International Journal of Scientific & Engineering Research, Volume 5, Issue 4, April-2014 318
ISSN 2229-5518
Survey on Proactive and Reactive Protocols in
MANETs
Arpitha C N, Dr. Arun Biradar
—————————— ——————————
A mobile ad-hoc network or MANET is a collection of mobile nodes sharing a wireless channel without any centralized con- trol or established communication backbone. They have no fixed routers with all nodes capable of movement and arbitrar- ily dynamic. These nodes can act as both end systems and routers at the same time. When acting as routers, they discover and maintain routes to other nodes in the network. The topol- ogy of the ad hoc network depends on the transmission power of the nodes and the location of the mobile nodes, which may change from time to time [1].
The routing protocols for Ad hoc wireless network are classi-
fied as follows:
• Table driven or proactive routing protocol: Routing
table holds and maintains the topological information of the nodes. Routing Information is obtained by ex- changing routing tables within the network. Whenev- er a node requires a path to destination it runs an ap- propriate path finding algorithm on the topology in- formation it maintains.
(DSDV), Wireless Routing Protocol (WRP), Source – Tree Adaptive Routing Protocol (STAR) , Cluster- Head Gateway Switch Routing Protocol (CGSR).
• On demand or reactive routing protocols: The proto- cols do not maintain the network topology infor- mation. These protocols execute the path-finding pro- cess and exchange routing information only when a path is required by a node to communicate with des- tination. Hence periodical exchange of routing infor- mation among the nodes is not seen.
Ad hoc On-Demand Distance Vector Routing Protocol
(AODV), Temporally Ordered Routing algorithm
(TORA).
• Hybrid Routing Protocols: The protocols form the
routing with a specified zone using proactive routing scheme and reactive routing scheme is used for nodes which are beyond the zone.
Hierarchical Link State Routing protocol (ZHLS).
-DSDV -AODV -ZRP
-CGSR -DSR -FSLS
-WRP -TORA -ZHLS etc
-GSR -ABR
-FSR etc. -SMR etc.
Fig 1: Classification of Routing Protocols
Numerous routing protocols are already implemented and also perform the comparison between those protocols. In [2] they compare the performance of AODV, AOMDV, DSR,DSDV under MANET concerning Power aware routing and the re- sults show that AOMDV consumes minimum energy com- pared to AODV, DSR and DSDV protocols. AOMDV is ana- lyzed as the best protocol compared to AODV, DSR and DSDV when energy efficiency is taken into consideration.
DSDV is a modification of the conventional Bellman-Ford routing algorithm [3]. It addresses the drawbacks related to the poor looping properties of RIP in the face of broken links. The main drawbacks of both link-state and distance-vector
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protocol are that they take too long to converge and have a high message complexity. Because of the limited bandwidth of wireless links in an ad hoc network, message complexity must be kept low. In addition, the rapidly changing topology re- quires that the routing protocols can find routes quickly. So new routing protocols have to be developed to fulfill this basic philosophy.
The destination sequenced distance vector (DSDV) protocol [4] is an adaptation of the classical Bellman-Ford [5] routing pro- tocols. It is specifically targeted for the adhoc networks. It ad- dresses the long-lived loops and counting to infinity problems of the conventional distance-vector routing protocols. In DSDV, the time complexity is O(d = network diameter) [6], and the communication complexity (link addition/failure) is O(N = number of nodes in the network) .In DSDV it is difficult to determine the maximum setting time and it does not sup- port multi-path routing. The destination central synchroniza- tion suffers from latency problem. It has excessive communi- cation overhead due to periodic and triggered updates.
