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2012-05-19

A+: TCP/IP Applications and Technologies

TCP/IP actually is a suite of protocols used on the Internet for routing and transporting information. Here are   some of the application protocols that are part of the TCP/IP suite, as well as some of the services and technologies that relate to TCP/IP.


ISP: An ISP (Internet service provider) provides the connection between an individual PC or network and the Internet. ISPs use routers connected to high-speed, high-bandwidth connections to route Internet traffic from their clients to their destinations.


HTTP/HTTPS: Hypertext Transfer Protocol (HTTP) is the protocol used by web browsers, such as Internet Explorer and Netscape Navigator, to access websites and content. Normal (unsecured) sites use the prefix http:// when accessed in a web browser. Sites that are secured with various encryption schemes are identified with the prefix https://.   Most browsers connecting with a secured site will also display a closed padlock symbol onscreen.


SSL: Secure Socket Layers (SSL) is an encryption technology used by secured (https://) websites. To access a secured website, the web browser must support the same encryption level used by the secured website (normally 128-bit encryption) and the same version(s) of SSL used by the website (normally SSL version 2.0 or 3.0).


TLS: Transport Layer Security (TLS) is the successor to SSL. SSL3 was somewhat of a prototype to TLS, and was not fully standardized. TLS was ratified by the IETF in 1999. However, many people and companies may still refer to it as SSL.


HTML: Hypertext Markup Language (HTML) is the language used by web pages. An HTML page is a specially formatted text page that uses tags (commands contained in angle brackets) to change text appearance, insert links to other pages, display pictures, incorporate scripting languages, and provide other features. Web browsers, such as Microsoft Internet Explorer and Netscape Navigator, are used to view and interpret the contents of web pages, which have typical file extensions such as .HTM, .HTML, .ASP (Active Server pages generated by a database), and others.

You can see the HTML code used to create the web page in a browser by using the View Source or View Page Source menu option provided by your browser.

Tags such as <P> are used by themselves, and other tags are used in pairs. For example, <A HREF...> is used to indicate the start of a hyperlink (which will display another page or site in your browser window), and </A> indicates the end of a hyperlink.

The World Wide Web Consortium (http://www.w3c.org) sets the official standards for HTML tags and syntax, but major browser vendors, such as Microsoft and Netscape, often modify or extend official HTML standards with their own tags and syntax.


FTP: File Transfer Protocol (FTP) is a protocol used by both web browsers and specialized FTP programs to access dedicated file transfer servers for file downloads and uploads. When you access an FTP site, the site uses the prefix ftp://.

Windows contains ftp.exe, a command-line FTP program; type FTP, press Enter, and then type ? at the FTP prompt to see the commands you can use.

FTP sites with downloads available to any user support anonymous FTP; if any credentials are required, it’s typically the user’s email address as a password (the username is preset to anonymous). Some FTP sites require the user to log in with a specified username and password.

Although you can use Windows’ built-in FTP client for file uploads and downloads with both secured and unsecured FTP sites, you should consider using third-party FTP products such as FileZilla (http://filezilla-project.org/) or WS_FTP Pro (http://www.ipswitchft.com/products/ws_ftp_professional/). These programs enable you to create a customized setup for each FTP site you visit, and will store passwords, server types, and other necessary information. They also enable faster downloads than typical web browsers running in ftp:// mode.


Telnet: Telnet enables a user to make a text-based connection to a remote computer or networking device and use it as if he were a regular user sitting in front of it, rather than simply downloading pages and files as he would with an http:// or ftp:// connection. Windows contains a command-line Telnet program. To open a connection to a remote computer, enter a command such as        telnet a.computer.com

To use other commands, open a command prompt, type telnet, and press the Enter key. To see other commands, type ?/help.

The remote computer must be configured to accept a Telnet login. Typically, TCP port 23 on the remote computer must be open before a login can take place.


