Manual interpretation of ns2 trace file

If you have generated a trace file from running a ns tcl script, you should be able to analyze it without the use of any tools. This could come handy in emergencies when you don’t have any tools (Tracegraph,perl scripts etc) at hand.

The following method has been suggested at a ns mailing list.

To find the interpretation of all possible trace format when you do the wireless simulation, you’d better read the code of ns2 in file ns2home/trace/cmu-trace{.h, .cc}.

where ns2home denotes the location of ns-allinone-* installation folder.

Usually the format looks like this:

ACTION: [s|r|D|f]: s -- sent, r -- received, D -- dropped,f -- forwarded
WHEN: the time when the action happened
WHERE: the node where the action happened
LAYER: AGT -- application,
 RTR -- routing,
 LL  -- link layer (ARP is done here)
 IFQ -- outgoing packet queue (between link and mac layer)
 MAC -- mac,
 PHY -- physical
SEQNO: the sequence number of the packet
TYPE: the packet type
  cbr -- CBR data stream packet
  DSR -- DSR routing packet (control packet generated by routing)
  RTS -- RTS packet generated by MAC 802.11
  ARP -- link layer ARP packet
SIZE: the size of packet at current layer, when packet goes down,
  size increases, goes up size decreases
[a b c d]: a -- the packet duration in mac layer header
  b -- the mac address of destination
  c -- the mac address of source
  d -- the mac type of the packet body
[......]: [
  source node ip : port_number
  destination node ip (-1 means broadcast) : port_number
  ip header ttl
  ip of next hop (0 means node 0 or broadcast)

So if you have a line like this

s 76.000000000 _98_ AGT – – – – 1812 cbr 32 [0 0 0 0] ——- [98:0 0:0 32 0]

in your trace file.

You should interpret it as

Application 0 (port number) on node 98 sent a CBR packet whose ID is 1812 and size is 32 bytes, at time 76.0 second, to application 0 on node 0 with TTL is 32 hops. The next hop is not decided yet.

Similarly, You should be able to interpret a line such as this:

r 0.010176954 _9_ RTR – – – – 1 gpsr 29 [0 ffffffff 8 800] ——- [8:255 -1:255 32 0]


The routing agent on node 9 received a GPSR broadcast (mac address 0xff, and ip address is -1, either of them means broadcast) routing packet whose ID is 1 and size is 29 bytes, at time 0.010176954 second, from node 8 (both mac and ip addresses are 8), port 255 (routing agent).

If you choose to play safe by making use of Tracegraph, then <this> post might help you.


Recently, I chanced to read <this manual> by Eitman Altman and manual is well organised for intermediate learners in ns2. I have extraced the ns2 trace file part from that and presented it below.

r 40.639943289 _1_ AGT —- 1569 tcp 1032 [a2 1 2 800] —-  [0:0 1:0 32 1] [35 0] 2 0

* The first field is a letter that can have the values r,s,f,D for “received”,”sent”,”forwarded” and “dropped”, respectively.It can also be < for giving a location or a movement indication.
* The second field is the time.
* The third field is the node number.
* The fourth field is MAC to indicate if the packet concerns a MAC layer, it is AGT to indicate the transport layer(e.g. tcp) packet, or RTR if it concerns the routed packet. It can also be IFQ to indicate events related to the interference priority queue(like drop of packets).
* After the dashes come the global sequence number of the packet(this is not the tcp sequence number).
* At the next field comes more information on the packet type(eg. tcp,ack or udp).
* Then comes the packet size in bytes.
* The 4 numbers in the first square brackets concern the mac layer information. The first hexadecimal number,a2(which equals 162 in decimal) specifies the expected time in seconds to send this data packet over the wireless channel. The second number,1, stands for the MAC-id of the sending node, and the third,2, is that of the receiving node. The fourth number,800, specifies that the MAC type is ETHERTYPE_IP.
* The next numbers in the second square brackets concern the IP source and destination addresses, then the ttl(Time To Live) of the packet(in our case 32),
* The third bracket concern the tcp information: its sequence number and the acknowledgment number.

This article is proudly sponsored by Evansys Technologies

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Introduction to Network Simulator NS2

Eitman Altman’s NS2 Tutorial for Beginners

Alternative Reading:

* How to interpret ns2 trace file for wireless simulation?

Recommended Reading:

* Using Eclipse to enhance your experience of ns2

* How to scale your simulation to more nodes (500 nodes) and speed up it?

* Method to analyse ns2 trace file

[ns error] Parsing error in event.

Question: After I run a network simulation in nam(Network Animator) on the nam file generated by my tcl script, I get the following errors in my terminal:

Missing required flag -x in: W -t 500
Missing required flag -y in: W -t 500

Parsing error in event.

What could be wrong?

Answer: It isn’t a problem with the ns script.It is a problem associated with nam.It has turned out to be that if I use the slide-bar (TIME) to go to  a period of time instead of running the whole simulation time until it reaches the desired period of time NAM places (at least in my computer) the nodes in a wrong position that doesn’t match the reality. I’ve discovered it because when I slide the bar these messages appear in the console:

Missing required flag -x in: W -t 500
Missing required flag -y in: W -t 500
Parsing error in event.

So, the solution is clear: Let the simulation run until the desired time instead of using the slide-bar.

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Customising Gedit for tcl scripting

I spent a whole evening trying to find out some IDE or editor that would help me in coding tcl scripts as a part of ns simulations. The major feature I expected was autocompletion and keyword highlighter. Every editor/IDE that I stumbled upon contained one or the other, but not all. I tried Komodo Edit, Visual TCL,Alpha(tk) etc. Some of these even tested my patience in installing them.

Frustrated, I took recourse to Gedit and by chance I noticed that there are certain plugins available for Gedit, which I found would help satisfy my requirements I had mentioned in the para above. One notable plugin is the “Autocompletion” plugin. While you type the code/some word, this plugin shows a popup of words which were used before in the same document. In simple, it “autosuggests”. This one was interesting.

Along with this, you can enable some more plugins like “Bracket Completion”,”Embedded Terminal” and “Session saver”, whose purpose is pretty much self explained. And thus you almost have an IDE customised to code tcl or almost any language, needless to say that gedit provides better code highlights.

This is where you find the plugins….


For more on installing gedit plugins in Ubuntu, see my previous post.

<Here> is a complete list of Gedit plugins and don’t miss out the Latex plugin 🙂



Move Window Buttons Back to the Right in Ubuntu 10.04 / 10.10