Study and Comparison of Mesh and Tree- Based Multicast Routing Protocols for MANETs

Study and Comparison of Mesh and Tree- Based Multicast Routing Protocols for MANETs Rajneesh Gujral Associate Proffesor (CSE Deptt.) Maharishi Markandeshwar University, Mullana, Ambala Sanjeev Rana Associate Proffesor (CSE deptt.) Maharishi Markandeshwar University, Mullana, Ambala Amrita Chaudhary M.Tech (Student) Maharishi Markandeshwar University, Mullana, Ambala Abstract- Many network applications require transmitting the same single copy of data packets concurrently to many destinations, it is called multicasting. The Multicast routing plays a substantial part in MANETs. Network usage efficiency is important for network applications, such as audio, video-streaming, which are sensitive to data delivery delay. Researches in this area have been done in the last ten years. In this paper, we present an overview of major directions in previous researches on mesh & tree based multicast routing protocol in MANET. Although these protocols perform well under specific mobility scenarios, traffic loads, and network conditions, no single protocol has been shown to be optimal in all scenarios.the primary focus is on applications and traffic management, rather than device attachment. We first review the pertinent aspects of network architecture and discuss the main differences between mesh and tree based multicast routing protocol, and with a motive of providing a complete understanding of these multicast routing protocols and presents the scope of future research in this field. Further, the paper specifically discusses the current development in the development of mesh based and tree based multicasting routing protocols. Keywords MANET, Multicast routing protocol, Comparison, Tree based multicast routing protocol, Mesh based routing protocol. I. INTRODUCTION 1.1 MULTICAST ROUTING PROTOCOL IN MANET MANETs are useful in many environments and do not need any infrastructure support. Collaborative computing and communications in smaller areas (buildings, organizations, conferences, etc.) can be set up using MANETs. Communications in battlefields and disaster recovery areas are other examples of application environments [6]. The increasing use of collaborative applications and wireless devices may further add to the needs and usages of MANETs. IP multicasting is an extension to Internet architecture to support multiple clients at network layer. The fundamental motivation behind IP multicasting is to save network and bandwidth resource via transmitting a single copy of data to reach multiple receivers simultaneously. Vol. 1 Issue 2 July 2012 58 ISSN: 2278-621X

Ad hoc multicasting protocols in existing literature have either evolved from the Internet multicast protocol, or designed specifically for ad hoc networks. Most of these protocols attempt to adapt to the network dynamics in ad hoc networks [6]. The primary goal of ad hoc multicasting protocols should be to construct/maintain a robust & efficient multicasting route even during high network dynamics. Multicasting techniques in MANETs can be classified based on group dynamics or network dynamics. A primary issue for managing multicast group dynamics is the routing path that is built for data forwarding [9]. Good multicast routing protocol should involved characteristic as below: Robustness: For many reasons, some data packets can be dropped In Mobile Ad-Hoc Networks (MANETs). This dropping process causes a low packet delivery ratio. Therefore, a multicast routing protocol should be robust enough to withstand the mobility of nodes and achieve a high packet delivery ratio. Efficiency: Multicast efficiency is defined as the ratio of the total number of received packets from the receivers to the total number of transmitted data and control packets in the network. Control overhead: The limitation of bandwidth is very important in MANETs. Thus, the design of a multicast protocol should minimize the total number of control packets transmitted for maintaining the multicast group. Quality of service: It is essential in multicast routing in most cases and the data transferred in a multicastsession is time-sensitive. Dependency on the unicast routing protocol: Sometimes multicast routing protocol needs to deals with deferent networks, then it is very difficult for the multicast protocol to work in heterogeneous networks. Therefore, the multicast routing protocol is independent of unicast routing protocol. Resource management: In Multicast routing protocol, resource management like power management and memory usage are very important issues to make ad-hoc networks works well. To reduce the number of packet transmissions, multicast routing protocol try to minimize the power resource. To reduce memory usage, it should use minimum state information [9]. There are many characteristics and challenges that should