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 measure 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 the 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 getting transmitted in the link between Transmitter_ID and Receiver_ID
  • Phy_Layer_End_Time -- Time at which packet reaches Phy_Layer of Receiver_ID

Queuing time at Transmitter_ID (if a router) = Phy_layer_arrival_time - Nw_layer_Arrival_time

Transmission time from Transmitter_ID to Receiver_ID = Phy_layer_Start_Time - Phy_Layer_Arrival_Time

Propagation delay from Transmitter_ID to Receiver_ID = Phy_Layer_End_Time - Phy_Layer_Start_Time

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

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