# A Novel Effective Multipath Routing Technique Providing High Availability in Wireless Networks
## 2 Related Works
### Mp-Aodv  
MP-AODV [10] is a modification of AODV that discovers and establishes two node-disjoint routes, two link-disjoint routes, or two hybrid routes between a source and a destination in a wireless network. MP-AODV divides the route discovery process into two phases: the main route discovery and the backup route discovery. MP-AODV first discovers and establishes the main route and then performs the second route discovery. MP-AODV maintains only one alternate path. The paths established between the source and destination are either node-disjoint or link-disjoint. MP-AODV first attempts to establish two node-disjoint routes. If it does not find two such routes, it then discovers and sets up two link-disjoint routes to improve the reliability of data transmission. MP-AODV uses an additional one-bit flag to distinguish between control messages in the main routes (RREQ, RREP) and the backup route (RREQ_2, RREP_2). To establish the main route, the source broadcasts an RREQ. Upon receiving the RREQ, intermediate nodes store information about the RREQ's identification (RREQ ID) and the source node in a seen table. When the destination receives the RREQ, it sends an RREP back to the source along the reverse path. When an intermediate node that belongs to the main route receives the RREP, it increases the RREQ ID value in the seen table and then forwards the RREP to the source. Whenthe source receives the RREP, the main route is established, and the source starts data transmission and initiates the route discovery process for the backup route by broadcasting an RREQ_2. When an intermediate node receives the RREQ_2, it compares the ID of the RREQ_2 with that stored in the seen table. If it is identical, the node discards the RREQ_2. Otherwise, the node re-broadcasts the RREQ_2. At intermediate nodes belonging to the main route, the ID of the RREQ_2 and the stored ID are the same because MP-AODV has already increased the stored ID during the main route discovery process. Therefore, these intermediate nodes discard the RREQ_2. When the RREQ_2 reaches the destination, the backup route is discovered, and the destination sends an RREP_2 back to the source. When the source receives the RREP_2, the backup route is established. Unlike in the main route discovery process, intermediate nodes in the backup route discovery process do not increase the RREQ ID value stored in the seen table when they receive the RREP_2. Therefore, intermediate nodes along the main route have a higher RREQ ID value than nodes in the backup route. If a node-disjoint route does not exist, MP-AODV will find a link-disjoint route. The process of link-disjoint route discovery is similar to that of node-disjoint route discovery  
Figure 1b shows the process used by MP-AODV to discover and establish node-disjoint routes. The route discovery is a four-way handshake process. MP-AODV has high control overhead for discovering and establishing node-disjoint routes. Additionally, MP-AODV requires a long period to establish node-disjoint routes due to the four-way handshake route discovery process. Out of the existing multipath routing techniques, AOMDV is a link-disjoint multipath routing technique, whereas AODVM and MP-AODV node-disjoint multipath routing techniques. These techniques generate too many duplicates of control messages due to the use of many control messages and the distribution of the control messages. In addition, the node-disjoint multipath routing techniques, including AODVM and MP-AODV, use three-way and four-way route discovery process, respectively that take a long route discovery time. The motivation of this research is to propose a novel multipath routing variant of AODV that reduces the duplicates of control messages as well as decreases the route discovery time.