NS2中802.11的trace功能利用cmu-trace对象来实现，并建议了一种新的trace格式，这种新格式目前是适用于无线网模拟，并且向前与老版本的trace格式兼容。下边分别看下新老两种trace格式：
1.1 New trace format
In order to use new trace format, the following command:
$ns use-newtrace
must be called before the universal trace command $ns trace-all
An example of the new trace format is as following:
The new trace format can be divided into following fields:
1). Event type. the first field describes the type of event taking place at the nodeand can be one of the four types:
s - send
r - receive
d - drop
f - forward
2). General tag. The second field starting with "-t" may stand for time or global setting.
-t time
-t * (global setting)
3). Next hop info. This field provides next hop info and the tag starts with a leading "-H".
-Hs: id for this node
-Hd: id for next hop towards the destination.
4). Node property tags. This field denotes the node properties like node-id, the level at which tracing is being done like agent, router or MAC. The tags start with a leading "-N" and are listed as below:
-Ni: node id
-Nx: node’s x-coordinate
-Ny: node’s y-coordinate
-Nz: node’s z-coordinate
-Ne: node energy level
-Nl: trace level, such as AGT, RTR, MAC
-Nw: reason for the event. The different reasons for dropping a packet are given below:
"END" DROP_END_OF_SIMULATION
"COL" DROP_MAC_COLLISION
"DUP" DROP_MAC_DUPLICATE
"ERR" DROP_MAC_PACKET_ERROR
"RET" DROP_MAC_RETRY_COUNT_EXCEEDED
"STA" DROP_MAC_INVALID_STATE
"BSY" DROP_MAC_BUSY
"NRTE" DROP_RTR_NO_ROUTE i.e no route is available.
"LOOP" DROP_RTR_ROUTE_LOOP i.e there is a routing loop
"TTL" DROP_RTR_TTL i.e TTL has reached zero.
"TOUT" DROP_RTR_QTIMEOUT i.e packet has expired.
"CBK" DROP_RTR_MAC_CALLBACK
"IFQ" DROP_IFQ_QFULL i.e no buffer space in IFQ.
"ARP" DROP_IFQ_ARP_FULL i.e dropped by ARP
"OUT" DROP_OUTSIDE_SUBNET i.e dropped by base stations on receiving routing updates from nodes outside its domain.
5). Packet info at MAC level. This field gives MAC layer information and starts with a leading "-M" as shown below:
-Ma: duration
-Md: dst’s ethernet address
-Ms: src’s ethernet address
-Mt: ethernet type
6). Packet information at IP level. The tags for this field start with a leading "-I" and are listed along with their explanations asfollowing:
-Is: source address.source port number
-Id: dest address.dest port number
-It: packet type
-Il: packet size
-If: flow id
-Ii: unique id
-Iv: ttl value
7). Packet info at "Application level". The packet information at application level consists of the type of application like ARP,TCP, the type of adhoc routing protocol like DSDV, DSR, AODV etc being traced. This field consists of a leading "-P" and list of tags for different application is listed as below:
-P arp Address Resolution Protocol. Details for ARP is given by the following tags:
-Po: ARP Request/Reply
-Pm: src mac address
-Ps: src address
-Pa: dst mac address
-Pd: dst address
-P dsr This denotes the adhoc routing protocol called Dynamic source routing. Information on DSR is represented bythe following tags:
-Pn: how many nodes traversed
-Pq: routing request flag
-Pi: route request sequence number
-Pp: routing reply flag
-Pl: reply length
-Pe: src of srcrouting->dst of the source routing
-Pw: error report flag ?
-Pm: number of errors
-Pc: report to whom
-Pb: link error from linka->linkb
-P cbr Constant bit rate. Information about the CBR application is represented by the following tags:
-Pi: sequence number
-Pf: how many times this pkt was forwarded
-Po: optimal number of forwards
-P tcp Information about TCP flow is given by the following subtags:
-Ps: seq number
-Pa: ack number
-Pf: how many times this pkt was forwarded
-Po: optimal number of forwards
This field is still under development and new tags shall be added for other applications as they get included along theway.
1.2 Old trace format
By default, NS2 uses old trace format in 802.11 simulation.
An example of the old trace format is as following:
The old trace format can be divided into following fields:
1). ACTION [s r D] s - sent, r - received, D - dropped
2). WHEN: the time when the action happened
3). WHERE: the node where the action happened
4). 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
5). SEQNO: the sequence number of the packet
6). 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
7). 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
8). 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)
]
2. Analyzing by using perl
3. Tools for trace analysis