History & Technologies of the Internet Lecture 1 – September 22, 2016 ―Lincoln Towers University‖ Sept. 22 – Oct. 13, 2016 Thursdays 7:30-9 pm, 150 WEA Community Room Instructor: Stephen Weinstein [email protected], (646) 267-5904 Lecture notes posting site: projectopenlincolntowers.org/lincolntowersuniversity Your instructor A mostly retired engineer living in Lincoln Towers, with a PhD in electrical engineering from U.C. Berkeley and extensive experience in the communications industry. I am a member of the Boards of the 150WEA Owners Corp. and of Project Open*. My consulting website, cttcservices.com, has further personal background information. *I maintain the Project Open web site, projectopenlincolntowers.org Goals of this course 1. Provide an intuitive explanation, not requiring an engineering or computer science background, of -Internet history -The technical foundations of the Internet -Relevant basic concepts of communications and information technology. 2. Answer your questions. Don’t be afraid to ask! Please have confidence in yourself to understand basic technical concepts! Important note: This is not a course on how to use computers and Internet services. It is a course on how the Internet came to be, what it is, and from a science and engineering perspective, how it works. Topics Covered in Four Lectures Lecture 1: Internet background and Digital Media -Definitions of a few basic terms (data, digital, bit, packet & packet switching, network, protocol). -Internet definition and organizations. -Internet history (and more in future classes). If there is time, we may introduce digital media, but this will probably be left to Lecture 2. Lecture 2: Digital Media and Communications -Basic concepts: frequency, wavelength, bandwidth & data rate. -History of digital/data and wireless communication. -Why digital? - and how conventional analog media (voice, images, video) are converted to digital. -Modulation and modems. -The different kinds of communication networks supporting the Internet; protocol stacks. Lecture 3: Internet architecture & technologies -Internet architecture (routers, domain name service, …). -Connection-oriented vs. connectionless (datagram). -The most important communication protocols used in the Internet: IP, TCP, UDP, and some others. -Translating a web address (like projectopenlincolntowers.org) to an IP address. -Avoiding address depletion. Lecture 4: Internet applications -The original application level protocols: ftp, smtp, telnet -The World Wide Web: History, browsers, and web pages. -Audio and video streaming, voice over IP. -Cloud computing. -Security attacks (e.g., denial of service). -The Internet of Things. Lecture 1: Internet background and digital media Basic terms. Internet definition, organizations, and history. Digital media. BASIC TERMS Data: A set or stream of symbols or numbers that represent information. This information can be voice, video, a picture, your tax return - virtually any kind of meaningful content. These days we keep data in digital storage devices such as computer hard drives and USB memory sticks. The data is in digital format (described on the next slide). Digital: Expressed as a group of numbers chosen from a small set. We have ten fingers and that is why we use decimal numbers from the set: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 We represent an integer by multiples of powers of 10. Example: 14 (decimal) = 1x10 + 4x1 If we had two fingers, like electronic memories, we would use binary numbers to represent an integer by multiples of powers of 2. Example: 14 (decimal) is the same as 1110 (binary) = 1x8 + 1x4 + 1x2 + 0x1 14 and 1110 are both digital representations of the same quantity! Data Stream: A sequence of digital numbers (sometimes called digital ―words‖) representing an information object such as a movie. Example of decimal and binary digital data streams for the same information: 14 05 12 15 02 ….. 1110 0101 1100 1111 0010 ….. Movies streamed from Netflix or other Internet sources come in binary data streams like that above. Bit: A quantity of information, equivalent to the information generated by the toss of an unbiased coin (head or tail). Byte: 8 bits. Megabyte (MB): A million bits. Gigabyte (GB): a billion bits. A bit of information is commonly represented by ―1‖ or ―0‖ rather than ―head‖ or ―tail‖, which fits nicely into a digital data stream! We will, in the next class, explain how a speech or video signal can be represented by a data sequence of bits. Sound pressure wave in air (analog) Analog to digital conversion A/D …0111 0000 1101 0100 ... Network (for data communications): A set of originating and terminating entities, forwarding nodes, and the transport links connecting them, for conveying data traffic. Terminating device (phone, Switch (in traditional telephone network) computer, cell phone, etc.) or router (in Internet and other packet networks). Packet: A data package conveying, through a network, bits representing part or all of a message. Complete message (digital data) A series of packets, each carrying part of the message It’s a lot like packing a large shipment into a series of trucks that may possibly be of different sizes. Packet multiplexing: A mixed stream of packets from different sources. The sources are represented here by the numbers 1,2,3,4. 