Lec10_Internet

Lec10_Internet - Internet: Backbone and Protocols ISOM...

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Unformatted text preview: Internet: Backbone and Protocols ISOM 2010, Spring 2012 Lecture 10 HKUST Business School Overview What is the “Internet architecture”? How does the Internet work? Who manage the Internet? Raymond G. Sin © 2 HKUST Business School Internet Architecture (1) According to Webster*, “Architecture” means: 1 : the art or science of building; specifically : the art or practice of designing and building structures and especially habitable ones 2 a : formation or construction as or as if as the result of conscious act <the architecture of the garden> b : a unifying or coherent form or structure <the novel lacks architecture> 3 : architectural product or work 4 : a method or style of building 5 : the manner in which the components of a computer or computer system are organized and integrated *www.webster.com Raymond G. Sin © 3 HKUST Business School Internet Architecture (1) According to Webster*, “Architecture” means: 1 : the art or science of building; specifically : the art or practice of designing and building structures and especially habitable ones 2 a : formation or construction as or as if as the result of conscious act <the architecture of the garden> b : a unifying or coherent form or structure <the novel lacks architecture> 3 : architectural product or work 4 : a method or style of building 5 : the manner in which the components of a computer or computer system are organized and integrated *www.webster.com Raymond G. Sin © 4 HKUST Business School Internet Architecture (2) Internet Architecture: the manner in which the components of an Inter-connected network are organized and integrated In fact, the term Internet is derived from “internetworking” – connecting host computers and their networks to form even larger networks Internet is a world-wide collection of networks that use a common protocol (which one?) to communicate with each others Raymond G. Sin © 5 HKUST Business School Internet Architecture (3) Brief history of the Internet: Began as an experimental project on ways to interconnect different kinds of networks by the U.S. Defense Advanced Research Projects Agency (DARPA) in the late 60’s Goal: to build a communication network that can survive a nuclear war The research resulted in ARPANET (Advanced Research Projects Agency Network), a large WAN and precursor of the Internet Which were the first two nodes on ARPANET? Raymond G. Sin © 6 HKUST Business School Internet Architecture (4) Brief history (cont’d) ARPANET quickly evolved and was combined with other networks – e.g. NSFNET in 1986, which became a major component of the Internet NSFNET was terminated in 1994 due to privatization of the Internet Four network access points (NAPs) were established to provide a method for exchanging traffic among ISPs. Where were the four initial NAPs? Raymond G. Sin © 7 HKUST Business School Internet Architecture (5) ISPs Internet service providers give consumers access to the Internet for a fee, and make up most of the individual networks When you connect to your ISP, you become part of their network. The ISP may then connect to a larger network and become part of their network. The Internet is simply a network of networks. A user may connect to an ISP in a number of ways… POTS, ISDN, DSL, cable modems, satellite… What happens next? Raymond G. Sin © 8 HKUST Business School Internet Architecture (6) ISPs connect to one another through network access points (NAPs) What is the alternative mechanism and how does it work? NAPs are… high-speed routers that determine how traffic is routed and are often points of most Internet congestion a key component of the Internet backbone – fiber optic trunk lines, each with multiple fiber optic cables combined together to increase the capacity Who created the first high-speed backbone with a T1 line? Raymond G. Sin © 9 HKUST Business School In summary, the Internet follows a hierarchical structure that is very similar to the highway system Interstate highways -> city streets -> neighborhood streets Everyone has to share the highway and follow traffic control signs to arrive safely at the destination Raymond G. Sin © 10 HKUST Business School How the Internet Works (1) Now we know that data travels through networks very much like vehicles travel through streets and highways… But how exactly do they get to the destinations? How does an email gets from computer A to halfway across the world through several different networks and arrive at computer B in a split second? Even fiber optic cables have their limitation… What happens if there are many slow, heavy “trucks” on the road? Raymond G. Sin © 11 HKUST Business School How the Internet Works (2) The Internet relies on packet-switching technology to deliver data and information across networks Packet switching enables millions of users to send large and small chunks of data across the Internet at the same time Raymond G. Sin © 12 HKUST Business School How the Internet Works (3) Each computer “takes turn” on sending out data To minimize delays, network technologies limit the amount of data that a computer can transfer on each turn The idea is breaking the data into many small pieces (packets), which are sent in many rounds and reassembled at their respective destinations Raymond G. Sin © 13 HKUST Business School Suppose Tamama wants to send a Gundam model to Keroro… Raymond G. Sin © 14 HKUST Business School Suppose Tamama is sending a Gundam model to Keroro… But the box is too large to fit into the mailbox Solution? Raymond G. Sin © 15 Raymond G. Sin © 16 HKUST Business School HKUST Business School How the Internet Works (5) Key concepts on communications protocol Packet switched protocol No end-to-end connection is required Each message is broken down into small pieces called packets Packets possibly routed to destination over different paths IP datagram A data packet that conforms to the IP specification Raymond G. Sin © 17 HKUST Business School How the Internet Works (6) Key concepts (cont’d) Transmission Control Protocol (TCP) Breaks messages into packets