internet some slides taken from: computer science: an overview tenth edition. j. glenn brookshear
TRANSCRIPT
Internet
Some slides taken from: Computer Science: An Overview Tenth Edition. J. Glenn Brookshear
Internet
• Networks
• The Internet
• The World Wide Web
• Internet Protocols
• Security
• Search Engines
Network Classifications
• Scope– Local area network (LAN)– Metropolitan area (MAN)– Wide area network (WAN)
• Ownership– Closed versus open
• Topology (configuration)– Bus (Ethernet)– Star (Wireless networks with central Access
Point)
Network topologies
Network topologies (continued)
The Internet
• The Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide.
• It is a network of networks that consists of millions of private and public, academic, business, and government networks of local to global scope that are linked by a broad array of electronic and optical networking technologies.
Internet Architecture
• Internet Service Provider (ISP)– Tier-1– Tier-2
• Access ISP: Provides connectivity to the Internet– Traditional telephone (dial up connection)– Cable connections– DSL– Wireless
Figure 4.7 Internet Composition
Internet Addressing
• IP address: pattern of 32 or 128 bits often represented in dotted decimal notation
• Mnemonic address:– Domain names– Top-Level Domains
• Domain name system (DNS)– Name servers– DNS lookup
Internet Corporation for Assigned Names & Numbers
(ICANN)• Allocates IP addresses to ISPs who then
assign those addresses within their regions.
• Oversees the registration of domains and domain names.
Traditional Internet Applications
• Electronic Mail (email)– Domain mail server collects incoming mail
and transmits outing mail– Mail server delivers collected incoming mail to
clients via POP3 or IMAP– Mail clients
• Outlook• Mozilla Thunderbird
• File Transfer Protocol (FTP)
More Recent Applications
• Voice Over IP (VoIP)
• Internet Radio– N-unicast– Multicast
World Wide Web
• Hypertext and HTTP
• Browser gets documents from Web server
• Documents identified by URLs
A typical URL
TCP/IP and DNS
Hypertext Document Format• Encoded as text file
• Contains tags to communicate with browser
– Appearance • <h1> to start a level one heading• <p> to start a new paragraph
– Links to other documents and content• <a href = . . . >
– Insert images• <img src = . . . >
Figure 4.9 A simple Web page
Figure 4.9 A simple Web page (continued)
Figure 4.10 An enhanced simple Web page
Figure 4.10 An enhanced simple Web page (continued)
Extensible Markup Language (XML)
• XML: A language for constructing markup languages similar to HTML– A descendant of SGML– Opens door to a World Wide Semantic Web
Using XML
<staff clef = “treble”> <key>C minor</key> <time> 2/4 </time><measure> < rest> egth </rest> <notes>
egth G, egth G, egth G </notes></measure><measure> <notes> hlf E
</notes></measure></staff>
The first two bars of Beethoven’s Fifth Symphony
Client Side Versus Server Side
• Client-side activities– Examples: java applets, javascript,
Macromedia Flash• Server-side activities
– Common Gateway Interface (CGI)– Servlets– PHP
Security
• Attacks– Malware (viruses, worms, Trojan horses,
spyware, phishing software)– Denial of service– Spam
• Protection– Firewalls– Spam filters– Proxy Servers– Antivirus software
Search Engines
• General– Ask.com (formerly Ask Jeeves)– Baidu (Chinese)– Bing (formerly MSN Search and Live Search)– Cuil– Duck Duck Go– Google– Kosmix– Sogou (Chinese)– Sohu (Chinese)– Yahoo! Search– Yandex (Russian)– Yebol
Search Engines
• Geographical limited scope– Accoona, China/US– Alleba, Philippines– Ansearch, Australia/US/UK/NZ– Baidu, China– Daum, Korea– Goo, Japan– Guruji.com, India– Leit.is, Iceland– Maktoob, Arab World– Onkosh, Arab World– Miner.hu, Hungary
Search Engines
• Business– Business.com– GlobalSpec– Nexis (Lexis Nexis)– Thomasnet (United States)
Search Engines
• Enterprise– AskMeNow: S3 - Semantic Search Solution– Concept Searching Limited: concept search products– Dieselpoint: Search & Navigation– dtSearch: dtSearch Engine(SDK), dtSearch Web– Endeca: Information Access Platform– Exalead: exalead one:enterprise– Expert System S.p.A.: Cogito– Fast Search & Transfer: Enterprise Search Platform
(ESP), RetrievalWare (formerly Convera)
Search Engines
• Other– Medical– News– People– News– Real Property– etc
Google Search
• Advanced Search– Specify AND also with “ “– Specify OR by writing OR– Unwanted words– Language– Format– File type– Pages in a domain
Google Search
• Advanced Search– Date– Rights– Where keywords are– Region
Google Addwords Keyword Tool
• How to make your page appear in high positions in Google Search?– Sword– Master Albania– Cars Albania– New York Tirana
Google Rankings
• http://www.googlerankings.com/
• Check ranking– http://www.prchecker.info/
• www,unyt.edu.al• www.km.gov.al
Exam rules
• Powerpoint 50 pts
• Access 48 pts
• Latex 2 pts– Only one formula with Latex material open