Homework 16

Details

1. (6) Hope does not allow access to KnowHope from machines that are off campus without first entering a username and password.
   1. Which network layer determines whether or not a username and password will need to be entered? Explain. (Think carefully. What information is used and what layer deals with that information? This question is not about the layer that asks for a username and password.)
   2. How can Hope's web server determine whether or not a machine requesting access to KnowHope is on campus. Give your answer in terms of IP address, subnet mask, network base address, and an appropriate computation.
2. (14) Being the unsavory sort of person you are, you decide to snoop on the network. You see the following packet (which follows the notation from the handout you read):
   

   12:ab:22:83:f8:40|aa:02:ef:23:00:12|198.110.97.7|34.45.125.17|1175|25|2 of 4|nt to do somet
   

   Label machines related to this packet as follows:
   • S is the original source of the packet
   • D is the final destination
   • M1 is the intermediate node that this message just came from
   • M2 is the intermediate node that this message is just being sent to.
   Keep in mind that it is possible that these are not 4 different machines. You need to answer several questions based on the information in the packet.
   • If the information to answer a question is absolutely not contained in the packet, write impossible to determine.
   • If the information to answer a question might be contained in the packet but you cannot be certain, write uncertain, but it might be X, where X is the the possible answer(s).
   Here are the questions.
   1. What is the IP address of S?
   2. What is the IP address of D?
   3. What is the IP address of M1?
   4. What is the IP address of M2?
   5. What is the Ethernet address of S?
   6. What is the Ethernet address of D?
   7. What is the Ethernet address of M1?
   8. What is the Ethernet address of M2?
   9. What is the port number of the application on S that sent the message?
   10. What is the port number of the application on D that the message is being sent to?
   11. What kind of application sent the message?
   12. What kind of application is the message destined for?
   13. What is the content of the message?
   14. Does this packet contain the entire message for the application? How do you know?

   Note: An actual packet will not look like the one above. It will just be raw data that needs to be interpreted to look like the packet above. An actual packet represented in hexadecimal might look like:

       12ab2283f840aa02ef230012e678fc9a128832e6ca89e38eecfdac23549acd0f0ae345ccff52e

   To simplify things for you (so you don't have to do a whole lot of converting), I have simply interpreted the packet for you already. This comment has no bearing on this problem, but I thought it was important enough to point out.