Networks Review

decisioncrunchNetworking and Communications

Nov 20, 2013 (3 years and 6 months ago)

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ICS3U/4U


A collection of computers and other
hardware components interconnected by
communication channels that allow
sharing of resources and information


Share Internet connection


Share devices (printers, scanners)


Share file libraries


Stream music or video


Peer
-
to
-
Peer


Client/Server


Peer
-
to
-
Peer


No hierarchy


everyone has equal rights


Often 2
-
10 machines/users


Found in homes or small business



Advantages


Easy/cheap to set up/maintain



Disadvantages


Security (must trust everyone else on network)


No servers and therefore no network services



Client/Server Model


Area networks


Computers connected through a central server
(provides “services”)


Found in schools and larger businesses


Unlimited number users



Advantages


All the services the server(s) provide



Disadvantages


Cost of server & ongoing maintenance



LAN (Local Area
Network)


Usually constrained
to a single building


Typically 10
-
500
users


Found in schools,
businesses


WAN (Wide Area
Network)


A network of LANs


Can connect regional
offices to a central
office, or schools to the
school board


Clients can have access
at multiple sites


500+ users



MAN (Metropolitan Area
Network)


A network of LANs


Used by regional or
municipal organizations
within a municipality (i.e.
campuses, libraries, city
-
run businesses, etc.)



The physical layout or arrangement of a
network


Basic


A single connection
method


Hybrid


To or more basic
topologies


Linear (or Bus)


Computers connected to a single trunk or cable


Prone to collisions


Ends of trunk must be ‘terminated’


A break anywhere will halt network


Ring


Computers arranged in a
circle*
, connected to a
single trunk or cable


Packets are passed in one
direction only (eliminating
collisions)


Single break still takes
down entire network


Star


Computers connected to
a central hub


Still prone to collisions


Break only affects one
computer


Mesh


Computers connected
directly to each other


As many individual
connections as you like


More costly to set up
and configure



Tree


Hierarchical (has a root
node)


Star/bus combination


Each branch has a hub


Can be quite complex


Breaks only affect
downstream stations


Star/Circle



SONET


Synchronous Optical
Network


Dual unidirectional
optical networks


No collisions


IP Address


The computer’s address on a network


Assigned by the server


Expires in a day or two, and a new one is
assigned


Consists of 4 octets ranging from 0 to 255


MAC Address


All network devices have a unique, permanent
Media Access Control device address, assigned
by the manufacturer


Includes computers, smartphones, smart TVs,
network printers,


Consists of 6 hexadecimal octets, from 00
-
FF

00

: 80 : a0 : b2 : 81 :
fe

0000 0000

1000

0000

1010

0000

1011 0010

1000 0001

1111 1110

Protocol

Definition

ftp

File Transfer Protocol


standard for sending files from one
host to another over TCP network

http://

Hypertext Transfer

Protocol


language describing format
and actions for web pages; format tags, links to other pages

smtp

Simple Mail Transfer Protocol


Internet standard for email
transmission across IP networks

TCP/IP

Transmission Control Protocol / Internet Protocol


communications protocols for the Internet (based on
ARPANET)

VOIP

Voice Over

Internet Protocol


live audio conversation,
Skype, Rogers home phone


Asynchronous


ATM


Data is transmitted
and received one
direction at a time


Talk/Listen


Usually 90% listen,
10% talk


S
ynchronous


STM


Data is transmitted
and received
simultaneously


Can use dual
frequencies to carry
data in both
directions on the
same cable


Wireless
Equivalent Privacy
(WEP)


1999


Encoded/decoded
by a 10 or 26
-
digit
hexadecimal key


Has been
demonstrated to have
numerous flaws


WiFi

Protected Access (WPA)


2003


Uses Temporal Key Integrity Protocol (TKIP)


A per
-
packet key, meaning it generates a 128
-
bit key
for each packet


WPA2


2004


CCMP encryption mode with strong security


Mandatory for
WiFi

trademark certification


MAC Filtering


Router can
‘blacklist’ or
‘whitelist’ network
devices, based on
their unique 48
-
bit
MAC addresses


Must physically
type MAC
addresses into
router


Firewall


Software or hardware
-
based network security


Examines incoming and outgoing network traffic
to determine if packets should be allowed
through


All packets are destined for one of the
computer’s thousands of ports


Mail


TCP port 25


WWW system TCP port 80