A comparison based overview of destination distance sequence vector routing (DSDV) and mobile ad hoc on demand data delivery protocol (MAODDP) Humayun Bakht School of Computing and Mathematical Sciences Liverpool John Moores University Byrom Street, Liverpool L3 3AF, UK Email: firstname.lastname@example.org Abstract Mobile ad hoc network is an autonomous system networks are known as base stations. As the of mobile nodes establishing ad hoc or short live mobile travels out of range of one base station network without the intervention of any fixed and into the range of another, a “handoff” occurs infrastructure. Routing in these types of network from the old base station to the new, and the is an unresolved issue. Effort is going on to mobile is able to continue communication establish an effective routing mechanism for seamlessly throughout the network. Typical mobile ad hoc networks. Proposed protocols for applications of this type of network include mobile ad hoc network can be categorized into office wireless local area networks (WLAN). two types i.e. table‟s driven and on-demand routing protocols. The second type of mobile wireless network is Destination sequence distance vector routing is mobile ad-hoc network or infrastructure-less one of tables driven earliest proposed algorithms. mobile networks. A mobile ad-hoc network is a DSDV maintains the consistent overview of the collection of wireless mobile nodes dynamically network. DSDV requires participating nodes forming a temporary network without the use of broadcast updates after a regular interval of time. any existing network infrastructure or centralized Most of the tables driven type protocol is either a administration[4, 5]. Mobile ad-hoc networks are extension or modified form of DSDV. deployed in applications such as disaster Mobile ad-hoc on demand data delivery protocol recovery and distributed collaborative computing follows an intermediate approach in compression where routes are mostly multi-hop and network with tables driven and on demand routing hosts communicate via packet radios. protocols. The key feature of MAODDP is to Examples include infrared, wireless RF, establish the route and deliver the data Bluetooth, ad-hoc sensor networks or even simultaneously at the same time one after the wired based transceivers used when emulating ad other. hoc networks. There is current and future need This paper is an effort to describe the detail for dynamic ad hoc networking technology . functioning of these protocols. This paper also The emerging field of mobile and nomadic covers an analytical and discussion section to computing, with its current emphasis on mobile compare the various aspects of these protocols IP operations should gradually broaden and with each other. require highly-adaptive mobile networking technology to effectively manage multi-hop, mobile ad-hoc network clusters which can 1. Introduction operate autonomously or, more than likely, be attached at some point to the bigger network With the advancement in radio technologies like such as the Internet. Bluetooth, IEEE 802.11 or Hiperlan, a new concept of networking has emerged which make Most of the existing Internet protocols were wireless networks increasingly popular in the designed to aid routing in a network with fixed computing industry[1, 2]. This is particularly infrastructure. These protocols therefore are not true within the past decade which has seen considered good enough to support routing in an wireless networks being adapted to enable ad-hoc networking environment. One of the mobility. There are currently two variations of first routing solutions was based on the idea of wireless networks. The first is known as considering each mobile nodes of an ad hoc Infrastructure networks i.e. those networks with network as a router and running some fixed and wired gateways. The bridges for these conventional routing protocol. However This scheme was not very successful as mobile ad-hoc network suffers from frequent topology changes Mobile ad-hoc on demand data delivery protocol which results a large number of packets to be dropped or lost. Later on numbers of Bandwidth Security different protocols have been proposed as a Constraint routing solution for mobile ad hoc networks. These can be classified as either tables driven or on-demand protocol types. Routing Pro-active protocols follow an approach similar to the one used in wired routing protocols. By Multicasting Battery Life continuously evaluating the known route and attempting to discover new routes, they try to maintain the most up-to-date map of the Figure 1 Model of MAODDP network. This allows them to efficiently forward packets as the route is known at the time when the packet arrives at the node. Pro-active or table-driven protocols, in order to maintain the MAODDP uses destination sequence numbers to constantly changing network graph due to new ensure loop free routing. The primary concerns moving or failing nodes require continuous in mobile ad-hoc networks are bandwidth updates which may consume large amounts of limitations and unpredictable topology changes. bandwidth. In contrast, reactive protocols Thus, efficient utilization of routing packets and determine the proper route only when required. immediate recovery of route breaks are critical in Therefore, when a packet needs to be