Transcript Going Online - Victoria College

Going Online
Chapter 3a
Connectivity
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Computer strength
Ability of computers to communicate with
each other at computer speeds
Ultimate example is Internet
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Interconnected Networks
Collection of independent networks w/ Internet
host connected 24/7
Internet
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Began in 1969 as APRANET project of Dept
of Defense
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Build a communications network for military,
scientists, researchers across nation
Important stipulation – network should remain
functional even if parts were down
Resulted in network with no central computer and
multiple communication pathways between sites
Internet (contd)
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1990 government project ended
Today Internet is commercial
Governed by international group of
volunteers
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Sets standards
Coordinate global operation
Ingredients to go online
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Communications channel
Connection method
Communications protocol
Communications software
Communication channels
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Rated by bandwidth
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Number of bits transmitted per second (bps)
Low bandwidth = narrow bandwidth
High bandwidth = broadband
Broadband is now generic term for
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High–speed Internet access
Always on
Communication channels
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Dialup access with POTS
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Narrowband
Temporary connection
Required modem to convert
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Computer digital signals
Phone line analog signals
ISP provides access to a host Internet server
56 Kbps
Communication channels
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Cable
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Broadband
Available from cable TV companies
Limited to metropolitan areas
Requires cable modem
10 Mbps
Communication channels
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DSL or digital subscriber line
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New broadband technology using POTS
Required DSL modem
Limited to metropolitan areas
Two speeds
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Downstream rate (to client) 9 Mbps
Upstream rate (to server) 1.5 Mbps
Communications channels
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Satellite
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Broadband
Must have southern exposure
Problems
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Latency = lag in response time of ¼ second
Weather dependence
Requires satellite dish and satellite modem
1.5 Mbps
Communication channels
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Wireless
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Requires access point or a link to a wired network
Uses short-range radio waves
Wi-Fi is the umbrella for several wireless
standards (IEEE 802.11)
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Wireless-B (IEEE 802.11b) 11 Mbps, up to 300 ft
Wireless-A (IEEE 802.11a) 54 Mbps, up to 50 ft
Wireless-G (IEEE 802.11g) 54 Mbps, up to 300 ft
Connection methods
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ISP = Internet service provider
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Commercial service via dialup, cable, DSL,
satellite
Each channel requires a modem
Network = Local Area network (LAN)
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Network has a host Internet server
Broadband access shared by all users in network
Requires network interface card (NIC) on each
PC
Communication protocols
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Communication relies on protocols
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Set of rules computers use to communicate with
each other
Establish, maintain, terminate connection
Many different protocols
A single computer can support multiple protocols
To communicate both computers must use the
same protocol
Communication protocols
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Protocol of the Internet is TCP/IP
Uses an IP address to uniquely identify each
user on the Internet
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Four number (0-255), separated by periods
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i.e. 206.28.104.10
IP address is assigned by ISP or network
TCP/IP
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Numbers are difficult to remember so TCP/IP
includes DNS service
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Translates domain names to IP address
Users use domain names to access Internet
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i.e. www.victoriacollege.edu
Names must be registered
Charge is assessed to support Internet operations
DNS
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Domain names are read from right to left
To determine IP address of
www.victoriacollege.edu.
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First, goes to root DNS server (.) for addresses of
next level DNS server (edu)
Next, goes to edu server and retrieves address for
next level DNS server (victoriacollege)
Finally, goes to victoriacollege DNS server to
retrieves address for www (host PC)
Communications software
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To be continued…