Week 3: Direct Link Networks (1)

Summary: We consider the problems of sending data reliably between two computers directly connected by a network.

Goals:

• Consider the physical layer: nodes and links.
• Compare approaches to encoding binary data and messages as signals transmitted over a medium.
• Develop approaches to detecting and correcting bit errors, burst errors, and lost frames.
• Get a handle on the workload for this class. As we discussed, please keep track of the amount of time you spend on different assignments this week.

• On to Week 4, Direct Link Networks (2)

Monday, February 2: Hardware, coding, and framing

Read:

• P&D, 2.0 - 2.3, p. 64-92

Briefly answer the following questions. Send your answers in the body of an email to me (davisjan@cs.grinnell.edu) by 11 a.m. Please use "CSC-364 02-02" as the subject line of your email. For problems, write a one-line answer. You need not present your entire approach.

1. What is the most important thing that you learned from the reading?
2. What's a question you still have about the reading?
3. Explain the purpose of character stuffing and bit stuffing. How does SONET avoid using them?
4. P&D exercise 2.8
5. P&D exercise 2.9
6. About how long did you spend on the reading and problems?

Tuesday, February 3, 5 p.m.: Abstract 2 due

Submit an abstract. You may choose between the following assignments.

• RFC 2026, "The Internet Standards Process." 
• Continue learning about IETF process. Does the process seem effective? fair? efficient? What tradeoffs did the IETF make in designing its process? What critique would you offer?
  
• A. Cox (1996). Network buffers and memory management. Linux Journal, October 1996. Accessed January 24, 2007, at http://www.linuxjournal.com/article/1312. 
• Read about network buffers in Linux. Explain and critique this approach. If you are interesting in going further, do some additional research on the FreeBSD mbuf data structure and compare to Linux's sk_buf.

Wednesday, February 4: Reliable transmission

Read:

• P&D 2.4 - 2.5, p. 92-116

Briefly answer the following questions. Send your answers in the body of an email to me (davisjan@cs.grinnell.edu) by 11 a.m. Please use "CSC-364 02-04" as the subject line of your email.  For problems, write a one-line answer. You need not present your entire approach.

1. What is the most important thing that you learned from the reading?
2. What's a question you still have about the reading?
3. P&D exercise 2.11. There are three cases to consider for the locations of the three errors; try writing one sentence for each case.
4. P&D exercise 2.22. Focus on the last part of the exercise: Why do we prefer ACKs to NAKs?
5. P&D exercise 2.23
6. About how long did you spend on the readings and problems?

Friday, February 6: Lab 4

• Report on hours spent on different assignments this week. Please email me your tabulation of hours and let me know how you feel about it.
• Lab 3: Measuring throughput with ttcp

Assigned: 

• Lab 4: Observing an Ethernet with Wireshark

Janet Davis (davisjan@cs.grinnell.edu)