forwarded routing and multicasting protocols. MAODDP In this instance the node floods the network with intial specification taken into account these two a route-request and builds the route on demand factors besides number of other factors. from the responses it receives. This technique MAODDP could proved to be an effective does not require constant broadcasts and solution particularly in terms of minimizing discovery, but on the other hand causes delays bandwidth consumption and maximizing battery since the routes are not already available. life of the mobile nodes in an ad hoc network. Additionally, the flooding of the network may lead to additional control traffic, again putting Rest of the paper is organized as follows in strain on the limited bandwidth. section 2 we discuss routing problems in mobile ad hoc networks, section 3 and 4 covers details Mobile ad-hoc on Demand Data Delivery functioning of destination sequence distance protocol (MAODDP) follows a centralized vector routing and mobile ad hoc on demand on approached figure 1 is based on the idea of demand data delivery protocol, analysis and accomplishing route discovery and data delivery discussion is given in section 5 while references simultaneously at the same time one after the are listed in section 6. other. It is an on-demand routing protocol type it builds routes between nodes only as desired by source nodes. MAODDP offers loop-free routing 2. Routing in mobile ad hoc network with the help of sequence number, self-starting. MAODDP offers quick adaptation to dynamic Despite the numerous advantages and potential link conditions, low processing and memory application possibilities, ad-hoc networks are overhead, low network utilization, and yet far from being deployed on large-scale determines routes to destinations within the commercial basis. To enable communication mobile ad-hoc network. within a MANET, a routing protocol is required to establish routes between participating nodes. Because of limited transmission range, multiple network hops may be needed to enable data communication between two nodes in the network. Since MANET is an infrastructure less network, each mobile node operates not only as a host but also as a router, forwarding packets for other mobile nodes in the network. There are frequent unpredictable topological node. As the number of nodes in the network changes in these networks, which makes the task grows, the size of the routing tables and the of finding and maintaining routes are bandwidth required to update them also grows. difficult[14-16]. Conventional routing protocols This overhead is considered to be the main based on distance vector algorithms are not very weakness of DSDV. suitable for such situations as the amount of routing related traffic would consume a large 3.1 Overview portion of the wireless bandwidth, and such discovered routes would soon become crucial Every mobile node in the network maintains a due to mobility of nodes. Although good routing table, as shown in figure 1 in which all of numbers of routing protocols are suggested and the possible destinations within the network and tested for mobile ad-hoc networks. Research the number of hops to each destination are shows performance metrics like throughput, recorded. Each entry is marked with a sequence delay and protocol overhead in relation to number assigned by the destination node. The successfully transmitted data still need better sequence numbers enable the mobile nodes to optimization. distinguish stale routes from new ones, thereby avoiding the formation of routing loops. Routing These all problems make efficient dynamic tables updates are periodically transmitted routing an important research challenge in ad hoc throughout the network in order to maintain table networks. Here new protocols especially reactive consistency. types could be considered as very useful because they often generate much lower routing New route broadcasts contain the address of the overheads in comparison with proactive routing destination, the number of hops to reach the protocols. destination, the sequence number of the destination as well as a new sequence number Thus from the above discussion we concluded a unique to broadcast. The route labelled with the most recent sequence number is always used. In clear need of developing more efficient strategies the event that two updates have the same for routing in mobile ad-hoc network. Based on sequence number, the route with the smaller carried research the proposed scheme should be metric is used in order to optimise the path. capable of delivering an effective routing solution while addressing other routing related Routing is achieved by using routing tables issues along with routing. In this context the maintained by each node. some of the desirable characteristics of the proposed algorithm are bandwidth efficient, 3.2) DSDV Route Advertisement consume less battery power and be able or can be extended to support both uni-cast and multicast DSDV requires nodes to periodically transmit routing. routing table update packets, regardless of network traffic. These update packets are broadcast throughout the network. Therefore, 3. Destination sequence distance vector every node in the network knows how to reach routing protocol every other node. However due to the dynamically varying