2-voice 3-keyboard 1-video 1-video 1-video 1-video Packet switching (routing) vs. traditional line switching at a network node Line switching: For a particular information flow for which the entire path through the network is reserved in advance, a connection is made between the input line carrying this flow and an output line on the prearranged route. Packet switching (routing) vs. traditional line switching: Packet switching, ―datagram‖ model: Without reserving a route in advance, a particular packet is transferred to a buffer for an output line that the router selects as the best next ―hop‖. If the buffer is too full, the packet will be discarded. The Internet implements this ―unreliable‖ routing mechanism, but with enough capacity, packet discards (or long delays) will be minimal. (Communication) protocol: A formal description of the format and rules for a message exchange. Several layers of protocols are usually needed to completely specify an information exchange. A packet protocol, for example, will specify, in the packet ―header‖, sending and receiving addresses, information quantity, and information type. Simple packet model: Header Information field (payload) Source & destination addresses, etc. Definitions of an internet and the Internet An internet (not the Internet) is a combination of several distinct communication networks capable of conveying data between endpoints on different networks. Access Core networks Networks Local Area Networks Bluetooth Satellite Personal Area Networks Cellular Infrared mobile WiFi Optical Core Network, (IEEE 802.11) Cable (HFC) Bluetooth metropolitan & long haul DSL Ethernet Optical fiber The Internet is the publicly available combination of multiple distinct communication networks augmented by the Internet Protocol (IP) and subscribing to Internet standards in order to convey data through this multi-network environment. IP Domain Name The Internet is one example of Server an internet Router Cellular mobile WiFi Cable (HFC) Optical Core Network, Bluetooth Wireless router metropolitan & long haul IP Ethernet Optical fiber History of the Internet Donald Davies Lawrence Roberts Paul Baran Leonard Kleinrock J.C.R. Licklider Robert Jon Vinton Kahn Postel Cerf 1961-62: MIT Prof. J.C.R. Licklider envisioned a "Galactic Network" as a globally interconnected set of computers through which everyone could quickly access data and programs from any site. Leonard Kleinrock published first paper on relevant packet switching theory. Kleinrock message switching1: "Basically, what I did for my PhD research in 1961–1962 was to establish a mathematical theory of packet networks...―. Refs: https://www.internetsociety.org/internet/what-internet/history-internet/brief-history- internet 1 L. Kleinrock, "Information Flow in Large Communication Nets", MIT RLE Quarterly Progress Report, July 1961. Mid 60s: Publications on packet switching from RAND (Paul Baran) and the National Physical Lab in the U.K. (Donald Davies). RAND was studying network survivability after nuclear war: ―If war does not mean the end of the earth in a black and white manner, then it follows that we should do those things that make the shade of grey as slight as possible: to plan now to minimize potential destruction and to do all those things necessary to permit the survivors of the holocaust to shuck their ashes and reconstruct the economy swiftly.‖1 His concept was a distributed system in which a broken route could easily be replaced by another.2 He called it ―hot potato‖ routing or adaptive ―message block switching.‖ 1 Paul Baran, ―Reliable Digital Communications Systems Using Unreliable Network Repeater Nodes‖, the RAND Corp. report P-1995, 5/27/60, www.rand.org/content/dam/rand/pubs/papers/2008/P1995.pdf 2 http://www.rand.org/about/history/baran.list.html Donald Davies invented the terms ―packet‖ and ―packet switching‖ and built early experimental packet networks. He initially worked at the National Physical Laboratory under Alan Turing, the great pioneer of computing whose WWII work broke the Enigma code and greatly contributed to the allied victory. Turing Davies NPL PS: packet switch UM: User machine (computer) T: Terminal TP: Terminal Processor R. Scantlebury & P. Wilkinson, ―The National Physical