Subject Name Computer Networks II Subject Code 10
Subject Name: Computer Networks - II Subject Code: 10 CS 64 Prepared By: Madhuleena Das, Santhiya M Department: Computer Science & Engineering Date : 16. 5. 15 9/5/2021
Engineered for Tomorrow Wireless Ad-hoc & sensor network Date 16 -05 -15 9/5/2021 By, Madhuleena Das, Assistant Professor Dept of CSE MVJCE, B’Lore
Overview of Wireless Ad-Hoc Networks • Wireless mobile ad-hoc network (MANET) technology is designed for the establishment of a network anywhere and anytime, without any fixed infrastructure to support the mobility of the users in the network. • In other words, a wireless ad-hoc network is a collection of mobile nodes with a dynamic network infrastructure forming a temporary network. • No central server or base station for providing connectivity 9/5/2021
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Ad-hoc networks have several types of applications • Rescue operations. In an emergency public disaster, such as an earthquake, ad-hoc networks can be set up at a location where no infrastructure is present. • Military. Ad-hoc networks can be used in a battle zone, for a military command mobile units. • Law enforcement and security operations. An ad-hoc network can be used in a temporary security operation, acting as a mobile surveillance network. • Home networks. An ad-hoc network can be used to support seamless connectivity among various devices. • Conferencing. Ad-hoc networks can be set up for a presentation. 9/5/2021
Classification of Routing Protocols • Ad-hoc routing protocols can be classified into two broad categories: – Centralized versus distributed. In centralized routing protocols, the routing decision is made at a central node. In distributed routing protocols, the routing decision is made by all the network nodes. – Static versus adaptive. In static routing protocols, a route of a source/destination pair does not change because of any traffic condition or link failure. In adaptive routing protocols, routes may change because of any congestion. 9/5/2021
Table-Driven Routing Protocols • Table-driven, or proactive, routing protocols find routes to all possible destinations ahead of time. are needed. The routes are recorded in the nodes' routing tables and are updated within the predefined intervals. • Proactive protocols are faster in decision making but need more time to converge to a steady state, causing problems if the topology of the network continually changes. 9/5/2021
Source-Initiated Routing Protocols • Source-initiated, or reactive, routing protocols, are on-demand procedures and create routes only when requested to do so by source nodes. • A route request initiates a route-discovery process in the network and is completed once a route is discovered. 9/5/2021
Routing Protocols for Ad-Hoc Networks • Table-driven protocols are – Destination-Sequenced Distance Vector (DSDV) protocol, – Cluster-Head Gateway Switch Routing (CGSR) protocol, and – Wireless Routing Protocol (WRP). • Source-initiated, or reactive, routing protocols are – – Dynamic source Routing (DSR) protocol Temporally Ordered Routing Algorithm (TORA) Associative Based Routing (ABR) protocol Ad Hoc On Demand Distance Vector (AODV) protocol 9/5/2021
Destination-Sequenced Distance Vector (DSDV) Protocol • The DSDV is table driven based routing algorithm. DSDV is improved version of Bellman Ford routing algorithm. • Each DSDV node maintain two routing tables: - table forwarding packets, and table for advertising incremental updates. • The nodes will maintain a routing table that consists of a sequence number. • The routing table periodically exchanged so that every node will have latest information. • DSDV is suitable for small networks. 9/5/2021
• The algorithm works as follows • A node or a mobile device will make an update in its routing table and send the information to its neighbor upon receiving the updated information and make an update in its own routing table. • The update is made by comparing the sequence number received is greater than present sequence number than the new one will be used. • If there is a link failure in one of the node will change the metric value to infinity and broadcast the message. 9/5/2021
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Cluster-Head Gateway Switch Routing Protocol (CGSR) • CGSR is also a table driven routing protocol. • In this algorithm the mobile devices will be grouped to form a cluster the grouping is based on the range and each cluster is controlled by cluster head. • All the mobile devices will maintain 2 tables cluster member table and routing table. • The cluster member table will have the information about the cluster head for each destination the routing table will have routing information. • In this protocol the packet cannot be directly sent to the destination instead cluster heads are used for routing. CGSR routing involves cluster routing, where a node finds the best route over cluster heads from the cluster member table. 9/5/2021
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Wireless Routing Protocol (WRP) • The Wireless Routing Protocol (WRP) is a table-based protocol maintaining routing information among all nodes in the network. This protocol is based on the distributed Bellman-Ford algorithm. • The main advantage of WRP is that it reduces the number of routing loops. With this protocol, each node in a network maintains four tables, as follows: 9/5/2021
• Distance table, which holds the destination, next hop, distance, and predecessors of each destination and each neighbor. • Routing table, which saves the destination address, next hop, distance, predecessor, and a marker for each destination, specifying whether that entry corresponds to a simple path. • Link-cost table, which provides the link cost to each neighbor and also the number of periodic update periods elapsed since the node received any error-freemessage from it. • Message transmission-list table, which records which updates in an update message are to be retransmitted and which neighbors need to acknowledge the retransmission. The table provides the sequence number of the update message, a retransmission counter, acknowledgments, and a list of updates sent in the update message. 9/5/2021
Dynamic Source Routing (DSR) Protocol • DSR is a source initiated or on demand routing protocol in which source finds unexpired route to the destination to send the packet. • It is used in the network where mobile nodes move with moderate speed. • Overhead is significantly reduced, since nodes do not exchange routing table information. it has 2 phases. – Route discovery – Route maintenance
• Route discovery and maintenance • The source which wants to send the information to the destination will create a route request message by adding its own identification number and broadcasts them in the network. The intermediate nodes will continue the broadcast but adding their own identification number. • When the destination is reached a route reply message is generated which will be sent back to the source. The source can receive multiple route replies indicating the presence of multiple paths. • The source will pick up one of the path and will use for transmission. If there is a link failure one of the node will detect and will create a route error message which will be sent back to the source in this case the path has to be reestablished for further transmission.
