In our example, the SURAnet FTP address is ftp.sura.net, so I would type

ftp ftp.sura.net

Once I hit the enter key, the following appears on my screen:

   ftp ftp.sura.net
  Connecting to ftp.sura.net 128.167.254.179, port 21
  220 nic.sura.net FTP server (Version wu-2.4(1) Fri May 20 10:20:58
  EDT 1994) ready.
  USER (identify yourself to the host):

If I had an account on the SURAnet system, I would enter my SURAnet user ID. But, since I don't have an account on this system, I have to find another way to access the system. ;)

This is where the "anonymous" FTP I mentioned earlier comes in :) The other way to access some FTP sites -- at least those FTP sites that allow outside access -- is to use the userid "anonymous". By using the name "anonymous", you are telling that FTP site that you aren't a regular user of that site, but you would still like to access that FTP site, look around, and retrieve files.

So, where it says USER, I type the word

anonymous

   >>>USER anonymous
  331 Guest login ok, send your complete e-mail address as password.
  Password:

Out of politeness to the FTP site, if you login as "anonymous", you need to use your full Internet address as your password. This helps the FTP site keep track of who has visited its site.

So, since it wants my password, and since the password for any anonymous FTP session is my full Internet address, I type

pcrispe1@ua1vm.ua.edu

   >>>PASS ********
  230-    SURAnet ftp server running wuarchive experimental ftpd
  230-
  230-Welcome to the SURAnet ftp server.  If you have any problems with
  230-the server please mail the to systems@sura.net. If you do have problems,
  230-please try using a dash (-) as the first character of your password
  230- -- this will turn off the continuation messages that may be confusing
  230-your ftp client.
  ...
  230 Guest login ok, access restrictions apply.
  Command:

Okay ... now what? I've started-up my FTP client, I've given the client an FTP address to connect to, I've identified myself to the remote site (I told it that I am anonymous), and I've given the site my password.

Now it's time to see what sort of files and directories are around, and to get those files ... which we will do in the next lesson :)

Posted bySumedh at 11:49 PM 0 comments  

Labels: Internet

TELNET

We are about to enter a new section of this workshop. For the past few lessons, we have talked about communicating on a one-to-one basis (e-mail) and on a one-to-many basis (LISTSERV and Usenet).

Now, I'm going to show you how to log in to other computers around the world and take full advantage of the public programs and services that these other computers offer.

There is some bad news, though. Some of you, especially a good number of you with "level one" Internet access, do not have access to TELNET. If this is true for you, please accept my apologies. I promise to make it up to you when I show you File Transfer Protocol -- and besides, you can always take this lesson and the next lesson and bug your local Internet provider into offering TELNET (you can also save this lesson for the day that you do have TELNET access).

With TELNET, the commands that you type on your keyboard are sent from your terminal to your local Internet service provider, and then from your provider to the remote computer that you have accessed. Unlike the LISTSERV commands that you sent in MAP05: LISTSERVs and MAP06: Other Mail Servers that took CENTURIES to process (okay, a slight exaggeration), TELNET commands (usually) travel so fast that you can't even tell that you are using a remote computer.

So what can you do with this ability to log into remote computers? If your local Internet provider allows it, it is possible for you to TELNET into your account from another city and check your e-mail while you are on vacation or away on business. You can also TELNET into huge databases to do research, or even TELNET into libraries around the world to check if they have a certain book that you are looking for. TELNET also offers an easy entry into the world of Gophers and the World Wide Web for those people who may not otherwise have access to these tools.

In MAP04: E-Mail, I showed you that an Internet address for a user looked something like: user@address. Well, since we are no longer interested in the person -- we want to access the computer, not the person -- we can throw away both the "user" and the "@" part. All we care about now is the stuff after the @.

TELNET addresses look something like this:

     seabass.st.usm.edu        cybernet.cse.fau.edu
    bbhost.hq.eso.org         fedworld.gov
    128.118.36.5              192.160.13.1

You may also see TELNET addresses with numbers stuck on the END of them. Those numbers are "port" numbers. Port numbers don't have anything to do with hardware ports on the computer; instead they are (sort of) a way for you to tell the remote computer which program or server you want it to pull up. A TELNET address with a port number allows you not only to access a remote computer, but to also pull up a specific program or server on that remote computer (BTW, the standard port number is port 23):

     seabass.st.usm.edu 23     cybernet.cse.fau.edu 2010
    bbhost.hq.eso.org 6969    fedworld.gov 4242
    128.118.36.5 23           192.160.13.1 66

There are seven steps to a successful TELNET session. These steps are all based on simple common sense, and I will explain them all in a minute. But first, here are the seven steps:

1. Start-up the TELNET program.
2. Give the TELNET program an address to connect to.
   (BTW, some really nifty TELNET packages allow you to combine steps 1 and 2 into one simple step!)
3. Make a note of what the "escape character" is.
4. Log in to the remote computer.
5. Set the "terminal emulation".
6. Play around on the remote computer.
7. Quit.