The widespread use of mobile and handheld devices is likely to popularize ad hoc networks, which do not re-quire any wired infrastructure for intercommunication, in which each node can move in any direction & acts as a router. To assist communication in such network, a routing protocol is vital whose primary aspiration is to set up proficient route among pair of nodes, due to this lot of reactive, proactive & hybrid routing protocols have been proposed. Out of which one of most popular one is Adhoc on-demand distance vector rout- ing (AODV) due to its high performance gain compared to other protocols in MANET, therefore its performance needs to be evaluated by making use of various metrics such as end to end delay, packet delivery ratio (PDR) & Packet loss[7]. They conclude that there is non-linear change in the values of these metrics also realized working & control massages involved in AODV protocol
AOMDV was designed primarily for highly dynamic ad hoc
networks where link failures and route breaks occur frequent-
ly. It maintains routes for destinations in active communica- tion and uses sequence numbers to determine the freshness of routing information to prevent routing loops. It is a timer- based protocol and provides a way for mobile nodes to re- spond to link breaks and topology changes [8] they compare the performance of AODV,DSR and proved AOMDV gives better performance as compared to AODV and DSR in terms of packet delivery fraction and throughput but worst in terms of end-to end delay.
Ad-hoc On-demand Multipath Distance Vector Routing
(AOMDV) [9] protocol is an extension to the AODV protocol for computing multiple loop-free and link disjoint paths. The routing entries for each destination contain a list of the next- hops along with the corresponding hop counts. All the next
hops have the same sequence number. This helps in keeping track of a route.
In [10] under MANET the routing protocols like DSR, AODV, FSR, ZRP are compared by passing parameter metrics like Jitter, Throughput, Average end-to-end delay, Packet delivery ratio, Pause time and showed that DSR shows best perfor- mance than AODV, FSR and ZRP in terms of packet delivery ratio and throughput as a function of pause time. FSR show lowest end-to-end delay and ZRP has less average jittering than DSR, AODV and FSR. DSR and AODV performed the worst in case of average jitter and ZRP performed the worst in case of throughput.
D.D.Chaudhary, Pranav Pawar[11] perform comparison of following routing protocols AODV, AOMDV, DSDV by pass- ing parameter metrics like End-to-End Delay, Energy Con- sumption in Wireless Sensor Networks and finally DSDV, AODV and AOMDV are compared with 802.11 and 802.15.4
IEEE standards. From the all the graphical results, which are explored using NS2 simulator, it is observed that, for delay- sensitive applications, it obligatory to adopt the 802.15.4 IEEE standard with DSDV routing protocol. The energy consump- tion is also low in this combination.
Three protocols discussed here are DSDV, AODV and
AOMDV
Destination-Sequenced Distance-Vector Routing (DSDV) is a proactive and table driven routing protocol [14], based on classical Bellman-ford routing mechanism basic improvement made includes freedom from loops in routing tables , more dynamic and takes less convergence time. It maintains the topological information in the form of tables at every node. Routing table contains list of all known destination nodes within the network along with number of hops required to reach particular node, next node and sequence number as- signed by destination node. At regular intervals these tables are exchanged between the neighbors, this helps to maintain up to date view of the network topology. Table is maintained at the every node, contains the shortest distance and the first node on the shortest path to every other node in the network. The table is updated with increasing sequence number tags which prevent loops, to counter count-to-infinity problem and for faster convergence. Destination initiates table updates with a new sequence number which is greater than the previous one. As and when the table updates are received, updating of tables at the nodes is based on the received information or holds it for some time to select the best metric received from multiple versions of the same update table from different neighboring nodes. Depending on the sequence number of the table update, it may forward or reject the table. The time in- volved in route setup process is less due to the availability of
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routes to all destinations at all times. Table update is of two types- incremental update and full dump. Incremental update takes a single network data packet unit (NDPU) , these type of updates are used when a node does not observe significant changes in local topology. Full dumps may take multiple NDPUs, a full dump is done either when the local topology changes significantly or when an incremental update requires more than a single NDPU.
