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ROUTE MAINTENANCE: When originating or forwarding a packet using a source route, each node transmitting the packet is responsible for confirming that data can flow over the link from that node to the next hop. For example, in the situation shown below, node A has originated a packet for node E using a source route through intermediate nodes B, C, and D: +-----+ +-----+ +-----+ +-----+ +-----+ A ----> B ----> C -->? D E +-----+ +-----+ +-----+ +-----+ +-----+ FIGURE 1.6 ROUTE MAINTENANCE In this case, node A is responsible for the link from A to B, node B is responsible for the link from B to C, node C is responsible for the link from C to D, node D is responsible for the link from D to E. An acknowledgement can provide confirmation that a link is capable of carrying data, and in wireless networks, acknowledgements are often provided at no cost, either as an existing standard part of the MAC protocol in use (such as the link-layer acknowledgement frame defined by IEEE 802.11), or by a "passive acknowledgement" (in which, for example, B confirms receipt at C by overhearing C transmit the packet when forwarding it on to D). If a built-in acknowledgement mechanism is not available, the node transmitting the packet can explicitly request a DSR-specific software acknowledgement be returned by the next node along the route; this software acknowledgement will normally be transmitted directly to the sending node, but if the link between these two nodes is unidirectional, this software acknowledgement could travel over a different, multi-hop path. After an acknowledgement has been received from some neighbor, a node may choose to not require acknowledgements from that neighbor for a brief period of time, unless the network interface connecting a node to that neighbor always receives an acknowledgement in response to unicast traffic. When a software acknowledgement is used, the acknowledgement request should be retransmitted up to a maximum number of times. A retransmission of the acknowledgement request can be sent as a separate packet, piggybacked on a retransmission of the original data packet, or piggybacked on any packet with the same next-hop destination that does not also contain a software acknowledgement. After the acknowledgement request has been retransmitted the maximum number of times, if no acknowledgement has been received, then the sender treats the link to this next-hop destination as currently "broken". It should remove this link from its Route Cache and should return a "Route Error" to each node that has sent a packet routed over that link since an acknowledgement was last received. For example, in the situation shown above, if C does not receive an acknowledgement from D after some number of requests, it would return a Route Error to A, as well as any other node that may have used the link from C to D since C last received an acknowledgement from D. Node A then removes this broken link from its cache; any retransmission of the original packet can be performed by upper layer protocols such as TCP, if necessary. For sending such a retransmission or other packets to this same destination E, if A has in its Route Cache another route to E (for example, from additional Route Replies from its earlier Route Discovery, or from having overheard sufficient routing information from other packets), it can send the packet using the new route immediately. Otherwise, it should perform a new Route Discovery for this target. Free download bca project Hi you can download free BCA Computer Science Final Year Project, BE, BCA, MCA, B TECH ASP.net projects free download mca final year project PROJECT DEVELOPMENT 2.1 ALGORITHM USED In this thesis, three algorithms were used. They are as follows • Expanded Ring Search Algorithm • Tree creation Algorithm • Core resolution Algorithm DATA SECURITY USING RSA: • Source sends the encrypted data packet to the destination through the route discovered. • Destination decrypts the data packet received from the source and sends the acknowledgement. INPUT AND OUTPUT PARAMETERS : Input parameters: • At source a file is choosen to send to the destination node. • Then the encrypted data packets are sent with destination address and route request. Output parameters: • At the destination the packets are received. • Receiving positive acknowledgement with efficient and reliable packet transmission. ALGORITHM STEP BY STEP DESCRIPTION 1. If the user wants to send data: • Get the Destination identifier and the encrypted data to be transferred. • Initialize the buffer with the encrypted data to be transferred. • Setup a Request Zone. • Build a Route Request packet having the information about the source and the Destination identifiers, and the Request Zone information. • Broadcast the Route Request to its neighbors. • Setup a timer for receiving Route Reply. 2. If the node receives a packet a. Find the type of the packet received. b. Depending on the type of packet received do one of the following processes. • Process Route Request. • Process Route Reply. • Process Data Packet. • Process Decryption. • Process Acknowledgement. • Process Route Disconnect. • Process Route Disconnect reply. • Process Timer Run Out. PROCESS DESCRIPTION: PROCESS 1 To initiate the Route Discovery, node transmits a "Route Request" as a single local broadcast packet, which is received by (approximately) all nodes currently on the transmission range of, including node. Each Route Request identifies the initiator and target of the Route Discovery, and also contains a unique request identification determined by the initiator of the Request. Each Route Request also contains a record listing the address of each intermediate node through which this particular copy of the Route Request has been forwarded. PROCESS 2 After route discovery, to find the core node of the system then compares code node and user defined node in core class. If the core node and user defined destination node are same then it transmit the file to the corresponding destination node. PROCESS 3 When originating or forwarding a packet using a source route, each node transmitting the packet is responsible for confirming that data can flow over the link from that node to the next hop. PROCESS 4 • Source sends the encrypted data packet to the destination through the route discovered. • Destination decrypts the data packet received from the source and sends the acknowledgement. PERFORMANCE REQUIREMENTS • Minimum four terminals DESIGN CONSTRAINS • It takes more time for transmission. 2.1.2 MESH CREATION: • Mesh creation is used to establish connectivity • might have loop at member discovery phase • but increase robustness • use expanding ring search based on TTL-limited broadcast • A new node designate itself as a core of 1-node mesh • all core nodes periodically broadcast JOIN-REQ (the period is proportional to TTL associated with the last JOIN-REQ) • when a member receive JOIN-REQ from different a mesh, it responds back with JOIN-ACK, and a tunnel is established • Upon receiving a JOIN-REQ • if I’m a core • if the message is from myself => drop it • if the source of message is in my group and I don’t have a mesh/tree link to it => return a JOIN-ACK • otherwise, decrement the TTL and re-broadcast • if I’m a non-core member • if the message is from my core or for another group => decrement the TTL and re-broadcast • if it’s from a different core => return JOIN-ACK and mark the source as a mesh neighbor • To leave a group => send JOIN-NAK to neighboring nodes • when the number of links exceed LINK-THRESHOLD, a node must break some links by sending JOIN-NAK(might result temporary data loss & additional overhead)
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