Essay: Mobile Ad Hoc Networks - Overview Of Routing Protocols.

Infrastructure less network and infrastructure network

Mobile ad hoc network(MANET) is an advance technology of mobile allowing communication without the help of base framing or station. The rapid development of mobility is closely related to automation of communication. In the current generation of technology, a static strategy to reduce electronic devices, tallying desirable shape of new components allowing accessibility in public market is very essential. Over the past decades MANET has play an imperative role in automating communication. Mobile ad hoc networks are imperatively used in combat ground communication, rescue operation and damaging recovery when the wired network is inaccessible. There exist two different types of mobile wireless network they include infrastructure less network and infrastructure network. Infrastructure less network is most appropriate where there is high demand of localized telecommunication and it is the main class of wireless network. On the other hand, infrastructure networks consist of communication mobile networks that are connected with base station and a fixed infrastructure network. However, unlike fixed cable nets wireless mobile networks are generally more exposed to security threats. There is an increased chance of eavesdropping and attacks such as denial of services which need to be considered carefully. MANET has proven its usefulness through it flexibility hence applicable in areas such as civilian environment, remote construction sites, commercial projects, law enforcement and environmental monitoring.

Developers often find quality of service a complex task to accomplish., this is due to regular change of ad hoc network topology. It is quite challenging to support certain quality of service and to reserve resource when there is a constant change in the network situation.

Since ad hoc networks are connected to other devices in the neighborhood, routing continues to be a major problem to solve. There is no available default route due to multi hop routing. Each node forward their packet by acting as a router so as to let sharing sequence among mobile nodes.

Generally, a wireless network is way more expose to security threats than a wired link. Security is one of the unsolved issues in ad hoc network. It is therefore imperative to solve this issues to ensure adequate performance of MANET.

The routing protocol has to take into account power resource limitation of the wireless mobile nodes. That is to say that they should be energy aware and efficient,

Sine MANET is at times interconnected with a fixed network, the routing protocol should consider the existence of other routing protocols.

To solve this issues, different routing schemes have been developed. The foremost purpose of this paper is to deliver a detailed analysis of mobile ad hoc network by conducting a comprehensive analysis on reactive and proactive routing protocols meant to resolve the above mentioned issues.

Routing refer to selection of network paths. It is normally performed by special device called router. Generally, it is the act of transferring data from a foundation to a destination and across inter-network. Routing has two special types, that is dynamic sate routing meant to open up chances of loops for routing and link state routing meant to collect best paths from routing table nodes. Every node in ad hoc network should be able to accelerate data to other nodes.  To effectively do that various routing protocols have been developed to produce adequate presentation of ad hoc network. MANET routing has therefore be categorized into hybrid routing, reactive routing and proactive routing. The below figure shows the classification

Quality of Service

Sometimes, nodes look for routing data in network. Since this protocols are free to traffics profile, there is a possibility to fix cost and a fixed upper bound. Proactive protocols are usually denoted to as table driven protocols. It main function is to minimize latency of message produced by route discovery, it does so by ensuring maintenance of up to date moving data from respectively node to another at all times. This is achieved through broadcast of control packets containing routing table information. For the first time, these protocols enflame a large overhead signal in order to make a route. Additionally, during modification of topology as a result of node failure or mobility, the topology information which has been updated are being broadcast to each network node. “Proactive routing protocols include; OLSR-optimized link state routing protocol, DSDV- destination sequence distance vector, DSR- demand signal repository STAR- Source tree adaptive routing protocol and FSR- fisheye state routing.” Destination sequence distance vector DSDVand OLSR  are the selected protocol to be evaluated in this study.

It belongs to proactive family and is an improved type of dispersed Bellman ford algorithm. In DSDV there is continuous maintenance and updating of correct route leading to any node in the network. The improvement made from the previous version include loops freedom in routing table through the use of sequence number. In DSDV protocols each performing nodes are assumed to be routers in wireless sensor network. All nodes usually keep a routing table that contain all the potential destination.  The destination address identifiers are found in every in entry of the routing table. It also consists of the shortest metric distance to the destination and is measured in hop count. The initial hop on the shorter path to the destination is the destination address identifier. A routing table is maintained by all mobile nodes in the system, all hop numbers and potential destination are recorded. In the meantime, every host propagated route is being periodically updated so as to achieve the most accurate and the latest routing table. Each path or route is marked with a structured quantity for which destination node allocated. The route with the highest structured number is normally used and the number helps in identification of stale routes in the new ones therefore avoiding loops formation. There are two major types of packets in the system that helps in minimization of traffic. One is called full dump and it plays an essential role in carrying all the necessary information concerning change. However, incremental packet is normally used when the regular movements in the network occurs. Incremental packet carries only the changes therefore increasing the system’s overall efficiency. DSDV needs an occasional routing table updates, which requires a lot of battery-operated power and a bandwidth in lesser quantity despite the network topology is not changing.  A new sequence of number is always needed before the re-converges of network whenever there is a change in the topology of network. This is to say that, DSDV is not measurable in the ad hoc network which is highly dynamic in terms of topology network and has small amount of bandwidth. Availability of routes in all destinations means that less and lesser interruption in the process of route setup is involved.  The inavailibity of a scalable standard makes some parameters of the protocol to lack clear definition.

