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Ad hoc Networks


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  • Hello I am Engineer Nabil ask you to help me help as possible at the masters ask that you make an assessment of the performance of your code is a type of protocols in ad hoc networks mac protocol csma/ca
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  • 2. Ad Hoc Networks Seminar Submitted in partial fulfillment of the requirements For the degree of Bachelor of Technology In Computer Engineering By DARPAN DEKIVADIYA 09BCE008DEPARTMENT OF COMPUTER SCIENCE AND ENGINEERING AHMEDABAD-382481 April 2011
  • 3. Certificate This is to certify that the Seminar entitled ”Ad Hoc Networks” submitted by DARPANDEKIVADIYA(09BCE008), towards the partial fulfillment of the requirements for the degreeof Bachelor of Technology in Computer Engineering of Nirma University of Science andTechnology, Ahmedabad is the record of work carried out by him under my supervision andguidance. In my opinion, the submitted work has reached a level required for being acceptedfor examination. The results embodied in this Seminar, to the best of my knowledge, haven’tbeen submitted to any other university or institution for award of any degree or diploma. Prof.Vijay Ukani Prof. D. J. Patel Assistant Professor, Professor and Head, Dept. of Computer Science & Engg., Dept. of Computer Science & Engg., Institute of Technology, Institute of Technology, Nirma University, Ahmedabad Nirma University, AhmedabadProf. Manish ChaturvediGuide and Assistant Professor,Institute of Technology,Nirma University, Ahmedabad iii
  • 4. Abstract iv Now a days in the many areas of the network types of the network are used.Ad hocnetwork are one of the network. It is the mobile no de network and which all are connectedwith wireless link.There are many types of the ad hoc network.The most useful ad hocnetwork is in the security purpose.Routing algorithm is same as the wired network but somevariation are made in it.There is two types table-driven and on-demand protocols for therouting in ad hoc network. iv
  • 5. Acknowledgements v I would like to express my heartfelt gratitude to Prof. Manish Chaturvedi,Professor inDepartment of computer science and engineering for her valuable time and guidance thatmade the seminar project work a success. Thanking all my friends and all those who hadhelped me in carrying out this work. I am also indebted to the library resources centre andinterest services that enabled us to ponder over the vast subject of ”Ad Hoc Networks”. - DARPAN DEKIVADIYA 09BCE008 v
  • 6. ContentsAbstract ivAcknowledgements v1 Introduction 1 1.1 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.3 Major Issues and Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.4 Ad Hoc versus Infrastructure based Networks . . . . . . . . . . . . . . . . . 32 Architecture of Ad Hoc Network 4 2.1 IEE 802.11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1.1 History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Ad Hoc Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.2.1 Medium Access Control Layer . . . . . . . . . . . . . . . . . . . . . . 5 2.2.2 Basic DFWMAC-DCF using CSMA/CA . . . . . . . . . . . . . . . . 6 2.2.3 DFWMAC-DCF with RTS/CTS . . . . . . . . . . . . . . . . . . . . 73 Routing In Ad-Hoc Networks 8 3.1 Requirement of the Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2 General Issues for Ad Hoc Network Routing . . . . . . . . . . . . . . . . . . 94 Routing Protocols 10 4.1 Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1.1 Based on the routing information update mechanism . . . . . . . . . 10 4.1.2 Based on the use of Temporal information for Routing . . . . . . . . 10 4.1.3 Based on Routing Topology . . . . . . . . . . . . . . . . . . . . . . . 11 4.1.4 Based on the Utilization of specific Resources . . . . . . . . . . . . . 11 4.2 Proactive or table-driven routing protocols . . . . . . . . . . . . . . . . . . . 11 4.2.1 Destination sequenced distance-vector protocol . . . . . . . . . . . . . 11 4.2.2 Wireless routing protocol . . . . . . . . . . . . . . . . . . . . . . . . . 13 4.2.3 Cluster head Gateway Switch Routing protocol . . . . . . . . . . . . 14 4.3 On-Demand routing protocols . . . . . . . . . . . . . . . . . . . . . . . . . . 15 4.3.1 Dynamic Source Routing Protocol . . . . . . . . . . . . . . . . . . . . 15 4.3.2 Ad Hoc On-Demand Distance Vector Routing Protocol . . . . . . . . 17 4.4 Hybrid routing protocols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 4.4.1 Zone Routing Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . 19 vi
