Natan_mallinger's List: Web Design

• This whitepaper explains the underlying infrastructure and technologies that make the Internet work.
• DHCP (Dynamic Host Configuration Protocol)
• protocol stack
• Protocol Layer  Comments   Application Protocols Layer  Protocols specific to applications such as WWW, e-mail, FTP, etc.   Transmission Control Protocol Layer  TCP directs packets to a specific application on a computer using a port number.   Internet Protocol Layer  IP directs packets to a specific computer using an IP address.   Hardware Layer  Converts binary packet data to network signals and back.
    (E.g. ethernet network card, modem for phone lines, etc.)
• • "User --> Application --> TCP --> IP --> HardWare --> Internet --> Hardware --> IP --> TCP --> Application -->  User"
• one is called traceroute and it shows the path your packets are taking to a given Internet destination.
• known as Network Service Providers or NSPs. Some of the large NSPs are UUNet, CerfNet, IBM, BBN Planet, SprintNet, PSINet, as well as others. These networks peer with each other to exchange packet traffic. Each NSP is required to connect to three Network Access Points or NAPs. At the NAPs, packet traffic may jump from one NSP's backbone to another NSP's backbone. NSPs also interconnect at Metropolitan Area Exchanges or MAEs. MAEs serve the same purpose as the NAPs but are privately owned. NAPs were the original Internet interconnect points. Both NAPs and MAEs are referred to as Internet Exchange Points or IXs.

• When you type a URL into a web browser, this is what happens:

    

   
  1. If the URL contains a domain name, the browser first connects to a  domain name server and retrieves the corresponding IP address for the  web server.
   
  2. The web browser connects to the web server and sends an HTTP request  (via the protocol stack) for the desired web page.
   
  3. The web server receives the request and checks for the desired page.  If the page exists, the web server sends it. If the server cannot  find the requested page, it will send an HTTP 404 error message.  (404 means 'Page Not Found' as anyone who has surfed the web probably  knows.)
   
  4. The web browser receives the page back and the connection is closed.
   
  5. The browser then parses through the page and looks for other page  elements it needs to complete the web page. These usually include  images, applets, etc.
   
  6. For each element needed, the browser makes additional connections and  HTTP requests to the server for each element.
   
  7. When the browser has finished loading all images, applets, etc. the  page will be completely loaded in the browser window.
• E-mail uses an application level protocol called Simple Mail Transfer Protocol or SMTP

• When you open your mail client to read your e-mail, this is what typically happens:

    

   
  1. The mail client (Netscape Mail, Lotus Notes, Microsoft Outlook, etc.)  opens a connection to it's default mail server. The mail server's  IP address or domain name is typically setup when the mail client is  installed.
   
  2. The mail server will always transmit the first message to identify  itself.
   
  3. The client will send an SMTP HELO command to which the server will  respond with a 250 OK message.
   
  4. Depending on whether the client is checking mail, sending mail, etc.  the appropriate SMTP commands will be sent to the server, which will  respond accordingly.
   
  5. This request/response transaction will continue until the client sends  an SMTP QUIT command. The server will then say goodbye and the  connection will be closed.
• A simple 'conversation' between an SMTP client and SMTP server is shown below. R: denotes messages sent by the server (receiver) and S: denotes messages sent by the client (sender).
• TCP is responsible for routing application protocols to the correct application on the destination computer
• TCP is a connection-oriented, reliable, byte stream service.
• Listed below are the port numbers for some of the more commonly used Internet services.

   

   

  FTP	20/21
  Telnet	23
  SMTP	25
  HTTP	80
  Quake III Arena	27960
• IP's job is too send and route packets to other computers

• Resources

    Below are some interesting links associated with some of the topics discussed. (I hope they all still work. All open in new window.)

    http://www.ietf.org is the home page of the Internet Engineering Task Force. This body is greatly responsible for the development of Internet protocols and the like.

    http://www.internic.org is the organization responsible for administering domain names.

    <!-- <a href="http://www.nexor.com/standards/rfc" target="_blank">http://www.nexor.com/standards/rfc</a> is an excellent RFC search engine useful for finding any RFC. <p> -->  http://www.faqs.org/rfcs/rfcsearch.html is an excellent RFC search engine useful for finding any RFC.

    <!-- <a href="http://www.internetweather.com" target="_blank">http://www.internetweather.com</a> shows animated maps of Internet latency. <p>  <a href="http://routes.clubnet.net/iw/" target="_blank">http://routes.clubnet.net/iw/</a> is Internet Weather from ClubNET. This page shows packet loss for various carriers. <p> -->  http://navigators.com/isp.html is Russ Haynal's ISP Page. This is a great site with links to most NSPs and their backbone infrastructure maps.

    http://www.investintech.com/content/historyinternet/ is A Brief Guide to the History of the Internet, sent by Kendra.

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