1. Chapter 1 Communication Networks and Services
Network Architecture and Services

2. Communication Technology Applications
voice mail
Twitter
instant messaging
chat rooms
newsgroups
telephony
videoconferencing
collaboration
groupware
global positioning system (GPS)

3. Communication Services & Applications
A communication service enables the exchange of information between users at different locations.
Communication services & applications are everywhere.
server
Exchange of messages via servers

4. Communication Services & Applications
A communication service enables the exchange of information between users at different locations.
Communication services & applications are everywhere.
Web Browsing
Web server
Retrieval of information from web servers

5. Communication Services & Applications
A communication service enables the exchange of information between users at different locations.
Communication services & applications are everywhere.
Instant Messaging
Direct exchange of text messages

6. Communication Services & Applications
A communication service enables the exchange of information between users at different locations.
Communication services & applications are everywhere.
Telephone
1876, Scottish emigrant Alexander Graham Bell
Real-time bidirectional voice exchange

7. Communication Services & Applications
A communication service enables the exchange of information between users at different locations.
Communication services & applications are everywhere.
Cell phone
In 1917, Finnish inventor Eric Tigerstedt filed a patent for a "pocket-size folding telephone
Real-time voice exchange with mobile users

8. Communication Services & Applications
A communication service enables the exchange of information between users at different locations.
Communication services & applications are everywhere.
Short Message Service
Fast delivery of short text messages

9. Many other examples! Peer-to-peer applications Audio & video streaming
Napster, Gnutella, Kazaa file exchange
Searching for ExtraTerrestrial Intelligence (SETI)
Audio & video streaming
Network games
On-line purchasing
Text messaging in PDAs, cell phones (SMS)
Voice-over-Internet

10. Services & Applications
Service: Basic information transfer capability
Internet transfer of individual block of information
Internet reliable transfer of a stream of bytes
Real-time transfer of a voice signal
Applications build on communication services
& web build on reliable stream service
Fax and modems build on basic telephone service
New applications build on multiple networks
SMS builds on Internet reliable stream service and cellular telephone text messaging

11. What is a communication network?
The equipment (hardware & software) and facilities that provide the basic communication service
Virtually invisible to the user; Usually represented by a cloud
Equipment
Routers, servers, switches, multiplexers, hubs, modems, …
Facilities
Copper wires, coaxial cables, optical fiber
Ducts, conduits, telephone poles …
How are communication networks designed and operated?

12. Communication Devices
Any type of hardware capable of transmitting data, instructions, and information between devices
Functioning as receiver, transmitter, adaptor, converter
Basic characteristics: How fast, how far, how much data!
Examples: Dial-up modems, ISDN, DSL modems, network interface cards
Dial-up modem: uses standard phone lines
Converts digital information into analog
Consists of a modulator and a demodulator
Can be external, internal, wireless
ISDN and DSL Modem: Allows digital communication between networks and computers
Requires a digital modem
Digital is better than analog – why?
Cable modem: a modem that transmits and receives data over the cable television (CATV) network
Also called broadband modem (carrying multiple signals)
The incoming signal is split
Requires a cable modem
Network interface cards: Adaptor cards residing in the computer to transmit and receiver data over the network (NIC)
Operate with different network technologies (e.g., Ethernet)

13. Communication Channels
A channel is a path between two communication devices
Channel capacity: How much data can be passed through the channel (bit/sec)
Also called channel bandwidth
The smaller the pipe the slower data transfer!
Consists of one or more transmission media
Materials carrying the signal
Two types:
Physical: wire cable
Wireless: Air
destination network server
T1 lines
T3 lines

14. Physical Transmission Media
A tangible media
Examples: Twisted-pair cable, coaxial cable, Fiber-optics, etc.
Twisted-pair cable:
One or more twisted wires bundled together (why?)
Made of copper
Coax-Cable:
Consists of single copper wire surrounded by three layers of insulating and metal materials
Typically used for cable TV
Fiber-optics:
Strands of glass or plastic used to transmit light
Very high capacity, low noise, small size, less suitable to natural disturbances

15. Physical Transmission Media
plastic outer coating
woven or braided metal
insulating material
copper wire
twisted-pair cable
twisted-pair wire
protective coating
glass cladding
optical fiber core

16. Wireless Transmission Media
Broadcast Radio
Distribute signals through the air over long distance
Uses an antenna
Typically for stationary locations
Can be short range
Cellular Radio
A form of broadcast radio used for mobile communication
High frequency radio waves to transmit voice or data
Utilizes frequency-reuse

17. Computer Network Evolution Overview
1950s: Telegraph technology adapted to computers
1960s: Dumb terminals access shared host computer
SABRE airline reservation system
1970s: Computers connect directly to each other
ARPANET packet switching network
TCP/IP internet protocols
Ethernet local area network
1980s & 1990s: New applications and Internet growth
Commercialization of Internet
, file transfer, web, P2P, . . .
Internet traffic surpasses voice traffic

18. What is a protocol?
Communications between computers requires very specific unambiguous rules
A protocol is a set of rules that governs how two or more communicating parties are to interact
Internet Protocol (IP)
Transmission Control Protocol (TCP)
HyperText Transfer Protocol (HTTP)
Simple Mail Transfer Protocol (SMTP)

19. Error Control Protocol
Communication lines introduced errors
Error checking codes used on frames
“Cyclic Redundancy Check” (CRC) calculated based on frame header and information payload, and appended
Header also carries ACK/NAK control information
Retransmission requested when errors detected
Header Information CRC
CRC Information Header
Terminal

20. Success Factors for New Services
Technology not only factor in success of a new service
Three factors considered in new telecom services
Can there be demand for the service?
Can it be implemented cost-effectively?
Market
New Service
Technology
Is the service allowed?
Regulation