  • 7. Chapter 1Introduction In computer networking, an Ad Hoc Network refers to a network connection establishedfor a single session and does not require a router or a wireless base station. Mobile nodes that are within each other’s radio range communicate directly via wirelesslinks that. Here mobile nodes are cause the different topology in the networks. In the above diagram nodes A and D have direct connection between them. In the firstradio station shows that in same radio stations both A and D are directly connected. Butas the show in the second radio station, when nodes d are goes away from the these stationthe connection link was broken between them. But still A and D are connected via nodesA-B-C-D. So this type of networks connections is held in ad hoc networks. So it is widelyused in the military application and other temporary networks. For example, military units(e.g., soldiers, tanks, or planes), equipped with wireless communication devices, could forman ad hoc network when they roam in a battlefield. Ad hoc networks can also be used foremergency, law enforcement, and rescue missions. 1
  • 8. 1.1 Characteristics ˆ Operating without a central coordinator ˆ Multi-hop radio relaying ˆ Frequent link breakage due to mobile nodes ˆ Constraint resources (bandwidth, computing power, battery lifetime) ˆ Instant deployment1.2 Applications ˆ Military applications ˆ Collaborative computing ˆ Emergency rescue ˆ Mesh networks ˆ Wireless sensor networks ˆ Multi-hop cellular networks ˆ Wireless Community Network1.3 Major Issues and Challenges ˆ Hidden terminal problem ˆ Exposed terminal problem ˆ Channel efficiency ˆ Access delay and fairness ˆ Differential service ˆ Realistic mobility modeling ˆ power-aware routing ˆ Constructing virtual backbone ˆ Distinguish contention, packet drop, and noise errors ˆ Security ˆ Efficient multicasting 2
  • 9. 1.4 Ad Hoc versus Infrastructure based Networks In infrastructure based Networks , communication typically takes place only between thewireless nodes and the access point , but not directly between the wireless nodes. Infrastructure Networks contain special nodes called access points(APs), which are con-nected via existing networks. APs are special in the sense that they can interact with wirelessnodes as well as with the existing wired network. The other wireless nodes , also known asmobile stations , communicate via APs. The APs also act as bridges with other networks. Ad hoc LANs do not need any fixed infrastructure. These networks can be set up on thefly at any place. Nodes communicate directly with each other or forward messages throughother nodes that are directly accessible. The design of infrastructure based networks issimpler because most of the network functionality lies within the access point ,whereas theclient can remain quite simple. In Ad hoc networks, the complexity of each node is higher because every node has toimplement medium access mechanisms to provide certain quality of service. Infrastructurebased networks lose some of the flexibility which wireless networks can offer. They cannotbe used for disaster relief in cases where no infrastructure is left, where ad hoc networks canbe used. 3
  • 10. Chapter 2Architecture of Ad Hoc Network The architecture of ad hoc network can be explained by IEEE 802.11 standards.2.1 IEE 802.11 IEEE 802.11 is a set of IEEE standards that govern wireless networking transmissionmethods.2.1.1 History 802.11 technology has its origins in a 1985 ruling by the U.S. Federal CommunicationsCommission that released the ISM band for unlicensed use. In 1991 NCR Corporation (nowAlcatel-Lucent and LSI Corporation) invented the precursor to 802.11 in Nieuwegein, TheNetherlands. The inventors initially intended to use the technology for cashier systems; thefirst wireless products were brought on the market under the name WaveLAN with raw datarates of 1 Mbit/s and 2 Mbit/s. Vic Hayes, who held the chair of IEEE 802.11 for 10 years and has been called the”father of Wi-Fi” was involved in designing the initial 802.11b and 802.11a standards withinthe IEEE. In 1992, the Commonwealth Scientific and Industrial Research Organisation (CSIRO)obtained a patent in Australia for a method of wireless data transfer technology based onthe use of Fourier transforms to ”unsmear” the signal. In 1996, CSIRO obtained a patentfor the same technology in the US. In April 2009, 14 tech companies selling Wi-Fi devices,including Dell, HP, Microsoft, Intel, Nintendo, and Toshiba, agreed to pay CSIRO 250 dollorsmillion for infringements on the CSIRO patents Mobile terminals can operate in two modes under IEEE 802.11 : ˆ Infrastructure Mode ˆ Ad Hoc Mode 4
  • 11. 2.2 Ad Hoc Mode IEEE 802.11 only covers PHY layer and MAC layer PHY layer is subdivided into ˆ Physical Layer Convergence Protocol (PLCP) ˆ Physical Medium Dependent sub layer (PMD) PHY management include channel tuning and responsible for higher layer functions (e.g.control of bridging). MAC management controls authentication mechanism and power man-agement to save battery power.2.2.1 Medium Access Control Layer The basic servies provided by the MAC layer are the mandatory ”Asynchronous dataservice” and an optional ”Time bounded service”. while 802.11 only offers the Asynchronousdata service in ad-hoc mode,both service types can be offered using an Infrastructure basednetwork. The following three mechanisms for IEEE 802.11 : The mandatory basic method basedon a version of CSMA/CA, an optional method avoiding the hidden terminal problem,andfinally a contention free polling method for time bounded service. The first two methods arealso summarized as ”Ditributed Coordination Function(DCF)”, the third method is called”Point Coordination Function(PCF)”. The MAC Mechanisms are also called ”DistributedFoundation Wireless Medium Access Control(DFWMAC)”. 5
