The columns in the trace are to be interpreted as follows:

 

  • Source_ID -- The source of the packet
  • Destination_ID -- The final destination of the packet
  • Transmitter_ID -- The current node which is transmitting the packet. 
  • Receiver_ID -- The current node which is receiving the packet

 

Say if you have a packet going from 1 to 4 via 2 and 3 i.e 1 --> 2 --> 3 --> 4. The packet trace at 2 would indicate Source_ID as 1, Destination_ID as 4, Transmitter_ID as 2 and Receiver ID as 4.


With regards to Timing, each device has multiple 'layers' as per the TCP / IP stack and different protocols run in each layer. NetSim has probes that measures time at each layer. This requires a very high level of accuracy and hence time is measured in microseconds.


  • App_Layer_Arrival_Time -- Time at which packet is at the Application_Layer of Source_ID. This is usually the time at which the packet is generated at Source_ID
  • Trx_Layer_Arrival_Time -- Time at which packet reaches the Transport_layer from the application layer. This will usually be the same as Application_layer_Arrival_Time unless there are TCP re-transmissions
  • Nw_Layer_Arrival_Time -- Time at which packet reaches the Network_Layer of Transmitter_ID if this is a Router (or) Time at which packet reaches the Network_layer of previous Router / Source_ID (immediate previous Layer 3 or higher device) if current device is Switch / Access Point. 
  • MAC_Layer_Arrival_Time -- Time at which reaches MAC_Layer of Transmitter_ID
  • Phy_layer_Arrival_Time -- Time at which packet reaches PHY_layer of Transmitter_ID
  • Phy_Layer_Start_Time -- Time at which packet starts betting transmitted in the link between Transmitter_ID and Receiver_ID
  • Phy_Layer_End_Time -- Time at which packet reaches Phy_Layer of Receiver_ID


Time taken for transmission between Transmitter_ID to Receiver_ID = Phy_layer_End_Time - Phy_Layer_Start_Time

Queuing time at Transmitter_ID (if a router) = Phy_layer_start_time - Nw_layer_start_time

Total Time taken for a packet to travel from Transmitter_ID to Receiver_ID = Transmission_Time + Queuing_Time