Here is an activity that you can do with your class to demonstrate how e-mail messages are delivered on the Internet.

You will need some string or yarn and a duplicated copy of the Demonstration E-Mail Message pages that follow the Background Information and Directions sections of this lesson. This Demonstration E-Mail Message will be cut into "packets" for the activity.

Background Information:

When you send a message via the traditional postal service, you compose the entire message on a piece of paper, put it in an envelope, attach a stamp and drop the envelope in a mailbox.

A mail carrier picks up the letter and takes it back to the local post office. Here a postal worker checks the address and postal code, and drops it in a mailbag headed to the destination shown on the envelope. The mailbag is transported by truck or airplane to the target destination.

At the destination post office, another postal worker reads the local address, and adds the letter to a pile of mail about to be delivered by another mail carrier. If all goes well, the letter arrives at the destination you specified on the envelope.

The method by which e-mail messages are delivered has some similarities and several important differences. Here's how it works.

You compose the e-mail message on your e-mail software and address it to the e-mail address of the recipient. When you log on to your Internet Service Provider and send the e-mail, the message is delivered to the mail server computer at your ISP.

At this point a major difference from surface mail occurs. The mail server computer examines the e-mail address of the recipient, breaks the message up into "packets" (smaller pieces of a whole message), adds some header codes to keep track of how many packets should be in the message, and starts the packets on their way to the destination e-mail address.

Since the Internet was designed to operate in the event of the worst-case scenario of a nuclear war with the possibility of broken communication links, not all the packets will necessarily travel by the same route. If a link is temporarily unavailable, the Internet just re-routes the message to a different link.

As the packets begin arriving at the mail server of the destination address, this computer reads the header message and reassembles the message. If some packets are missing, a request is sent back to the original server asking for retransmission of the missing packets.

When all the packets have arrived, the mail server notifies the recipient that they have an e-mail message ready for delivery ("You've Got Mail"). The recipient of your original e-mail message may be getting a message that has traveled through many different Internet Links to reach its final destination. Some e-mail software packages include the header codes at the bottom of the message. (You were wondering what all that gibberish was, weren't you?)

Directions:

1. Cut 3 to 5 foot pieces of string or yarn for every member of your class.
2. Starting in one corner of the room, distribute the string to class members.
3. The sending "mail server" at the beginning of the path should have several links of string leading away from their location.
4. Other class members may have one or more links entering and leaving their location.
5. The links should travel across the classroom and end in multiple links to the receiving "mail server" at the other end of the room.
6. Point out to the students that there are multiple paths leading across the room. (You will note that this actually resembles the "web" analogy that is mentioned so often when referring to the Internet.
7. The sending "mail server" starts the demonstration by passing the "Packets" (message pieces) in random order to any other student who is connected to them by a length of string.
8. Students who receive a "packet" (message) will in turn pass it along to another student who is connected to them by a length of string.
9. As the "packets" begin their journey across the room, the teacher (or a responsible student) will move about the room with a scissors, randomly cutting pieces of string.
10. As the "links go down", students will need to re-route the messages via other connected students (be sure to leave a few links in operation!).
11. The "packets" should all eventually arrive at the receiving "mail server" on the other side of the room where they can be reassembled into the original coherent message.
12. Have the receiving "mail server" read the message to the sending "mail server" for confirmation of the original message and reinforcement of the lesson for the class.
13. Repeat the exercise, re-routing the "packets" in the opposite direction for reinforcement.
14. If you have a "live" internet connection available in the classroom, send yourself an e-mail message. "Check your mail" until the message appears in your "in-box".
15. If any of your students have an e-mail address, send messages to their address. Have them send a return message that can be retrieved the next day.

Click here to print the Demonstration E-Mail Message

Notes: Feel free to substitute a message of your own in place of this one. Merely select an article or short story and subdivide it into smaller "packets". Label each "packet" with a sequential number so the story or article can be reassembled at the receiver end.

If you choose not to complete this optional activity or if your work assignment does not permit easy access to a group of students, just make note of that in the logbook and move on to the next assignment.

Record the date you completed this activity in your logbook.

Credit where credit is due: Many thanks to Carlos French for sharing the original concept of this activity.

The HowStuffWorks site has an interesting article (with illustrations) on How E-Mail Works that older students might find interesting.

How E-Mail Works

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