  • 12. 2.2.2 Basic DFWMAC-DCF using CSMA/CA The mandatory access mechanism of IEE 802.11 is based on Carrier Sense MultipleAccess with Collision Avoidance(CSMA/CA) ,which is random access scheme with carriersense and collision avoidance through random backoff. The basic CSMA/CA mechanismshown in figure 2.1: Figure 2.1: Cotention window and waiting time If medium is idle for at least the duration of DIFS , a node can access the medium atonce.This allows for short access delay under light load. If medium is busy , nodes have to wait for the duration of DIFS , entering a contentionphase afterwards. Each node now choose a random back off time within a contention window and delaysmedium access for this random amount of time. The node cntinues to sense the medium. As soon as a node senses the channel is busy ,it has lost this cycle and has to wait for the next chance. But if the randomized additionalwaiting time for a node is over and the medium is still idle ,the node can access the mediumimmediately. The basic CSMA/CA mechanism is not fair.Independent of the overall time a node hasalready waited for transmission;each node has the same chances for transmitting data in thenext cycle.To provide fairness , IEEE 802.11 adds back off timer. Each node selects randomamount of waiting time within the range of contention window. If certain station does not get access to the medium in first cycle, it stops its back offtimer , waits for the channel to be idle again for DIFS and starts the counter again. As soonas the counter expires, the node accesses medium. This means that deffered stations do notchoose a randomized backoff time again, but continue to countdown. Stations that have waited longer have the advantage over stations that have just en-tered,in that they only have to wait for the remainder of their backoff timer from the previouscycle. 6
  • 13. 2.2.3 DFWMAC-DCF with RTS/CTS Hidden terminal problem may occur in 802.11, if one station can receive two others, butthose cannot receive each other. To deal with this problem, mechanism using two control packets , RTS and CTS. After waiting for DIFS , the sender can issue a request to send (RTS) control packet. Every node receiving this RTS now has to set its net allocation vector (NAV) in accor-dance with the duration field The NAV than specifies earliest point at which the station can try to access the medium. If the receiver receives the RTS , it answers with the clear to send (CTS) waiting forSIFS. This CTS packet contains duration field and receivers have to adjust their NAV. Now all nodes within receiving distance around sender and receiver are informed thatthey have to wait more time before accessing the medium. This mechanism reserves the medium for one sender exclusively. It is also called a Virtual Reservation Scheme. 7
  • 14. Chapter 3Routing In Ad-Hoc Networks3.1 Requirement of the Routing ˆ It should be fully distributed, as centralized routing involves high control overhead and hence is not scalable. Distributed routing is more fault-tolerant than centralized routing, which involves the risk of single point of failure. ˆ It must be adaptive to frequent topology changes caused by the mobility of nodes. ˆ It must be localized, as global state maintenance involves a huge state propagation control overhead. ˆ It must be loop-free and free from stale routes. ˆ It must converge to optimal routes once the network topology becomes stable. The convergence must be quick. ˆ It must optimally use scare resources such as bandwidth, computing power, memory and battery power. ˆ It should be able to provide a certain level of quality of service (Qos) as demanded by the applications,and should also offer support for time-sensitive traffic. ˆ The flooding must be less. 8
  • 15. 3.2 General Issues for Ad Hoc Network Routing Secure delivery and the capability to handle constant connectivity are the most importantissues for routing protocols in wireless mobile ad hoc networks. Once the path will establishbetween the source end destination, the source will send message to the destination withoutworried.If the connectivity of any two nodes changes and routes are affected by this change,the routing protocol should be able to recover if an alternate path exists. There are some other issues related to routing in wireless ad hoc networks. For example: ˆ overhead is particularly important in a wireless network with limited bandwidth. ˆ Power consumption may also be a problem in an ad hoc network with battery-powered nodes. ˆ Quality of service may be required in an ad hoc network supporting delay sensitive applications such as video conferencing . ˆ A routing protocol may need to balance traffic based on the traffic load on links. ˆ Scalability of routing protocols is an important issue for large networks . The routing protocol may need to implement security to protect against attacks, suchas sniffer, man-in-the-middle. Routing protocols may rely on information based on otherlayers. For example, the Global Positioning System (GPS) can be used in wireless ad hocnetworks deployed in battlefields or connecting vehicles. Mobility prediction can improverouting in wireless networks with known movement patterns, such as the IRIDIUM systemsatellite network . Information from the medium access control layer may be propagated tothe network layer so that neighbours can be detected via MAC layer protocols. The powerof received signals from a neighbouring node can be used to decide whether neighbour ismoving closer or further away . 9