Starting the TELNET program is easy. All most of you have to do is type the word TELNET on your command line, and the program will start right up. If you are using Windows or a Macintosh (or an equivalent), double-click on the TELNET icon.

The second step is to give the TELNET program the address of the computer that you want to access. This is where the programs start to differ. Some programs will automatically ask you to enter the address of the remote host, but most won't. If your program does not automatically ask you for the address, you need to type

open

Remember when I said that some nifty TELNET programs allow you start-up the TELNET program and access the address all in one easy step? Instead of doing the two steps I just went over, you may be able to just type

telnet

After you have told TELNET which computer you want it to access, and right before you gain access to the remote computer's login screen, you will see something like this:

     telnet YALEINFO.YALE.EDU 7000
    Trying 130.132.21.53 Port 7000 ...
    Connected to YALEINFO.YALE.EDU
    Escape character is ...

The next step is to log in to the remote computer. Everyone should know how to log in to a computer by now ;) <=== a winking smiley

If you are accessing a public site, the "login" -- the "password" that you need to access the remote computer -- will probably be publicly known. For example, in the next lesson I will show you a list of several dozen TELNET sites, including their addresses and logins. Some public sites even TELL you what the login is when you TELNET to them! Heck, some TELNET sites are wide open and do not require a login or password at all!!

The fifth step is to set the terminal emulation. All this means is that you are going to tell the remote site how data should be shown on your screen. The most common terminal emulation setting is VT100, which is the standard for terminal-based communications.

If you do not have a VT100 terminal, or a terminal that can pretend its a VT100 terminal. you may have to set your terminal emulation to either your correct terminal type or, if you do not know your your correct terminal type, to a "dumb" terminal emulation.

Fortunately, some TELNET sites automatically take care setting the terminal emulation for you, so you don't even have to worry about it.

If you end up with a screen full of gibberish, chances are you did not use the correct terminal emulation setting. Your best bet if this happens is to disconnect from the site and try again.

I think you can figure out the sixth step -- play around on the remote computer -- all by yourself :)

The final step is to quit. Some sites are nice and tell you how to do this, but most expect you to figure out how to quit on your own. That is where the escape character comes in!

Remember that once you access the remote computer, every keystroke of yours will be carried out not on your computer but on the remote computer! Typing the escape character (usually the control key and the right bracket key pressed at the same time) temporarily interrupts your TELNET session and puts you into the TELNET command mode.

Once you are in the command mode, you can use a couple of commands:

CLOSE

Closes your TELNET connection to the remote computer and either returns you to the command mode (if you started in the command mode) or quits TELNET.

QUIT

Quits the TELNET program; if you are connected to a remote computer, QUIT will disconnect you from the remote computer and then quit TELNET.

SET ECHO

If you can't see what you are typing, or if you type and see double, this command should take care of the problem

(or )

Pressing the enter or return key will take you out of TELNET command mode and return you to your TELNET session.

OPEN

Opens a connection to a remote computer

One last thing and I will let you go: regular TELNET does not work if you are trying to TELNET to an IBM 3270 mainframe computer. You'll have to use TN3270 instead. It works just like TELNET, only the keys on your keyboard may change a little (IBM uses something called map3270 to lay out the keys, and IBM uses a lot of function keys).

Posted bySumedh at 11:49 PM 0 comments  

Labels: Internet

Internet Security

How prevalent is this? According to Mike Godwin, Chief Legal Counsel for the Electronic Frontier Foundation, it's "fairly common." (1)

The main defense against people who want to break into your account -- a.k.a. "crackers" -- is your password. Keep your password secure, and you should never have anything to worry about. Give your password to others, or write your password down and put it near your computer, and ... well, you get the picture.

There are some KEY points you need to remember to protect yourself and your account:

• NEVER give your password to anyone (1). The whole purpose of having a password in the first place is to ensure that no one other than you can use your account.
  
  
• NEVER write your password down, and especially never write your password anywhere near your computer.
  
  
• NEVER let anyone look over your shoulder while you enter your password. "Shoulder Surfing" is the most common way that accounts are hacked.
  
  
• NEVER e-mail your password to anyone.
  
  
• DO change your password on a regular basis (1). There is no better way to thwart a would-be cracker than to change your password as often as possible. Your local Internet service provider will be able to tell you your system's recommendation on how often you should change your password, but a good rule of thumb is to change it at least every three months.
  
