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  • 1. Internet History and Growth KOS 1110 COMPUTER IN SCIENCE
  • 2. What Was the “Victorian Internet”      The Telegraph - invented in the 1840s Signals sent over wires that were established over vast distances Used extensively by the U.S. Government during the American Civil War, 1861 - 1865 Morse Code was dots and dashes, or short signals and long signals The electronic signal standard of +/- 15 v. is still used in network interface cards today
  • 3. Famous Quote From Sir Isaac Newton  “If I have been able to see farther than others, it was because I stood on the shoulders of giants.”
  • 4. What Is the Internet?   A network of networks, joining many government, university and private computers together and providing an infrastructure for the use of E-mail, bulletin boards, file archives, hypertext documents, databases and other computational resources The vast collection of computer networks which form and act as a single huge network for transport of data and messages across distances which can be anywhere from the same office to anywhere in the world
  • 5. What is the Internet?    The largest network of networks in the world Uses TCP/IP protocols and packet switching Runs on any communications substrate From Dr. Vinton Cerf, Co-Creator of TCP/IP
  • 6. Brief History of the Internet   1968 - DARPA (Defense Advanced Research Projects Agency) contracts with BBN (Bolt, Beranek & Newman) to create ARPAnet 1970 - First five nodes:        UCLA Stanford UC Santa Barbara U of Utah, and BBN 1974 - TCP specification by Vint Cerf 1984 – On January 1, the Internet with its 1000 hosts converts en masse to using TCP/IP for its messaging
  • 7. *** Internet History ***
  • 8. A Brief Summary of the Evolution of the Internet First Vast Computer Network Silicon Envisioned Chip A 1962 Mathematical 1958 Theory of Communication Memex 1948 Conceived Packet Switching Invented 1964 Hypertext Invented 1965 TCP/IP Created ARPANET 1972 1969 Mosaic WWW Created Internet Created 1993 Named 1989 and Goes TCP/IP 1984 Age of eCommerce Begins 1995 1945 1945 1995
  • 9. From Simple, But Significant Ideas Bigger Ones Grow 1940s to 1969 We will prove that packet switching works over a WAN. Hypertext can be used to allow rapid access to text data Packet switching can be used to send digitized data though computer networks We can accomplish a lot by having a vast network of computers to use for accessing information and exchanging ideas We can do it cheaply by using Digital circuits etched in silicon. We do it reliably with “bits”, sending and receiving data We can access information using electronic computers 1945 1969
  • 10. From Simple, But Significant Ideas Bigger Ones Grow 1970s to 1995 Great efficiencies can be accomplished if we use The Internet and the World Wide Web to conduct business. The World Wide Web is easier to use if we have a browser that To browser web pages, running in a graphical user interface context. Computers connected via the Internet can be used more easily if hypertext links are enabled using HTML and URLs: it’s called World Wide Web The ARPANET needs to convert to a standard protocol and be renamed to The Internet We need a protocol for Efficient and Reliable transmission of Packets over a WAN: TCP/IP Ideas from 1940s to 1969 1970 1995
  • 11. The Creation of the Internet  The creation of the Internet solved the following challenges:  Basically inventing digital networking as we know it  Survivability of an infrastructure to send / receive high-speed electronic messages  Reliability of computer messaging
  • 12. The Universal Resource Locator (URL) Each page of information on the web has a unique address called the URL at which it can be found http://faculty.uscupstate.edu/atzacheva/lecture1.html The document can be obtained using the Hypertext Transfer Protocol (HTTP) 1 Protocol Host Name The Name of Web Server 2 Host Name Path to the Web Page File Name Denotes that the File is Written in HTML HyperText Markup Language 3 File Name
  • 13. Protocols that may appear in URL’s Protocols Names Use ftp:// File transfer http:// Hypertext https:// Hypertext Secure Mailto: Sending email News: Requesting news telnet:// Remote login Much of the power of browsers is that they are multiprotocol. That is, they can retrieve and render information from a variety of servers and sources.
  • 14. Web Client/Server Architecture
  • 15. The Problem  Before Internet: different packet-switching networks (e.g., ARPANET, ARPA packet radio)  only nodes on the same network could communicate
  • 16. A Translation-based Solution ALG ALG ALG  application-layer gateways      inevitable loss of some semantics difficult to deploy new internet-wide applications hard to diagnose and remedy end-to-end problems stateful gateways inhibited dynamic routing around failures no global addressability  ALG ad-hoc, application-specific solutions
  • 17. The Internetworking Problem  Two nodes communicating across a “network of networks”…  How to transport packets through this heterogeneous mass ? A B Cloud Cloud Cloud
  • 18. Declared Goal  “…both economic and technical considerations lead us to prefer that the interface be as simple and reliable as possible and deal primarily with passing data between networks using different packet switching strategies” V. G. Cerf and R. E. Kahn, 1974
  • 19. The Challenge: Heterogeneity   Share resources of different packet switching networks  interconnect existing networks … but, packet switching networks differ widely    different services  e.g., degree of reliability different interfaces  e.g., length of the packet that can be transmitted, address format different protocols  e.g., routing protocols
  • 20. The Challenge: Scale  Allow universal interconnection   Mantra: Connectivity is its own reward … but, core protocols had scalability issues     Routing algorithms were limited in the number of nodes/links they could handle and were unstable after a point Universal addressing to go with routing As large numbers of users are multiplexed on a shared system, a congestion control paradigm is necessary for stability No universal, scalable naming system…
  • 21. The Internetworking Problem   Problems: heterogeneity and scaling Heterogeneity:    How to interconnect a large number of disparate networks ? (lower layers) How to support a wide variety of applications ? (upper layers) Scaling:  How to support a large number of end-nodes and applications in this interconnected network ?
