Application Layer
What are some potential disadvantages with e-mail as a communication medium? Can you describe some occasions when you have run into these disadvantages of e-mail?
A huge disadvantage is spam. Another problem is that particularly among friends, email encourages people to "shoot" emails before thinking. Finally, I have occasionally sent emails to lists when I meant to just send the mail to an individual. This could have been ruinous for me had I made adverse remarks about someone in the mail. Finally, a potential disadvantage, one that I have not personally experienced, is that if I made adverse remarks about someone in an email, that email may get circulated around and reach the subject of my remarks, hurting personal relations between us.
What is a hyperlink?
A hyperlink is a link from one web page to another web page.
What is a killer application?
A killer application is an industry term used to describe a computer application to die for. It is an application that is so useful that it causes people to buy a large, expensive system just to get the functionality of the killer app. Internet entrepreneurs are always on the lookout for the next killer app.
What is presence in the context of IM?
Presence is the ability of users to subscribe to each other and be notified of changes in state in users, such as when they come online or get busy or go away.
Provide an overview of the structure of a web page.
A web page has a head and a body. The head has meta-information about the page and the contents of the header are not displayed to the user. The contents of the body are displayed to the user.
Using examples from your own life, describe some advantages of e-mail as a communication medium compared to your other choices (such as cell phones, meetings).
Email offers a few big advantages over other forms of communication. It allows me and my collaborators to respond at times convenient to us. Another advantage is that the email thread maintains a record of the entire conversation. Finally, the inbox is a great information storage where I can search for messages using keywords, dates etc.
What is FTP?
FTP is an application layer protocol for transferring files from one computer to another, regardless of the hardware and software configurations of the two computers.
What is instant messaging? How is IM different from e-mail?
IM is an application layer protocol that allows users to send short quick messages to each other. The primary difference between IM and email is the absence of a mailbox in IM. If you need a record of an IM conversation, you are required to do that by manually saving the communication after it is completed. (Of course, corporate IM systems save IM conversations for legal purposes, but they are automatically deleted after the period specified by corporate policy).
What is an inlink? What information about a web page can be inferred from inlinks to the page?
Links on other web pages that point to a page are called inlinks. Therefore, the more inlinks to a page, the more likely it is that the page contains relevant information. Inlinks help website owners identify other web sites that link to their site. Inlinks to a web page therefore provide a measure of interest in the page on the web.
What is the role of POP/ IMAP in e-mail?
POP and IMAP are protocols used by MUAs to retrieve and manipulate email in mailboxes located on the MTAs (mail servers).
What is the role of SMTP in e-mail?
SMTP is the Simple Mail Transfer Protocol. SMTP is the protocol used by MTAs to transfer email between mail servers.
What is flaming?
Sending emails while angry or email that provoke others to get angry is called flaming.
How has the web been most useful to you?
The web enables me to search for information quickly. It has also become one of my most important shopping channels.
What is URL? Describe the parts of a typical web URL.
A URL, or uniform resource locator, is a character string describing the location and access method of a resource on the Internet. It is a way to represent any resource available through the internet. The first part of the URL begins with the protocol used (e.g. http.) The second part of the URL identifies the host. The third part is optional and specifies the port number. The fourth part of a URL specifies the resource on the host
What is HTML?
HTML is the language that is used to create web pages. It defines how a certain piece of text should be displayed on the screen and what page the browser should load if the user clicks on a hyperlink.
Describe some changes in the patterns of Internet usage based on changes in the list of most popular websites globally.
In 2005, the most popular sites were information providing sites. In 2008, many social media sites were extremely popular. In 2010, again the information providing sites seem to have become popular again.
Describe the differences between pull and push forms of communication, using the web and e-mail as examples.
In the pull form of communication, the receiver decides what information to pull from a repository. This happens on the web, where there is no assurance that a web page will be read by a potential customer. In the push form of communication, the sender decides who to send the message to and when to send the message. Since email uses the push form of communication, email ensures that a message will reach the recipient's mailbox. Of course, this has resulted in the problem of spam, where a lot of email reaching our inboxes is unsolicited.
In what ways do you use e-mail in your daily life? When do you prefer to use e-mail over the postal system? When do you prefer the postal system over e-mail?
Most people use email to send short messages and articles, pictures etc as attachments. For most kinds of information transfer, people prefer email over the postal system. The postal system is used when sending bulky items such as books or gifts, or legal documents such as contracts.
What are some important differences between POP and IMAP?
POP is the early MUA protocol and did not allow multiple email clients to maintain synchronization with each other and the mailbox. IMAP was created to overcome this limitation of POP. IMAP adds message IDs to every message on the mailbox. These IDs can be used by multiple clients to synchronize themselves with the mailbox on the server. IMAP also allows clients to conveniently manipulate the mailbox by performing operations such as creating, deleting, and renaming mailboxes, setting and clearing flags, and selective fetching of messages.
What are an MTA and an MUA in the context of e-mail?
The MTA is the mail transfer agent and is the email server. It is always connected to the Internet. It sends and receives email on behalf of its users. The MUA is the mail user agent and is the software used by the end user to access their mail server.
What are the functions of the application layer? How were the earliest application-layer protocols defined? What application do you spend the most time on?
The application layer enables end user applications to use TCP and UDP in meaningful ways, for example to send email or to download web pages. The primary function of the Application layer is to hide the details of TCP and IP from end user applications. The earliest application layer protocols defined were SMTP, FTP, HTTP, and Telnet.
Describe the high-level structure of the e-mail system.
The email system is composed to mail servers (MTAs) and clients (MUAs). Each email user uses a client to access their mailbox on a server. Outgoing email is sent by their server to the receiver's server. The receiver's server delivers the email to the recipient's mailbox. The recipient sees this mail the next time they access their mailbox.
What are the three most popular websites in the world today? What primary service does each site offer?
The three most popular websites today are Google, Facebook and YouTube. Google helps people search for information, Facebook is the primary social media site and YouTube helps people upload short videos for anyone to see.
Why is the web gaining popularity as a marketing tool over traditional methods such as yellow pages?
The web is gaining popularity because most users have access to the web through the computer or phones at all times. The web enables highly targeted marketing which serves the interests of both customers and vendors. Finally, the major search engines have created cost-effective programs for advertisers who pay only when an ad brings a customer to their site.
How is FTP different from HTTP?
Whereas HTTP only creates one channel of communication, FTP creates two channels of communication, one for commands and one for the data. This allows FTP users to abruptly stop data transfer if necessary.