  
• DON'T pick a password that is found in the dictionary (1). When you set your password, it is encrypted and stored into a file. It is really easy for a "cracker" to find your password by encrypting every word in the dictionary, and then looking for a match between the words in his encrypted dictionary and your encrypted password. If he finds a match, he has your password and can start using your account at will.
  
  
• DON'T use passwords that are foreign words. The hacker can get a foreign dictionary, and ...
  
  
• NEVER use your userid as your password. This is the easiest password to crack.
  
  
• DON'T choose a password that relates to you personally (2) or that can easily be tied to you. Some good examples of BAD passwords are: your name, your relatives' names, nicknames, birth dates, license plate numbers, social security numbers (US), work ID numbers, and telephone numbers.
  
  
• DO use a password that is at least eight characters long and that has a mix of letters and numbers. The minimum length of a password should be four to six characters long.
  
  
• NEVER use the same password on other systems or accounts.
  
  
• ALWAYS be especially careful when you telnet or rlogin to access another computer over the Net. When you telnet or rlogin, your system sends your password in plain text over the Net. Some crackers have planted planted programs on Internet gateways for the purpose of finding and stealing these passwords. If you have to telnet frequently, change your password just as frequently. If you only telnet occasionally, say, for business trips, set up a new password (or even a new account) just for the trip. When you return, change that password (or close out that account).

Here are a couple of other good passwords:

   Sentence                                Possible password

  In 1976 I moved to Tulsa, Oklahoma      I76IMTTO
  The conference lost 12,000 dollars      TCL12KD
  U of A Crimson Tide Football is #1      UACTFI#1

Do NOT use well known abbreviations (for example: wysiwyg), and do NOT use keyboard patterns (for example: qwerty) as your password.

If you notice weird things happening with your account:

1. Change your password IMMEDIATELY!
2. Tell your local Internet service provider about it.

Finally, there is one last thing that I want to say before I close: I feel that "hacking" and "cracking" so violates the spirit of the Internet that I will do everything in my power to help put the overgrown babies who engage in such activities where they belong -- behind bars. Until that time comes, however, I'm going to change my password as often as possible.

Posted bySumedh at 11:48 PM 0 comments  

Labels: Internet

E-mail

Almost all e-mail programs have similar, universal functions. The problem is that all of the e-mail programs use completely different commands to access these functions (example: to reply to the author of a current message using the "elm" or "pine" e-mail programs, you type the letter "r"; to do the same function in the VM Mailbook program you have to hit the PF5 key).

I'm not going to be able to discuss all of these functions, but what sort of functions do most e-mail programs have in common? Well, most mail programs have

• a function that will allow you to access and read your incoming mail;
• another to save incoming mail in a file;
• one to print incoming mail;
• one to send new messages;
• one to reply to a message;
• another to include a file in a mail message;
• and one to import/export special objects into your mail messages.

With all of the different e-mail programs out there, and all of the different commands required to run each program, how are you ever going to find out what commands are right for YOUR e-mail program? Easy! Ask your local e-mail service provider! This may shock you, but almost every mail provider provides some sort of instruction sheet or file that will teach you how to use the e-mail program that your provider is running. All you have to do is ask!

I want to take a moment to show you how to actually read an Internet address. I have to admit that when I first started learning how to use e-mail, I was intimidated by the length of all of the Internet addresses. However, once I learned to read the addresses BACKWARDS -- from right to left -- Internet addresses ceased to be a thing of mystery.

Sample Internet Address (mine): PCRISPE1@UA1VM.UA.EDU

The mail server address (the UA1VM.UA.EDU part of the above example) is actually called the "domain" name, and it is based on something called an IP (or Internet Protocol) address.

Each server connected to the Internet has a numerical IP address. The IP address is four sets of numbers connected with periods (for example, the IP address for the mail server that I am using at the University of Alabama is 130.160.4.100).

Fortunately, the powers that be realized that people remember NAMES better than numbers, and they created the domain name system. The domain name system associates the numerical IP address with an easier to remember "name" (for example, thanks to the domain name system, the IP address 130.160.4.100 becomes a much easier to remember UA1VM.UA.EDU).

You may run into IP addresses from time to time when you are FTPing or telnetting (we'll talk about both of these tools in several lessons later on). Just remember than an IP address (the four sets of numbers connected with periods) is simply another way to write a domain name, and you will do fine. Both IP addresses and domain names should work equally well.

Anyway, back to the "p-crispy-one" example. Remember that my domain name is UA1VM.UA.EDU? Well, as I said earlier, the best way to read an Internet address -- and, for that matter, a domain name -- is from right to left. Domain names are broken down as follows:

     EDU     Educational sites in the U.S.
    COM     Commercial sites in the U.S.
    GOV     U.S. Government sites
    NET     Network administrative organizations
    MIL     U.S. Military sites
    ORG     U.S. Organizations that don't fit into other categories
    SU      Soviet Union (yes, there is still a Soviet Union ...
            at least on the Internet)
    FR      France
    CA      Canada
    ...     (other counties have their own country code)

The rest of the UA1VM.UA.EDU domain name lists the "subdomains" that tell you where my mail server is actually located. UA is the University of Alabama, and UA1VM is the name of my mail server's machine.

