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Networking

Networking. What is a Network?. Computer network a set of computers using common protocols to communicate over connecting transmission media. Protocol a formal description of message formats and the rules two or more machines follow to exchange messages. . TCP connection reply.

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Networking

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  1. Networking

  2. What is a Network? • Computer network • a set of computers using common protocols to communicate over connecting transmission media. • Protocol • a formal description of message formats and the rules two or more machines follow to exchange messages.

  3. TCP connection reply. Get http://gaia.cs.umass.edu/index.htm Got the time? 2:00 <file> time Protocols Hi TCP connection req. Hi

  4. Classifying Networks • Networks can be classified by size • Local Area Networks (small) • privately-owned • cover a small area • high data rates • Wide Area Networks (large) • owned/operated by a network provider • large capacity • often have an irregular topology

  5. Internetworks • An internetwork, or internet, is formed when two networks are connected together. • Two networks are joined using a computer that is directly connected to both networks. • A computer that joins two networks is called a gateway

  6. An Internet A Network A Network Service Provider’s Network

  7. The Internet The Internet is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of networking technologies.

  8. A Network of Networks

  9. Enlarged Section

  10. The Internet in the US

  11. How Did It Get Started? • The Internet started as the ARPAnet • Started in the mid 60s, working in early 70s • Designed for the military • Could only be used by the military • Applications of the ARPAnet included • Electronic Mail • Remote Access • File Transfer

  12. NSFNet • In the late 80s NSF supported the creation of 5 supercomputer centers. • NSF Decided to use ARPAnet technology to provide remote access, but could not use the ARPAnet to do this. • In 1985 NSF announced its decision to build the NSFnet.

  13. NSFNet Backbone

  14. Commercialization • During NSF's support of the Internet commercial use was forbidden by law. • On April 30th, 1995 NSF pulled the plug on the NSFnet and turned it over to the private sector. • Since that time commercial use of the Internet has grown dramatically.

  15. Routers • An internet consists of a number of independent networks • Networks are connected by routers • Routers selectively interchanges messages between the networks they connect

  16. Switches • Like a network in a box • Think of it like a “power strip” for a network • Also called a hub • Sometimes a router has a switch built into it

  17. ISP • Most of us cannot afford to establish our own connection to the Internet • An Internet Service Provider (ISP) provides you a connection to the Internet for a fee • Some examples… • Time Warner • DSL

  18. tymann.us Grumpy Switch Cable Modem Router Buster Internet Bucky

  19. tymann.us The Glue Grumpy Switch Cable Modem Router Buster Internet Bucky Network Network

  20. The TCP/IP Protocol Suite • TCP/IP is a set of protocols that were created specifically to allow development of network and internetwork communications on a global scale. • TCP/IP is the most commonly used protocols within the internet.

  21. Standardization • Who controls the TCP/IP protoocol suite? • The Internet Society (ISOC) a professional society to facilitate, support, and promote the evolution and growth of the Internet • The Internet Architecture Board (IAB) the technical oversight and coordination body • The Internet Engineering Task Force (IETF) is the near-term, standards-oriented group. • The Internet Research Task Force (IRTF) pursues long-term research projects.

  22. RFCs • All official standards in the internet community are published as a Request for Comments, or RFC. • All RFCs are available at no charge through electronic mail, FTP, or the Web. • A nice place to get RFCs is at • http://www.rfc-editor.org/

  23. IP: Internet Protocol • IP is the workhorse protocol of the TCP/IP protocol suite. • IP provides an unreliable, connectionless, datagram delivery service. • RFC791 is the official specification of IP.

  24. IP Addresses • Every host on the internet must have a unique Internet Address (an IP address) • IP addresses are 32-bit numbers and are divided into two components: the host address and the network address • The number of bits assigned to the host and network varies depending on the class of the address

  25. Dotted Decimal Notation • IP addresses are normally written as four numbers, one for each byte of the address. • 129.21.38.169

  26. DHCP • Protocol used to assign IP address to machines • In a normal home setup the router runs DHCP and assigns IP addresses as they are requested • Exactly what happens at RIT when you use the wireless network

  27. tymann.us Grumpy Switch 192.168.1.1 Cable Modem Router Buster Internet 192.168.1.254 192.168.1.2 Bucky 74.65.0.57 Assigned by Time Warner via DHCP 192.168.1.9

  28. Transmission Control Protocol • TCP provides a connection-oriented, reliable, byte stream service (RFC793) • TCP is an independent, general purpose protocol that can be adapted for use with delivery systems other than IP.

  29. TCP Ports • TCP uses protocol port numbers to identify the ultimate destination within a machine. • How does one determine the port to communicate with? • Well-known Ports • Randomly Assigned Ports

  30. Client/Server Computing Client sends request to server Server sends results to client

  31. The World Wide Web • Developed by Tim Berners-Lee at CERN • Original system built in 1980 • Designed to publish documentation • Uses Client-Server Computing • Servers store documents • Clients request documents from servers

  32. Another Form of Poverty?

  33. Basic Components • Basic Components of the Web • Web Servers • HTTP protocol • Used to send requests and transfer results • Web Browsers • HTML • Hypertext markup language • Used to define the documents

  34. Web Browsers • Many to choose from • Some implement standards better than others • Another place for “religion” • Client side computing is done within the browser • Server side computing is done on the server

  35. HTML • HTML is the primary language for building/creating web pages. • HTML uses markup tags to define the elements of a web page • Many online tutorials • http://www.w3schools.com/web/web_html.asp <html>< body>< h1>My First Heading</h1>< p>My first paragraph.</p>< /body>< /html>

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