topology, the entries in this Based on conventional routing protocol, RIP list may change quite frequently over time, thus adapted for use in ad-hoc network, the requires, route advertisement to be made quite destination sequenced distance vector routing often . This is to ensure that every mobile node protocol is an extension of classical bellman can almost locate every other node in the ford routing mechanism. In DSDV routing is network. In addition each mobile node agrees to achieved by using routing tables maintained by relay data packets to other nodes upon requests. each node. The main complexity in DSDV is in In this way even though a node does not have a generating and maintaining these routing tables. direct link with a particular node in the network, DSDV requires nodes to periodically transmit it will still be able to exchange data with that routing table updates packets, regardless of node. network traffic. These update packets are broadcast throughout the network so every node Whenever a node broadcast data, a sequence in the network knows how to reach every other number is generated. In addition to data the broadcast contains other useful information such Any mobile node receiving new broadcast can as destination ID, number of hops to the find the fresh route by comparing receiving destination and destination sequence number. information with those that are previously Receiver on receiving this data make sure that recorded in its routing table. Route with recent the received sequence number is less the sequence number is considered as fresh route previously recorded sequence number in receiver while the older sequence number one‟s are routing table. Example of a route advertised table discarded. is shown is figure 1. If the sequence number found to be same, then the route with better metric will be selected. Destination Sequence Metric number 4. Mobile ad hoc on demand data delivery F 0 F-670 protocol G 1 G-780 4.1) Introduction H 3 H-890 MAODDP stands for mobile on-demand data Figure 2 Route advertisement in DSDV delivery protocol. It was first proposed pproceedings of the 3rd Annual Post-Graduate The receiver also advertises route received in Symposium on the Convergence of broadcast its routing information. The receivers Telecommunications, Networking and also add an increment to the metric before Broadcasting. Since then the protocols has advertising the route since further incoming gone through a series of modifications[2, 5]. packets will require one more hop to reach the Several functions to support both multicasting destination. and unicasting routing and to secure data The settling time is calculated by maintaining a transmission have been added in the initial running over the most recent updates of the specification of MAODDP. routes for each destination. The most recent On demand routing measurement of the settling time is calculated by Loop free routing with the use of sequence maintaining weighted average over the most numbers recent updates of the route for each destination. Saving battery power of the participating A parameter also selected to indicate how long a nodes route has to remain stable before it is counted as Faster network converge truly stable. Any route more stable then this Guaranteed data delivery to the destination. parameter will cause a triggered update if it is ever replaced by another route with different In general, whenever a source node requires a next hop or metric. route to deliver data packets to the destination for which it does not have any recorded route in 3.3) Sequence Number its routing tables. It initiates route discovery and data delivery process by broadcasting ROUTE Broken link, which is mainly due to topology DISCOVERY AND DATA DELIVERY changes is described by ∞ metric which could be PACKET (RREQD). There are three possibilities any value greater then the maximum allowed when this packet reaches to the intermediate metric. Whenever a link to next hop is broken, node. The first one if the node has a suitable path any route through the next hop is assigned ∞ for the destination, as enclosed in the header of metric and an updated sequence number. RREQD packet then its forward the packet to the Therefore the only situation when mobile node intended destination. The second possibility other then destination node generates sequence when node does not have any direct path for the number is when there is a broken link. destination node but have idea about the closest In summary there are two conditions when the neighbours, in this case, node forward this sequence number could be generated. packet to that node. The final possibility nodes Whenever a new broadcast is issued. have no information whatsoever about the When a broken link is found destination node as specified in the RREQD, in this case the node forward this packet to its next 3.4) Route selection hop neighbours. This process is repeated until the packet reach to the destination. Once the packet has reached to the destination node It broadcasts an acknowledge packet (ACK) back Immediately before a node broadcast a to the source node. This acknowledge packet RREQD, it increments its own confirm the source node that the previous sequence number. This prevents transmission was successful. It also help the problems with deleted reverse routes to intermediate node and the