So, PCRISPE1@UA1VM.UA.EDU is the Internet address for someone named "p-crispy-one" (stop laughing!!) at some U.S. educational site. Further investigation shows that the site is at the University of Alabama, and that the machine "p-crispy-one" is using is called UA1VM.

Another Sample Internet Address: w.v.braun@hq.msfc.nasa.gov

So we know that w.v.braun@hq.msfc.nasa.gov is the address of some person named w.v.braun whose mail server is at the Headquarters of the Marshall Space Flight Center, and that the Marshall Space Flight Center is part of NASA, which itself is part of the U.S. government.

What can you tell from the Internet address ike@saceur.pentagon.army.mil? A lot, especially if you are a history buff, and if you know that "saceur" is the military abbreviation for Supreme Allied Commander-Europe.

The best rule of thumb I can give you about Internet addresses is this: if the address is not of the form described above and does not end with one of the standard top-level domain abbreviations or country codes, the address is not an Internet address. You may still be able to send mail to non-Internet addresses through a gateway, though.

Homework:

Also, please remember that you must send your GET commands in the body of a new e-mail letter to LISTSERV@UA1VM.UA.EDU.

1. I want you to find the following two commands for your mailer:
   • the command that allows you to delete an e-mail letter without having to read the letter
     
   • the command that allows you to delete an e-mail letter after you have read the letter
   You will soon discover that these two commands are the most important, and most used, e-mail commands you will ever use.
   
   
2. If you have "Level Two" or "Level Three" connectivity and are on a UNIX, VAX/VMS, or VM system, there are three files I want you to GET from the University of Alabama's LISTSERV file server (see MAP02: LISTSERV File Server Commands for a review of the GET command). The files are from Richard Smith's "Navigating the Internet" workshop, and Richard was kind enough to give me permission to use them in this workshop.
   The first file covers the basic e-mail commands for the UNIX, VAX/VMS, or VM systems. The second file covers the commands to send e-mail, and the third file covers the reply function.
   Remember when using the GET command that your commands must be sent to the LISTSERV address, not to the list or to me.

         UNIX USERS:                       VAX/VMS USERS:
          filename    filetype              filename    filetype
            UNIX        1                     VMS         1
            UNIX        2                     VMS         2
            UNIX        3                     VMS         3
   
        VM USERS:
          filename    filetype
            VM          1
            VM          2
            VM          3
   

   You will have to use three GET commands (one for each file), but you can put all three GET commands in one letter. For example, if I wanted to get all three of the VM files, the body of my letter would look like this:

             GET VM 1 F=MAIL
            GET VM 2 F=MAIL
            GET VM 3 F=MAIL
   

   Please remember to send your GET commands -- or *any* other LISTSERV commands -- in the *body* of an e-mail letter sent to LISTSERV@UA1VM.UA.EDU.
   
   
3. If you are not on a UNIX VAX/VMS, or VM system -- or if you are not sure what sort of system you are on -- contact your local Internet provider and ask for some information on how to use your mail program.
   In particular, you should ask for information on how to:
   • access your e-mail program
   • open and read an e-mail letter sent to you
   • save an e-mail letter to a file
   • print an e-mail letter
   • send a new e-mail letter to someone
   • reply to an e-mail letter sent to you
   • include text in a reply (and how to edit this text)
   You probably know how to do most of these things, but it never hurts to review it from time to time.
   
   
4. If you would like to get a list of all of the Internet Country Codes, use the GET command to get the file COUNTRY CODES from the University of Alabama's LISTSERV file server.

Posted bySumedh at 11:47 PM 0 comments  

Labels: Internet

Levels of Internet Connectivity

There are generally three levels of Internet connectivity (although there are several variations on the three levels). For our purposes, I am just going to call these three levels "Level One," "Level Two," and "Level Three."

Before I talk about the three levels of connectivity, experience shows that I have to say the following to keep myself from being overrun with e-mail: the "three-level approach" to Internet connectivity is a very simplified view of the different ways that you can access the Internet. It does not take into account UUCP, TIA, Trumpet Winsock, or the recent expansion of some BBS' into a combination Level I and Level II access. This over-simplification is on purpose! Please recognize that I have taken some editorial liberties in this lesson to make the lesson easier to understand for the new users (aka. "newbies").

