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TDT4105 - IT Grunnkurs

Nettverk, Del 2

Communications, Networks

and Safeguards

Bjørn J. Villa PhD Candidate

Institute for Telematics, NTNU bv@item.ntnu.no

Topics

From the Analog to the Digital Age

Networks: benefits, types etc

Wired Communcations Media

Wireless Communications Media

Cyberthreats, Hackers &

Safeguards

...a global, unifying network” ”The lnternet..

Section 6 of text book ”Using Information Technology”

3

Chapter 6.1

From the Analog to the Digital Age

© 2010 The McGraw-Hill Companies, Inc. All rights reserved.

4

From the Analog to the

Digital Age

Analog signals use variation of a wave form

to send information

Radios send signals this way

–  In FM signals the Frequency is varied (Modulated) –  In AM signals the Amplitude is varied (Modulated)

Hearing and phones work this way

Human vision

Modems

….

“As humans, we perceive the world in analog. Everything we see and hear is a continuous transmission of information to our senses. This continuous stream is what defines analog data”

(2)

From the Analog to the Digital Age

Digital signals send data in terms of 1s and 0s. The binary number system Analogue->Digital is modulation, while Digital->Analgoue is demodulation Why do this ?:

- Computers are digital

- Modern networks are digital

From the Analog to the Digital Age

•  Sound is air pressure waves which is

interpreted by the human ear. •  A microphone can pick up these waves

and convert them to a variation in electric power or current in a cable.

…100011010110011001…

Frequent sampling => good quality!

Not frequent sampling => loss of quality!

•  The electric variations are ”sampled” and each of these samples are represented binary (1’s and 0’s) •  All samples together can then be

stored on a digital media (e.g. CD) for later use

7

From the Analog to the Digital Age

•  CD –  44 100 samples pr sec –  2 Byte pr sample –  2 channels (stereo) –  1.4Mbps •  Telephony: –  8000 samples pr sec –  1 byte per sample –  64kb/sek

•  GSM

–  More complex method –  Less samples –  Value predictions –  13kb/sek

Sampling frequency and associated algorithms are chosen based on quality and other requirements

Remember: It is difficult (if not impossible) to make the digital version as good as the original analogue

8

Chapter 6.2

Networks

© 2010 The McGraw-Hill Companies, Inc. All rights reserved.

(3)

Networks

A system of interconnected computers,

telephones, or other communications devices

that can communicate with one another and

share applications and data

Before we had computer networks, people used

sneakernet

” to share data between computers

–  Person 1 saved their document to a floppy disk –  Then they walked over to person 2’s desk (wearing

sneakers, of course) and handed over the disk to person 2 –  Person 2 loaded the disk into their computer to read and

edit the document

Networks

•  WAN – Wide Area Network (e.g an ISP network)

Covers a wide geographic area, such as a country or the world •  MAN – Metropolitan Area Network (e.g. Trådløse Trondheim)

Covers a city or a suburb

•  LAN – Local Area Network (e.g. your network at home)

Connects computers and devices in a limited geographic area such as an office, building, or at home

•  PAN – Personal Area Network (e.g. mobile printing / AirPrint) Uses short-range wireless technology to connect an individual’s

personal electronics WAN MAN LAN PAN 11

Networks

(Internet Structure)

Telenor WAN Tele2 WAN Tele2 MAN NIX Ventelo MAN Telenor MAN TSIC Level3

LAN LAN LAN

End Users / Customers National ISP’s International ISP’s (Tier 1 Networks) National Internet Exchange Points Located in Oslo, operated by UiO (non-profit) Optional direct peering 12

Networks

Communication models

–  Client/Server

•  Consists of clients, which are computers that request data, and servers, which are computers that supply data

•  Examples: File servers, database servers, print servers etc

•  Gives a typical “Star” topology (logical) in the communication

–  Peer-to-Peer

•  Clients on the network communicate directly with each other without relying on a server •  Example: content sharing networks

•  Gives a typical “Mesh” topology (logical) in the communication

(4)

Networks

!

Topologies can be both

logical

and

physical

!  Star – all nodes are connected through a central host

!  Mesh – all nodes are connected to all others

!  Bus – all nodes are connected to a single wire or cable

!  Ring – all nodes are connected in a continuous loop

Bus

Ring

Star

Networks

Intranets

–  An organization’s private network that uses the infrastructure and standards of the internet and the web

–  Example: The network used by the employees in a bank

Extranets

–  Private internets that connect not only internal personnel but also selected suppliers and other strategic parties

–  Example: Web resources accessible to partners and customers

Virtual Private Networks

(VPN)

–  Private networks that use a public network, usually the internet, to connect remote sites

–  Example: people working from home through a secure VPN (sometimes also referred to as a “tunnel”)

15

Networks

Protocols

Defines the

format

and

sequence

of

messages

exchanged between

communicating entities, and

actions

expected / allowed.