  • 16. Chapter 4Routing Protocols4.1 Classification Routing protocols for ad hoc wireless networks can be classified into several types basedon different criteria. The routing protocols for ad hoc wireless networks can be broadlyclassified into four categories base on :- ˆ Routing Information update mechanism ˆ Use of Temporal information for routing ˆ Routing Topology ˆ Utilization of specific resources4.1.1 Based on the routing information update mechanism ˆ Proactive or table-driven routing protocols ˆ Reactive or on demand routing protocols ˆ Hybrid routing protocols4.1.2 Based on the use of Temporal information for Routing Since ad hoc wireless networks are highly dynamic and path breaks are much morefrequent than in wired networks, the use of temporal information regarding the lifetime ofthe wireless links and the lifetime of the path selected assumes significance. ˆ Routing protocols using past temporal information ˆ Routing protocols that use future temporal information 10
  • 17. 4.1.3 Based on Routing Topology Routing topology being used in the Internet is hierarchical in order to reduce the stateinformation maintain at the core routers. ˆ Flat topology routing protocols ˆ Hierarchical topology routing protocols4.1.4 Based on the Utilization of specific Resources ˆ Power aware routing ˆ Geographical information assisted routing4.2 Proactive or table-driven routing protocols These protocols are extension of the wired network routing protocols. They maintainthe global topology information in the form of the tables at every node. These tables areupdated frequently in order to maintain consistent and accurate network state information.The distance-vector routing protocol (DSDV),wireless routing protocol (WRP),source-treeadaptive routing protocol (STAR),and cluster-head gateway switch routing protocol (CGSR)are some example for the protocols that belong to this category.4.2.1 Destination sequenced distance-vector protocol This protocol also called as the DSDV routing protocol. It is the enhanced version ofthe distributed Bellman-Ford algorithm where each node maintains a table that contains theshortest distance and the first node on the shortest path to every other node in the network.It incorporate table update with increasing sequence number tag to prevent loops, to counterto the count-to-infinity problem, and for faster convergences. As describe this is the tabledriven so that at finite interval the tables of the each node exchange to update and whichare reachable from all the nodes. If the topologies of the network are change then all tablesare forwarded to their neighbor. Here in the table updating, we have two types:- One isthe full dump in which done either when the local topology changed significantly or when amore incremental change required in the table. Second is the incremental update in whichnode does not observe change in the topology. Here one example is given for table updatingand node table creation. 11
  • 18. Figure 4.1: DSDV Protocol Desination Next Hop Distance A A 0 B B 1 C C 1 D D 1 E D 2 F D 2 Table 4.1: Routing Table of DSDV Protocol Here consider the example, here node A is the source node and F is the destinationnode. Here in the table first Column is destination node which is all nodes in the network.Second Column is the next node in the shortest path to the source path. Third column isthe distance between two nodes- source to destination. And fourth column is the sequencenumber of each packet to be received by them. Here routing table for node A is indicating that the shortest path to the destination nodeF is available through node D and the distance to it is two. And the packets to be receivedat that place which has number as shown in table. If any link between two node is brokenthen the distance is assign infinite to that node and update the all node’s routing table. 12
