Reference no: EM133218020

Question 1. See if you can compute the checksum as TCP/IP does. Run the applet, using any message. Select a data packet, but don't select the last packet because it might be too short, less than 10 characters.

Question 2. Count up the characters, including blanks. If they do not equal 10, assume there are blanks at the end so that the character count is 10.

Question 3. Using the "Text Encoding in ASCII" applet from lab2, type in the characters from the data packet, and click on translate text. (You can use an ASCII chart instead if you'd prefer).

Question 4. Add up the values for each of the characters. Then take the modulus of this number using 256. The modulus operator is available on some computer calculators and is represented by mod, but you can easily compute it by dividing the total by 256 and saving only the remainder. For instance, suppose the total is 650. Since 650 ÷ 256 = 2.5390, but we only want the remainder or 138 which is obtained as: (650 - (2 * 256) = 138).

Question 5. Compare your manually computed checksum (use the approach that was given in the class and question 4) for the first packet of the message Introduction to Computer Science against what the applet shows for the packet. Do they agree?

Question 6. Now damage your packet by altering one character (for instance change the C to any other character). Re-compute the checksum. You should realize how the applet can spot errors?

Question 7. Think of a way that a packet can be damaged and still have the same checksum as the undamaged version (There are several possibilities. Imagine that two or more bytes are altered at the same time). Give one example for this scenario.