be taking into consideration when developing a multicast routing protocols, like: the dynamic of the network topology, the constraints energy, limitation of network scalability, and the different characteristics between wireless links and wired links such as limited bandwidth and poor security [1]. One of the most popular methods to classify multicast routing protocols for MANETs is based on how distribution paths among group members are constructed [2]. According to this Method, existing multicast routing approaches for MANETs can be divided into tree-based multicast protocols, mesh based multicast protocols and hybrid multicast protocols Tree-based multicast routing protocol. Mesh-based multicast routing protocol. Hybrid multicast routing protocol The classification of these routing protocols will be mentioned under as shown in Figure 1. Vol. 1 Issue 2 July 2012 59 ISSN: 2278-621X

Figure 1: Multicast routing protocols in MANET. 1.2 TREE-BASED MULTICAST ROUTING PROTOCOL In the tree-based multicasting, structure can be highly unstable in multicast ad-hoc routing protocols, as it needs frequent re-configuration in dynamic networks, an example for these type is Multicast extension for Ad-Hoc On- Demand Distance Vector (MAODV) and Adaptive Demand- Driven Multicast Routing protocol (ADMR). Treebased multicast routing protocols can be further divided into source- rooted and core-rooted schemes according to the roots of the multicast trees [1] [2]. 1.2.1 Source-rooted tree multicast routing protocol In a source-rooted tree-based multicast routing protocol, source nodes are roots of multicast trees and execute algorithms for distribution tree construction and maintenance. This requires a source to be aware of the topology information and addresses of all its receivers in the multicast group. Therefore, source-rooted tree-based multicast routing protocols suffer from high traffic overhead when used for dynamic networks. AMRoute is an example for source-rooted tree multicast routing protocol [2]. 1.2.2 Core-rooted tree multicast routing protocol In a core-rooted tree multicast routing protocol, cores are nodes with special functions such as multicast data distribution and membership management. Some core-rooted multicast routing protocols utilize tree structures [10]. But unlike source-rooted tree-based multicast routing, multicast trees are only rooted at core nodes. For different source-rooted multicast routing protocols, core nodes may perform various routing and management functions. Shared Tree Ad-hoc Multicast Protocol (STAMP) and Adaptive Core-based Multicast Routing protocol (ACMP) are core-based multicast routing protocols proposed for MANETs. Tree-based protocols provide high data forwarding efficiency at the expense of low robustness [2]. Their advantage is their simplicity. Their disadvantage is that until the tree is reconstructed after movement of a node, packets possibly have to be dropped. A tree-based multicast routing protocol establishes and maintains a shared multicast routing tree to deliver data from a source to receivers of a multicast group. A well-known example of tree-based multicast routing protocols are the Multicast Ad hoc On-demand Distance Vector routing protocol (MAODV)[3]. Figure 2: Path Discovery in the MAODV Protocol Vol. 1 Issue 2 July 2012 60 ISSN: 2278-621X

MAODV is a multicast extension for AODV protocol. MAODV based on shared trees on-demand to connect multicast group members. MAODV has capability of unicast, broadcast, and multicast. MAODV protocol can be route information obtained when searching for multicast; it can also increase unicast routing knowledge and viceversa. When a node wishes to join a multicast group or it has data to send to the group but does not has a route to that group, it originates a route request (RREQ) message. Only the members of the multicast group respond to the join RREQ [7]. If an intermediate node receives a join RREQ for a multicast group of which it is not a member or it receives a route RREQ and it does not have a route to that group, it rebroadcast the RREQ to its neighbors. But if the RREQ is not a join request any node of the multicast group may respond. 1.3 MESH-BASED MULTICAST ROUTING PROTOCOL Mesh-based multicast routing protocols are more than one path may exist between a source receiver pair, Core- Assisted Mesh Protocol (CAMP) and On-Demand Multicast Routing Protocol (ODMRP) are an example for these type of classification. 