source nodes to the source of a RREQD. updates their routing information about all the nodes in the path from source to the destination.. However if the nodes do not hear any thing back Immediately before a destination node from the destination node before the expiry time broadcast an acknowledged (ACK) of RREQD packet. It will consider the previous message in response to a route request attempt as unsuccessful. and data delivery packet (RRQED), it updates its own sequence number to 4.1) Generating Route Request and data the maximum of its current sequence delivery packet (RREQD) number and the destination sequence number in the acknowledged packet A node floods a RREQD when it determines that (ACK). it needs a route to deliver data to a destination and does not have one available in its routing Every route table entry at every node MUST table. This can happen if the destination is include the latest information available about the previously unknown to the node, or if a sequence number for the IP address of the previously valid route to the destination expires destination node for which the route table entry or is broken. The destination sequence number is maintained. This sequence number is called field in the RREQD is considered as the last the "destination sequence number". It is updated known destination sequence number for this whenever a node receives new information about destination and is copied from the destination the sequence number from RREQD packet, ACK sequence number field in the routing table. If no packet, or RERR messages that may be received sequence number is known, a sequence number related to that destination. of zero is used. The source sequence number in the RREQD is the node's own sequence number. In summary, a node may change the sequence The Flooding ID field is incremented by one number for a particular destination only if: from the last Flooding ID used by the current node. Each node maintains only one Flooding It is itself the destination node, and ID. The Hop Count field is set to zero. offers a new route to itself A source node often expects to have bidirectional It receives an MAODDP messages i.e. communications with a destination node. In RREQD OR ACK, with new such cases, it is not sufficient for the source node information about the sequence number to have a route to the destination node; the for some other destination node destination must also have a route back to the source node. In order for this to happen as The path towards the destination node efficiently as possible, any generation of an expires or breaks. acknowledge packet by the destination node for delivery to the source node, should be 4.3) Generating acknowledge message (ACK) accompanied by some action which notifies the If a RREQD is successfully deliver to the destination about a route back to the source node. destined destination. It is the responsibility of the destination node to issue acknowledge packet 4.5) Maintaining Sequence number (ACK) back to the source node. Destination node MAODDP depends on each node in the network MUST update its own sequence number to the to own and maintain a sequence number to maximum of its current sequence number and the guarantee the loop-freedom of all the routes destination sequence number in the RREQD towards that node. MAODDP uses combination packet. The destination node places the value of sequence number and broadcast ID as a zero in the Hop Count field of the ACK message. precaution to avoid message looping. The sequence number is incremented in one of two circumstances 5. Analysis and discussion Mobile ad hoc networks suffer with high node mobility causes continuously changing mobility, frequent topology changes, bandwidth topology in which routes break unpredictably constraints, limited power and hidden terminal and new routes form dynamically. problem. Our research concluded that almost all of these issues are interrelated with the over In mobile ad-hoc network, an efficient group all routing mechanism. Therefore for a routing communication model can ease effective mechanism to be good enough for such an communication among various groups in the environment, it should be able to address some network. At present, multicasting routing in or all of these issues at a certain level. mobile ad-hoc networks is gained by adopting one of two approaches: flooding and tree-based Most of the tables driven protocols address routing. Flooding offers the lowest control routing without addressing the side effects on the overheads with very high data traffic, while tree- other related issues such as limited bandwidth based routing reduces data traffic in the network and battery power of ad-hoc networks. Like but requires many control data exchanges. other tables driven protocols, DSDV maintain a Studies show less efficient performance of these consistent overview of the network by forcing techniques on mobile ad-hoc network. Like most each mobile nodes to broadcast continuous of the other tables driven protocols DSDV in its updates after a regular interval of time. This present form does not address multicast routing. approach clearly not very feasible for ad hoc networking environment. Apart from bandwidth Security is one of the important aspects of this and battery power it could also create technology and it needs some serious unnecessary network