1. Communications and Networks
Reading: Chapter 9

2. Why are networks so useful?60
They facilitate communications
They allow for sharing of resources
Both of the above

3. Network Uses of communications technologies Network Internet
Global Positioning System (GPS)
Short Message Service (SMS)
Network
Interconnected group of computers and devices connected via communications devices and media
Facilitates sharing of resources and supports communications
Requires
Sending & receiving devices
Communications devices
Communications channel or path
Network OS (NOS)

4. Networks – Communications Devices
Hardware capable of sending/receiving data
Convert signals so that they are suitable for the communications channel
May convert between analog and digital
Common types
Dial-up modems
ISDN and DSL modems
Cable modems
Network interface cards
Wireless access points
Routers

5. Networks – Communications Devices
Dial-up Modem
Modulate/demodulate
External modem
Connects to serial or RS-232 port
Internal modem
Card inserted to expansion slot/PC Slot
ISDN and DSL Modems
Do not modulate/demodulate
External
Sends and receives data over a digital telephone line
ISDN line
DSL line

6. Networks – Communications Devices
Cable modem
Cable television network
Faster than dial-up access or ISDN line
Splitter runs separate cables to TV’s and cable modem
External
USB port or Ethernet NIC via a cable
Network Interface Card (NIC)
Coordinates transmission/receipt of data to/from the device
Card installed in an expansion slot of a PC, printer, PC slot
Wireless transmission includes antenna
Works with a particular network technology
Ethernet or token ring

7. Networks – Communications Devices
Hub
Provides a central point of connectivity for cables in a network
May include a router
Router
Connects multiple computers and routers together
Transmits packets to correct destination
May include built-in firewall
Wireless access point
Allows computers and devices to communicate wirelessly
Allows data transfer to a wired network

8. Communications devices include ______.45
routers
hubs
modems
NICs
All of the above

9. Networks – Communications Channels
Communications path between two devices
Transmission rate
Speed at which data flows through the channel
Bandwidth of the channel
Bits per second (bps), Hertz (cycles per second)
Transmission media
Materials or techniques capable of carrying one or more signals
Baseband media – carry one signal at a time
Broadband media – carry multiple signals concurrently
Physical transmission media
Twisted pair, Coaxial, Fiber Optic
Wireless transmission media
Infrared, Radio Frequency, Infrared, Microwave

10. Networks – Physical Transmission Media
Twisted-pair cable
Used for network cabling and telephone systems
One or more twisted-pair wires bundled together
Each pair has two insulated copper wires twisted together
Coaxial cable (coax)
Used for network cabling and cable TV
Single copper wire surrounded by 3 layers
Insulating material
Woven/braided metal
Plastic outer coating

11. Networks – Physical Transmission Media
glass cladding
optical fiber core
Fiber optic cable
Light used to send signals
Thin glass or plastic strands
Surrounded by insulating glass cladding and a protective coating
Carries many signals
High speed
Less noise
Smaller size
Expensive, difficult to install and modify
Protective coating

12. Networks – Physical Transmission Media

13. All of the following except ______ are examples of physical media.45
coaxial cable
twisted pair
microwave cable
fiber optic cable

14. Networks – Wireless Transmission Media
Radio Frequency
Antenna, transmitter, receiver
Bluetooth (2.45 GHz)
802.11b & g (2.4 GHz)
Cellular Radio Waves
Cell phones, mobile devices
High frequency radio waves
824 to 849 MHz
Microwaves
High-speed signal transmission
Signals sent between microwave stations
Fixed-point wireless
Requires line-of-sight
Communications Satellites
Satellite receives microwave signal and amplifies
Retransmits over wide-area, to a number of land-based stations
Infrared Signals
IR light waves with line-of-sight transmission

15. Networks – Wireless Transmission Media

16. All of the following except ______ are examples of wireless media.45
microwaves
satellites
radio frequency waves
fiber optic waves

17. Networks Classified according to Geography – Geographic Distribution
LAN
MAN
WAN
Architecture
Topology
Protocol/Communications Technology

18. Networks – Geographic Distribution
Local Area Network (LAN)
Connects computers in a limited geographical area
Each computer and device is a node
Metropolitan Area Network (MAN)
High-speed network that connects LANs in a metropolitan area
Managed by a consortium of users or a single network provider

19. Networks – Geographic Distribution
Wide Area Network (WAN)
Connects computers and devices in a large geographical area
Connected via many types of media
One large network or two or more interconnected LANs, MANs
Others
CAN
HAN
TAN

20. A ______ is a network that encompasses a limited geographic area.45
MAN
WAN
LAN
PAN

21. Networks Classified according to
Geography
Architecture – Broad outline of the network
Peer-to-Peer
Client/Server
Topology
Protocol/Communications Technology

