Chapter 7Chapter 7

TelecommunicationsTelecommunications

Bonus Quiz!Bonus Quiz!1.1. ENIAC was the first modern computer ENIAC was the first modern computer

not to use vacuum tubes: T/F?not to use vacuum tubes: T/F?

2.2. What is a “UPS” – United Parcel Service What is a “UPS” – United Parcel Service NOT ACCEPTED.NOT ACCEPTED.

3.3. Define Dual-booting.Define Dual-booting.

Quiz!Quiz!1.1. FF

2.2. Uninterruptible Power Supply.Uninterruptible Power Supply.

3.3. Dual-booting is having two Operating Dual-booting is having two Operating Systems (OSes) running on the same Systems (OSes) running on the same machine.machine.

Digital/AnalogDigital/Analog

Digital signals are composed of discrete Digital signals are composed of discrete 1s and 0s1s and 0s

Analog signals vary continuouslyAnalog signals vary continuously

This discrepancy has led to technologies This discrepancy has led to technologies like the modem, whose only purpose is to like the modem, whose only purpose is to convert from digital to analog and vice-convert from digital to analog and vice-versaversa

Digital/AnalogDigital/Analog

Analog signals contain ALL the information Analog signals contain ALL the information about something, which makes them about something, which makes them “perfect” copies“perfect” copies

The downside is that they’re HUGEThe downside is that they’re HUGE

Digital signals store the “important” parts Digital signals store the “important” parts of the signal, drastically reducing its sizeof the signal, drastically reducing its size

Like traditional animation, we’re fooled into Like traditional animation, we’re fooled into thinking these “slices” are the real thingthinking these “slices” are the real thing

HDTVHDTV

The next generation of TVs use high-quality The next generation of TVs use high-quality digital signals to transmit amazingly clear digital signals to transmit amazingly clear picturespictures

Currently, nice HDTV sets go for $2,000-$3,000 Currently, nice HDTV sets go for $2,000-$3,000 (in 2001, it was $7,000)(in 2001, it was $7,000)

Originally, by May 2006 all TV broadcasting Originally, by May 2006 all TV broadcasting would switch to the HDTV standard, but….would switch to the HDTV standard, but….

Now that date has been moved to February 17, Now that date has been moved to February 17, 2009 2009

The last-mile problemThe last-mile problem

There are 3 major types of cables used to There are 3 major types of cables used to carry data into modern householdscarry data into modern householdsTwisted pair wire consists of two braided Twisted pair wire consists of two braided copper wires twisted around each othercopper wires twisted around each otherTwisted pair wire transmits data at 1-128 Twisted pair wire transmits data at 1-128 MbpsMbpsStandard phone lines are twisted-pair, and Standard phone lines are twisted-pair, and most households use this to connect to the most households use this to connect to the netnet

The last-mile problemThe last-mile problem

Coaxial cable (commonly called coax) is a Coaxial cable (commonly called coax) is a copper wire wrapped in an insulted metal copper wire wrapped in an insulted metal shieldshield

It’s commonly used for cable TV, and can It’s commonly used for cable TV, and can transmit at up to 200 Mbpstransmit at up to 200 Mbps

Cable modems use this type of connectionCable modems use this type of connection

The last-mile problemThe last-mile problem

Fiber-optic cable consists of hundreds of Fiber-optic cable consists of hundreds of hair-thin glass or plastic fibers bundled hair-thin glass or plastic fibers bundled togethertogether

Data is transmitted at 100 Mbps to 2 Data is transmitted at 100 Mbps to 2 Gbps, using pulses of lightGbps, using pulses of light

T1s and T3s use fiber-opticsT1s and T3s use fiber-optics

The last-mile problemThe last-mile problem

The last-mile problems refers to the fact The last-mile problems refers to the fact that while the cost to put fast fiber-optic that while the cost to put fast fiber-optic connections from a provider to a town or connections from a provider to a town or neighborhood is minimal, the cost to neighborhood is minimal, the cost to replace the “last mile” of copper wire going replace the “last mile” of copper wire going into all the houses is very, very highinto all the houses is very, very highThat’s why we don’t all have T1 That’s why we don’t all have T1 connections at home (off-campus, of connections at home (off-campus, of course)course)

