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2004-2005 Academic Year, Spring Semester Bilkent University - Faculty of Art, Design and Architecture Department of Communication and Design CS 153 Introduction to Computing I Lesson 2 Network A group of computers and associated devices connected by communications facilities (both hardware and software) to share information and peripheral devices, such as printers and modems. Any time you connect 2 or more computers together so that they can share resources, you have a computer network. Connect 2 or more networks together and you have an internet. Types of Networks Server Based Single or multiple servers “serve” the resources (data and even the processing power) to the clients. Peer to Peer Thin Client, Thick Client? The members of the network share each other’s resources Hybrid Most of the networks fall on this category, combination of both technologies. Types of Network( Size)s LAN Local Area Network A data communications network covering a small area, usually within the confines of a building or floors within a building; a relatively high-speed computer communications network for in-building data transfer and applications. Cheap, and easy to setup! Examples: A company network of several hundered PCs that might be partly open to public. A home network of few PCs. Uses: Ethernet Token Ring (no longer widely used) Ethernet, Token Ring Token Ring Ethernet Types of Network( Size)s WAN Wide Area Network. The networks of LANs and some more... A system of interconnecting many computers over a large geographic area, making use of telephone lines, satellite links, and other long-range communications technologies. Because of the much greater hardware expense, reduced bandwidth, and the reliance on existing infrastructure that is shared by general-purpose communications, different protocols are used in WANs from those typically used in LANs. Examples: Internet! Army, police networks. Private large firms networks. Uses: Modem (MOdulator DEModulator): standard phone lines (called POTS (Plain Old Telephone Service) PSTN (Public Switched Telephone Network)), ISDN (Integrated Services Digital Network), Frame Relay, ATM (Asynchronous Transfer Mode) or other high speed services Types of Network Connections BUS TOKEN RING STAR Types of Network Connections BUS PC to PC (to PC to PC...) For each pair of connection 2 Network Cards Required. Star PCs to a Hub or Switch. A hub/switch is needed and for per connection a network card is needed. Types of Network Connections (cont’d) Ring Better than BUS. For each computer a Network Card is enough. If connected A B C D A If A wants to send data to C, it sends to B, B forwards to C. Performance of these connections: Star >= Bus > Ring Hub, Switch and Router Hub Most simple central connection device. It basicly connects all the computers that are connected to it. The problem with a hub is: when two PC’s are talking at the full speed, the other PC’s connected to Hub have connection speed problems. Switch Same as Hub, but solves the speed problem of the hub. Hub, Switch and Router Router Routers allow completely different networks, (ie LANs or WANs) to talk to each other. The networks are connected through a router. Consider a home network (LAN) is connected to the Internet through ADSL. You cannot connect ADSL modem directly to a switch or a hub. You need a router to seperate the LAN and the Internet (WAN). Types of Cables Twisted Pair Coaxial Cheap Telephone lines Slow TV Fast Coaxial Fiber Optic Expensive Longest Range Highest Speed Fiber Optic Twisted Pair Some Examples of Connections and Speeds Speed of connection is measured through bits per second. Carrier Technology Description Speed* Physical Medium Dial-up Access On demand access using a modem and regular telephone line. 2400 bps to 56 Kbps Twisted pair (regular phone lines) ISDN Dedicated telephone line and router required. 64 Kbps to 128 Kbps Twisted pair Cable Special cable modem and cable line required. 512 Kbps to 10 Mbps Coaxial cable; in some cases telephone lines used for upstream requests. ADSL Asymmetric Digital Subscriber Line This technology uses the unused digital portion of a regular copper telephone line (i.e. your fax line) to transmit and receive information. ADSL is asymmetric since it recieves at 6 to 9 Mbps per second but can only send data at between 16 to 640 Kbps. A special modem and adapter card are required. 128 Kbps to 9 Mbps Twisted pair (used as a digital, broadband medium) Carrier Technology Description Speed* Physical Medium Wireless (LMCS) Access is gained by connection to a high speed cellular like local multi-point communications system (LMCS) network via wireless transmitter/receiver. 2 Mbps or more Airwaves Requires outside antenna. Satellite The computer sends request for information to an ISP via normal phone dial-up communications and data is returned via high speed satellite to rooftop dish, which relays it to the computer via a decoder box. 400 Kbps Airwaves Requires outside antenna. Frame Relay Provides a type of "party line" connection to the Internet. Requires a FRAD (Frame Relay Access Device) similar to a modem, or a DSU/CSU. 56 Kbps to 1.544 Mbps Various Carrier Technology Description Speed* Physical Medium Fractional T1 (Flexible DS1) Only a portion of the 23 channels available in a T1 line is actually used. 64 Kbps to 1.544 Mbps Twisted-pair or coaxial cable T1 Special lines and equipment (DSU/CSU and router) required. 