Built into the hardware or software

you are using

Examples are:

•  TCP/IP for LANs and internet •  SIP for Voice over IP (VoIP) •  ….and thousands of other

16

Networks

Scalability

–  The ability of the network to handle a growing amount of traffic, number of customers or coverage – in a seamless and controlled way.

Availability

–  The ability of the network to provide a set of services at a given (or any) instant of time

Reliability

–  The ability of the network to provide uninterrupted service

Performance

–  The ability of the network to provide the resources needed to deliver its services

11.01.2011:

NetCom bytter ut nettet

NetCom bytter ut hele mobilnettet med nytt og fremtidsrettet utstyr 3G-dekning til 95 % og 4G til 89 % av befolkningen når det nye nettet er klart Skifter ut gamle basestasjoner og bygger flere tusen nye Økte hastigheter og ny dekning fortløpende Investerer 1 mrd kroner i nytt supernett

(5)

Networks

Scalability

–  The ability of the network to handle a growing amount of traffic, number of customers or coverage – in a seamless and controlled way.

Availability

–  The ability of the network to provide a set of services at a given (or any) instant of time

Reliability

–  The ability of the network to provide uninterrupted service

Performance

–  The ability of the network to provide the resources needed to deliver its services

17.06.2011:

Telenor har problemer - igjen!

Telenor mobil-kunder i store deler av landet har problemer med å ringe til hverandre.

Mellom to og tre millioner kunder ble rammet sist gang Telenor hadde problemer (en uke siden). Hvor mange som er rammet denne gangen, er fortsatt usikkert

Networks

Scalability

–  The ability of the network to handle a growing amount of traffic, number of customers or coverage – in a seamless and controlled way.

Availability

–  The ability of the network to provide a set of services at a given (or any) instant of time

Reliability

–  The ability of the network to provide uninterrupted service

Performance

–  The ability of the network to provide the resources needed to deliver its services

20.09.2011:

Nextgentel-kunder kom ikke inn på utenlandske nettsider

I tre timer i natt var ~200.000 nordmenn uten «internasjonal nettilgang». I tillegg til at Nextgentels kunder ikke kom på internett, ble heller ikke e-poster mottatt og sendt over landegrensene. Trolig har heller ikke tjenester som Skype eller MSN fungert.

19

Networks

Scalability

–  The ability of the network to handle a growing amount of traffic, number of customers or coverage – in a seamless and controlled way.

Availability

–  The ability of the network to provide a set of services at a given (or any) instant of time

Reliability

–  The ability of the network to provide uninterrupted service

Performance

–  The ability of the network to provide the resources needed to deliver its services

11-13.Mai 2011:

En ny forretningsmodell på nett

En eksplosiv vekst av levende bilder (video) på nettet oppleves. For internett- leverandørene er dette en utfordring. Bredbåndsselskapene må hele tiden investere i ny teknologi for å øke kapasiteten i nettet. Innholdsleverandører som vil ha tjenestekvalitet på internett må betale for det. Dagens forretningsmodell må revurderes

20

Chapter 6.3

Wired Communication Media

© 2010 The McGraw-Hill Companies, Inc. All rights reserved.

(6)

Wired Communications

Communications media carry signals along a path

–  Twisted-Pair Wire

2 strands of insulated copper wire twisted around

each other

Used for telephony and DSL based Internet

–  Coaxial Cable

Insulated copper wire wrapped in a metal shield

and then in an external plastic cover

Used for cable TV and cable internet

–  Fiber-optic cable

Thin strands of glass or plastic that transmit beams

of light

Used in WAN/MAN networks, for both Internet

and other network types

Wired Communications

Why different cable types for communication ?

When to use which type ?

Constraints or limitations are not fixed for each

type as innovations take place all the time, so a

capacity limit today is most likely not valid today

23

Wired Communications

In your home

Ethernet

– “Ethernet” is more than just a cable, it is also a definition of protocols – The cable part consist of several pairs of twisted copper cable pairs – The quality of the these cables are categorized (cat3, cat5, cat6..) – Bandwidth provided are typically 10Mbps,100Mbps and1Gbps

However, not all houses have at least cat5 cabling so that

ethernet can connect directly (for distribution inside the house).