Level One connectivity ("access through a gateway") is access to the Internet from a network that really isn't "on" the Internet. Picture two circles that touch each other at only one point. One of the circles is the Internet, and the other circle is a non-Internet network. The point where the two networks touch is called a gateway. The gateway allows the two networks to "talk" to each other, but users of the non-Internet network are limited in their ability to fully access all of the tools of the Internet. With Level One connectivity, you are limited to what you can access on the Internet by what your service provider allows you to access.

A good example of networks with Level One connectivity is America On-Line (AOL), Compuserve, Prodigy, and many of the other commercial on-line services. AOL is, in effect, its own little network. It has a great number of different programs that its subscribers can use, but ALL of these programs only run on the AOL network.

AOL subscribers, and the subscribers to most of the other commercial on-line services, are lucky in the fact that they can still access SOME of the tools of the Internet through their gateway. A lot of people with Level One connectivity only have e-mail access (by the way, if you have Level One connectivity, do not worry -- I'll show you how to access a lot of the Internet's tools using e-mail (it's not easy, but you can do it)).

Level Two Internet access ("remote modem access") is access through a dial-up terminal connection. This is where, through the use of a modem, you access a "host" and your computer acts like it is a terminal on that mainframe. You may type the commands on your own computer, but it is the host that carries out your commands.

Level Two connectivity is the most "popular" (in the sense that more people have Level Two connectivity than any other level) and the most misunderstood level of connectivity.

To begin with, Level Two connectivity limits you to using the programs (also known as "clients") that are running on the host. If, for example, you hear of this hot new client called "Mosaic" and you want to try it out, if your host does not have a Mosaic client on it you are out of luck! Putting a copy of the Mosaic client software on your own computer won't do ANYTHING for you -- remember that the only programs that you can use when you have Level Two connectivity are the programs that the host has!

Also, with Level Two connectivity you must always remember that everything you are doing is through the host, NOT through your own computer. If you download a file from somewhere (like we did in MAP02: LISTSERV File Server Commands with the GET command) that file will go to the host, NOT to your own personal computer. You'll need to download the file one more time -- this time from the host to your computer -- if you want the file to be on YOUR computer. (Your local Internet provider can tell you more about this).

Level Three connectivity ("Direct Internet Access") is the highest, and most expensive, level of connectivity there is. With Level Three connectivity, you are directly wired into the Internet using high-speed telephone lines, and you are "on-line" twenty-four hours a day, seven days a week. Level Three connectivity is great if you are a mainframe or a major site with hundreds of users, but is not too advantageous if you are a sole user with a beat-up PC.

Besides, Level Three Internet access is so incredibly expensive (1) (the University of Alabama pays $29,000.00 (US) each and every year just to connect to the Internet, and that doesn't include the software, hardware, facility, and staff expenses) that, until recently, Level Three connectivity was limited to large corporations and Universities. Also, because Level Three connectivity is limited mostly to mainframes, you as a user are still limited to using the programs that are already loaded on the mainframe.

Thanks to some recent breakthroughs in modems and telephone lines, there is a new branch of Level Three connectivity which is called "On-Demand Direct Connectivity." Since you probably aren't going to spend twenty-four hours a day on the Internet, there are some sites out there that will let you connect to the Internet whenever you want using a high speed modem and something called "Point-to-Point Protocol (PPP)" or "Serial Line Internet Protocol (SLIP)" connection.

There are two cool things about PPP and SLIP connections. First, because you aren't connected to the Internet all day long, it doesn't cost as much as regular Level Three connectivity (you can find sites that will only charge you about $40 or $50 US (that's about $29,547,952.00 Canadian -- I'm kidding :) -- per month for a PPP or SLIP connection). The second cool thing about PPP and SLIP connections is that the client software is stored on YOUR computer. Want to play with Mosaic? Load it onto your computer and play with it (you can't do this with any of the other levels of connectivity).

The one bad thing about PPP and SLIP connections is that they are a relatively scarce commodity. Not many Internet service providers offer PPP and SLIP connections, but the number of providers offering PPP and SLIP connections will certainly increase over time :)

In review, there are three levels of Internet connectivity:

     LEVEL     DESCRIPTION                 COMMENTS

    One       Access through a Gateway    Limited Internet access.

    Two       Remote modem access         Most "popular".
                                          Commands executed by host.
                                          All programs on host.
                                          Can only run client software
                                            already on the host.
                                          All files on host unless
                                            you download to your computer.

    Three     Direct Access               EXPENSIVE! (1)
                                          24 hour connection.
                                          All software on mainframe.

    --        PPP/SLIP                    Not all that expensive.
                                          Connect when you want.
                                          Client software on YOUR computer!

