A)
The Language of Computer Networks
a.
Computer
network – an interconnected group of computers and computing equipment
using either wires or radio waves that can share data and computing resources
i.
Wireless
– computer networks that use radio waves. Can involve broadcast radio,
microwaves, or satellite transmission
b.
Types of networks
i.
Personal
area networks (PANs) – networks spanning an area of several meters around
an individual. Include laptop, computers, smart cell phones, music players, and
wireless connections
ii.
Local
area networks (LANs) – networks spanning a room, a floor within a building,
or an entire building
iii.
Campus
area networks (CANs) – collections of local area networks that cover a
campus (college campus or business campus)
iv.
Metropolitan
area network (MANs) – networks that serve an area up to roughly 50
kilometers. They are high-speed networks that interconnect businesses with
other businesses and the internet
v.
Wide area
networks (WANs) – large networks encompassing parts of states, multiple
states, countries, and the world
c.
Cloud
i.
Network
cloud and cloud computing
d.
Data and signal
i.
Data –
information that has been translated into a form more conductive to storage,
transmission, and calculation.
ii.
Signal
– used to transmit data
e.
Data communications
– transfer of digital or analog data using digital or analog signals. Once
created, these analog and signals are then transmitted over conducted media or
wireless media
i.
Interfacing
– sending one signal over a medium at one time
ii.
Multiplexing
– the transmission of multiple signals on one medium. To transmit multiple
signals simultaneously, they must be altered to not interfere with each other
iii.
Compression
– squeezing data into a smaller package, thus reducing the amount of time
needed to transmit the data
f.
Voice
and data networks
i.
Merging of voice and data networks is an example
of convergence
B)
The Big Picture of Networks
a.
Work
stations – personal computers (microcomputers, desktops, laptops, or
tablets) or smartphones
b.
Servers
– computers that store network software and shared or private user files
c.
Switches
– collection points for the wires that interconnect the workstations
d.
Routers
– connecting devices between local area networks and wide area networks such as
the internet
e.
Nodes
– computing devices that allow workstations to connect to the network and that
make the decisions about where to route a piece of data
f.
Subnetwork
– consists of the nodes and transmission lines, collected into a cohesive unit
C)
Common Examples of Communications Networks
a.
The desktop computer and the internet
i.
Client/server
system – client machines issues request for some form of data or service.
Could be for database record from database server or request for a Web page
from a Web server
b.
A laptop and a wireless connection
i.
Data communication protocols – sets of rules used by communication devices
c.
Cell phone system
d.
Other common network systems
i.
Computer terminal
– a device that was essentially a keyboard and screen with no large hard
drives, no gigabytes of memory, and little, if any, processing power
D)
Convergence – process of coming together toward
a single point
E)
Network architectures
a.
Network
architecture (communications model) – places the appropriate network pieces
in layers. Each layer in the model defines what services either the hardware or
software provides
i.
TCP/IP
protocol suite – working model (currently used on the internet)
1.
Application
layer – supports the network applications and in some cases include
additional services such as encryption or compression
a.
Hypertext
Transfer Protocol (HTTP) – allow Web browsers and servers to send and receive
World Wide Web pages
b.
Simple
Mail Transfer Protocol (SMTP) – allow users to send and receive electronic
mail
c.
File
Transfer Protocol (FTP) – transfer files from one computer system to
another
d.
Telnet
- allow a remote user to log in to another computer system
e.
Simple
Network Management Protocol (SNMP) – the numerous elements within a
computer network that are managed from a single point
2.
Transport
layer – uses TCP to maintain an error-free end-to-end connection.
a.
Includes error control information in case one packet
from a sequence of packets does not arrive at the final destination and package
sequencing information so that all packets stay in the proper order.
b.
Performs end-to-end error control and end-to-end
flow control
3.
Network
layer (internet layer or IP layer) – used to transfer data within and
between networks
a.
Internet protocol (IP) – software that prepares
a packet of data so that it can move from one network to another on the
internet or within a set of corporate networks
i.
Generates the network addressing necessary for
the system to recognize the next intended receiver
4.
Network
access layer – layer that gets the data from the user workstation to the
internet
a.
Prepares a data package (called a frame) for transmission from the user
workstation to a router sitting between the local area network and the Internet
5.
Physical
layer – layer in which the actual transmission of data occurs
a.
Physical layer handles voltage levels, plug and
connector dimensions, pin configurations and other electrical and mechanical
issues
b.
Also determines encoding or modulation technique
to be used in the network
ii.
Open
Systems Interconnection (OSI) model – originally designed to be a working
model but has been used as a theoretical model
1.
Application
layer – where the application using the network resides
2.
Presentation
layer – performs a series of miscellaneous functions necessary for presenting
the data package properly to the sender or receiver
3.
Session
layer – responsible for establishing sessions between users
a.
Can support token
management, a service that controls which user’s computer talks during the
current sessions by passing a software token back and forth
b.
Also establishes synchronization points – backup points used in case of errors or
failures
4.
Transport
layer – ensures that the data packet that arrives at the final destination
is identical to the data packet that left the originating stations
5.
Network layer
– responsible for getting the data packets from router to router
6.
Data link
layer – responsible for taking data from the network layer and transforming
it into a frame
7.
Physical layer
– handles the transmission of bits over a communications channel
iii.
Logical and physical connections
1.
Logical connection
– nonphysical connection between sender and receiver that allows an exchange of
commands and responses
2.
Physical
connection – only direct connection between sender and receiver and is at
the physical layer, where actual 1s and 0s – the digital content of the message
– are transmitted over wires and airwaves
F)
Encapsulation
– control information to a package as it moves through the layers
No comments:
Post a Comment