  • 22. Solution Network Layer Gateways
  • 23. The IP Solution … IP IP IP     IP internet-layer gateways & global addresses simple, application-independent, lowest denominator network service: best-effort datagrams stateless gateways could easily route around failures with application-specific knowledge out of gateways:  NSPs no longer had monopoly on new services  Internet: a platform for rapid, competitive innovation
  • 24. Network-layer Overlay model  Define a new protocol (IP) and map all applications/networks to IP Require only one mapping (IP -> new protocol) when a new protocol/app is added  Global address space can be created for universal addressibility and scaling 
  • 25. Before IP (FTP – File Transfer Protocol, NFS – Network File Transfer, HTTP – World Wide Web protocol) Application Transmission Media  Telnet FTP Coaxial cable NFS Fiber optic HTTP Packet radio No network level overlay: each new application has to be re-implemented for every network technology!
  • 26. IP  Key ideas:   Overlay: better than anyany translation. Fewer, simpler mappings. Network-layer: efficient implementation, global addressing Application Telnet FTP NFS HTTP Intermediate Layer (IP) Transmission Media Coaxial cable Fiber optic Packet radio
  • 27. Original TCP/IP (Cerf & Kahn)   No separation between transport (TCP) and network (IP) layers One common header  use ports to multiplex multiple TCP connections on the same host 32 Source/Port   32 Source/Port 16 16 8n Window ACK Text Byte-based sequence number (Why?) Flow control, but not congestion control
  • 28. Today’s TCP/IP  Separate transport (TCP) and network (IP) layer (why?)    split the common header in: TCP and UDP headers fragmentation reassembly done by IP Congestion control
  • 29. Addressing  How to find if destination is in the same network ?  IP address = network ID + host ID.   Source and destination network IDs match => same network (I.e. direct connectivity) Splitting address into multiple parts is called hierarchical addressing Network Boundary Host
  • 30. Converting a 32-bit Internet Address to Dotted Decimal Format Recall binary to decimal conversion     An Internet address, known as an IP address for “Internet Protocol” is comprised of four binary octets, making it a 32-bit address. IP addresses, difficult for humans to read in binary format, are often converted to “dotted decimal format” To convert the 32-bit binary address to dotted decimal format, divide the address into four 8-bit octets and then convert each octet to a decimal number. Each octet will have one of 256 values (0 through 255) (Example of an IP address in dotted decimal form)
  • 31. IP address conversion Convert the following 32-bit Internet address into dotted decimal format: 01011110000101001100001111011100 1) Divide the IP address into four octets 01011110 00010100 11000011 11011100 2) Convert each binary octet into a decimal number 01011110 = 64+16+8+4+2 = 94 00010100 = 16+4 = 20 11000011 = 128+64+2+1 = 195 11011100 = 128+64+16+8+4 = 220 3) Write out the decimal values separated by periods
  • 32. The Internet Network layer Host, router network layer functions: This image cannot currently be display ed. Transport layer: TCP, UDP Network layer IP protocol •addressing conventions •datagram format •packet handling conventions Routing protocols •path selection •RIP, OSPF, BGP routing table ICMP protocol •error reporting •router “signaling” Link layer physical layer
  • 33. IP Addressing: introduction    IP address: 32-bit identifier for host, router interface Interface: connection between host, router and physical link  router’s typically have multiple interfaces  host may have multiple interfaces  IP addresses associated with interface, not host, router Hosts in the same network have same network ID = 11011111 00000001 00000001 00000001 223 1 1 1
  • 34. IP Address Classes    There are 5 different classes of IP addresses: A, B, C, D and E. A, B, and C are available for commercial use For example, a Class A network could support 126 networks, each with 16,777,216 hosts
  • 35. Subnet Addressing   Classful addressing inefficient: Everyone wants class B addresses Can we split class A, B addresses spaces and accommodate more networks ?  Need another level of hierarchy. Defined by “subnet mask”, which in general specifies the sets of bits belonging to the network address and host address respectively Network Host Boundary is flexible, and defined by subnet mask
  • 36. The Domain Name System  We would go crazy if we would have to remember the IP addresses of all the web sites that we wanted to visit  The Domain Name System translates between domain names and IP addresses of devices connected to the Internet – A domain name (a part of the URL) is a unique alphanumeric name such as gmu.edu – The top level domain name is edu and the secondary level domain name is gmu in the above example (there could be up to 127 levels, but more than 4 is rare)
  • 37. Examples of top level domains  Generic top level domains .com  .biz  .info  .edu  .mil  .net, etc. Country codes (2 character codes)  .jp, .sw, .us, etc.  
  • 38. DNS IP ADDRESSES Every device connected has a unique 32-bit address Machine Readable e.g. DOMAIN NAMES DNS Translation Between domain Names and IP Addresses Human Readable cnn.com Every device connected has an alphanumeric address  IP address and domain name allocation requires central administration to avoid duplication  Previously administered by U.S. government contract (NSI)  In 1998, technical coordination assigned to ICANN (Internet Corporation for Assigned Names and Numbers).