  • 19. Advantages ˆ The availability of the routers to all destination at all times implies that much less delay is involved in the route setup process. ˆ The mechanism of incremental updates with sequence number tags makes the existing wired network protocol adaptable to ad hoc networks. Hence wired network protocol can be applied to the ad hoc network by less modification. Disadvantages ˆ A small network with high mobility or a large network with low mobility can completely choke the available bandwidth. Hence this protocol suffers from excessive control overhead that is proportional to the number of nodes in the network. ˆ In order to obtain information about a particular destination node, a node has to wait for a table update message initiated by the same destination node.4.2.2 Wireless routing protocol The WRP protocols is the basically same as the DSDV protocols, but it is differ fromit only in the their routing protocol. The routing table contain the up-to-date view of thenetwork for the network for all known destination. The routing table keeps the shortestdistance, the predecessor node and flag indicating the status of the path. The path statusmay be a simple path(correct) ,or a loop(error) ,or the destination node not marked(null).The LTC(Link cost table) contain the cost of relaying message through each link. TheMRL(Message transmission list) contains an entry for the every update message that is tobe retransmitted and maintain the counter for the each entry. When a node detects a linkbreak, it sends an update message to its all neighbors with the link cost is infinite (?). Andthat all neighbors find the alternate path to reach the destination and resend the message. Advantages ˆ It is the faster convergence and involves fewer table updates. Disadvantages ˆ Complexity of maintenance of multiple tables demands a larger memory and greater processing power from the nodes. ˆ At the high mobility, the control overhead involved in updating table entries is almost the same as DSDV. So it is not suitable for highly dynamic and also for very large ad hoc networks. 13
  • 20. 4.2.3 Cluster head Gateway Switch Routing protocol The CGSR protocol uses a hierarchical network topology that employs at topologies.CGSR organizes nodes into clusters, with coordination among the member of each clusterinstructed nodes named ”cluster head”. This cluster head selected dynamically by employinga least cluster change (LCC) algorithm. According to this algorithm ,nodes creates to bea cluster-head only if it comes under the range of another cluster-head, where tie is brokeneither using the lower ID or highest connectivity algorithm. CGSR protocol creates afixedregion in the network. Each node in the cluster region is known as cluster member andthey all are connected with pivot node which is called cluster-head .Two cluster region areconnected via node which are place in intersection region of two cluster region and calledcluster-gateway. Figure 4.2: CGSR protocol Here in the figure three cluster area are shown ,the all are overlapped in each other .sobetween their intersection one node is placed as the gateway which transfer the informationof one cluster area to the other. 14
  • 21. Advantages ˆ CGSR is a hierarchical routing scheme which enables partial coordination between nodes by electing cluster-heads. Hence , better bandwidth utilization is possible. ˆ It is easy to implement priority scheduling scheme with token scheduling and gateway code scheduling. Disadvantages ˆ It increases in path length and instability in the system at high mobility when the rate of change of cluster-heads is high. ˆ To avoid gateway conflicts, more resources are required. ˆ The power consumption at the cluster-head node is also a matter of concern because the battery-draining rate at the cluster-head is higher than that at a normal node.4.3 On-Demand routing protocols This type of protocols execute the path finding process and exchange routing informationonly when path is required by the node to communicate with a destination. There some ofthe routing protocols like Dynamic Source Routing Protocol (DSR) , Ad Hoc On-DemandDistance Vector Routing Protocol (AODV) .4.3.1 Dynamic Source Routing Protocol This type of routing protocol is design to restrict the bandwidth consumed by controlpackets in ad wireless networks by eliminating the periodic table-update message requiredin the table driven approach. In this routing protocol does not require periodic ’hello’packet transmission, which are used by a node to inform its neighbors of its presence. Thebasic approach of this protocol during the routing construction phase is to establish a routeby flooding Route-Request packets in the network. The destination node, On receiving aRoute-Request packet, respond by sending Route-Reply packets back to the resource. 15
  • 22. Figure 4.3: DSR Protocol Here shown in the figure, the node 1 is the source node and the node 5 is the destinationnode. when 1 has data packet to sent to the node 5, it initiate a Route-Request as BLUEarrow in figure ,and sent it to all its neighbors or flooded. Each node receiving this requestpacket check if it is the destination then it generate Reply packet and send to sender. Ifit is not proper destination then again that node send request packets to their neighboruntil destination node not found. Each packet has unique sequence number so that in thenetwork while flooding loop will not generate. If duplicate the packet at any node then itwill discarded by the particular node where redundancy will observe. 16
