telecommunications & the internet. basic telecom model computer channel interface channel...
TRANSCRIPT
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Telecommunications&
The Internet
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Basic Telecom Model
Computer Computer
Channelinterface
Channelinterface
Communication Channel
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Typical Home Telecom Model
Computer Computer
Modem ModemAudio Phone Lines
Digitalsignals
Digitalsignals
Analog signals
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Channels• Twisted wire (twisted pair)
• Coaxial Cable
• Fiber Optics
• Microwave
• Newer Wireless
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Twisted Pair
• Low cost
• easy to work with
• installed infrastructure
• crosstalk
• 300bps to 100Mbps• “This modem is 56Kbps capable. However, current
regulations limit download speeds to 53Kbps,” the fine print from a typical modem advertisement.
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DSL
• Uses existing twisted pair
• 256Kbps to 40Mbps
• Loop length max about 18,000 ft.
• More correctly ADSL (Asymmetric Digital Subscriber Line) with download speeds different from upload speeds.
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Coaxial Cable
• More expensive
• harder to work with
• not as extensive an existing infrastructure– cable TV companies are changing this
• 56Kbps to 550Mbps
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Fiber Optics
• Very expensive
• difficult to work with
• existing infrastructure limit to backbones
• 500Kbps to 30Gbps
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Microwave
• Not as expensive as land lines
• Limited to line of site, (towers)– reasonable infrastructure
• Satellite bounce, increases expense– geo-synchronous (22,000 miles)– low earth orbit (cheaper, lower power)
• 256Kbps to 100Mbps
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Newer Wireless
– Cellular– mobile data networks– personal communications services (PCS)
– note: pagers & PDAs are not channels, they would be nodes on one end of a channel
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Transmission Speed
• BPS, bits-per-second, the amount of information that can be transmitted through a channel
• BAUD - a binary event, a signal change from positive to negative or vice versa.
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Speed II
• At higher speeds a single signal change can transmit more than one bit at a time, so the bit rate will generally be higher that the baud rate.
• Transmission capacity is a function of the frequency, higher frequency means higher capacity
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More Speed
• Bandwidth = range of frequencies that a channel can support (difference between highest and lowest frequency).
• Greater range means greater bandwidth.
• Greater bandwidth means greater transmission capacity.
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Faster Yet
• Bandwidth is like pipe diameter.
• Larger diameter pipes can transmit more water in a given period of time.
• Personal Communication Services, PCSs, have a greater bandwidth than fiber optics.
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Communications Processors
Front EndProcessor
CPU
Controller
Computer
Channel
Multiplexer
PC PC PC
T
T
T
T
ConcentratorChannel
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Network Topology
• Star Network
• Bus Network
• Ring Network
C
C CC
C C
C
C
C
C C
C
P
P
P
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Networks
• Local Area Network, LAN
• Wide Area Network, WAN
• Value Added Network, VAN
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Network Terms
• File server
• Print server• Gateway - connects dissimilar networks
• Bridge - connects similar networks
• Routers - connects networks & directs traffic
• Similar networks = same network protocols
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20Chapter 8
Transmission on LANs
• Token Ring– can talk only when you have the token– cost more than Ethernet– better for high volume traffic
• Ethernet– talk whenever you want– send again if collision– works best with low volume traffic
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Transmission on WANs & VANs
• Packet Switching– message broken into packets– packets may take various routes– message reassembled at destination– allows load balancing on channels
• Frame Relay– like packet switching, no error correction
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The Internet
• What is the Internet?
• Who owns the Internet?
• Why does the Internet exist?
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Evolution of the Internet
• 1970 ARPANET - 15 nodes
• 1972 first email
• 1982 TCP/IP becomes internet standard– Transmission Control Protocol/Internet Protocol
• 1984 ARPANET - 1,000 nodes
• 1986 NSF-Net backbone on ARPANET
• 1987 ARPANET - 10,000 nodes
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Evolution of the Internet
• 1988 - businesses begin to connect to system for research purposes
• 1989 ARPANET - 100,000 nodes
• 1989 link email between CompuServe and ARPANET
• 1990 ARPANET becomes the Internet
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Public NetworksCompuServe
• 1969 started in Cleveland with single computer
• 1979 provided first email
• 1980 started national service
• Mid-1980s largest online service
• 1995 3 Million users
• 1997 purchased by AOL
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Public NetworksProdigy
• 1986 pilot in Atlanta, Hartford, San Francisco
• 1988 national service launched
• 1994 1st to offer WWW access
• 1999 Prodigy Classic discontinued (209,000 members)
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Public NetworksAOL
• 1991 AOL for DOS
• 1993 AOL for Windows
• 1997 bought CompuServe
• 1999 10 Million users
• Estimated to have distributed over 1 Billion discs of over 1,000 different disk/CD styles
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Internet Statistics
• http://www.internetworldstats.com/stats.htm– User Counts, updated daily
• http://whois.sc/internet-statistics/– Domain Counts, updated daily
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The Keys to Internet Growth
• 1991 WAIS and Gopher provide Internet search and navigation
• 1992 WWW hyperlink software released
• 1992 NSF relaxes its restriction on commercial Internet traffic
• 1992+ explosive growth in usage
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Internet Capabilities
• Communications– E-mail
– Usenet
– Chatting
– Telnet
• Information Retrieval– Gopher
– Archie
– WAIS
– FTP
http://sunland.gsfc.nasa.gov/info/guide/Using_archie_Today.html
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World Wide Web
• Set of standards for storing, retrieving, formatting, and displaying information using a client/server architecture
• Hypertext markup Language (HTML)
• browser
• search engines
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Putting It All Together
AT&T Level 3
Centurylink
I29 Cable One
Consumer Consumer Consumer
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Some Upper Tier Providers
• AT&T• Bell Atlantic• Bell South• Cable and Wireless• Cable One• GTE
• IBM• MCI• Pacific Bell• QUEST• Sprint• US West
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Tier 1 Networks
• The largest backbones on the Internet:• Centurylink, Telecom Italia, Verizon, Sprint,
TeliaSonera International, NTT Communications, Deutsche Telekom, Level 3, AT&T
• These top branded backbones only trade peering traffic among themselves.
