Title: Communications and Networks
1Communications and Networks
Reading Chapter 9
2Why are networks so useful?
- They facilitate communications
- They allow for sharing of resources
- Both of the above
3Network
- Uses of communications technologies
- 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)
4Networks Communications Devices
- Communications Device
- 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
5Networks 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
6Networks Communications Devices
- Cable modem
- Cable television network
- Faster than dial-up access or ISDN line
- Splitter runs separate cables to TVs 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
7Networks 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
8Communications devices include ______.
- routers
- hubs
- modems
- NICs
- All of the above
9Networks Communications Channels
- Channel
- 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
10Networks 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
11Networks Physical Transmission Media
- 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
12Networks Physical Transmission Media
13All of the following except ______ are examples
of physical media.
- coaxial cable
- twisted pair
- microwave cable
- fiber optic cable
14Networks Wireless Transmission Media
- 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
- 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
- Infrared Signals
- IR light waves with line-of-sight transmission
15Networks Wireless Transmission Media
16All of the following except ______ are examples
of wireless media.
- microwaves
- satellites
- radio frequency waves
- fiber optic waves
17Networks
- Classified according to
- Geography Geographic Distribution
- LAN
- MAN
- WAN
- Architecture
- Topology
- Protocol/Communications Technology
18Networks 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
19Networks 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
20A ______ is a network that encompasses a limited
geographic area.
- MAN
- WAN
- LAN
- PAN
21Networks
- Classified according to
- Geography
- Architecture Broad outline of the network
- Peer-to-Peer
- Client/Server
- Topology
- Protocol/Communications Technology
22Network Architectures Client/Server and
Peer-to-Peer
- 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 others hard disk
- Popular, inexpensive
23Networks
- 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
24Network 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
25Network 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
26With ______ topology, the devices on the network
are connected together in a closed loop.
- bus
- ring
- star
- tree
27Networks
- 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
28Networks Network Communications Technologies
- Communications Protocol
- Set of rules and procedures for exchanging
information among computers - Ethernet
- Token ring
- TCP/IP
- WAP
- Others
29Network Communications Technologies Ethernet
- Ethernet
- Widely used LAN standard
- Developed by Xerox, DEC, Intel - 1976
- Fast Ethernet (100Base-T) - 100 Mbps
- Gigabit Ethernet - 1000 Mbps
- 10-Gigabit Ethernet 10 Gbps
- Bus or star topology
- PCs in the network to contend for access
- Collision
30Network Communications Technologies Token Ring
- 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
31Network Communications Technologies TCP/IP
- 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
32Network 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
33Network Communications Technologies 802.11,
Bluetooth, IrDA
- IEEE 802.11 (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
34With TCP/IP is used to send data over the
Internet, the data is divided into small pieces
or ______.
- bundles
- packets
- tokens
- hubs
35Networks 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
36Networks 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, 802.11b 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
37Do you have a home area network?
- Yes
- No
38Networks 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, 802.11, others
- Intranets and Firewalls
- Home Networks