MGT318 Chapter 6

Base Concept in data communication systems
amount of data can be transferred from one point to another in a certain period of time
loss of power in a signal as it travels from the sender to receiver
notion that the pulse of electricity that is sent out to give info will eventually fade
multiple pieces of data, sent simultaneously to increase the transmission rate
voice-grade transmission channel capable of transmitting a limited amount of info
Rules that govern data communication:
>Error detection
>Message length
>Transmission speed
Form of sender and receiver device
1. Input/output device (doesn’t actually process the data)
2. Terminal (connects to a comp where processing is done; relies fully on network)
3. Personal computer/ notebook (can do processing themselves; sends it out on network)
4. Mainframes and supercomputers (alllll of the processing!)

*processing levels increase as we go down the list

2 Types of Communication Media
Transmission media:
1. Conducted
2. Radiated
–>Wires/ twisted pair (STP & UTP) (telephone and computer chargers)
–>Coaxial Cable (more insulated but low control, can be tapped and is susceptible to disruption)
–>Fiber Optic (fast and more secure, but expensive and breakable)
–>Infrared (light beams; ex a remote control but it must be point directly at object)
–>Radio frequencies (goes through walls)
–>Cellular Networks
–>Microwave (pulls one signal in, sends one out. limited to how far they will go because of Earth’s shape; must be within 30 miles from each other)
Modems (modulator demodulator)
devices that connect a computer to the internet
-dial up
– digital subscriber line (DSL)

satellite tv does NOT require a modem

agreed on methods and rules that are standardized for
–>Hardware connections
–>Data transmissions
–>File transfers (Wifi, Ethernet)
they specify the format of message packets sent between computers
Packet and routing
*packet*- a collection of binary digits sent from a computer to computer over a network
*routing*- the process of deciding which path the data takes
a. static (stays the same)
b. dynamic (changes)
Always send 2 packages on different routes just in case one doesn’t get there
Open Systems Interconnection (OSI) Model= 7 LAYERS!!!
7 layers:

Data Link

One side creates packet, the other side is creating a message

Transmission Control Protocol
–establishes a link between hosts
–ensures message integrity, sequencing and acknowledging packet delivery
–regulates data flow between source and destination nodes
Internet Protocol- responsible for packet forwarding
—Network address
—Node address
On the same side of the body
Local, Wide, Metropolitan
Network Topologies
Star, Ring, Bus, Heirarchical, Mesh
Local area networks
-networks that exist within an operational facility
-they are considered within local operational control
Wide area networks
-much larger than LAN
-connect computers that are miles apart
Metropolitan area networks
-a set of connected networks within the same city or metropolitan area but not in immediate proximity to each other
-network that operates over a college campus or city
Client-Server model
Software runs on the local computer and communicates with the remote server to request information or services
–>Server is a remote computer on the network that provides information or services in response to request
Client-Server model concerns
Data Management
types of architecture
two-tier architecture
the client communicates directly with the server
effective in small workgroups

Advantage: consists of application development speed, simplicity, and power
Drawback: changes in application logic require modifications of clients resulting in upgrade and modification costs

n-tier architecture
balance the workload between client and server by removing application processing from the client and server and placing it on a middle-tier server
(three-tier architecture)

Advantage: improved network performance
Drawbacks: consists of more network traffic and testing software is difficult

three-tier architecture
Wireless and Mobile Networks advantages
-Ease of installation
-Low cost
Wireless and Mobile Networks disadvantages
-Limited throughput
-Limited range
-In-building penetration problems
-Vulnerability to frequency noise
Wireless and Mobile Networks disadvantages