1.3.1 Source-Initiated Mesh Based Multicast Routing Protocols 1.3.1.1 On Demand Multicast Routing Protocol (ODMRP) ODMRP is an on-demand mesh based, besides it is a multicast routing protocol, ODMRP protocol can make use of unicast technique to send multicast data packet form the sender nodes toward the receivers in the multicasting group. To carry multicast data via scoped flooding it uses forwarding group concept. The source, in ODMRP, establishes and maintains group membership. If source wishes to send packet to a multicast group but has no route to that group, it simply broadcasts JOIN_DATA control packet to the entire network. When an intermediate node receives the JOIN_DATA packet it stores source address and sequence number in its cache to detect duplicate as shown in figure 3. It performs necessary routing table updates for reverse path back to the source[1][9]. A multicast receiver constructs a JOIN_TABLE upon getting JOIN_DATA packet and broadcasts it to its neighbors. When a node receives a JOIN_TABLE, it resolves whether it is on the way to the source by consulting earlier cached data. Figure 3: JOIN_DATA propagation Considering the matched entry this node builds new join table and broadcasts it. In this way JOIN_TABLE is propagated with the help of forwarding group members and ultimately it reaches to the multicast source. A multicast table is built on each node to carry multicast data. This process either constructs or revises the routes from sources to receivers and forms a mesh. 1.3.1.2 Dynamic Core Based Multicast Routing Protocol (DCMP) DCMP is source initiated mesh based soft state multicast routing protocol. DCMP selects only limited senders to be as cores. This protocol forms mesh by having three sources for broadcasting JREQ packet: active, passive and core active. Active and core active sources flood the JREQ packets and passive sources transmit these packets to the core Vol. 1 Issue 2 July 2012 61 ISSN: 2278-621X

active nodes, and moreover these packets broadcast through the mesh. Distance between passive and core active node should be less for higher delivery ratio of data. Here there are parameters such as: MaxHop and MaxPassSize. MaxHop represents no of links between passive and active core node. MaxPassSize represents the number of passive sources that are present. Advantage is it is more scalable, high packet delivery ratio. Disadvantage is if core active source fails then multicast operation will fail [4]. 1.3.1.3 Neighbour Supporting Multicast Protocol (NSMP) NSMP is source initiated mesh based soft state multicast routing protocol. In this, source will broadcast request to all the nodes. When a receiver receives the packet, it will reply to the upstream node and nodes will store node status in the routing table for the reverse path. The receiver will select route request packet by considering the weight factor which is based on forwarding and not forwarding nodes along the path Source will locally broadcasts route discovery packets to update the routes and mesh. Any node want to join, node has to wait for this local route discovery process and has to join. Any links that have to be repaired is transmitted to the source. Here the condition is the only distance with 3 or 2 hops has to join. Otherwise, it has to broadcast the request. Advantage is it reduces control overhead by performing only local route discovery and high packet delivery ratio. Disadvantage is weight metric is fixed it will have a problem when there is high network variations. 1.3.1.4 Enhanced-On Demand Multicast Routing Protocol (E-ODMRP) E-ODMRP is source initiated mesh based hard state multicast routing protocol. It is same as ODMRP but it uses dynamic broadcasting to reduce the control overhead in ODMRP. This protocol also performs local route discovery by using ERS. ERS requires more processing. It's not suitable for low end mobile devices. Packet delivery will be same as in ODMRP. Advantage is it reduces control overhead. Disadvantage is it suffers from scalability and nodes will perform ERS that leads to malicious activities. It requires more processing overhead. 1.3.1.5 Optimized Polymorph in Hybrid Multicast Routing Protocol (OPHMR) OPHMR is source initiated mesh based hard state multicast routing protocol. This protocol uses proactive routing within the zone and reactive between zones or groups. Mobile nodes contain two modes: proactive and reactive modes [4]. If a node wants to join groups of multicast nodes, node will perform broadcasting JREQ messages in reactive mode. If the node is in proactive mode it will check its routing table that whether there is a route to join to multicast group, then it will unicast the packet, else broadcast JREQ packet. Nodes will record the route status while JREQ message is passing along the route. Advantage is packet delivery will be increased and delay will be decreased. Disadvantage is delivery ratio decreases when mobile node increases. 