze

requirements

Develop

logical

design

Develop

physical

designTest, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network

Planeamento 8

Phase 4 –

Testing, Optimizing, and Documenting the

Network Design

♦ Optimize the network design

♦ Document the network design

Analyze

requirements

Develop

logical

design

Develop

physical

design

Test, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network







Analyze

requirement

s

Develop

logical

design

Develop

physical

design

Test, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network

Planeamento 10

Business Goals

♦ What is the new (improved) network required for?

» Help increase revenue?

» Reduce operating costs?

» Improve communications?

» Shorten product development cycle?

» Expand into worldwide markets?

» Build partnerships with other companies?

» Offer better customer support or new customer services?

Planeamento 11

The Scope of the Design

♦ Small in scope?

» E.g. Allow sales people to access network via a VPN

♦ Large in scope?

» E.g. An entire redesign of an enterprise network

♦ Use the OSI model to clarify the scope

» Support of new financial reporting application?

» Add routing?

» Wireless access?

Planeamento 12

Gather Information

♦ What applications are expected to be used?

♦ How critical are they?

» very critical, somewhat critical, not critical

Planeamento 13

Register Applications

Name of

Application

Type of

Application

New

Application?

Criticality Comments







Analyze

requirement

s

Develop

logical

design

Develop

physical

design

Test, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network

Planeamento 15

Key Technical Goals

♦ Scalability

♦ Availability

♦ Performance

♦ But also

» Security, manageability, …

Planeamento 16

Scalability

♦ Scalability refers to the ability of the network to grow

♦ Try to learn

» Number of sites to be added

» What will be needed at each of these sites

» How many users will be added

» How many more servers will be added

Planeamento 17

Availability

♦ Availability

» percent uptime per year, month, week, day, or hour. For instance:

– 24h, 7 day/week operation; network up for 165 in 168 hour � Availability = 98.21%

» or, Availability = MTBF/(MTBF + MTTR)

– MTBF - mean time between failures

– MTTR - mean time to repair (MTTR)

♦ Some enterprises may want 99.999% (Five Nines) availability

» may require triple redundancy

Enterprise

ISP 1 ISP 2 ISP 3

Planeamento 18

Performance

♦ Key performance factors include

» Throughput

» Delay (latency), delay variation, response time

Planeamento 19

Factors Affecting Throughput

♦ Size of packets, distance, errors

♦ Protocols: layer 2, transport, applications, DNS

♦ Packets-per-second switched by network elements

♦ Network topology

♦ Client and server speeds

Offered Load

ThroughputActual

Ideal

100 % of

Capacity

100 % of

Capacity

Planeamento 20

Delay Perspectives

♦ User’s view

» Response Time– Depends on the application / equipment application is running; not just the network

– Most users expect to see something on the screen in 100 to 200 milliseconds

♦ Engineer’s view

» End-to-end delay, delay variation

» Caused by– Propagation delay

– Transmission delay

– Packet-switching delay

– Queuing delay

Planeamento 21

Queueing Delay - Example

• Switch has 5 users, each offering 10 pac/s

• Average packet length = 1024 bits

• Packet switch transmits this data over a 64 kbit/s WAN circuit– Load = 5 x 10 x 1024 = 51 200 bit/s

– Utilization = 51200/64000 = 80%

– Average number of packets in queue = (0.8)/(1-0.8) = 4 packets

0

3

6

9

12

15

0.5 0.6 0.7 0.8 0.9 1

Average Utilization

Average Queue Depth

Number of packets in a queue

increases exponentially as

utilization increases

Planeamento 22Network ApplicationsTechnical Requirements

Name of

Application

Cost of

Downtime

Acceptable

MTBF

Acceptable

MTTR

Throughput

Goal

Delay Must be

Less Than:

Delay

Variation

Must be Less

Than:







Analyze

requirement

s

Develop

logical

design

Develop

physical

design

Test, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network

Planeamento 24Characterize the Existing

Internetwork

♦ Its infrastructure

» Logical structure (modularity, hierarchy, topology)

» Physical structure

♦ Addressing and naming

♦ Wiring and media

Planeamento 25

Get a Network Map

Gigabit

Ethernet

Eugene

Ethernet

20 users

Web/FTP server

Grants Pass

HQ

16 Mbps

Token Ring

FEP

(Front End

Processor)

IBM

MainframeT1

Medford

Fast Ethernet

50 users

Roseburg

Fast Ethernet

30 usersFrame Relay

CIR = 56 Kbps

DLCI = 5

Frame Relay

CIR = 56 Kbps

DLCI = 4

Grants Pass

HQ

Fast Ethernet

75 users

InternetT1

Planeamento 26Characterize Addressing and

Naming

♦ IP addressing for

» major devices, client networks, server networks

♦ Addressing oddities, such as discontiguous subnets

♦ Strategies for addressing and naming

» For example, sites may be named using airport codes

– San Francisco = SFO, Oakland = OAK

Planeamento 27

Characterize the Wiring and Media

♦ Single-mode fiber

♦ Multi-mode fiber

♦ Shielded twisted pair (STP) copper

♦ Unshielded-twisted-pair (UTP) copper

♦ Coaxial cable

♦ Microwave

♦ Laser

♦ Radio

♦ Infra-red

Planeamento 28

Telecommunications

Wiring Closet

Horizontal

Wiring

Work-Area

Wiring

Wallplate

Main Cross-Connect Room

(or Main Distribution Frame)