Routing in MANET

OLSR refers to pure state algorithm optimization, multi point relays theory is used to forward control traffic, proposed into the entire network distribution. The multi point relays is selected in such a way that  all nodes situated two hops apart are all covered. It is an essential type of proactive protocol as it is measurable and scalable. It plays a major role in optimizing pure state algorithm and in forwarding traffic control, hence reducing traffic in the system. OLSR works closely with periodic messages replace such as topology control and hello messages and it is only through its multi point relays. The parameters that are being used by OLSR tin controlling the protocol overheads are topology control intervals parameters, Hello intervals parameters, topology control intervals parameter and multi point reporting parameters.

The key idea in the OLSR protocol is the multipoint relay which is imperative in reducing exchange of information overhead, multi point relay function by reducing the host number propagating information in the network instead of pure flooding.to allow efficiency in the protocol, multi point relay set a host which is usually kept small throughout the process. To allow topological information exchange, multi point relay nodes are required to send topology control message. These messages are propagated throughout the network and multi point relay is the only one allowed to send topology control messages.   

The above discussion can be summarized as shown in the below table

Table driven / proactive routing protocol

These type of routing protocol is usually referred to as “on demand” routing protocol, this is because, the routes between the nodes are only being built as per the requirement of the source nodes. The routing protocol explains the perfect ad hoc network nature. The networked is described to be much more dynamic as compared to infrastructure networks. When a routing requirement is presented, routing information in the reactive routing protocol is updated from time to time. These reduces the control overhead, majorly in high mobility networks with the help of periodical update guiding towards significant useless overhead.

Reactive routing protocols was developed to reduce the overheads produces by proactive routing protocol through maintenance of information only on active routes. Once the route has been determined, the route maintenance procedure tries to maintain it until the route is no longer needed or until there is inaccessibility of the destination. Reactive routing protocols are more appropriate in dynamic environments although it leads to a higher latency and its paths needs to be established using control packet in a source initiated flooding. Hayat et al., (2019) stated that  “Ad hoc on demand distance vector (AODDV), dynamic state routing protocol (DSR), location aided routing protocol (LAR), Associativity base routing (ABR), and Ad hoc on demand multipath distance vector are examples of reactive routing protocols.”

According to Alslaim, Alaqel, and Zaghloul ,(2014) “AODV is a reactive routing protocol developed for wireless ad hoc networks and is able to both unicast and multicast routing. Since it is an on demand algorithm, nodes between the routes are built only as required by the source nodes. Once the route has been determined, the route maintenance procedure tries to maintain it until the route is no longer needed or until there is inaccessibility of the destination.” Reactive routing protocols are more appropriate in dynamic environments although it leads to a higher latency and its paths needs to be established using control packet in a source initiated flooding. When a routing requirement is presented, routing information in the reactive routing protocol is updated from time to time. “These reduces the control overhead, majorly in high mobility networks with the help of periodical update guiding towards significant useless overhead.” (Hayat et al, 2019)

Proactive Routing Protocols: DSDV and OLSR

AODV is an improved version of DSDV as it allows minimization of sequence number of the needed broadcast through creation of routes only on demand basis. It uses a demand mechanism to carry out a route discovery procedure. During discovery of routes process, the protocol function by the use route request (RREQ) and route reply (RREP)message  

This type of reactive protocol is associated with fixed link state protocol. The way of distributing sequences in DSR has been enhanced unlike in liked state algorithm. It does so restricting messages update in only in the intermediate nodes. In this type of protocol every node is maintained depending on the information updates received from the neighboring nodes, and it exchanges its kink state data from time to time with only the neighboring. As a results the number of transmitted message has much reduce in the network the size of messages updated is however large and they become even much higher as the size of network grows. Routing is a procedure of making decisions in which the router (which is a hardware device used in networking to receive and send data in the form of packets on a network) selects the best path to make data transfer from source to destination. A router exists in the network layer in the OSI as well as TCP/IP model. Some functions of a router are:

Building an ideal way on an organization to arrive at its objective (wherein static and dynamic steering happen).

Taking directing choices.

Adjusting load.

Sorts of Routing:

• Static directing
• Default directing
• Dynamic directing

Static and Default directing has a few downsides, because of which Dynamic Routing was presented.

It is a difficult undertaking to summarize or add-on each course physically to the directing guide in an enormous organization.

Dealing with its requesting is tedious.

It can't reroute traffic in the event that some connection falls flat.

Downsides of Default directing was:

In the event that the organization is intricate, it is more hard to set up.

To defeat the inadequacies of static and default directing, Back during the 1980s, the very first Dynamic steering was utilized in a PC and the convention which was utilized in it was the RIP(routing data convention).