Posted bySumedh at 11:47 PM 0 comments  

Labels: Internet

LISTSERV File Server Commands

LISTSERV@UA1VM.UA.EDU

SUBSCRIBE ROADMAP YOURFIRSTNAME YOURLASTNAME

SUBSCRIBE listname <>

First off, what is a LISTSERV? Well, a LISTSERV is a mailing list program designed to copy and distribute electronic mail to everyone subscribed to a particular mailing list. We will talk much more about LISTSERVs and LISTSERV commands in MAP05: LISTSERVs and MAP06: Other Mail Servers, but LISTSERVs work on a concept called "mail explosion." A single piece of e-mail is sent to a central address (the LISTSERV's address), and the LISTSERV then "explodes" the letter by duplicating that single letter and sending one copy of that letter to every single person subscribed to a particular mailing list (1). This "mail explosion" concept is what allows anyone subscribed to a LISTSERV to communicate with all the other subscribers with just a single e-mail letter sent to a central address.

Note from the Roadmap Workshop Webmaster:
When I was subscribed to the Third Roadmap Workshop (the one you're reading right now), this is how I received all the lessons.

What we are going to talk about, however, is the LISTSERV file server. In an effort to keep this group's mail volume to a minimum, I've placed many of the "optional" workshop files on the University of Alabama's LISTSERV file server.

What is a LISTSERV file server? Well, besides distributing letters, LISTSERVs can also serve as a "library" of files -- files that you can retrieve using nothing but a simple e-mail letter sent to the LISTSERV's address with a few simple commands in the body of that letter.

If you had subscribed to the Roadmap list, you would have mailed an e-mail letter to LISTSERV@UA1VM.UA.EDU with this command in the body of your letter:

SUBSCRIBE list-name <>

GET filename filetype F=format

GET

tells the LISTSERV that you want it to send a file to you.

filename filetype

tells the LISTSERV the name of the file that want it to get
(for example: COPY NOTICE, ROADMAP 94-00001, RFC 1462, etc.).

F=format

tells the LISTSERV how you want the file sent to you. For what we are doing, lets use F=MAIL (that way the LISTSERV will e-mail the files to you).

1. Address an e-mail letter to LISTSERV@UA1VM.UA.EDU (remember, you are about to send a command, and all commands must be sent to the LISTSERV address).
   
   
2. In the body of your letter type GET COPY NOTICE F=MAIL

Think you can handle this? I hope so ... because this is your first homework assignment (eeeeek!). There are three files on the LISTSERV file server at the University of Alabama (LISTSERV@UA1VM.UA.EDU). Those files are:

     filename   filetype          description

    COPY       NOTICE            The Copyright notice for the entire
                                 Roadmap workshop, along with the
                                 workshop's acknowledgments.

    NET        INTRO             My own special explanation of what
                                 the Internet is and how it works.

    RFC        1462              The OFFICIAL "What is the Internet"
                                 RFC/FYI by Krol and Hoffman (this is
                                 kind of advanced stuff)

That's your homework.

IMPORTANT NOTE: You must write a new letter to LISTSERV@UA1VM.UA.EDU for your GET commands to work. Replying to this letter will not work!

If, after an incredible amount of time has passed, you have not heard back from the LISTSERV,

1. Double check that you used the correct address:
   LISTSERV@UA1VM.UA.EDU
   That's "you-ay-won-vee-em".
2. Make sure the GET command is in the BODY of your letter.
3. Finally, make sure that you have included all of the parts of the GET command:
   
   GET filename filetype f=format

Have fun :)

Posted bySumedh at 11:46 PM 0 comments  

Labels: Internet

Current Web Architecture
Thursday, November 27, 2008

Introduction

This section of the Internet Tool Survey describes the current architecture of the World Wide Web (WWW). The NCSA Glossary is a useful starting point for Web terms. Another is the ILC glossary of Internet Terms.

The following sections describe

• the basic two-tier architecture of the web in which static web pages (documents) are transferred from information servers to browser clients world-wide,
• extensions that permit three-tiered architectures where content pages can be constructed dynamically and where programs as well as data can be transferred,
• other information transfer protocols, and
• related standards.

Basic Web Architecture

The basic web architecture is two-tiered and characterized by a web client that displays information content and a web server that transfers information to the client. This architecture depends on three key standards: HTML for encoding document content, URLs for naming remote information objects in a global namespace, and HTTP for staging the transfer.

