CMPE 401 - Computer Interfacing

Assignment #3

Due: In the CMPE 401 assignment box at 15:45 on Friday, Oct. 28, 2005

  1. Briefly explain how the 68681 DUART provides features that support hardware flow control using the RS-232C signals request-to-send (RTS) and clear-to-send (CTS).

  2. In TCP/IP, error detection and recovery occurs on an end-to-end basis. For example, errors in a data stream that is transmitted from a source node to a destination node are only detected when the data reaches the destination node. Minimal effort is expended ensuring reliable transmission over each individual node-to-node link along a communication path. Does this strategy (error control at a relatively high protocol layer) make sense when the probability of transmission errors is relatively high or relatively low across each node-to-node link. Be sure to carefully justify your answer. Hint: The older X25 computer communications protocol performed error detection on a node-to-node basis.

  3. TCP/IP provides reliable transport of an ordered stream of data bytes for all higher layers. No packet boundaries or higher-level structure in the data is recognized. Comment on whether or not this approach would be either an advantage or a disadvantage to ensuring the widespread adoption of TCP/IP over interconnections of a variety of different computer networks.

  4. Use whatever resources that you can find to determine what the Internet protocols FTP, SMTP and SNMP are used for. In your own words, briefly explain what the protocols accomplish. Be sure to indicate all of the references that you used to obtain your answers.

  5. UDP is considered to be a lightweight alternative to TCP. What is meant by the word "lightweight" in this context? For which applications would a lightweight protocol be preferred over a "heavyweight" protocol? In which applications would a lightweight protocol be undesirable? Be sure to carefully explain your answers.

  6. The Hypertext Transfer Protocol (HTTP) encodes the "request" and "response" messages using human-readable ASCII character strings. Briefly explain what some of the advantages and disadvantages would be of using ASCII strings in this context. Why would the advantages outweight the disadvantages in the specific case of this protocol?