(a)
Dest | NextHop | Dist | Seqno | Cost | ||
1 | 1 | 1 | 12 | 2 | ||
2 | 1 | 2 | 16 | 5 | ||
3 | 1 | 2 | 18 | 6 | ||
4 | 4 | 1 | 20 | 3 | ||
5 | 4 | 2 | 22 | 8 | ||
D | 1 | 3 | 24 | 6 |
(b)
Using DSDV we are finding shortest path from source S to the
destination D, the topology of the network is shown in fig 2(a). Each node maintains the routing table, fig 2(b) shows the rout- ing table maintained by source node S. To reach from S to D the DSDV protocol finds that the hop count is 3 and cost is 6. Fig 2(c) shows the routing table updated when the link break between nodes 1 and 2 occurs. When a node finds that a route is broken it increments the sequence number of the route and advertises it with infinite metric. Destination advertises new sequence number. In this scenario the new sequence number for node 2 is 26 as shown in routing table.
(c)
Fig 2: (a): Topology graph of the network (b): Routing table
for node S (c): Route maintenance in DSDV.
Ad hoc On-Demand Distance Vector (AODV) routing protocol used to find routes by on demand scheme[12]. Route is found only when the source is in need to transmit data packets.It is a unipath routing protocol. Routes Requests (RREQs), Route Replies (RREPs),Route Errors (RERRs) and Route Reply Ac- knowledgment (RREP-ACK) are the message types defined by AODV. If the route is not available for the desired destina- tion then the source node floods the Route Request packet in the network and then it obtains many different routes to dif- ferent destinations from a single Route Request. An AODV Route Request packet holds the source identifier, the destina- tion identifier, the source sequence number, the destination sequence number, the broadcast identifier, and time to live field. In order to determine an up-to-date path and freshness of the route to the destination, AODV uses a destination se- quence number. As the Route Request packet is received by the intermediate node, it forwards the packet or Route Reply is prepared if it has a valid route to destination, for which va- lidity of route is indicated by the destination sequence num- ber. Route Reply packets are sent to the source by all of the intermediate nodes which are having the valid routes to desti- nation or the destination node itself are allowed to send Route Reply packets to source. As the node receives the Route Reply packet, it forwards the data packet with the help of the previ- ous node Information from which the Route Reply packet was received. If a path break is detected at an intermediate node, the node informs the end nodes by sending an Route Error message with the hop count set as infinity. The end nodes de- lete the corresponding entries from their tables. The source node reinitiates the path-finding process with the new broad-
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cast identifier and the previous destination sequence number. Each time RREQ broadcasted to its neighbor a reverse path is created because of this reverse path a unique ID is assigned when a RREQ message is generated, each node will check this ID and the address of the initiator and discards the message if it had already processed that request. During route mainte- nance adjacent nodes exchange periodic HELLO messages.
(a)
(b)
(c)
(d)
Fig 3: (a) Propagation of RREQ, (b) Route request in reverse direction, (c) RREP path to the source (d) Route Maintenance
in AODV
Fig 3(a) shows that when the route is required source node
forwarded the RREQ packets to its neighbor nodes 1 and 2. The nodes 1 and 2 in turn send RREQ to its neighbor, fig 3(b) shows that RREQ packets also forwarded to source node 1 in reverse direction. Fig 3(c) shows that propagation of RREP towards source node through node 2 and 1. Finally the link between nodes 1 and 2 gets broken then nodes 1 and 2 invali- dates route to D in route table and sends Route Error message to its neighbors.