1.3.1.6. Mesh Based Multicast Routing Protocol with Consolidated Query Packets (CQMP) CQMP is a source initiated mesh based hard state multicast routing protocol. It uses a consolidated query packet mechanism [4][9]. A source will multicasts query packet. It contains (sender ID and sequence number) name of sources, query sequence number, last hop ID, multicast group ID, current seq, next seq and hop count. The receiver receives many query packets from different sources. Each source will be represented as a, first field will be next seq of source. To consolidate query packet, it first compares the senderid and sequence number with the cache that is present. If it matches, it is treated as duplicate and discards packet. Otherwise it is processed, for each source query that contains sourceid and current seq will be checked with the cache and saves its id, nextseq and INT values in its routing table (RT). The Numsources field will be incremented every time. The receiver will forwards reply packet after checking everything, and if node detects, that it is the next node, and then it will change path status to source node which is forwarding group. When a packet reaches along source path, a source for the receiver route is formed. Nodes will be formed as forwarding the packets to that group. Advantage is, it does not include any additional transmissions as it contain query already transmitted field. It becomes more effective, even there are more sources. And less control overhead is achieved by consolidating the query packets. Disadvantage is the data delivery ratio will be reduced in high mobility conditions. 1.3.1.7 Bandwidth Optimized and Delay Sensitive (BODS) BODS is source initiated mesh based hard state multicast routing protocol. It is suitable for both bandwidth and delay sensitive applications ex: multimedia applications. The source node will broadcast query packet that contains Vol. 1 Issue 2 July 2012 62 ISSN: 2278-621X

nearest participant and distance to nearest participant. Receiver will check the nearest participant field by using priority i.e. highest and lowest. When the MREQ packet reaches by the path contain nodes that are members of a group, then it has higher priority. Otherwise it has lower priority [4]. It will be known by the field nearest participant which contains any value. The highest priority will reduce the delay. Timer will be used in a packet that is transmitted. It will expire after some time. If there is more than one path, then it will set to the non empty nearest distance field. BODS is an algorithm that is used by any protocol. In this algorithm, nearest participant and the distance will be added to the header of the join query packet and a delay timer set. When it expires, it will rebroadcast the packet. Advantage is it has more effective bandwidth, control overhead will be very less and packet delivery ratio will be more. Disadvantage is it will be suited for low mobility situations. 1.4 Receiver-Initiated Mesh Based Multicast Routing Protocols 1.4.1 Forward Group Management Protocol (FGMP): FGMP is a receiver or sender initiated shared tree based soft state protocol. It is completely based on a group of nodes that has to be forwarded. Each node maintains a group of nodes that forwards the packets. If the receiver or sender wants to join there are two methods: FGMP-RA receiver advertising and FGMP-SA sender advertising. In FGMP-RA, the receiver will advertise its presence by JREQ packets and sender that receives the packet, will update its table with group of receivers. In FGMP-SA, the sender will advertise its presence and receiver will update its table with a group of senders and broadcasts this joining table to form forwarding group. The forwarding table consists of receiver Ids and joining table consists of sender Ids. Advantage is it will flood its packets to forwarding group only, as it reduces control overhead and storage overhead. Disadvantage, it does not work for high mobile environments. It works better for, when the number of receivers is more than senders. 1.4.2 Advantages and Disadvantages of Mesh-Based Approaches In general there are three resources namely bandwidth, processing power and storage, which are important in ad hoc networks. Mesh-based approaches require more bandwidth, more overall network processing power and more storage space at each network node as compared to tree-based approaches [11]. This high consumption of resources in the case of mesh-based approaches is due to the presence of redundant routes for efficient handling of link failure and node mobility during multicast session. Another disadvantage in mesh-based approaches, due to having multiple routes to reach a particular mobile node, is the presence of routing loops. Special measure has to be taken to avoid looping and multiple delivery of same data packet to each mobile node, which increases the complexity of meshbased multicast routing algorithms [5]. 