• HyperText Markup Language (HTML) - the common representation language for hypertext documents on the Web. HTML had a first public release as HTML 0.0 in 1990, was Internet draft HTML 1.0 in 1993, and HTML 2.0 in 1994. The September 22 1995 draft of the HTML 2.0 specification has been approved as a standard by the IETF Application Area HTML Working Group. HTML 3.0 and Netscape HTML are competing next generations of HTML 2.0. Proposed features in HTML 3.0 include: forms, style sheets, mathematical markup, and text flow around figures. For more detailed information, see the HTML Reference Manual.
  HTML is an application of the Standard Generalized Markup Language (SGML ISO-8879), an international standard approved in 1986, which specifies a formal meta-language for defining document markup systems (more here and here). An SGML Document Type Definition (DTD) specifies valid tag names and element attributes. HTML consists of embedded content separated by hierarchical case sensitive start and end tag names which may contain embedded element attributes in the start tag. These attributes may be required, optional, or empty. In addition, documents can be inter or intra linked by establishing source and target anchor points. Many HTML documents are the result of manual authoring or word processing HTML converters, but now several WYSIWYG editors support HTML styles -- see listing at W3C and the Internet Tools Survey section on Authoring HTML.
  HTML files are viewed using a WWW client browser (software), the primary user interface to the Web. HTML allows for embedding of images, sounds, video streams, form fields and simple text formatting. References, called hyperlinks, to other objects are embedded using URLs (see below). When an object is selected by a hyperlink, the browser takes an action based on the URL's type, e.g., retrieve a file, connect to another Web site and display a HTML file stored there, or launch an application such as an E-mail or newsgroup reader.
• Universal Resource Identifier (URI) - an IETF addressing protocol for objects in the WWW ("if it's out there, we can point at it"). There are two types of URIs, Universal Resource Names (URN) and the Universal Resource Locators (URL). The current IETF URI spec is here and the URL spec is here.
  URLs are location dependent and contain four distinct parts: the protocol type, the machine name, the directory path and the file name. There are several kinds of URLs: file URLs, FTP URLs, Gopher URLs, News URLs, and HTTP URLs. URLs may be relative to a directory or offsets into a document. Arguments to CGI programs (see below) may be embedded in URLs after the ? character.
• HyperText Transfer Protocol (HTTP) - an application-level network protocol for the WWW. Tim Berners-Lee, father of the Web, describes it as a "generic stateless object-oriented protocol." Stateless means neither the client nor the server store information about the state of the other side of an ongoing connection. Statelessness is a scalability property but is not necessarily efficient since HTTP sets up a new connection for each request, which is not desirable for situations requiring sessions or transactions.
• In HTTP, commands (request methods) can be associated with particular types of network objects (files, documents, network services). Commands are provided for
• establishing a TCP/IP connection to a WWW server,
• sending a request to the server (containing a method to be applied to a specific network object identified by the object's identifier, and the HTTP protocol version, followed by information encoded in a header style),
• returning a response from the server to the client (consisting of three parts: a status line, a response header, and response data), and
• closing the connection.
• HTTP supports dynamic data representation through client-server negotiation. The requesting client specifies it can accept certain MIME content types (more on this below) and the server responds with one of these. All WWW clients can handle text/plain and text/html.
• HTTP/1.0 Internet Draft 05 (the seventh release of HTTP/1.0) is targeted as an Internet Informational RFC. The next immediate version of HTTP is HTTP/1.1 Internet Draft 01.

Web Architecture Extensibility

This basic web architecture is fast evolving to serve a wider variety of needs beyond static document access and browsing. The Common Gateway Interface (CGI) extends the architecture to three-tiers by adding a back-end server that provides services to the Web server on behalf of the Web client, permitting dynamic composition of web pages. Helpers/plug-ins and Java/JavaScript provide other interesting Web architecture extensions.

• Common Gateway Interface(CGI) - CGI is a standard for interfacing external programs with Web servers (see Figure 1). The server hands client requests encoded in URLs to the appropriate registered CGI program, which executes and returns results encoded as MIME messages back to the server. CGI's openness avoids the need to extend HTTP. The most common CGI applications handle HTML
  and commands.

  • CGI programs are executable programs that run on the Web server. They can be written in any scripting language (interpreted) or programming language (must be compiled first) available to be executed on a Web server, including C, C++, Fortran, PERL, TCL, Unix shells, Visual Basic, Applescript, and others. Security precautions typically require that CGI programs be run from a specified directory (e.g, /cgi-bin) under control of the webmaster (Web system administrator), that is, they must be registered with the system.
  • Arguments to CGI programs are transmitted from client to server via environment variables encoded in URLs. The CGI program typically returns HTML pages that it constructs on the fly.
  • Some problems with CGI are:
  • the CGI interface requires the server to execute a program
  • the CGI interface does not provide a way to share data and communications resources so if a program must access an external resource, it must open and close that resource. It is difficult to construct transactional interactions using CGI.
  • The current version is CGI/1.1. W3C and others are experimenting with next generation object-oriented APIs based on OMG IDL; Netscape provides Netscape Server API (NSAPI) and Progress Software and Microsoft provide Internet Server API (ISAPI).



