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InternetTechnology.md

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Internet Technologies

Contents:

## Overview + Internet - introduction + global interconnected computer networks + use TCP/IP protocol + unique IP address, identify computer location + DNS resolves name to IP address - advantage - disadvantage + Intranet - introduction + private network within organization + unique IP address in Intranet - benefits + communication + time saving + collaboration + platform independency + more + Extranet - introduction + network within organization, use Internet to connect with outside in a controlled manner + implemented as Virtual Private Networks(VPN), offering secure network in public Internet + VPN uses Internet Protocol Security Architecture(IPSEC) and add additional security layer to TCP/IP protocol - benefits/issues

Reference Models

  • overview
    • provide a way how devices can communicate regardless their architecture
    • hypothetical model: OSI model
    • practical model: TCP/IP model
  • OSI model
    • Open System Interface(OSI)
    • physical layer
      • maintain physical connection
      • convert digital to electrical signal
      • decide simplex,half duplex or full duplex
    • data link layer
      • synchronization and error control
      • error detection and add error detection bits
    • network layer
      • route signals through channels
      • network controller, decide the route
      • divide outgoing message and assemble incoming message
    • transport layer
      • decide whether transmission should take place
      • multiplexing
      • guarantee transmission of data from one to another end
    • session layer
      • manage conversations between two applications
      • log on and log off, user identification
    • application layer
      • provide services
      • login and check password, etc
  • TCP/IP model
    • application layer: TELNET,FTP,SMTP,DN,HTTP,NNTP
    • transport layer: TCP/IP,UDP
    • Internet layer: IP
    • host-to-network layer: ARPANET,LAN,SATNET
## DNS(Domain Name System) + IP address - uniquely assigned to each host on Internet - network component and host component + Uniform Resource Locator(URL) - refer to a web address - uniquely identify a document - absolute URL + address = protocol used + server name + path name + file name + protocol that create URL: FTP,https,mailto - relative URL + used for internal links + omit protocol and server from address + Domain Name System - Domain Names + symbolic string associated with IP address + examples: com,edu.gov,net - Domain Name Space + hierarchy in Internet naming structure - Name Server + DNS distributed database + root server, primary server, secondary server ## Services + communication service - email, telnet, VoIp, IM, IRC + information retrieval services - FTPm Gopher, Archie + web services - exchange information between applications + World Wide Web + Video Conferencing ## Connection + Internet Service Providers(ISP) - Internet access - domain name registration - dial-up access - leased line access + connection - dial-up connection - ISDN - DSL - cable TV - satellite - wireless

Protocols

  • Transmission Control Protocol(TCP)
    • reliable and connection oriented
    • retransmit unacknowledged bytes
    • services
      • stream deliver
      • sending and receiving buffers
      • segmentation
      • full duplex
      • connection oriented
      • reliable service
  • Internet Protocol(IP)
    • connectionless and unreliable
    • no guarantee on successful transmission
  • User Datagram Protocol(UDP)
    • connectionless and unreliable
    • no guarantee on receiving data
    • transmit in datagram
    • used for application transmitting small data at one time
  • File Transfer Protocol(FTP)
    • copy files from one host to another
    • control process and data transfer process
    • control connection and data connection
    • port 21 for control connection and port 20 for data connection
  • Telnet
    • log into remote computer on the internet
  • Hyper Text Transfer Protocol(HTTP)
    • communication between browser and web server
    • HTTP request: request line, header fields, message body
    • HTTP response: status line, headers, message body