# Building Realistic Mobility Models for Mobile Ad Hoc Networks
## 4 Manet Routing Protocol Evaluation  
A vast number of routing protocols have been proposed for use in MANETs, and a comprehensive taxonomy has been built by [PERSON] et al. (2011) [PERSON] et al. (2011). Surveys on subsets of MANET protocols have been conducted (see [PERSON] et al., 2013, [148]; [PERSON] et al., 2013, [149]). The majority of the research involves the use of simulations and the comparison of a new protocol against one of the commonly used existing protocols (e.g., AODV, DSDV, and DSR). The discussion of procedures and techniques for evaluating new MANET protocols against previous work is almost ubiquitous and could be found in early papers, such as [PERSON] et al. (1998) and [PERSON] et al. (2001), right through to recent publications, such as [PERSON] et al. (2013) [PERSON] et al. (2013) [PERSON] et al. (2013) [PERSON] et al. (2013). The approach taken is to perform simulations using some combination of movement, node counts, and other (not always clearly specified) parameters and running the new protocol to yield performance data. In order to provide quantitative comparisons between protocols, it is necessary to consider meaningful and measurable metrics by which protocols can be compared. ns-2 generates extensive trace files. These trace files contain detailed records of all significant events in a simulation run, with each event shown as a separate entry. The exact information included in each entry is dependent on the implementation of the protocols being used, because each protocol is coded independently. Take the following as an example:  
r 111.930048923_32_MAC -- 0 AODV 44 [13a 20 22 800] [34:255 52:255 30 32]  
[0 \(\times\) 4 3 [0 104] 9.00000] (REPLY)  
In summary, the above shows that at timestamp 111.930048923 (simulated seconds into the run), node 32 received an AODV routing protocol reply at its MAC layer. The entry contains more information than necessary for the comparison of protocol performance, but there are sets of information contained within the trace files for common protocols, such as those considered in this paper that could be used to compare the different performances of those protocols. The trace files themselves could be very large with simulated time runs of one hour and producing files of over 2 Gb. The size of the trace files and the level of detail contained within them make it necessary to process them to extract useful statistics. This is possible by using an awk script (Network Simulators, 2013, [152]) written for nS-2 to process the data and analyze the trace file, followed by producing a set of reports covering the key network performance metrics. Packet delivery ratio (PDR), also known as packet delivery fraction, is the number of received data packets compared with the number of sent data packets, usually expressed as a ratio or percentage. Data packets contain user or application data and may therefore, be considered \"useful\", as opposed to control and routing protocol packets, which are considered overheads. The data packet delivery ratio shows the ratio of data packets that reach their final destination compared with the number of packets transmitted from an original source. It is also an indicator of whether the network is connected (note: it is not connected if no data packet reaches its destination). PDR provides a measure of the effectiveness of the protocol in transmitting user data to its target. Normalized routing load (NRL) is calculated by the number of the routing packets sent divided by the number of the data packets received. The normalized routing load (usually a percentage), shows how much routing traffic is generated per packet delivered ([PERSON] et al., 2005, [153]). NRL could be the \"efficiency\" of the routing protocol, as it presents a comparison of the number of control packets (overheads) required to deliver each user data packet. Average end-to-end delay is a measure of the time data packets take to travel from the source to the final destination.