Saturday, 25 August 2012

Trace File Format in NS2

In the previous post, I showed you how to create a “trace file” in NS2. In this post, I will show you the interpretation of an NS2 trace file.

Example of trace files :-

When using trace-all in NS2, a trace string is created in a trace file. The trace file would look like this.


Trace file format :-

The format of a trace string is shown below:




where 12 fields of the trace string are as follows.

1. Type Identifier:

 • “+”: a packet enque event
 • “-”: a packet deque event
 • “r”: a packet reception event
 • “d”: a packet drop (e.g., sent to dropHead_) event
 • “c”: a packet collision at the MAC level

2. Time: at which the packet tracing string is created .

3-4. Source Node and Destination Node: denote the IDs of the source and the destination nodes of the tracing object.

5. Packet Name: Name of the packet type

6. Packet Size: Size of the packet in bytes.

7. Flags: A 7-digit flag string

 • “-”: disable
 • 1st = “E”: ECN (Explicit Congestion Notification) echo is enabled.
 • 2nd = “P”: the priority in the IP header is enabled.
 • 3rd : Not in use
 • 4th = “A”: Congestion action
 • 5th = “E”: Congestion has occurred.
 • 6th = “F”: The TCP fast start is used.
 • 7th = “N”: Explicit Congestion Notification (ECN) is on.

8. Flow ID

9-10. Source Address and Destination Address: the format of these two fields is “a.b”, where “a” is the address and “b” is the port.


11. Sequence Number

12. Packet Unique ID