Week 4: The Transport Layer

Goals:

• Learn to use the sockets API and, optionally, select, to implement a simple chat application.
  
• Understand how UDP and TCP provide basic transport layer services: multiplexing and reliability.

Monday, February 13: Multiplexing; UDP

Read:

• Kurose & Ross 3.0 - 3.3, pp. 197 - 216
  

Answer the following questions. Send your answers in the body of an email to me (davisjan@cs.grinnell.edu) by 9 a.m. Please use "CSC-364 02-13" as the subject line of your email.

1. How does demultiplexing in TCP differ from demultiplexing in UDP?
   
2. Kurose & Ross 3.P3
   
3. What was the most surprising and/or confusing point in today's reading?
   
   
4. Think back to our game on the first day of class (sending a message via sticky notes). What techniques did you use to transmit the message reliably? (If you were not part of this game, what techniques might you use?)
   
5. I strongly encourage you to work with a partner on the next lab because it involves programming in C and learning new APIs. Please indicate your preference as follows:

   [ ] Please assign me a partner.
   [ ] I prefer to work by myself or find my own partner.
   

Due:

• Lab 4: Application Protocols

• Lab 5: Sockets

Wednesday, February 15: Reliable data transfer

Read:

• Kurose & Ross 3.4, pp. 216 - 242

• Go-Back-N Protocol applet
• Selective Repeat Protocol applet

Answer the following questions. Send your answers in the body of an email to me (davisjan@cs.grinnell.edu) by 9 a.m. Please use "CSC-364 02-15" as the subject line of your email.

1. What new mechanism is required for reliability if packets can be lost?
   
2. What is the most important drawback of a stop-and-wait protocol? How do we overcome that drawback?
   
3. What is the essential difference between Go-Back-N and Selective Repeat?
   
4. I would like to focus on pipelined protocols (3.4.2 - 3.4.4) unless there are big questions about section 3.4.1. What questions would you like to talk about in class?
   

Friday, February 17: TCP

Read:

• Kurose & Ross 3.5, pp. 242 - 271

• Flow Control applet

Answer the following questions. Send your answers in the body of an email to me (davisjan@cs.grinnell.edu) by 9 a.m. Please use "CSC-364 02-17" as the subject line of your email.

1. Respond to each of "true or false" questions in 3.R14. Briefly explain your reasoning and/or cite a page number and (top, middle, bottom) as your source.
   
2. What questions would you like to talk about in class?

Suggested problems: 3.P23, 3.P24, 3.P25. 3.P26, 3.P27

Janet Davis (davisjan@cs.grinnell.edu)