IEC'00 ns Lab 2 - advanced simulation in ns

It is equivalently important to understand the ns-2 output trace format and have some knowledge on how to extract relevant information for your research. This exercise is dedicated to familiarize you with ns-2's output format, in particular by namtrace-all, and techniques to do trace post-processing.

Trace Format

As a result of previous exercise, we obtain an output file, out.nam. It contains information of all packets enqueued (+), dequeued (-), transmitted over to another hop (h), and etc.

• Take a look at out.nam
  
• Ignore entries with -t *; these entries are to set up network topology in nam
  
• The rest of the entries look like:
  • [event type] -t [time] -s [src node] -d [dst node] -p [pkt type] -e [pkt size] -c [color] -i [pkt id] -a [flow id] -x {[src.port] [dst.port] [seqno] ------- null}
    
  • [event type]: +, -, h, d
• Guess what +, -, h, and d mean

Extracting Useful Information
Extract information from the out.nam file and compute the total bytes of TCP (tcp) and UDP (cbr) traffic over link 4-3 for the duration of the simulation. Then, compute total TCP and UDP/CBR traffic in bytes and ratios of TCP and UDP/CBR to the total. Finally, Comment on the bandwidth share of TCP vs. UDP/CBR.

• Fill in the blanks according to your understanding of trace format in the following awk command and compute total bytes of TCP traffic

  awk '$1=="r" && ??==4 && ??==3 && $9=="??" {a += ??} END {print a}'
      

• Modify your awk command to compute the total bytes of UDP/CBR traffic.
  
• Compute the total of TCP and UDP/CBR traffic
  
• Compute the ratios of TCP and UDP/CBR traffic
  Here is a more elaborated awk script
  
• Do you see more TCP or UDP/CBR traffic?
  
• Collect similar statistics for the same simulations that contain only the TCP or UDP/CBR flow

References:

• The main VINT/ns page
• The ns documentation page
• The ns on-line manual page
• An on-line C++ Tutorial