ACTION:	[s|r|D]: s -- sent, r -- received, D -- dropped
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
flags:
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
flags:
[......]:	[
		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)
		]

via Ke Liu’s NS2 Code and Q&A.