L4: Internet Basics


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L4: Internet Basics

  1. 1. Namecheap.com 11400 W. Olympic Blvd. Suite 200, Los Angeles, CA 90064, US Lecture 4 Internet BasicsNamecheap Guidelines Last update 20.08.2012
  2. 2. Internet Basics ABOUT INTERNETThe Internet is a worldwide, publicly accessible network of interconnected computer networks that transmit databy packet switching using the standard Internet Protocol (IP). It is a "network of networks" that consists of millionsof smaller domestic, academic, business, and government networks, which together carry various information andservices, such as electronic mail, online chat, file transfer, and the interlinked web pages and other documents ofthe world wide web. Fiber optic network infrastructure Internet network hierarchy Namecheap Guidelines Page 2 of 30
  3. 3. Internet Basics GLOBAL STRUCTURE OF THE NETWORK Internet packet routing is accomplished among various tiers of Internet Service ProvidersNamecheap Guidelines Page 3 of 30
  4. 4. Internet Basics LOGICAL STRUCTURE OF THE NETWORK Internet Main Server Main Switch Router Workgroup switch Hub BridgeNamecheap Guidelines Page 4 of 30
  5. 5. Internet Basics NETWORKING HARDWARE HUB is a device for connecting multiple Ethernet devices together and making them act as a single network segment. It has multiple input/output (I/O) ports, in which a signal introduced at the input of any port appears at the output of every port except the original incoming. BRIDGE is a network device used to allow two or more communication networks, or two or more network segments creating an aggregate network. E.g. bridging your network connection is a handy method for sharing your internet connection between two (or more) computers or networks. SWITCH or switching hub is a networking device that connects network segments. It receives a message from any device connected to it and then transmits the message only to the device for which the message was meant. This makes the switch a more intelligent device than a hub. ROUTER is a device that forwards data packets between computer networks, creating an overlay internetwork. A router is connected to two or more data lines from different networks. When a data packet comes in on one of the lines, the router reads the address information in the packet to determine its ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey. Routers perform the "traffic directing" functions on the Internet. GATEWAY is an internetworking system capable of joining together two networks that use different base protocols. A network gateway can be implemented completely in software, completely in hardware, or as a combination of both. So gateway is a network point that acts as an entrance to another network.Namecheap Guidelines Page 5 of 30
  6. 6. Internet Basics CONNECTING TO THE INTERNET To connect to the Internet, you need -Computing device -Connection device -Internet Service Provider (ISP)ISP is an organization that provides access to the Internet and can be either community-owned and non-profit, or privately owned and for-profit Namecheap Guidelines Page 6 of 30
  7. 7. Internet Basics BANDWIDTH BANDWIDTH in computer networking refers to the data rate supported by a network connection or interface. One most commonly expresses bandwidth in terms of bits per second (bps). Bandwidth Access technologies Bandwidth Access technologies 56 kbit/s Modem / Dialup 155 Mbit/s OC3/STM-1 1.5 Mbit/s ADSL Lite 600 Mbit/s Wireless 802.11n 1.544 Mbit/s T1/DS1 622 Mbit/s OC12/STM-4 10 Mbit/s Ethernet 1 Gbit/s Gigabit Ethernet 11 Mbit/s Wireless 802.11b 2.5 Gbit/s OC48/STM-16 44.736 Mbit/s T3/DS3 9.6 Gbit/s OC192/STM-64 54 Mbit/s Wireless 802.11g 10 Gbit/s 10 Gigabit Ethernet 100 Mbit/s Fast Ethernet 100 Gbit/s 100 Gigabit Ethernet One kilobit per second (Kbps) equals 1000 bits per second (bps). (Note: Kbps is sometimes also written as “kbps” - both carry the same meaning.) One megabit per second (Mbps) equals 1000 Kbps or one million bps. One gigabit per second (Gbps) equals 1000 Mbps or one million Kbps or one billion bps.Namecheap Guidelines Page 7 of 30
  8. 8. Internet Basics THE WORLD WIDE WEB The World Wide Web (abbreviated as WWW or W3 commonly known as the Web), is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia, and navigate between them via hyperlinks. Web and the Internet are technically two different terms:The Internet connects multiple computers and forms a network on which a computer can communicate withanother computer.The Web is a way of accessing and sharing information over the Internet by using Web browsers. WEB COMPONENTSWeb browser is a SW program that enables you to view and interact with various resources on the Web.Web page is a document on the Web. It is a formatted text document that a Web browser can display.Web site is one or more Web pages that reside on a single server. Namecheap Guidelines Page 8 of 30
