TDT4105 - IT Grunnkurs
Nettverk, Del 2
Communications, Networks
and Safeguards
Bjørn J. Villa PhD CandidateInstitute 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”
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 isinterpreted 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.
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
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”)
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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
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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
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.
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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
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Chapter 6.3
Wired Communication Media
© 2010 The McGraw-Hill Companies, Inc. All rights reserved.
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
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Chapter 6.4
Wireless Communcation Media
© 2010 The McGraw-Hill Companies, Inc. All rights reserved.
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 ?
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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
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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...
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
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
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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”