1.544 Mbps Twisted-pair, coaxial cable, or optical fiber T3 Typically used for ISP to Internet infrastructure. 44.736 Mbps Optical fiber OC-1 Typically used for ISP to Internet infrastructure within Internet infrastructure. 51.84 Mbps Optical fiber OC-3 Typically used for large company backbone or Internet backbone. 155.52 Mbps Optical fiber Connection of Networks Gateway A device that connects two dissimilar networks. Bridge If you want to connect a ATM network to a ISDN use Gateway A device that connects LANs, of the same type. Router A device that connects several networks. A router is smart enough to pick the right path for communications traffic. If there is a partial failure of the network, a router looks for an alternate route. Some Network Servers File Server Client Server Serves only files. Has huge amount of disk space. If you request something from this server, it sends the file. Serves processing power. Has huge amount of memory and very powerful processors. If you request something from this server, it sends the result to your screen. Web Server Has specialized software for serving web pages. Has very fast disks, big memory, fast internet connection. If it server dynamic web pages, should have fast processor. The Internet Internet is the collection of the different networks. Internet has started in 1969 as a military project for reliable and secure form of communication for the possibility of nuclear war. It expanded in 1970s for researchers and scientists to communicate their ideas and interests with their long-distance colleagues. Starting from the end of 1980s, it has been developing very fast. Homework: Read and check related links at http://en.wikipedia.org/wiki/Internet Read “A brief history of the Internet” from http://www.isoc.org/internet/history/ Possible Usages of the Internet The good: The World Wide Web Remote access Collaboration File-sharing Cultural awareness And the bad: Child abuse Copyright infringement Viruses Security cracking Dated technology Self-destructive subcultures The Domain Name System : DNS! The unique name that identifies an Internet site. Domain Names always have 2 or more parts, separated by dots. The part on the left is the most specific, and the part on the right is the most general. For example: Nasa.gov Stanford.edu Bilkent.edu.tr Garanti.com.tr The Domain Name System Consider www.bcc.bilkent.edu.tr www: is the server’s name. bcc: is a subdomain. bilkent: is the domain name. edu: domain suffix. tr: is the country (tr suffix is controlled by only METU). Country Suffixes http://ftp.ics.uci.edu/pub/websoft/wwwstat/c ountry-codes.txt .tr: Turkey .uk: United Kingdom .us: United States (but nearly no sites have .us in USA, why?) .fr: France .de: Germany .tv: Tuvalu (www.mtv.tv etc.) (why?) Tuvalu Domain Suffixes AERO Air-transport industry BIZ Businesses COM Unrestricted (but intended for commercial registrants) COOP Cooperatives EDU Educational institutions GOV Government INFO Unrestricted use INT Organizations established by international treaties between governments MIL Military MUSEUM Museums NAME For registration by individuals NET Unrestricted (but intended for network providers, etc.) ORG Unrestricted (but intended for organizations that do not fit elsewhere) PRO Accountants, lawyers, physicians, and other professionals Domain Suffixes (Turkey) Homework: find all the domain names at Turkish .tr suffix, with who can apply for it., restrictions, and yearly fees. IP IP is Internet Protocol. Every computer connected to the Internet should have an IP address. The IP address of Bilkent University web page is 139.179.10.16 Mtv’s web site is 217.147.241.192 Computer Science Department’s secretery’s machine is: 139.179.21.51... Back To DNS Each computer can be associated with a name. Each computer must have a IP address. Internet works on IP protocol. How do I know which computer has which IP? DNS Servers tell you that! www.mtv.tv DNS Server 217.147.241.192 Go to 217.147.241.192 Email Electronic Mail [email protected] [username]@[domain] DNS Server of [domain], tells to your mail server which server to drop the mails. POP3: protocol to get your mails SMTP: protocol to deliver your mails Email Fields To: write the full email address of the recipient Cc: (carbon copy) other recipients 1 or more (each email is separated by comma or semicolon from the next - each recipient will see the emails of the others) Bcc: (blind carbon copy) other recipients in the list will not be seen by others) Subject: Subject of the e-mail goes here. Common Email Actions reply all: Your reply to the message goes to all recipients in from and cc fields. reply: Your reply to the message goes to the recipient in from field. forward: To forward the e-mail to others. Do not do SPAM! Read http://www.spam.org.tr Ways of E-mail Web Based mail.yahoo.com www.hotmail.com www.gmail.com https://charon.bcc.bilkent.edu.tr/basilix POP3 Based E-mail clients Pine: login to your unix account, type pine, and your Bilkent mails are there. Outlook Express, Office Outlook, The Bat, Eudora Remote Connection: Telnet Telnet is an application program that allows remote log in to computer systems on the Internet. By Telnet, a user can remotely contact any e-mail account or even contact Internet resources. Hostname: you will supply a server name or full domain name for this field. Username: you will type your username. Password: you will type your password here but it will be displayed in the form of astrixes (*****). After entering to the system you can just run that operating