1.4.3 Mesh-Construction & Maintenance There are two approaches to elect and maintain FG of forwarding nodes. In the first approach known as FGMP-RA (Receiver Advertising), all the receivers of multicast group announce their membership (with their respective IDs) through periodic flooding of control messages [5]. Each sender after receiving the receiver advertisement updates its member table. Entries in the table are maintained using soft-states and those entries for which their corresponding timers have expired are deleted. Forwarding table (FW) is created after up-dating the member table and broadcasted to the neighbors. Each neighbor after receiving FW creates its own FW and further broadcast it and the process continues until all the receivers are reached. In FGMP-RA, FG is main-tained by the senders. In the second approach FGMP-SA (Sender Advertising), each sender floods the entire network with sender information. Receivers of multicast group after getting senders information will periodically broadcast Join Table messages to create and maintain FG just like FGMP-RA but in this cast the receivers will be sending sender IDs. Timers and FG are set by the node when it receives Join Table. In FGMP-SA, FG is maintained by the receivers [5]. Vol. 1 Issue 2 July 2012 63 ISSN: 2278-621X

II. HYBRID MULTICASTING It is the type of protocols which have the combination of both tree-based and mesh-based multicasting routing protocols e.g. Ad-Hoc Multicast Routing Protocol, AMRoute based on shared tree and has two faces: mesh and tree. AMRoute identifies and designates certain nodes as logical that are responsible for initiating the signaling operation and maintaining the multicast tree to the rest of the group members [8]. A non-core node only responds to messages. AMRoute does not address network dynamics and assumes the underlying unicast protocol to take care of it. 2.1 Performance Metrics There are several metrics for determining the performance of a protocol in mobile ad hoc networks [5]. The performance of the proposed algorithm is analyzed on the following metrics. 2.1.1. Data Packet Delivery Ratio: It is defined as the ratio of number of data packets successfully delivered to the number of data packets supposed to be received by the receivers of multicast group. It is also known as delivery ratio. This metric helps in determining the effectiveness of protocol for delivering the data packets. Large values are better than small values. 2.1.2 Data Forwarding Efficiency: It is defined as the number of data packets transmitted per data packet delivered. It is also known as delivery efficiency. The transmitted packets include all transmitted packets which are transmitted by the original sender of the packet and the retransmission of the same packet by the intermediate nodes. This is used in determining the bandwidth consumption of a protocol. The larger value indicates that data packet has been retransmitted more times by intermediate nodes. Small values are better than large values. 2.1.3. Protocol Efficiency: It is defined as the number of control packets transmitted per data packet delivered. It is also known as relative control packet overhead. This is helpful in measuring the efficiency of control packets for delivering data packets. In this case small values are better than large values[5]. III. CONCLUSION A study is given about two different multicast protocol and their comparison. All protocols have their own advantages and disadvantages. This paper explained various features of multicast protocol. The comparison includes the basic difference and similarities of mesh and tree based muticast protocol which can help to select which protocol is suitable in which situation. Multicast tree-based routing protocols are efficient and satisfy scalability issue, they have several drawbacks in ad hoc wireless networks due to mobile nature of nodes that participate during multicast session. In the mesh-based protocols provide more robustness against mobility and save the large size of control overhead used in tree maintenance. Hybrid multicast provides which are tree based as well as mesh based and gives the advantage of both types. IV. FUTURE SCOPE The work presented in this paper is survey work of mesh and tree based multicast routing protocol in MANET. Nothing in the world which can be said complete. There are many applications using these protocol. In future, a lot of work can be done to produce a new technologies to improve the performance regarding inference, efficiency, security and various other issues related to both the protocol in MANET. It is really difficult to design a multicast routing protocol considering all the above mentioned issues. Still it is an open problem for researchers to develop a single protocol which can satisfy as many goals as possible in the future. V REFERENCES [1]. citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.143 [2]. cse.unl.edu/~xueliu/publications/2008_computer_networks.pdf [3]. S. Guo and O. Yang, Energy-aware multicasting in wireless ad-hoc networks: A survey and discussion, Vol. 1 Issue 2 July 2012 64 ISSN: 2278-621X

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