SSH: Secure Shell (SSH) allows data to be exchanged between computers on a secured channel. This protocol offers a more secure replacement to FTP and TELNET. The Secure Shell server housing the data you want to access would have port 22 open.



DNS: The domain name system (DNS) is the name for the network of servers on the Internet that translate domain names, such as www.informit.com, and individual host names into their matching IP addresses. If you manually configure an IP address, you typically provide the IP addresses of one or more DNS servers as part of the configuration process.

Can’t access the site you’re looking for? Got the wrong site? You might have made one of these common mistakes:

        • Don’t assume that all domain names end in .com— Other popular domain name extensions include .net, .org, .gov, .us, .cc, and various national domains such as .uk (United Kingdom), .ca (Canada), and many others.

        • Don’t forget to use the entire domain name in the browser— Some browsers will add the www. prefix used on most domain names, but others will not. For best results, spell out the complete domain name.


If you want a unique domain name for either a website or email, the ISP that you will use to provide your email or web hosting service often provides a registration wizard you can use to access the domain name registration services provided by various companies such as VeriSign.

A domain name has three major sections, from the end of the name to the start:

    • The top-level domain (.com, .org, .net, and so on)

    • The name of the site

    • The server type; www indicates a web server, ftp indicates an FTP server, mail indicates a mail server, and search indicates a search server

For example, Microsoft.com is located in the .com domain, typically used for commercial companies. Microsoft is the domain name. The Microsoft.com domain has the following servers:

    • www.microsoft.com hosts web content, such as product information.

    • support.microsoft.com hosts the Microsoft.com support website, where users can search for Knowledge Base (KB) and other support documents.

    • ftp.microsoft.com hosts the File Transfer Protocol server of Microsoft.com; this portion of the Microsoft.com domain can be accessed by either a web browser or an FTP client.

Many companies have only WWW servers, or only WWW and FTP servers.

Some small websites use a folder under a domain hosted by an ISP: www.anisp.com/~asmallsite





Email: All email systems provide transfer of text messages, and most have provisions for file attachments, enabling you to send documents, graphics, video clips, and other types of computer data files to receivers for work or play. Email clients are included as part of web browsers, and are also available as limited-feature freely downloadable or more-powerful commercially purchased standalone email clients. Some email clients, such as Microsoft Outlook, are part of application suites (such as Microsoft Office) and also feature productivity and time-management features.

Users who travel away from corporate networks might prefer to use a web-based email account, such as Hotmail, or use Outlook Web Access to get access to email from any system with a properly configured web browser.

To configure any email client, you need

    • The name of the email server for incoming mail
    • The name of the email server for outgoing mail
    • The username and password for the email user
    • The type of email server (POP, IMAP, or HTTP)

Some email clients and servers might require additional configuration options.

To access web-based email, you need

    • The website for the email service
    • The username and password


SMTP: The simple mail transfer protocol (SMTP) is used to send email from a client system to an email server, which also uses SMTP to relay the message to the receiving email server.


POP: The post office protocol (POP) is the more popular of two leading methods for receiving email (IMAP is the other). In an email system based on POP, email is downloaded from the mail server to folders on a local system. POP is not a suitable email protocol for users who frequently switch between computers, because email might wind up on multiple computers. The POP3 version is the latest current standard. Users that utilize POP3 servers to retrieve email will typically use SMTP to send messages.

    For users who must use POP-based email and use multiple computers, a remote access solution, such as Windows Remote Desktop or a service such as GoToMyPC, is recommended. A remote access solution enables a user to remotely access the system that connects to the POP3 mail server so he or she can download and read email messages, no matter where he or she working.


IMAP: The Internet message access protocol (IMAP) is an email protocol that enables messages to remain on the email server so they can be retrieved from any location. IMAP also supports folders, so users can organize their messages as desired.

To configure an IMAP-based email account, you must select IMAP as the email server type, and specify the name of the server, your user name and password, and whether the server uses SSL.


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