• Helpers/Plug-ins - When a client browser retrieves a file, it launches an installed helper application or plug-in to process the file based on the file's MIME-type (see below). For example, it may launch a Postscript or Acrobat reader, or MPEG or QuickTime player. A helper application runs external to the browser while a plug-in runs within the browser. For information on how to create new Netscape Navigator plug-ins, see The Plug-in Developer's Guide.
• Common Client Gateway (CCI) - this gateway allows a third-party application to remotely control the Web browser client. Netscape Client APIs 2.0 (NCAPIs) depends on platform specific native methods of interprocess communication (IPC). They plan to support DDE and OLE2 for Windows clients, X properties for UNIX clients, and Apple Events for Macintosh clients.
• Extensions to HTTP. W3C and IETF Application Area HTTP Working Group are working together on current and future versions of HTTP. The HTTP-NG project is assessing two implementation approaches to HTTP "replacements":
• Spero's approach - allows many requests per connection, the requests can be asynchronous and the server can respond in any order, allowing several transfers in parallel. A "session layer" divides the connection into numerous channels. Control messages (GET requests, meta information) are returned in a control channel; each object is returned in its own channel.
• W3C approach - Jim Gettys at W3C is using Xerox ILU (a CORBA variant) to implement an ILU transport similar to Spero's session protocol. The advantages of this approach are openness with respect to pluggable transport protocols, support for multiple language environments, and a step towards viewing the "web of objects." Related to this approach, Netscape recently announced future support for OMG Internet Inter-ORB Protocol (IIOP) standard on both client and server. This will provide a uniform and language neutral object interchange format making it easier to construct distributed object applications.
• Java/ JavaScript - Java is a cross-platform WWW programming language modeled after C++ from Sun Microsystems. Java programs embedded in HTML documents are called applets and are specified using tags. The HTML for an applet contains a code attribute that specifies the URL of the compiled applet file. Applets are compiled to a platform-independent bytecode which can be safely downloaded and executed by the Java interpreter embedded into the Web browser. Browsers that support Java are said to be Java-enabled. If performance is critical, a Java applet can be compiled to native machine language on the fly. Such a compiler is known as a Just-In-Time (JIT) compiler.
  JavaScript is a scripting language designed for creating dynamic, interactive Web applications that link together objects and resources on both clients and servers. A client JavaScript can recognize and respond to user events such as mouse clicks, form input, and page navigation, and query the state or alter the performance of an applet or plug-in. A server JavaScript script can exhibit behavior similar to common gateway interface (CGI) programs. JavaScript scripts are embedded in HTML documents using

Posted bySumedh at 11:10 PM 0 comments  

Labels: Internet, WWW

Blogs and RSS
Wednesday, November 26, 2008

The Web is a welcoming medium for experimentation and user participation. It is becoming easier to post Web content and share comments with other users. The idea of the Web site is still very much alive, but Web participation is taking new forms and being driven by new technologies that foster social interaction. Here are two of the latest trends.

Blogs: A blog is an easy-to-create Web site that allows users to share their thoughts with the world managed by a lightweight content management system. The word "blog" comes from "Weblog" because a blog consists of a signed and dated log of individual postings. The topic of the blog can be anything, from the personal to the professional. A blog is what you make of it.

What is important about blogs is the content management system that manages the content. This system can offer a variety of features that can make the blog a useful tool. Examples include a calendar view of postings, organization of postings into categories, archived postings, options to send e-mail notification of new postings, and so on.

Blogging can be an interactive activity. Readers can add comments to a blogger's postings, other can respond, and a conversation ensues. Lately, bloggers have become well-known commentators on the political scene, but blogging can encompass any topic or no topic at all. If the blogging software allows it, bloggers can use RSS to distribute their postings.

Visit Technorati, a search engine devoted to locating blogs. You can set up your own blog by visiting Blogger.

RSS: RSS allows people to place news and other announcement-type items into a simple XML format that can then be pushed to RSS readers and Web pages. The initials RSS can stand for different things, including Rich Site Summary or Really Simple Syndication. Users can subscribe to the RSS newsfeeds of their choice, and then have access to the updated information as it comes in. RSS is used for all kinds of purposes, including the news itself and announcing new content on Web sites.

RSS content may be read by using an RSS reader, or aggregator. This is usually free software that you can install on your computer that posts new items and stores old ones in a graphical interface. An RSS reader similar to e-mail software in that it displays incoming items and can store content for offline reading. Subscribing to a newsfeed is usually as simple as entering the address of the RSS document.

A useful list of RSS readers is available on the site of RSS Compendium.

It is also possible to subscribe to and read your own collection of RSS feeds on Web sites devoted to this purpose. Bloglines is one such example. The advantage here is that you can access your RSS feeds from any computer that is connected to the Web.

Posted bySumedh at 11:08 PM 0 comments  

Labels: Internet, WWW