Temporally Ordered Routing Algorithm (TORA) • The Temporally Ordered Routing Algorithm (TORA) is a source -initiated routing algorithm and, thus, creates multiple routes for any source/destination pair. • The advantage of multiple routes to a destination is that route discovery is not required for every alteration in the network topology. • This feature conserves bandwidth usage and increases adaptability to topological changes by reducing communication overhead. • TORA is based on the following three rules: 1. Route creation/discovery 2. Route maintenance 3. Route erasure
• TORA uses three types of packets: Query Packets for route creation, Update Packets for both creation and maintenance, Clear Packets for route erasure • A receiving node processes a query packet as follows – If the receiving node realizes that there is no further downstream links, the query packet is again broadcaster. Otherwise the node discards the packet – If the receiving node realizes that there is at least one downstream link, the node updates its routing table to the new value and broadcasts an update packet It performs efficient routing in large networks and in mildly congested networks
Associative-Based Routing (ABR) Protocol • ABR is an efficient on-demand or source initiated routing protocol. In ABR, the destination node decides the best route, using node associativity. • ABR is suitable for small networks, as it provides fast route discovery and creates shortest paths through associativity. • Each node keeps track of associativity information by sending messages periodically. • If the associativity value is more means nodes mobility is less. • If the associativity value is less means nodes mobility is more.
• In ABR the source which wants to send the packet to the destination will create a query packet and broadcast in the network. Query packet generation is required for discovering the route. • The broadcast continues as long as destination is reached • Once the destination is reached it creates the reply packet and sends back to the source. • The query packet will have the following information. – – – Source id Destination id All intermediate node id Sequence number CRC and Time to live [TTL]
Ad-Hoc On-Demand Distance Vector (AODV) Protocol • The Ad-Hoc On-Demand Distance Vector (AODV) routing protocol is an improvement over DSDV and is a source-initiated routing scheme capable of both unicast and multicast routing. AODV establishes a required route only when it is needed as opposed to maintaining a complete list of routes, with DSDV.
• The algorithm consist of 2 phases 1. Route discovery phase 2. Route maintenance phase • In route discovery phase the path from source to destination is identified by broadcasting route request packet [RREQ]. When the intermediate node receive RREQ they will create a backward pointer and continue the broadcast when the route request packet reaches the destination a route reply would be generated [RREP]. The route reply will have information about the path that can be chosen for the packet transmission.
• The route request packet can have following information. 1. Source id 2. Destination id 3. Sequence number 4. Backward pointer information 5. CRC and 6. Time to live[TTL]
Security in adhoc networks • The following are the security threat in adhoc network. • Limited computational capabilities : the nodes in the mobile adhoc network are modular, independent and will have limited computational capability. It becomes a source of vulnerability when they handle public key cryptography. • Limited power supply : since nodes have limited power supply attacker can exhaust batteries by giving excessive computations to be carried out. • Challenging key management : the key management becomes extremely difficult as the mobile devices will be under movement.
Types of attack in adhoc network • The attack can be classified into 2 types 1. Passive 2. Active • In passive attack, the normal operation of routing protocol is not interrupted. The attacker just tries to gather the information • In active attack, the attacker can insert some arbitrary packets and therefore might affect the normal operation of network • Attack can also be one of the following types
• Pin attack : with the pin attack, an unauthorized node pretends to have shortest path to the destination. The attacker can listen to path setup phase and become the part of network. • Location disclosure attack : by knowing the locations of intermediate nodes, the attacker can find out the location of target node • Routing table overflow : the attacker can create some routes whose destination do not exist. It will have major impact on proactive based routing • Energy exhaustion attack : the attacker tries to forward unwanted packets or send unwanted requests which can conserve the battery of the nodes
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