Ad-hoc On-demand Multi path Distance Vector Routing pro- tocol is an extension to the AODV protocol for computing multiple loop-free and link disjoint paths [13]. The routing entries for each destination contain a list of the next-hops along with the corresponding hop counts. All the next hops have the same sequence number. This helps in keeping track of a route. For each destination, a node maintains the adver- tised hop count, which is defined as the maximum hop count for all the paths, which is used for sending route advertise- ments of the destination. Each duplicate route advertisement received by a node defines an alternate path to the destination. Loop freedom is assured for a node by accepting alternate paths to destination if it has a less hop count than the adver- tised hop count for that destination. Because the maximum hop count is used, the advertised hop count therefore does not change for the same sequence number. When a route adver- tisement is received for a destination with a greater sequence number, the next-hop list and the advertised hop count are reinitialized. AOMDV can be used to find node-disjoint or link-disjoint routes. To find node-disjoint routes, each node does not immediately reject duplicate RREQs. Each RREQs arriving via a different neighbor of the source defines a node- disjoint path. This is because nodes cannot be broadcast dupli- cate RREQs, so any two RREQs arriving at an intermediate node via a different neighbor of the source could not have traversed the same node. In an attempt to get multiple link- disjoint routes, the destination replies to duplicate RREQs, the destination only replies to RREQs arriving via unique neigh- bors. After the first hop, the RREPs follow the reverse paths, which are node disjoint and thus link-disjoint. The trajectories of each RREP may intersect at an intermediate node, but each takes a different reverse path to the source to ensure link dis- joint ness.
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(a)
iii) AODV used as a benchmark to reveal the strengths and limitations of multipath versus unipath. we con- firm that
multi-path routing protocols create less overhead compared
to single path routing protocols.
The following are the parameter metrics taken into considera- tion to compare the routing protocols
• Throughput: Refers to amount of data that can be trans-
ferred from sender to receiver in a given amount of time or Number of packets arriving at the sink or it is the ratio of the total amount of data that reaches a receiver form a sender to the time it takes for the receiver to get the last packet.
• End-to-End Delay: The average time taken by a data packet to arrive in the destination. It also includes the de- lay caused by route discovery process and the queue in data packet transmission. Only the data packets that suc- cessfully delivered to destinations that counted.
(b)
Fig 4: (a) Propagation of RREQs in AOMDV, (b) RREP multi path in AOMDV
AOMDV provides multipath from source to destination which
tions
∑ (Receive time – send time) / ∑ Number of connec-
The lower value of end to end delay means the better performance of the protocol.
are node disjoint and link disjoint. Fig 4(a) shows the broad-
cast of RREQ from source node S and fig4(b) shows multiple
route from destination node D to S which are node-disjoint and link-disjoint through neighbor nodes.
In proposed system we are taking three routing protocols namely DSDV[14], AODV[15] and AOMDV[16] to compare and analyze how proactive and reactive protocols react to changing network environment by passing some of the pa- rameter metrics using simulation. And also examine and vali- date the advantages and limitations of these protocols.
The main contribution of this present paper is as follows
i) Here we are comparing both unipath and multipath routing protocols .we show in the comparison that DSDV performs best in static network than AODV and AOMDV; AODV performs well in low mobility scenario. AOMDV outperforms the other protocols in highly mobile networks and offers best load bal- ancing and fault tolerance.
ii) we demonstrate that multi-path routing is only ad-
vantageous in networks of high node density or high network load compare to unipath routing protocol; and
• Packet Delivery Fraction : It is the ratio of data packets
delivered to the destination to those generated by the
source.
PDF = No. of packets received/No. of packet sent.
• Routing overhead: It is the total number of control packets
or routing packets generated by routing protocol during simulation.
• Normalized routing load: It is defined as the number of control packets transmitted per data packet arrived at the destination.
NRL = No. of routing packets / No. of packets re-
ceived.
The objective of this paper is to provide a quantitative compar- ison of both unipath and multi-path routing protocols for mo- bile ad-hoc networks, examine some of the advantages and also to find out one common limitation in all three protocols and to find solution for that problem. Our study shows that the AOMDV protocol is more robust and performs better in most of the simulated scenarios .The AODV protocol achieves best performance in scenarios with low mobility and higher node density. DSDV performs best in static networks, heavy routing overhead if the size of the network increases in pres- ence of mobility.
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• Arpitha C N is currently pursuing masters degree program in Computer Sci- ence and Engineering in Visvesvaraya Technological University, India, PH-
8495844451. E-mail: arpitha.aa89@gmail.com
• Dr.Arun Biradar is Professor and Head of the Department in Computer Sci-
ence and Engineering Department, EWIT, Bangalore,India, E-mail: hod- csea@gmail.com
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