The industry is creative in providing solutions to utilize “old” or

just whatever cables are in the house for distribution

– Homeplug: uses existing home electrical lines – HomePNA: uses old cat3 cables

24

Chapter 6.4

Wireless Communcation Media

© 2010 The McGraw-Hill Companies, Inc. All rights reserved.

(7)

Wireless Communications

•  Electromagnetic spectrum of radiation is the basis of all telecommunications signals (also the wired part)

•  Radio-frequency spectrum is the part of the electromagnetic spectrum that we use for radio communication

Wireless Communications Media

Infrared Transmission

Broadcast Radio

Cellular Radio

Microwave Radio

Communications Satellites

GPS

Pagers

GSM (1G, 2G, 3G, 4G)

WiFi / Wireless LAN

All these systems have a defined part of the spectrum where they should operate. Why ??

Some systems operate in licensed spectrum while others operated in

non-licensed spectrum. Why ??

Questions:

Does GSM operate in licensed or non-licensed ? How about WiFi ?

27

Wireless Communications Media

Short-range Wireless

Wi-Fi (802.11) networks (shared medium)

–  802.11b is old, transmits 11 Mbps

–  802.11g is 54 Mbps

–  Wi-Fi n – 200 Mbps

Bluetooth

–  Short-range wireless standard to link cellphones, PDAs, computers, and peripherals (Named after Harald Bluetooth, the Danish king who unified Denmark and Norway in the 10th century –  Transmits up to 3Mbps

ZigBee / Z-Wave

–  Power-efficient technology, for metering –  Can send data at 128 Kbps per second

….

Cisco predictions:

50 Billion things on the Internet by 2020

28

Wireless Communications Media

Internet is put on power cables (ref HomePlug), so why not onto light ? It’s “just” a matter of modulation.. Make the light carry 0’s and 1’s without people seeing it, but enabling devices to use it as a communication channel.

Ongoing reserch for several years...

(8)

Chapter 6.5

Cyberthreats, Hackers & Safeguards

© 2010 The McGraw-Hill Companies, Inc. All rights reserved.

Cyberthreats, Hackers, &

Safeguards

"'In this world nothing

can be said to be

certain, except death

and taxes."

Benjamin Franklin, 1789

This still applies, and Internet is no exception

31

Cyberthreats, Hackers, &

Safeguards

Initially

: The initial motivation for Internet was

to foster collaboration among universities and

scientists. All of which trusted each other, and

therefore few security mechanisms were built

into the internet

Today

: The Internet is a global network used

for all purposes, by anybody and at any time.

Trust is gone, threats are a reality

This change happened quite fast…

32

Cyberthreats, Hackers, &

Safeguards

One of the first (known) major securiy incidents on the Internet Code Red Worm in 2001 infected 359.000 PC’er++ around the world in14 hours

(9)

Cyberthreats, Hackers, &

Safeguards

Denial of Service Attacks

–  Overloading or interrupting a system so that it stops functioning

Worms

–  A program which spreads from device to device by itself, while performing some unknown operations / tasks (e.g. format disk)

Viruses

–  A program which causes unexpected and undesirable effects such as destroying or corrupting data

Trojan Horses

–  Programs that pretend to be a useful program such as a free game or screensaver, but may in fact be a virus or spyware

Cyberthreats, Hackers,

& Safeguards

•  Hackers

–  Computer enthusiasts, people who enjoy learning about programming and computers

–  People who gain unauthorized access to computers or networks, often for fun or to see if they can

•  Crackers

–  Malicious hackers who break into computers for malicious purposes

•  Break in for a political purpose •  Break in to steal or destroy information •  Terrorists attack computer systems to bring

physical or financial harm to groups, companies, or nations

35

Cyberthreats, Hackers, &

Safeguards

•  Safeguards

– Antivirus software, firewalls, robust passwords, antispyware software, encryption, back up date, strong AAA

(authentication, authorization, accounting), physical access control ……

Most important:

The less you know or care, the more exposed you are

36

One of many examples....

Sitat VG Nett 28.09.11:

Uvedkommende har, med en mobil og ett lett passord, både kunnet overta kontrollen av vannforsyningen og fysisk komme seg inn og forgifte vannet etter at det har vært gjennom rensing

DU

må bidra til at sånne ting skjer sjeldnere....

....etter at du er ferdig ved NTNU

(10)

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