  • 23. Advantages ˆ Do not exchange routing update periodically, so overhead transmission is greatly re- duced ˆ Can refer to cache for the new route when link fails. Disadvantages ˆ Scalability problem: High route discovery latency for large network. ˆ High mobility problem: although the packet dropped may not be substantional, the overhead traffic will increase a lot.4.3.2 Ad Hoc On-Demand Distance Vector Routing Protocol The Ad hoc On-demand Distance Vector (AODV) routing protocol is a reactive protocol.Similar to DSR,AODV broadcasts a route request to discover a route in a reactive mode. Thedifference is that in AODV, a field of the number of hops is used in the route record, insteadof a list of intermediate router addresses. Each intermediate router sets up a temporaryreverse link in the process of a route discovery. This link points to the router that forwardedthe request. Hence, the reply message can find its way back to the initiator when a route isdiscovered. When intermediate routers receive the reply, they can also set up correspondingforward routing entries. To prevent old routing information being used as a reply to thelatest request, a destination sequence number is used in the route discovery packet and theroute reply packet. A higher sequence number implies a more recent route request. We use the example topology shown in Figure to illustrate the discovery procedure ofAODV. Note that Routers A and C are disconnected from each other while both of themconnect to B. When Router A starts a route discovery to C, a route request is broadcast. Therequest packet contains the requested destination sequence number, which is 1 greater thanthe one currently kept at A. The intermediate routers reply to the source if they know theroute to that destination with the same or higher destination sequence number. We assumethat B does not have a record for a route to C. Therefore, B first sets up a temporary linkpointing back to A. In the second step, it increases the number of hops by 1 and rebroadcaststhe request. When C receives that request, it creates a new destination sequence number. Aroute reply with that new sequence number is sent by C. The initiator and all intermediaterouters build routing entries associated with this new sequence number when they receivethe reply. The number of hop values can be used to find a shorter path if a router receivestwo replies with the same destination sequence number. 17
  • 24. Figure 4.4: AODV ProtocolAdvantagesˆ AODV is loop-free due to the destination sequence numbers associated with routes. Therefore, it offers quick convergence when the ad hoc network topology changes which, typically, occurs when a node moves in the networkDisadvantagesˆ Poor scalability is a disadvantage of AODV. 18
  • 25. 4.4 Hybrid routing protocols4.4.1 Zone Routing Protocol The Zone Routing Protocol (ZRP) is a prototype routing protocol. ZRP is formed by twosub-protocols, the Intrazone Routing Protocol (IARP) and the Interzone Routing Protocol(IERP). IARP is ”a limited scope proactive routing protocol used to improve the performance ofexisting globally reactive routing protocols”. It relies on the service of a certain neighbordiscovery protocol (NDP) to provide neighbor information. IARP may use a scheme basedon the time-to-live (TTL) field in IP packets to control the zone range. IERP is the reactive routing component of ZRP. This scheme is responsible for finding aglobal path. It avoids global queries for destinations that would be sent to surrounding hopneighbors. When global queries are required, ”the routing zone based broadcast service canbe used to efficiently guide route queries outward, rather than blindly relaying queries fromneighbor to neighbor”. ZRP tries to combine the advantages of reactive and proactive routing protocols. Thepotential disad-vantage is the lack of route optimization. We use the example network inFigure to briefly show the concept of ZRP. The range of the zone is set to one. So routersin Subnets I and II use proactive IARP to find routes to other routers in the same subnet.For routes to the other subnet, reactive IERP is used. Figure 4.5: Zone Routing Protocol 19
  • 26. Advantagesˆ By combining the best features of proactive and reactive routing scheme, ZRP reduce the control overhead compared to the Route-Request flooding mechanism employed in on-demand approaches and the periodic flooding of routing information packets in table-driven approaches.Disadvantagesˆ In absence of a query control ,ZRP tends to produce higher control overhead than the aforementioned schemes. This can happen due to the large overlapping of nodes’ routing zones. The query control must ensure that redundant or duplicate Route- Request are not forwarded.ˆ The decision on the zone radius has a significant impact on the performance of the protocol. 20
  • 27. Referencesˆ Ad hoc wireless networks Architectures and protocols By C.Siva Ram Murthy and B.S. Manojˆ A Secure Routing Protocol for Ad Hoc network By Kimaya Sanzgirˆ Mobile Communications By Jochen H. Schiller 21