Numbers packets in order Collects the incoming datagrams and reorders them at the destination Checks for datagrams that may have been lost or corrupted en route from their source to destination Discards any duplicate copies of datagrams that may have been created by network hardware Internet Sends Protocol (IP) datagrams to the proper destination Raymond G. Sin © 18 HKUST Business School How are the “source” and “destination” addresses defined? What is the format of sender’s and recipient's addresses that can be understood by computers? Raymond G. Sin © 19 HKUST Business School How the Internet Works (7) Every computer connected to the Internet must have a unique IP address Format: xxx.xxx.xxx.xxx where xxx is a number between 0 and 255 0.0.0.0 through 255.255.255.255 –up to 232 unique IP addresses (~4.3 billion possible combinations!!) Why do I have a different IP address every time I log in? Is it always the case for everyone? What is bad about having a static IP address? i.e. Raymond G. Sin © 20 HKUST Business School How the Internet Works (8) However, numeric IP addresses are hard for us to remember What is the IP address of this machine? What is the IP address of “www.ust.hk”? A domain name is the unique name assigned to an IP address Raymond G. Sin © 21 HKUST Business School How the Internet Works (9) Domain name (cont’d) registered in the domain name system (DNS), stored in DNS servers They are used in Uniform Resource Locators (URLs) URL: a sequence of characters conforming to a standardized format, used for referring to resources Why do some websites have “www” in the URL while others don’t? www.ust.hk = ust.hk? Domain Name System (DNS) A distributed database of Internet names DNS Servers convert Internet names to IP addresses e.g. www.microsoft.com -> 207.46.245.222 Raymond G. Sin © 22 Raymond G. Sin © 23 HKUST Business School HKUST Business School if you know the exact IP, you can bypass the DNS server and type it in directly Raymond G. Sin © 24 HKUST Business School An Example… Raymond G. Sin © 25 HKUST Business School Domains (1) The seven main Top level domains (TLDs) com, edu, gov, int, mil, net, org Commercial sector Education sector Government organizations and departments International organizations (e.g. NATO) Military sites Network providers Non-profit organizations (e.g. Green Peace) plus a large number of country-specific TLDs Can you name a few examples? Raymond G. Sin © 26 HKUST Business School Domains (2) The country-specific TLDs: au Australia ca Canada Fr France de Germany se Sweden tw Taiwan ch Switzerland jp Japan cn China kr Korea za South Africa Raymond G. Sin © 27 HKUST Business School Internet Applications (1) E-mail, file transfer (FTP, P2P), instant messaging, Usenet newsgroups, streaming audio and video, VoIP, distributed processing Rationale behind distributed processing: Most computers are not continuously in use (many idle cycles) Internet can be used to harness these unused cycles A complex problem is broken into pieces These pieces are sent to various computers on a network/Internet Computers process these pieces information when not in use Solutions are then sent back to the host computer that combines all the pieces Application: complicated mathematical problems that require large amounts of computing capacity e.g. SETI@Home – the Search for extraterrestrial intelligence Raymond G. Sin © 28 HKUST Business School Internet Applications (2) SETI: Uses radio telescopes to “listen” for transmissions from outer space which may be evidence of the existence of ET civilization Not a Web site, but a screensaver The software downloads a set of data from SETI@Home server and processes it The program searches the data from the SETI’s radio telescopes When the computer finishes processing a piece, it uploads back to SETI and requests a new set >5.4 million users participated, ran >2 million years worth of CPU time Raymond G. Sin © 29 HKUST Business School Who Manage the Internet? Internet Engineering Task Force (IETF) Internet Engineering Steering Group (IESG) Helps manage an Internet Registry (central repository for Internet-related information) and provides maintenance of the DNS root database Internet Corporation for Assigned Names and Numbers (ICANN) An international professional membership society that helps shape the future of the Internet, also home of the IETF and IAB Internet Assigned Numbers Authority (IANA) The oversight authority for the standards development process Internet Society (ISOC) Approves or disapproves standards developed by the IETF Internet Architecture Board (IAB) Works in groups to develop standards Manages IP addresses, domain names, and assigns Internet addresses Originally established by NSF as InterNIC in 1993 World Wide Web Consortium (W3C) Promotes the WWW and develops new web technologies and standards Raymond G. Sin © 30 HKUST Business School Appendix A: Different Types of Internet Connection POTS (plain old telephone service) ISDN (Integrated services digital network) Uses special modulation schemes to fit more data onto copper wires (existing copper telephone lines) Up to 32 Mbps downstream to over 1Mbps upstream (speeds vary depending on the service level and restriction imposed by providers) ADSL (asymmetric DSL): downstream speed > upstream speed SDSL (symmetric DSL): downstream speed = upstream speed Cable modem Standard for worldwide digital communications Purely digital network (analog-to-digital/digital-to-analog conversion not required) Approx. 64 Kbps (supports up to two 64 Kbps channels plus one 16 Kbps channel = 144 Kbps) DSL (digital subscriber line) Standard telephone lines A.k.a. PSTN (public switched telephone network) Approx. 52 Kbps Uses coaxial cable (much greater bandwidth than phone lines) Up to 2 Mbps (upstream speed often limited by providers to approx. 128 Kbps) Satellite connections Internet over Satellite (IoS) Uses GEO satellites Connection speed is comparable to DSL, but in practice it is usually slower due to latency in signal transmission Raymond G. Sin © 31 HKUST Business School Appendix B: Egypt’s Disappearance Raymond G. Sin © 32 ...
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