Abstract 

Estimating the packet losses is the main aim of this project and for this purpose a simple wireless LAN is considered in terms of MANET and OPNET modeler is used for the simulation process. Three scenarios are created in the simulation environment against the three routing protocols like AODV, DSR and OLSR. Wireless LAN mobile workstations are created as the mobile nodes and almost 20 nodes are used and a single wireless LAN server is used to act as the destination for the email application. Three scenarios are compared against the email and wireless LAN performance metrics and from the analysis of the results key observations are given as below 

As the main aim of this simulation is to estimate the packet loss situations on the wireless, three scenarios are considered like AODV, OLSR and DSR and their performance against the packet losses are analyzed. Email application is used to generate the traffic on the network and from the analysis of the traffic patterns the corresponding packets are also analyzed. Few email metrics like download response time, upload response time, traffic sent and traffic received are analyzed against the packet loss from the overall analysis of the results it is clear the OLSR has shown an optimal performance in terms of packet loss at the upload and download response time.

When the packets loss is estimated against the traffic sent and traffic received are analyzed the packet loss is very less with the AODV routing protocol and thus it indicates that the overall performance of AODV is more to reduce the packet loss against the email application. When the wireless LAN server metrics are considered the performance of both AODV and OLSR at the optimal levels in every aspect considered and also the OLSR has shown an optimal performance in terms of delay, medium access delay, load, network load, throughput and retransmission attempts and the AODV has shown the required performance to reduce the packet loss at the wireless LAN server side. 

Introduction 

Project background 

A network can be considered a group of computers for a common purpose like communication or data transfer and in this context all these computers will act as nodes and the destination of all these nodes will lead towards a server. In general these computers can be connected in different manners and the key among them are wired and wireless where the wireless networks has gained lot of importance these days. Wireless networks has gained more popularity as it has reduced lot of risks in establishing the wired communication and also reduced the infrastructure requirements a lot.

In general the wireless networks has the tendency to establish the connection against the present conditions on the network and also they are affected with lot of topological conditions and the most important examples of wireless networks are ad hoc networks and wireless LAN’s where there are number of mobile nodes on the network.

Due to the mobility of the nodes on the wireless networks, the nodes can move randomly to the desired areas and process the communication requests and in this process they will be incurred with some issues like packet drop and packet loss. Among lot of issues faced by the wireless networks like ad hoc networks, packet losses can be considered as the main problem and there is lot of research done in this context and most of researchers has proposed some solutions in this context to reduce the packet loss across the network and they has been implemented to reduce the packet loss across the network. 

If the packet loss on the network is more then automatically the overall performance of the network is reduced and also the important data and communication aspects are dropped in the middle of the communication without reaching the destination. The total packet loss on the network in general depends on few aspects like type of traffic generated on the network and also the nature of the application used to generate this traffic. There are two types of traffic types like TCP and CBR and among these types TCP has more tendencies to lose the packets when compared to CBR traffic as across the CBR a constant bit rate is implemented.

As mentioned the kind of application plays an important role in deciding the TCP and CBR traffic and in this context the applications like FTP and email will generate the FTP traffic and the applications like voice and video will given the required CBR traffic across the network and this traffic has the significant role in estimating the packet loss across the network. Due to the packet loss across the network few important aspects like traffic sent, traffic received, load and throughput are affected and thus these metrics will affect the overall performance of the network as well. In general if the packet loss is more on the network the server and the corresponding nodes will gain the scope for the intruder attacks as well where the chance of attacks like DOS and packet flooding are increased and thus in this context the main problem for this project is identified and is as given below 

Problem definition

Estimating the packet loss across the wireless networks is the main problem considered in this project and for this purpose an ad hoc network level analysis is done. OPNET modeler is used as the desired simulation tool and a simple MANET is created with 20 mobile nodes and a single wireless LAN server. The mobile nodes are created using the wireless LAN mobile nodes and the destination server is used is created with the wireless LAN fixed server. As mentioned TCP traffic has much tendency to lose the packets and in this context a simple email application is used to generate the TCP traffic and the application is defined at the application configuration and profile configuration level.

Few routing protocols are considered to understand the packet loss performance of these routing protocols and they are AODV, DSR and OLSR and in general the routing protocols are the best source to estimate the packet loss as the complete scope to lose the packets mainly depends on the type of routing protocol implemented and also the kind of routing parameters followed to deliver the packets against the TCP traffic generated on the network.

Three different scenarios are created in this context, where AODV is used in the first scenario, DSR in the second scenario and OLSR is used across the third scenario and few performance metrics are also considered. Both the email and wireless LAN parameters are considered for the performance evaluation such that the level of packet loss across the three routing protocols for these metrics is estimated and the key performance metrics used in this context are as listed below 

Following are the performance metrics used to evaluate the performance of Email application in terms of packet loss for the three scenarios 

  • Download response time in seconds
  • Traffic received in bytes per sec
  • Traffic received in packets per sec
  • Traffic sent in bytes per sec
  • Traffic sent in packets per sec
  • Upload response time

Following are the wireless LAN performance metrics used to evaluate the wireless LAN aspects for the three routing protocols 

  • Data dropped due to buffer overflow
  • Data dropped due to retry threshold exceed limit
  • Delay
  • Load
  • Medium access delay
  • Network load
  • Retransmission attempts
  • Throughput

Same performance metrics are used across the three scenarios and the simulation is run for one hour to get the comparison results and they are explained in this document. The key aims and objective identified in this project are as listed below 

Aims and Objectives 

Aim: The main of this project is to estimate the packet losses across the MANETs against three routing protocols like AODV, OLSR and DSR and understand the impact of packet loss on the overall performance of the network. 

Objectives 

Following are the objectives identified in this project 

  • To critically review different routing protocols against the packet loss situations and understand the limitations of these routing protocols
  • To design the simulation procedure against the packet loss situations on the MANETs
  • To simulate a simple MANET with 20 mobile nodes and generate the TCP traffic using Email application and estimate the packet loss across the email and wireless LAN server
  • To compare the scenarios against the AODV, DSR and OLSR routing protocols
  • To analyze the results and conclude the packet loss situations on the MANET and also understand the best routing protocol in handling the packet loss and reducing this loss.