Announcements Sep 16, 2005

1
Announcements (Sep 16, 2005)

• Projects
• Project 1 posted, due on October 2, 2005 500PM
• Create/activate your cereal account at
  http//ilab.cs.rutgers.edu/newaccount.html. Email
  help_at_ilab.cs.rutgers.edu for help.
• Up to 3 students are allowed to work in a group
  for the project
• Midterm 1 is scheduled to be held on October 11,
  2005

2
Announcements (Sep 23, 2005)

• Further clarification about project 1 posted
• Midterm 1
• Scheduled on Oct 11, 2005 during class
• Covers up to network layer
• Sample questions will be posted during the
  weekend

3
Announcements (Sep 30, 2005)

• Midterm 1
• Scheduled on Oct 11, 2005 during class
• Request to attend makeup exams have to reach me
  at least a week before the exam
• Project 1
• Poll packet format

4
Announcements (Oct 4, 2005)

• Project 2 posted
• Due on Nov 6, 2005 500 PM

5
Announcements (Oct 7, 2005)

• Tentative schedule for project 3, midterm 2 and
  final exams posted
• Final (?)
• Dec 13, 2005 640 940 PM
• Dec 16, 2005 400 700 PM (make up)
• Modification on pipeline slides

6
Announcements (Oct 14, 2005)

• Tentative schedule for final exams posted
• Dec 13, 2005 640 940 PM
• Dec 16, 2005 400 700 PM (make up)
• Code review session on project 1
• Will be held during lecture time on Oct 18, 2005
  
• Group members must be present to answer questions
• Schedule for review sequence will be posted online

7
Midterm 1 Project 1 grades

• Midterm 1
• Min 24, Max 116, Avg 70.18, Median 72.5
• A 90,125, B 80,90), B 70,80), C
  60,70), C 50,60), D 40,50), F 0,40)
• Project 1
• Min 60, Max 100, Avg 90.64, Median 99.5
• A 90,100, B80,90), B70,80), C60,70)

8
Project 1 code review summary

• Do arguments checking before using them
• String file args0
• int port Integer.parseInt(args1)
• if(args.length ! 2) System.out.println("Usage
  \n")
• Avoid unnecessary creation of objects
• target t new target25
• t g.getnetwork(file,port)
• public target getnetwork (String file, int
  port)

9
Project 1 code review summary

• Avoid unnecessary allocation of memory
• Dont just use MAX when u can figure out the
  exact required size
• Avoid unnecessary/excessive sub-functions
• Enter/leave another function level causes
  overhead
• Identify correct (most efficient) program logic
• Construct the reply RIP packet outside the
  waiting loop once and for all
• Make use of java package methods
• API http//java.sun.com/j2se/1.5.0/docs/api/
• java.lang, java.util, java.net, java.io
• Comment your code! Again, no excess

10
int -gt byte4

• Normal int type could take up to 4 bytes. To
  convert such a int value to byte array. We need
  to shift the int 8 bits for 4 times and find out
  the byte value for each 8 bits.
• For our RIP metric, since the maximum value is
  16. One byte is sufficient to represent this
  value, so a simple way to do the conversion here
  is to set the first 3 bytes to zero and use the
  single byte value to fill the last bye (assuming
  big endian).

11
Reminder on project 2

• Correct the RIP poll packet checking
• It should contain only the 4 bytes header
• Dont wait till the last minute
• No late submission allowed
• For students cooperating across sections
• Note this down in all your submitted files
• Submit ONLY to ONE of the sections

12
Announcements (Oct 21, 2005)

• Tentative schedule for final exams posted
• Dec 13, 2005 640 940 PM
• Dec 16, 2005 400 700 PM (make up)

13
Announcements (Nov 11, 2005)

• Project 3 posted
• Midterm 2
• 8 questions (110 points)
• topics
• Error detection/correction, 1-d, 2-d parity, CRC
  codes
• Queuing/Traffic shaping - Leaky Bucket/Token
  Bucket
• MAC Layer protocols - Token Ring, x-persistent
  CSMA, CSMA/CD, bitmap protocol, binary countdown
• Ethernet

14
Project 2 code review summary

• Use of threads
• Efficiency in the number of threads
• main, update, purge
• Efficiency in the scheduling of threads
• when to schedule purge threads can be exactly
  calculated no need to enter a constant loop

15
Project 2 code review summary

• Synchronization
• Why we need synchronization?

16
Project 2 code review summary

• Concurrency in data structure itself
• ConcurrentModificationException
• thrown by methods that have detected concurrent
  modification of an object UDP socket can and
  should be reused.
• Note that this exception does not always indicate
  that an object has been concurrently modified by
  a different thread. If a single thread issues a
  sequence of method invocations that violates the
  contract of an object, the object may throw this
  exception. For example, if a thread modifies a
  collection directly while it is iterating over
  the collection with a fail-fast iterator, the
  iterator will throw this exception

17
Project 2 code review summary

• Local routing table is not necessarily the same
  as what will be sent in the RIP packet.
• Local table can contain a lot more fields to
  assist local operation like stale entry purge.
• Conversion from table to RIP packet is
  essentially the same as project 1 except that
  some care should be taken to implement the poison
  reverse.

18
Project 2 code review summary

• Time interval should be implemented by using
  Timer
• Counting does not directly map to seconds,
  minutes !