T01 - Overview of Computer Network

7/27/2019 T01 - Overview of Computer Network

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ECTE 182Internet Technology 1

Topic 01

An Overview of Computer

Network

What is a computer network?

Simple and general answer : A computer networkis a group of computers that are interconnected toshare hardware, software and data.

But then

How do we connect these computers together ?

How does these computers communicate with each other?

How can we make sure the communication is smooth andflawless ?

How do we make sure the communication is private andsecure ?

The study of networking courses is generally tounderstand the above questions and to answerthem.

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Data Communications

The essence of computer network is to allow datacommunications.

Goal: convey information

How to do it?

Hand signal, smoke, light, .?

Characteristics

Delivery/Reliability

Accuracy

Timeliness

Jitter

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Whats a computer network?Establishing a communication channel

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Wired (copper, fiber)

Wireless (electromagnetic, infra-red)

Information


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A home network

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Internet

Service Provider

- Wireless (IEEE 802.11a/b/g/n,

Bluetooth, USB (wired/wireless))- Wired (Firewire, USB, Ethernet(10/100/1000/10000 Mbps)).

ADSL, Cable Modem, Dial-Up,WiMAX (IEEE 802.16)

(56 Kbit/s 40 Mbit/s)

Internet structure: network of networks

Tier-2 ISPs: smaller (often regional) ISPs

Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs

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Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier-2 ISPTier-2 ISP

Tier-2 ISP

Tier-2 ISP

Tier-2 ISP pays tier-1

ISP for connectivity to

rest of the Internet

i.e., tier-2 ISP is

customerof tier-1

provider

Tier-2 ISP

Service Level Agreement

Throughput, Delay, Jitter,

Loss


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Internet structure: network of networks

A packet passes through many networks!

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Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

localISP

localISP

localISP

localISP

localISP

Tier 3ISP

localISP

localISP

localISP

Problems?

Network of NetworksAnother View

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LAN Local Area Network

MAN Metropolitan Local Area Network

WAN Wide Area Network

Wide Area Network

MAN

MAN

MAN

MAN

LAN

LAN

LAN

LAN

LAN

LAN

LANLAN

LAN

LAN

LAN

LAN

PAN Personal Area Network


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Category of Networks

Body Area Networks

Personal Area Networks

Local Area Network

Privately owned, links computer in a single building oroffice

Fixed transmission media and topology; e.g., WirelessLANs

Metropolitan Area Network

Covers a town or city

E.g., cable TV, wireless MANs (WiMAX)

Wide Area Network

Between continents

Satellites or oceanic fiber links.

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Physical StructureTypes of Connection

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Point-to-Point

Multipoint


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ys ca ruc ureTopology

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Each computer has a dedicated line to allstations

Number of links: N(N-1)/2, N is # of nodes. Lots of cabling Dedicated line, simultaneous transmissions Good fault tolerance Good privacy

Mesh

Star Hub relays data from all stations No point-to-point communications

Cheaper than mesh Single point of failure Easy to isolate link fault

Hub

ys ca ruc ureTopology

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Backbone laid on most efficient path Less cabling than mesh or star Break in backbone link disables the network Difficult to isolate fault Only one station can be using the backbone

at any given time bus is a shared resource

Bus

Ring Messages goes from station to station in onedirection

Each station repeats received message Only one station can be transmitting at any giventime.

Simpler fault isolation


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Physical StructureTopology

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Hybrid

Hub

Local Area Networks

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Dedicated

Shared


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Break

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Information Flow

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simplex

Half-Duplex

Time t1

Time t2

Duplex


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Packets

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0010110101010101010101

Packet

Your dataInserted byprotocol

information

Header Payload

Packet

Analogy

Given a 500 page book, and 1000 standard90x140mm envelopes.

Problem:

How do you send the book to your friend Bill Gates atMicrosoft Corp, One Microsoft Way, Washington, USA?

Assume free postage and handling.

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Packets/Envelopes

Header information

Source address

Destination address

Time to live

Length of header and payload

Timestamp

Security information

Packet type

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The InternetA Packet Switched Network

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Your

ISP

Telstra

Sprint

Level-3


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Whats a protocol?

human protocols:

whats the time?

I have a question

introductions

specific msgs sent

specific actions taken when msgs received, or otherevents

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network protocols:

machines rather thanhumans

all communicationactivities in Internetare governed byprotocols

protocols define format, order

of msgs sent and received

among network entities,

and actions taken on msg

transmission, receipt

Whats a protocol?

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Hi

HiGot thetime?

2:00

connectionreq

connectionresponse

Get http://www.uow.edu.au

time

Human Computer


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What does a protocol specify?

A set of rules that govern data communications

Syntax.

Fields in the header, and their size.

Semantics

The meaning of each bit in the packet

Timing

When data should be sent, and how fast?

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A simple protocol

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Computer-A Computer-B

Filename: ecte182.zip

Got it!

Heres bit 1 to 1000Got it!

Heres bit 1001 to 2000

I only received bits1001 to 1500

Heres bit 1500 to 2000again


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A Routing Example

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YourISP

Optus

Telstra

AT&T

R

R

R

Sprint

Level3

Google

RR

R

R

R

R

R

RR

Routing Problems How to get to Google? Which way is the bestroute? How to find out which way is best?

R Router

search: ecte182

Who standardize protocols?

Why do it?

To ensure interoperation between machines developed by

different vendors.

E.g., Bluetooth, Motorola Samsung

Standards creation committees

International Organization for Standardization (ISO)

International Telecommunication Union Telecommunication

Standards Sector (ITU-T)

American National Standards Institute (ANSI)

Institute of Electrical and Electronics Engineers (IEEE)

Electronic Industries Association (EIA)

Internet Engineering Task Force (IETF)

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IETF (www.ietf.org)

Protocol engineering and development arm of the Internet

Society ( founded in 1992 to provide leadership in Internetrelated standards, education, and policy)

Includes designers, operators, vendors and researchers. Open

to anyone

Produces two types of document

Internet drafts - no formal status

Request For Comment (RFC) are official documents.

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IETF Working Group

This is where the IETF primarily get its work done

Working group focused by charter agreed betweenchair(s) and area director restrictive charters with deliverables and milestones

working groups closed when their work is done

Charter approved by Internet Engineering SteeringGroup (IESG) with IAB (Internet Architecture Board)advice

Area Director with IESG has final say on charter &chair(s)

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IETF Working Group

rough consensus and running code...

no formal voting

- can do show of hands - but no count

does not require unanimity

disputes resolved by discussion

mailing list and face-to-face meetings

most work happens on mailing lists

all decisions must be verified on mailing list

face-to-face discussion to resolve disagreements

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Source: IETF Slides presented to newcomers.

ICANN

Internet Corporation for Assigned Names and Numbers

(ICANN) manages

IP addresses

Uniqueness

Domain names

.com, .edu, .net, etc

Port numbers

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SummaryKey Concepts

Internet Network of Networks

Topologies: mesh, bus, star, hybrid

Simplex, half-duplex, full duplex

LAN, MAN, WAN

Packets

Packet switched networks

Protocols

Standardization

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T01 - Overview of Computer Network

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