Telecommunications and the Internet rely on various transmission channels to transmit digital signals between computers and networks. Common channels include twisted pair wiring, coaxial cable, fiber optics, microwave transmission, and wireless technologies. These channels can transmit data at speeds ranging from 56 kbps for older modems up to several gigabits per second for newer fiber optic networks. The Internet itself is a global system of interconnected computer networks that uses standardized communication protocols like TCP/IP to link billions of devices worldwide.

1. Telecommunications
&
The Internet

2. Basic Telecom Model
Computer Computer
Channel
interface
Channel
interface
Communication
Channel

3. Typical Home Telecom Model
Computer Computer
Modem Modem
Audio Phone Lines
Digital
signals
Digital
signals
Analog signals

4. Channels
• Twisted wire (twisted pair)
• Coaxial Cable
• Fiber Optics
• Microwave
• Newer Wireless

5. 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.

6. 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.

7. Coaxial Cable
• More expensive
• harder to work with
• not as extensive an existing infrastructure
– cable TV companies are changing this
• 56Kbps to 550Mbps

8. Fiber Optics
• Very expensive
• difficult to work with
• existing infrastructure limit to backbones
• 500Kbps to 30Gbps

9. 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

10. 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

11. 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.

12. 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

13. 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.

14. 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.

15. Communications Processors
Front End
Processor
CPU
Controller
Computer
C
h
a
n
n
e
l
Multiplexer
PC PC PC
T
T
T
T
Concentrator
Channel

16. Network Topology
• Star Network
• Bus Network
• Ring Network
C
C C
C
C C
C
C
C
C C
C
P
P
P

17. Networks
• Local Area Network, LAN
• Wide Area Network, WAN
• Value Added Network, VAN

18. Network Terms
• File server
• Print server
• Gateway - connects dissimilar networks
• Bridge - connects similar networks
• Routers - connects networks & directs traffic
• Similar networks = same network protocols

19. 20
Chapter 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

20. 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

21. The Internet
• What is the Internet?
• Who owns the Internet?
• Why does the Internet exist?

22. 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

23. 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

24. Public Networks
CompuServe
• 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

25. Public Networks
Prodigy
• 1986 pilot in Atlanta, Hartford, San
Francisco
• 1988 national service launched
• 1994 1st to offer WWW access
• 1999 Prodigy Classic discontinued (209,000
members)

26. Public Networks
AOL
• 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

27. Internet Statistics
• http://www.internetworldstats.com/stats.htm
– User Counts, updated daily
• http://whois.sc/internet-statistics/
– Domain Counts, updated daily

28. 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

29. 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

30. 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

31. Putting It All Together
AT&T Level 3
Centurylink
I29 Cable One
Consumer Consumer Consumer

32. Some Upper Tier Providers
• AT&T
• Bell Atlantic
• Bell South
• Cable and Wireless
• Cable One
• GTE
• IBM
• MCI
• Pacific Bell
• QUEST
• Sprint
• US West

33. 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.

34. 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/

35. Upper Tier Bandwidths
OC-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

36. Organization Benefits of Internet
• Reducing Communication Costs
– virtual private net
• Enhancing Communication and Coordination
• Accelerating the Distribution of Knowledge
• Facilitating Electronic Commerce

37. 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

38. Internet Challenges
• Security
• Technology Problems
– incompatibility
– limited bandwidth
– telecommunications infrastructure
– internet specialists
• Legal Issues

39. 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.

40. 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

41. 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

42. 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

43. 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

44. 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

45. 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.

46. 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

47. 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

48. 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/