  9. 9. Internet Basics HYPERTEXT TRANSFER PROTOCOL The Hypertext Transfer Protocol (HTTP) is an application protocol for distributed, collaborative, hypermedia information systems. HTTP functions as a request-response protocol in the client-server computing model. A web browser, for example, may be the client and an application running on a computer hosting a web site may be the server. The client submits an HTTP request message to the server.The server, which provides resources such as HTML files and other content, or performs other functions onbehalf of the client, returns a response message to the client. HTTP resources are identified and located on the network by Uniform Resource Identifiers (URIs). URI is a string of characters used to identify a name or a resource. URIs can be classified as locators (URLs), as names (URNs), or as both.A uniform resource name (URN) functions like a persons name, while auniform resource locator (URL) resembles that persons street address.In other words: the URN defines an items identity, while the URL provides amethod for finding it. Namecheap Guidelines Page 9 of 30
  10. 10. Internet Basics HYPERTEXT TRANSFER PROTOCOLHyperlink (or link) is a reference to data that the reader can directly follow, or that is followed automatically. A hyperlink points to a whole document or to a specific element within a document. http://www.microsoft.com/learning/default.asp Element Description http:// Indicates the protocol to be used to access a file www Indicates that the Web site is on the World Wide Web microsoft Indicates the name of the Web site .com Indicates the type of domain /learning Indicates the path to the document /default.asp Indicates the name of the document Namecheap Guidelines Page 10 of 30
  11. 11. Internet Basics NETWORK ARCHITECTURE The CLIENT/SERVER model is a computing model that acts as a distributed application which partitions tasks or workloads between the providers of a resource or service, called servers, and service requesters, called clients. Client side Server side Web Server Database Server FTP Server Application Server Print Server Proxy Server Mail Server DNS ServerNamecheap Guidelines Page 11 of 30
  12. 12. Internet Basics PROTOCOLS The standard model for networking protocols and distributed applications is the International Standard Organizations Open System Interconnect (ISO/OSI) model. ISO/OSI model defines seven network layersControl is passed from one layer to the next, starting at the application layer in one station, andproceeding to the bottom layer, over the channel to the next station and back up the hierarchy. Namecheap Guidelines Page 12 of 30
  13. 13. Internet BasicsNamecheap Guidelines Page 13 of 30
  14. 14. Internet Basics PROTOCOLSApplication (Layer 7) This layer supports application and end-user processes. Communicationpartners are identified, quality of service is identified, user authentication and privacy areconsidered, and any constraints on data syntax are identified. Everything at this layer isapplication-specific. This layer provides application services for file transfers, e-mail, and othernetwork software services.Presentation (Layer 6) This layer provides independence from differences in datarepresentation (e.g., encryption) by translating from application to network format, and viceversa. This layer formats and encrypts data to be sent across a network, providing freedomfrom compatibility problems. It is sometimes called the syntax layer.Session (Layer 5) This layer establishes, manages and terminates connections betweenapplications. The session layer sets up, coordinates, and terminates conversations, exchanges,and dialogues between the applications at each end. It deals with session and connectioncoordination.Transport (Layer 4) This layer provides transparent transfer of data between end systems, orhosts, and is responsible for end-to-end error recovery and flow control. It ensures completedata transfer. Namecheap Guidelines Page 14 of 30
  15. 15. Internet Basics PROTOCOLSNetwork (Layer 3) This layer provides switching and routing technologies, creating logicalpaths, known as virtual circuits, for transmitting data from node to node. Routing andforwarding are functions of this layer, as well as addressing, internetworking, error handling,congestion control and packet sequencing.Data Link (Layer 2) At this layer, data packets are encoded and decoded into bits. It furnishestransmission protocol knowledge and management and handles errors in the physical layer,flow control and frame synchronization. The data link layer is divided into two sublayers: TheMedia Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayercontrols how a computer on the network gains access to the data and permission to transmit it.The LLC layer controls frame synchronization, flow control and error checking.Physical (Layer 1) This layer conveys the bit stream - electrical impulse, light or radio signal --through the network at the electrical and mechanical level. It provides the hardware means ofsending and receiving data on a carrier, including defining cables, cards and physical aspects. Namecheap Guidelines Page 15 of 30
  16. 16. Internet Basics PROTOCOLS So the end-to-end layers reside at the end-user devices only and consist of the Application, Presentation, Session, and Transport Layers.And the chained layers, Network, Data Link, and Physical, are the layers concerned with moving information through a data network. Namecheap Guidelines Page 16 of 30
  17. 17. Internet Basics PROTOCOLS The TCP/IP model or internet layering scheme and its relation to some common protocols1. The link layer contains communication technologies for a local network.2. The internet layer connects local networks, thus establishing internetworking.3. The transport layer handles host-to-host communication.4. The application layer contains all protocols for specific data communications services on a process-to-process level Namecheap Guidelines Page 17 of 30