Dynamic steering is known as a strategy of tracking down the best way for the information to go over an organization in this interaction a switch can send information through different various courses and arrive at its objective based on conditions around then of correspondence circuits.

Summary of reactive routing protocols can be described as in the table below.

Based on the above mention literature on proactive and reactive protocols, the two approaches have been critically asses to determine their difference and similarities in its performance. the parameters used in the analysis include, storage requirement, mobility support, routing scheme, storage capacity, routing overheads and routing information. The table below shows the comprehensive analysis of proactive and reactive routing protocols.  

In order to support the above assessment quantitative evaluation was carried out by selectig one sample protocol from each strategy and evaluating their performance under varying operating conditions.

To conduct an effective performance comparison, the study selected AODV and OLSR protocols from MANET topology. A network stimulator of ns-2 was used for this analysis.

The simulation parameters used in the study are as listed in the below table 

AODV and OLSR performance comparison was done by varying traffic, network size, and mobility. Their comparison is given based on the selected evaluation metrics. A 95% confidence interval was used to prove observation of the sample variation among the two protocols calculated. The below formula was used  

It can be concluded that there is a decrease in performance for both protocols as load increase. That is why the packet delivery rate decrease as the packet loss rate increase for both protocals  

Based on the result it can be said that,  OLSR overhead are minimal for minimal topologies, nevertheless performance of OLSR overhead are suggestively reduced by larger topologies. This result in creation snooping within network hence leading to packets loss. On the contrary, AODV generates minimal overhead significantly causing little collision despite the topologies being large therefore attaining better PDR. 

Conclusion

To conclude, MANET has play an imperative role in automating communication. MANET are imperatively used in combat ground communication, rescue operation and damaging recovery when the wired network is inaccessible. To effectively do that various routing protocols have been developed to produce adequate performance of ad hoc network. Mobile ad hoc network routing has therefore be categorized into hybrid routing, reactive routing and proactive routing. The below figure shows the classification. The major function of proactive protocol is to minimize latency of message produced by route discovery, it does so by ensuring maintenance of up to date routing data from respectively node to another at all times. This is achieved through broadcast of control packets containing routing table information. On the other hand, reactive protocol is an upgrade of proactive and it is intended to allow minimization of sequence number of the needed broadcast through creation of routes only on demand basis. It uses a demand mechanism to carry out a route discovery procedure

References 

1. Alslaim, M.N., Alaqel, H.A. and Zaghloul, S.S., 2014, April. A comparative study of MANET routing protocols. In The Third International Conference on e-Technologies and Networks for Development (ICeND2014)(pp. 178-182). IEEE.
2. Bhardwaj, P.K., Sharma, S. and Dubey, V., 2012. Comparative analysis of reactive and proactive protocol of mobile ad-hoc network. International Journal on Computer Science and Engineering, 4(7), p.1281.
3. Bilandi, N. and Verma, H.K., 2012. Comparative analysis of reactive, proactive and hybrid routing protocols in MANET. International Journal of Electronics and Computer Science Engineering, 1(3), pp.1660-1667.
4. De Rango, F., Cano, J.C., Fotino, M., Calafate, C., Manzoni, P. and Marano, S., 2008. OLSR vs DSR: A comparative analysis of proactive and reactive mechanisms from an energetic point of view in wireless ad hoc networks. Computer Communications, 31(16), pp.3843-3854.
5. Gill, A. and Diwaker, C., 2012. Comparative Analysis of routing in MANET. International Journal of Advanced Research in Computer Science and Software Engineering, 2(7)
6. Hayat, S., Liu, X., Li, Y. and Zhou, Y., 2019, May. Comparative analysis of vanet’s routing protocol classes: An overview of existing routing protocol classes and futuristic challenges. In 2019 IEEE 2nd International Conference on Electronics Technology (ICET)(pp. 1-7). IEEE.
7. Jamali, A., Naja, N. and El Ouadghiri, D., 2009, April. Comparative analysis of ad hoc networks routing protocols for multimedia streaming. In 2009 International Conference on Multimedia Computing and Systems(pp. 381-385). IEEE.
8. Rohankar, R., Bhatia, R., Shrivastava, V. and Sharma, D.K., 2012, March. Performance analysis of various routing protocols (proactive and reactive) for random mobility models of Adhoc networks. In 2012 1st international conference on Recent Advances in Information Technology (RAIT)(pp. 331-335). IEEE.
9. Sathish, S., Thangavel, K. and Boopathi, S., 2011. Comparative analysis of DSR, FSR and ZRP routing protocols in MANET. In International Conference on Information and Network Technology IPCSIT vol(Vol. 4).
10. Timcenko, V., Stojanovic, M. and Rakas, S.B., 2009, August. MANET routing protocols vs. mobility models: performance analysis and comparison. In Proceedings of the 9th WSEAS international conference on Applied informatics and communications(pp. 271-276).