system's commands. File Transfer Protocol: FTP One of the most common uses of computer to computer communications is to transfer files. Programs that manage this process include many file management features. Such a program will also handle the process of connecting to the other computer such as a FTP Server. Many of the names of these programs include the letters FTP, which stands for File Transfer Protocol. Downloading means to transfer a file to your computer from elsewhere. Uploading means to transfer a file from your computer to another. Transfer Types: ASCII, Binary Web Browser and WWW World Wide Web is a technology based upon hypertext which means that selected words in the text can forward the user to other locations in the WWW. These words are links to other documents which may take the form of text, images, movie or sound files. Browsers are software/program whose role is to present information resources on the Internet into a format with the capability of displaying graphical images, movies, and sound as well as text. In its simplest form, a browser such as Internet Explorer or Firefox will read a “page” or file from a server which is stored in a special format called HTML. This format allows text, image, movie and sound files to appear in side-by-side. Thus, when directing or “pointing” a browser to a certain “page”, the browser automatically decodes its HTML commands, including the text and images, and then presents them on the computer screen. Hypertext Transfer Protocol: HTTP Hyper Text Transfer Protocol is the standard protocol or language that allows hypertext information to be transferred between computers on the Internet. Hypertext is the basis for “linking” documents to one another and then navigating with the aid of a WWW browser program. Hypertext allows the reader to move easily from one document to another via a hyperlink. Hyperlink The unique feature of hypertext, a hyperlink is simply a special word, phrase, or object that takes the reader to another page. A text hyperlink is denoted by a different color. In many browsers, the hyperlink is underlined and blue in color. Once the mouse pointer is moved onto a hyperlink, the pointer arrow changes into a hand which means that it acknowledges the hyperlink. Unified Resource Locator: URL An acronym for Uniform Resource Locator, a URL is a form of address or, more specifically, the description of the location for a resource on the Internet. It is also referred to as a Location, or simply a WWW address. http://www.bilkent.edu.tr/~ussakli/index.html http:// protocol name. www.bilkent.edu.tr domain name /~ussakli folder name in the domain. /index.html the file name to open in the domain. Bookmark is a browser function that keeps a link to desired pages. To make a bookmark, simply find the desired web site and click on Bookmarks|Add Bookmark and the site is stored in the bookmark file. To return to a bookmarked location, simply click on Bookmarks and select the bookmark to return to. If an address starts with https: (HyperText Transfer Protocol, Secure.) then it is a good indication that information transfers are secure. Some Protocols Http: Hypertext transfer protocol Ftp: File transfer protocol Email: (opens your e-mail program) Gopher: Gopher is a Client and Server style program’s protocol. News: (opens your news reader) Search Engines Due to the increasing amount of information on the World Wide Web, universities and companies have constructed search engines which enable the user to locate indexes according to subject, author, dates, titles, or simply keywords. Some engines search titles or headers of documents, others search the documents themselves, and still others restrict their search to only indexes and/or directories. Most used search engines: www.google.com search.msn.com www.yahoo.com www.altavista.com End of Lesson But! I asked you what was Kibi Byte, Mebi Byte, Gibi Byte. Actually the term kilo in kilobyte means 1000 bytes. But it actually represents 1024 bytes. In order to clearify the difference between 1024 and 1000, it’s proposed to use kibi for 1024 and use kilo for 1000 bytes. Will we use kibi instead of kilo in the future? Who knows? Homework (%5) Name 2 Peer to Peer networks. Read and check related links at http://en.wikipedia.org/wiki/Internet Read “A brief history of the Internet” from http://www.isoc.org/internet/history/ List 10 web page addresses and do the following decompositon. http://www.bilkent.edu.tr/~ussakli/index.html 1. 2. 3. 4. 5. 6. 7. 8. 9. http:// protocol name. www.bilkent.edu.tr domain name /~ussakli folder name in the domain. /index.html the file name to open in the domain. Send a e-mail to me with the topic “Homework Question 5” and your name and number at the body, of which I cannot see who you send the mail to. (so my outlook will say Undisclosed recipients at to: field of the mail I receive.) Search and find five FTP Client Programs and a FTP Server program using your favorite web search engine. (Do not just take the list from your friends.) Define the cycle of processing and state which computer hardware is used in the cycle of processing. Which stages do we store data, if we don’t store the data what happens? Give two reasons why today we start to have 64 bit processors(i.e. Athlon 64, Itanium). Wasn’t 32 bit processor (i.e. Pentium 4, Athlon XP) enough for todays computing needs? What is a DVD and name and list the capacities of a DVD. Submit your work to [email protected], Topic: ID Number Surname Name Homework 5.