  18. 18. Internet Basics NETWORK ADDRESSING An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication. Two versions of the Internet Protocol (IP) are in use: IP Version 4 (IPv4) and IP Version 6 (IPv6) IPv4 IPv6 September 1981 6 June 2012Namecheap Guidelines Page 18 of 30
  19. 19. Internet Basics NETWORK ADDRESSING IPv4 uses 32-bit (four-byte) addresses, which limits the address space to 4,294,967,296 (232) addresses. IPv4 addresses are canonically IPv4 represented in dot-decimal notation, which consists of 4 decimal numbers, each ranging from 0 to 255, separated by dots, e.g., Size of network Size of rest Number Addresses Start Class End address number bit field bit field of networks per network addressClass A 8 24 128 (27) 16,777,216 (224) B 16 16 16,384 (214) 65,536 (216) C 24 8 2,097,152 (221) 256 (28) D (multicast) not defined not defined not defined not defined E (reserved) not defined not defined not defined not defined Namecheap Guidelines Page 19 of 30
  20. 20. Internet Basics NETWORK ADDRESSING IPv6 uses 128-bit addresses, allowing for 2128, or approximately 3.4×1038 addresses. IPv6 addresses, as commonly displayed IPv6 to users, consist of eight groups of four hexadecimal digits separated by colons, for example: 2001:0db8:85a3:0042:0000:8a2e:0370:7334An IPv6 address may be abbreviated by using one or more of the following rules:1. Remove leading zeroes from one or more groups of hexadecimal digits; this is normally done to all groups that have leading zeroes. (For example, convert the group 0042 to 42.)2. Combine consecutive sections of one or more zeroes, using a double colon (::) to denote the omitted sections. The double colon may only be used once in any given address, as the address would be indeterminate if it was used multiple times. (For example, 2001:db8::1:2 is valid, but 2001:db8::1::2 is not permitted.) Namecheap Guidelines Page 20 of 30
  21. 21. Internet Basics NETWORK ADDRESSING There are two methods to assigning IP addresses to computers: DYNAMIC and STATIC. Static IP addresses are used primarily for servers so that they dont appear to "move" while non-servers are usually assigned dynamic IP addresses. Most dynamic IP address users are users of internet service providers (ISPs) sincenot all the users of an ISP are online at one time and the ISPs can "get away" with not having enough IPaddresses for each user.Static IP addresses are manually assigned to a computer by an administrator.Dynamic IP addresses are most frequently assigned on LANs and broadband networks by Dynamic HostConfiguration Protocol (DHCP) servers. Namecheap Guidelines Page 21 of 30
  22. 22. Internet Basics NETWORK PORTS A NETWORK PORT is a number that identifies one side of a connection between two computers. Computers use port numbers to determine to which process a message should be delivered. As network addresses are like street address, port numbers are like suite or room numbers. PORT RANGES 0 - 1023 – Defaults for popular network services 1024 - 49151 – IANA reserved 49152 - 65535 – Dynamic or private ports Port Description Port Description 20/21 File Transfer Protocol (FTP) 110 Post Office Protocol (POP3) 22 Secure Shell (SSH) 115 Simple File Transfer Protocol (SFTP) 23 Telnet remote login service 143 Internet Message Access Protocol (IMAP) 25 Simple Mail Transfer Protocol (SMTP) 443 HTTP Secure (HTTPS) 53 Domain Name System (DNS) service 993 IMAP over SSL (IMAPS) 80 Hypertext Transfer Protocol (HTTP) 995 POP3 over SSL (POP3S)Any program may use any port, though some port numbers have a standard use and some programs maybe limited in which ports they can use for security reasons. Namecheap Guidelines Page 22 of 30
  23. 23. Internet Basics HTTP SESSIONNamecheap Guidelines Page 23 of 30
  24. 24. Internet Basics HTTP STATUS CODES The first digit of the status code specifies one of five classes of response: 1xx INFORMATIONAL 2xx SUCCESS 3xx REDIRECTION 4xx CLIENT ERROR 5xx SERVER ERRORNamecheap Guidelines Page 24 of 30
  25. 25. Internet Basics HTTP STATUS CODES 1xx INFORMATIONAL 100 CONTINUE Client should continue with request 101 SWITCHING PROTOCOLS Server is switching protocols 102 PROCESSING Server has received and is processing the request 122 REQUEST-URI TOO LONG URI is longer than a maximum of 2083 charactersNamecheap Guidelines Page 25 of 30
  26. 26. Internet Basics HTTP STATUS CODES 2xx SUCCESS 200 OK Standard response for successful HTTP requests 201 CREATED Request has been fulfilled; new resource created 202 Accepted Request accepted, processing pendingNamecheap Guidelines Page 26 of 30
  27. 27. Internet Basics HTTP STATUS CODES 3xx REDIRECTION 301 MOVED PERMANENTLY This and all future requests directed to the given URI 302 FOUND Response to request found via alternative URINamecheap Guidelines Page 27 of 30
  28. 28. Internet Basics HTTP STATUS CODES 4xx CLIENT ERROR 400 BAD REQUEST Request cannot be fulfilled due to bad syntax 403 FORBIDDEN Server refuses to respond to request 404 NOT FOUND Requested resource could not be found 408 REQUEST TIMEOUT Server timed out waiting for the requestNamecheap Guidelines Page 28 of 30
  29. 29. Internet Basics HTTP STATUS CODES 5xx SERVER ERROR 500 INTERNAL SERVER ERROR Generic error message 502 BAD GATEWAY Server received an invalid response from upstream server 503 SERVICE UNAVAILABLE Server is currently unavailable 504 GATEWAY TIMEOUT Gateway did not receive response from upstream serverNamecheap Guidelines Page 29 of 30
  30. 30. Internet Basics WELCOME TO OUR TEAMNamecheap Guidelines Page 30 of 30