head and could also a mean attention[24, 25]. Users within the network want of slowing down the over all routing operation. their communication to be secure. As current In  DSDV perform well for fairly static mobile ad-hoc networks do not have any stick topologies but become unreliable as node security policy, this could possibly lead active mobility and the number of traffic sources attackers to easily exploit or possibly disable the increase. Besides number of disadvantages, loop mobile ad-hoc network. Security goals in mobile free routing is considered to be one of the main ad-hoc networks are reached through benefits of DSDV. In DSDV Optimal values for cryptographic mechanisms such as public key parameters like settling time is not easy to encryption or digital signature. These determine. This might result in unnecessary mechanisms are backed by centralized key bandwidth consumption. Moreover, use of management where a trusted Certificate continuous updates could trigger network Authority (CA) provides public key certificate to overhead. Further more the protocol is not mobile nodes in order to develop mutual trust capable of supporting multicast routing. The size between nodes. Any disturbance with the of the routing table is also a problem as all nodes Certificate Authority can easily affect the are required to maintain location information of security of the entire network. the other nodes in the network, regardless weather or not this information is required. Security therefore, is one of the important aspect in ad-hoc networking environment. A Effective support of multicast or group routing protocol which offers a secure routing communication is essential for most ad-hoc mechanism could be considered as one of the network applications. There are many efficient solution. DSDV however does not applications where group communication is address security along with routing. However, a crucial task. Group communication, both one- besides number of disadvantages, loop free to-many and many-to-many, has become routing is considered to be one of the main increasingly important in mobile ad-hoc benefits of DSDV networks. In mobile ad-hoc network group communications, issues differ from those in MAODDP is one of the reactive or on-demand wired networks because of the variable and protocol which offers better route utilization, unpredictable nature of the wireless medium, faster network coverage by establishing route where the signal strength and propagation varies and delivering data simultaneously same time with the time and the environment. Moreover, one after the other. This approach is very feasible specially to maximize the battery life of the would prefer not to cooperate. When nodes do participating nodes. Unlike other on-demand cooperate they established the necessary ad-hoc routing protocols MAODDP reduces the number structure that can makes multi-hop of broadcasted packet by integrating the route communication possible by allowing traffic flow discovery and data packets together in a single from a node to reach those destinations that packet format i.e. route request and data delivery would either require a significant amount of packet (RREQD). Some of the unique features of transmission energy using single hop MAODDP are as follows. communication or simply not be possible Centralized approached without routing the traffic through other nodes. MAODDP addresses address issues security, This further means that nodes must be willing to bandwidth constraints and battery power along forward traffic for other nodes, and in this way with the routing mechanism.. spend energy without receiving any direct Security benefit. Thus the concept of introducing measure MAODDP offer secure routing by introducing its which can force participation nodes for own security mechanism. collaboration into the architecture of mobile ad- Multicasting hoc networks becomes one of the important MAODDP support both types of routing i.e. issues. unicast and multicast routing figure 3. Unlike most of the existing routing solution MAODDP address this issue by introducing its Sender own unique mechanism to identify „selfish‟ nodes and thus could be used to make network more reliable and secure. 6. Conclusion and future work In this paper, we have presented a study based comparison of destination sequence distance vector routing and mobile ad hoc on demand Figure3 Multicasting in mobile ad-hoc data delivery protocol. We highlighted different network aspects of these two techniques and presented a brief description of their applicability, Battery power operational details, suitability under different MAODDP does not require mobile nodes to be environments and their effects on the over all awake all the time. A node can go into sleep network performance. Our future work extends mode if it is not involved in an active this study based comparison into a simulation transmission. Thus save considerable battery based comparison which will be contributed to power of the mobile nodes. research community as a part of ongoing effort in this area. Automatic mechanism to find out if the transmission being failed 7. References MAODDP introduces a status time in the packet header of RREQD to find out the status of the previous transmission i.e. if the node does not . 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