There are a lot of things you can do on the Internet. The Web, while certainly the most popular, is not the only service the Internet offers, nor was it the first. Tonight's lesson summarizes the various services available on the Internet. Each section includes the protocol used by the service and the most popular or more common software programs which are used to implement the service.
Before we begin, though, some further mention needs to be given to DNS names. As discussed in the previous week's notes, the top-level portion of a DNS name is the LAST little wordlett (.com, .org, etc.). As you progress along the name from right to left, the name becomes more specific.
Thus, www.enol.com indicates that it is a company, named enol, and we are accessing the Web server portion. Likewise mail.codepoet.org is the mail server, and news.codepoet.org is the newsgroup server.
Protocol: SMTP Most popular MTA (Mail Transport Agent): Sendmail
Email was the Internet's first "killer app". It's what got people excited about it and gave them a reason to get on.
As mentioned in the first week of class, the medium of the Internet is flat, ASCII text. Email is no exception. The format of an email message consists of a header and a body. The header contains information about how / where the message was routed, and also contains information about who the message is to, who it is from, the subject of the message, and other items. The body simply contains the text of the message.
One good comparison of an email message would be to an individual TCP packet, which also contains a header and a body.
Protocol: NNTP Most popular Newsgroup server: INN (InterNet News)
One of the shortcomings of Email was that it was difficult to allow large groups of people to communicate/collaborate. To solve this problem, newsgroups were created. Newsgroups were built on the foundation of email, having a similar message format of a header, body, and notably a subject line. Messages are posted in threads: Somebody starts a thread by posting a top-level message and people can post replies to the top-level message, or to other replies.
Newsgroups were the birthplace of the culture of the Internet. Many textual and conversational conventions were born here and are used in nearly every other medium offered on the Internet.
Certain conventions are followed when naming newsgroups. Each newsgroup has a "top-level" category indicated by it's first prefix. Some of the more common ones are:
The little wordletts which follow the first further sub-divide the group into a smaller category.
One of the greatest things about newsgroups is that there's no authentication; anybody that wants to can post a message under any name or pseudoname. One of the worst things about newsgroups is that there's no authentication; anyone can post a message. As more people have gotten onto the Internet, newsgroups have become more and more polluted. There are some moderated newsgroups which are a bit nicer.
The following are terms which describe some people which show up on newsgroups.
Protocol: Also SMTP Most popular List server: Majordomo
Newsgroups have become more polluted in recent years and are a less attractive place for people to go because of it. A new form of collaboration has risen up which also builds on the foundation of email called mailing lists. The advantage to mailing lists is that they can be moderated a bit better, as there is a formal "joining" procedure when you want to join a mailing list. Also, not everyone has access to newsgroups, but most (if not all) people on the Internet have access to email.
Many usenet conventions are used on mailing lists: moderation, killfiles, threads, and the like.
Protocol: IRC (among others) There are a variety of chat programs/servers
One of the features of all of the previously mentioned services is that communication occurs asynchronously via the 'store and forward' approach of message delivery. Chat rooms provide a way for people to communicate in real time with each other. Typically you will connect to an IRC host with an IRC client, select a "channel" that you wish to talk on (similar to newsgroups).
Protocol: ICQ (among others) There are a variety of instant messaging servers/clients
Like newsgroups, Chat rooms can get a little noisy and polluted at times, and so instant messaging has come to pass. Like chat rooms, instant messaging provides a real-time means of communication. Like email, it is a person-to-person arrangement.
Protocol: FTP (also HTTP) Numerous FTP servers exist. wu-ftp and Pro-FTP are fairly common.
One of the oldest uses of the Internet is to transfer files between two locations. Numerous FTP sites can be found all over the world, storing all kinds of different stuff.
One common convention of FTP sites is to have "mirror" sites which contain the same files as the main site. Mirror sites exist to provide more speedy access / download times to people who live in areas which are geographically close to the mirror servers. Mirror sites also serve as "backup" in case the main site has a hard drive crash and loses all its files.
Protocol: HTTP Most popular Web server: Apache Most popular browser: Mozilla
This is perhaps the most popular service of the Internet, rivaled only by email. Prior to the advent of the Web, the Internet was a fairly exclusive place, but with an easy point-and-click interface and images & sounds as well as text, loads of people got onto the Internet.
The following are other services available, but they don't fit neatly into the other categories and aren't as widely used as some of the other services.