Intermediate Cross-Connect Room

(or Intermediate Distribution Frame)

Building A - Headquarters Building B

Vertical

Wiring

(Building

Backbone)

Campus

Backbone

Campus Network Wiring

Planeamento 29

Characterize Network Availability

Enterprise

Segment 1

Segment 2

Segment n

MTBF MTTR

Date and Duration of

Last Major

Downtime

Cause of Last

Major

Downtime

Planeamento 30

Network Utilization

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

17:00:00

16:00:00

15:00:00

14:00:00

13:00:00

Tim

e

Utilization

Series1

Measure Network Utilization in

Hour Intervals

Planeamento 31

Bandwidth Utilization by Protocol

Protocol 1

Protocol 2

Protocol 3

Protocol n

Relative

Network

Utilization

Absolute

Network

Utilization

Broadcast

Rate

Multicast

Rate

Planeamento 32

Characterize Response Time

Node A

Node B

Node C

Node D

Node A Node B Node C Node D

X

X

X

X






♦ Characterize network trafficAnalyze

requirement

s

Develop

logical

design

Develop

physical

design

Test, optimize,

and document

design

Monitor and

optimize

network

performance

Implement

and test

network

Planeamento 34

Network Traffic Factors

♦ Traffic flow

♦ Location of traffic sources and data stores

♦ Traffic load

Planeamento 35

User Communities

User

Community

Name

Size of

Community

(Number of

Users)

Location(s) of

Community

Application(s)

Used by

Community

Planeamento 36

Data Stores

Data Store Location Application(s) Used by User

Community(or

Communities)

Planeamento 37

Traffic Flow

Destination 1 Destination 2 Destination 3 Destination

MB/sec MB/sec MB/sec MB/sec

Source 1

Source 2

Source 3

Source n

Planeamento 38

Traffic Flow Example

Administration

Business and

Social Sciences

Math and

Sciences

50 PCs 25 Macs

50 PCs

50 PCs30 PCs

30 Library Patrons (PCs)

30 Macs and 60 PCs in

Computing Center

Library and Computing Center

App 1 108 Kbps

App 2 60 Kbps

App 3 192 Kbps

App 4 48 Kbps

App 7 400 Kbps

Total 808 Kbps

App 1 48 Kbps

App 2 32 Kbps

App 3 96 Kbps

App 4 24 Kbps

App 5 300 Kbps

App 6 200 Kbps

App 8 1200 Kbps

Total 1900 Kbps

App 1 30 Kbps

App 2 20 Kbps

App 3 60 Kbps

App 4 16 Kbps

Total 126 Kbps

App 2 20 Kbps

App 3 96 Kbps

App 4 24 Kbps

App 9 80 Kbps

Total 220 Kbps

Arts and

Humanities

Server Farm

10-Mbps Metro

Ethernet to Internet

Planeamento 39

Types of Traffic Flow

♦ Terminal/host

♦ Client/server

♦ Thin client

♦ Peer-to-peer

♦ Server/server

♦ Distributed computing

Planeamento 40Network Applications

Traffic Characteristics

Name of

Application

Type of

Traffic

Flow

Protocol(s)

Used by

Application

User

Communities

That Use the

Application

Data Stores

(Servers, Hosts,

and so on)

Approximate

Bandwidth

Requirements

QoS

Requirements

Planeamento 41

Collection of Tables

Planeamento 42

Register Applications

Name of

Application

Type of

Application

New

Application?

Criticality Comments

Planeamento 43Network ApplicationsTechnical Requirements

Name of

Application

Cost of

Downtime

Acceptable

MTBF

Acceptable

MTTR

Throughput

Goal

Delay Must be

Less Than:

Delay

Variation

Must be Less

Than:

Planeamento 44

Characterize Availability

Enterprise

Segment 1

Segment 2

Segment n

MTBF MTTR

Date and Duration of

Last Major

Downtime

Cause of Last

Major

Downtime

Planeamento 45

Bandwidth Utilization by Protocol

Protocol 1

Protocol 2

Protocol 3

Protocol n

Relative

Network

Utilization

Absolute

Network

Utilization

Broadcast

Rate

Multicast

Rate

Planeamento 46

Characterize Response Time

Node A

Node B

Node C

Node D

Node A Node B Node C Node D

X

X

X

X

Planeamento 47

User Communities

User

Community

Name

Size of

Community

(Number of

Users)

Location(s) of

Community

Application(s)

Used by

Community

Planeamento 48

Data Stores

Data Store Location Application(s) Used by User

Community(or

Communities)

Planeamento 49

Traffic Flow

Destination 1 Destination 2 Destination 3 Destination

MB/sec MB/sec MB/sec MB/sec

Source 1

Source 2

Source 3

Source n

Planeamento 50Network Applications

Traffic Characteristics

Name of

Application

Type of

Traffic

Flow

Protocol(s)

Used by

Application

User

Communities

That Use the

Application

Data Stores

(Servers, Hosts,

and so on)

Approximate

Bandwidth

Requirements

QoS

Requirements

Documents

Planeamentoe Gestãode Redes Análise de Requisitos