22. Network Architectures – Client/Server and Peer-to-Peer
printer
Client/Server
Server controls resources
More storage space, power
Serves as a repository
Dedicated servers
Client relies on the server for access to resources
Peer-to-Peer
Share peripheral devices
Up to 10 “peer” computers
NOS & applications software, storage
Internet Peer-to-Peer (P2P)
Users connect directly to each other’s hard disk
Popular, inexpensive

23. Networks Can be classified according to
Geography
Architecture
Topology – Physical arrangement of devices connected to the network
Bus
Ring
Star
Networks often use a combination of topologies
Protocol/Communications Technology

24. Network Topologies – Bus and Ring Networks
Bus Network
Single central cable connects computers and devices
Transmits in both directions
If a device fails, network continues to function
Reliable
Popular, inexpensive
Ring Network
Cable forms a closed ring
Transmits in only one direction
If one device fails, all those after the device cannot function
Spans larger distance than bus network
LANs and WANs

25. Network Topologies – Star and Other Networks
Star Network
Devices connect to a central computer
Hub
If one device fails, only that device is affected
Hub fails
Other Topologies
Mesh
Redundant interconnections between nodes
Tree
Star networks connected together via a bus

26. With ______ topology, the devices on the network are connected together in a closed loop.45
bus
ring
star
tree

27. Networks Can be classified according to
Geography
Architecture
Topology
Protocol/Communications Technology – Standards that govern how data/instructions flow over the network
Ethernet
Token Ring
TCP/IP
WAP
Others

28. Networks – Network Communications Technologies
Communications Protocol
Set of rules and procedures for exchanging information among computers
Ethernet
Token ring
TCP/IP
WAP
Others

29. Network Communications Technologies – Ethernet
Widely used LAN standard
Developed by Xerox, DEC, Intel
Fast Ethernet (100Base-T) Mbps
Gigabit Ethernet Mbps
10-Gigabit Ethernet – 10 Gbps
Bus or star topology
PCs in the network to contend for access
Collision

30. Network Communications Technologies – Token Ring
Ring or star topology
LAN standard
Passes a signal called a token
Special bit pattern
Only device with token can transmit
Device catches the token, attaches message , sends it to travel around the network to receiving device
Receiving device catches token, strips off the message, resends token

31. Network Communications Technologies – TCP/IP
Used to connect hosts on the Internet
Includes several protocols
Transmission Control Protocol and Internet Protocol
Data broken up into small packets
Origin information
Destination information
Sequence information
Data/information/instructions
Packet switching
Break up message into packets, route packets, destination reassembles the message
Routers direct packets individually along fastest path

32. Network Communications Technologies – WAP
Wireless Application Protocol (WAP)
Access Internet via mobile devices
2.0 Specification
Open Mobile Alliance (OMA)
Web sites provide wireless content to display on microbrowsers
WML – XML application designed for small screens

33. Network Communications Technologies – 802.11, Bluetooth, IrDA
IEEE (802.11b, g – “WiFi”)
Family of standards used with wireless LANs
Used for public Internet access points
Bluetooth
Devices contain special chip
Short-range radio waves transmit between Bluetooth devices
Short distance
IrDA
IrDA devices contain IrDA ports
Infrared light waves
Line-of-sight transmission

34. With TCP/IP is used to send data over the Internet, the data is divided into small pieces or ______.45
bundles
packets
tokens
hubs

35. Networks – Intranets Intranet
Internal network in an organization used to share information
Uses Internet technologies (TCP/IP, Web server, Web pages)
Enterprise network
Connects to the Internet
Extranet - Allows outside user access
Firewall
Designed to prevent unauthorized access to a private network
Firewall blocks messages that do not meet security criteria
Uses hardware, software, combination of both
All messages entering or leaving the intranet must pass through the firewall

36. Networks – Home Area Networks (HAN)
Network within a home
Connects digital devices
HomePLC – electrical lines; cables connect card/USB/parallel port to wall outlet
Phoneline – telephone lines; cables connect NIC/PC card to telephone jack
Network card that plugs into PCI slot and wall outlet for home power-line network
Howstuffworks.com
HomeRF, b – radio waves; NIC connects to transceiver with antenna or to wireless access point
Ethernet – twisted pair cables; Ethernet NIC cards and cables to connect devices

37. Do you have a home area network?30
Yes No

38. Networks Summary Uses of Communications Technology Networks
Communications Devices
Communications Channels
Physical and Wireless Transmission Media
Geographic
LAN, MAN, WAN
Architectures
Peer-to-Peer, Client/Server
Topologies
Bus, Ring, Star
Protocols
Ethernet, Token Ring, TCP/IP, WAP, , others
Intranets and Firewalls
Home Networks