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Common Bandwidths
• 56K modem 0.056 Mbps• ADSL 40 Mbps• Cable Modem 50 Mbps• T1 1.5 Mbps• Ethernet 10 to 1,000 Mbps• T3 44.7 Mbps• See http://bandwidthplace.com/
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Upper Tier BandwidthsOC-x mulitples of 51.85 Mbps
• OC-3 155 Mbps
• OC-12 622 Mbps
• OC-48 2,488 Mbps
• OC-96 4,977 Mbps
• OC-192 9,953 Mbps
• OC-768 39,812 Mbps
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Organization Benefits of Internet
• Reducing Communication Costs– virtual private net
• Enhancing Communication and Coordination
• Accelerating the Distribution of Knowledge
• Facilitating Electronic Commerce
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Intranets• An internal network based on World Wide
Web technology
• Firewall– security software to prevent unauthorized
access to an intranet
• Firebreak– a physical break between the Internet and
Intranet
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Internet Challenges
• Security
• Technology Problems– incompatibility– limited bandwidth– telecommunications infrastructure– internet specialists
• Legal Issues
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IP Addresses
• An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address.
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IP Address Classes
• Class A - 168.212.226.204• supports 16 million hosts on each of 127 networks • Class B - 168.212.226.204• supports 65,000 hosts on each of 16,000 networks
– NDUS has two Class B addresses• 134.129.xxx.xxx Eastern ND• 134.234.xxx.xxx Western ND
• Class C - 168.212.226.204• supports 254 hosts on each of 2 million networks
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IPv4 vs. IPv6
• IPv4– 32 bits used for address
– 4,294,967,296
– Addresses not assigned by geographic region (see map)
• IPv6– 128 bits used for address
– 340,282,366,920,938,463,374,607,431,768,211,456– That about 3.7x10^21 addresses per square inch of the earth’s surface
– Addresses will be assigned by geographic region
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IPv4 vs. IPv6
• IPv4 addresses written as four octets (8 bits) separated by periods.– 134.129.67.235
• IPv6 address written as eight 4-digit (16-bit) hexadecimal numbers separated by colons.– 1080:0:0:0:0:800:0:417A
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Uniform Resource Locator
• http://www.ndsu.nodak.edu/ndsu/latimer/index.html#events
• http:// communication protocol• www.ndsu.nodak.edu web server hosting the page• /ndsu/latimer/ path to the page on the host server• index.html filename of the page• #events anchor in the page
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IP & Domain Name Examples
• IP: 134.129.67.85
• URL: gdc.busad.ndsu.nodak.edu
• IP: 134.129.67.235
• URL: dyn235.minard-67.ndsu.nodak.edu
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ICANN • Internet Corporation for Assigned Names and Numbers• a private sector, nonprofit organization• responsibility for IP address space allocation, protocol parameter
assignment, domain name system management and root server system management functions previously performed under U.S. Government contract
• ICANN's diverse board consists of nineteen Directors, nine At-Large Directors, who serve one-year terms and will be succeeded by At-Large Directors elected by an at-large membership organization. None of the present interim directors may sit on the board once the permanent members are selected.
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IP Address Registries
• Regional Internet Registries:
• American Registry for Internet Numbers, ARIN
• Réseaux IP Européens Network Coordination Centre, RIPE NCC
• Asia Pacific Network Information Centre, APNIC
• Latin American and Caribbean Internet Addresses Registry, LACNIC
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Internet Assigned Numbers Authority
http://www.iana.org/
• Generic Top-Level Domains– http://www.iana.org/gtld/gtld.htm
• ccTLD Database (country codes)– http://www.iana.org/cctld/cctld-whois.htm
• IP Address Services– http://www.iana.org/ipaddress/ip-addresses.htm
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New Top-Level Domain Names (TLDs)
• ICANN is accepting applications for new TLDs.– Application window Jan. 12, 2012 to Apr. 12, 2012
– Application fee: $185,000
– Annual fee: $25,000
• Intent is to move towards more descriptive names
• Companies (organizations) can create– Brand domains e.g. .pepsi .coke
– Generic domains e.g. .car .green
• http://mashable.com/2011/06/20/icann-top-level-domains/