SatellitesSatellites

We’ll skip the discussion of satellite orbits We’ll skip the discussion of satellite orbits (GEO, MEO, LEO)(GEO, MEO, LEO)

GPS relies on signals from satellitesGPS relies on signals from satellites

3 signals are needed to establish position, 3 signals are needed to establish position, based on triangulationbased on triangulation

GPSGPSYou’re Here

Satellite A

Satellite B

Satellite C

Network TypesNetwork Types

WAN – Wide Area Network – A communications net that WAN – Wide Area Network – A communications net that covers a wide geographical area (Phone Company’s lines)covers a wide geographical area (Phone Company’s lines)

LAN – Local Area Network – the type of net we’re on here LAN – Local Area Network – the type of net we’re on here at IUat IU

MAN – Supposedly a Metropolitan Area Network, but MAN – Supposedly a Metropolitan Area Network, but nobody uses thisnobody uses this

LAN typesLAN types

Client/Server LAN – basically one very powerful Client/Server LAN – basically one very powerful computer (the server) interacts with multiple less computer (the server) interacts with multiple less powerful machines (the clients). Servers allow powerful machines (the clients). Servers allow communications between the clients and communications between the clients and regulate access to other resources, like printersregulate access to other resources, like printers

Peer-to-Peer (P2P) – All computers are equal in Peer-to-Peer (P2P) – All computers are equal in power and directly connected to one another. power and directly connected to one another. Also used to talk about file sharing systems. Also used to talk about file sharing systems. When used this way, Gnutella is a P2P app, and When used this way, Gnutella is a P2P app, and Napster was a C/S app.Napster was a C/S app.

TermTerm

Network Interface Card, or NIC, is an Network Interface Card, or NIC, is an expansion card added to a computer’s expansion card added to a computer’s system unit that allows it to interact with system unit that allows it to interact with other computersother computers

In common usage, this refers to an In common usage, this refers to an ethernet cardethernet card

TermsTerms

Router – a special computer that directs Router – a special computer that directs communicating messages when several communicating messages when several networks are connected togethernetworks are connected together

Bridge – an interface used to connect the Bridge – an interface used to connect the same types of networkssame types of networks

Gateway – an interface used to connect Gateway – an interface used to connect different types of networksdifferent types of networks

Network TopologiesNetwork Topologies

Star (C/S)Star (C/S)

Ring (P2P)Ring (P2P)

Bus (P2P)Bus (P2P)

C

C

CC

C

C

C

C

CCC

C

C

C C

C

C

S

C C C C

CC C C

C

NetworksNetworks

Intranet – pages/resources intended for Intranet – pages/resources intended for internal (inside a company) useinternal (inside a company) use

Extranet – pages/resources intended for Extranet – pages/resources intended for external (non-company) useexternal (non-company) use

Firewall – A system of hardware and/or Firewall – A system of hardware and/or software designed to block unauthorized software designed to block unauthorized access to the intranet and other resourcesaccess to the intranet and other resources

CensorwareCensorwareBlocking software – generally either filter based Blocking software – generally either filter based on keywords, a pre-generated list, or bothon keywords, a pre-generated list, or both

Problems – Middlesex and Essex in England Problems – Middlesex and Essex in England blocked accidentallyblocked accidentally

Political sites, sex and health information (breast Political sites, sex and health information (breast cancer), minority religious sites all blocked cancer), minority religious sites all blocked “accidentally”“accidentally”

Site lists are usually secretSite lists are usually secret

Thanks to new federal laws, public libraries and Thanks to new federal laws, public libraries and schools often must use it or loose fundingschools often must use it or loose funding