## 3 Detouring Service via Multiple Paths  
### Basic Detouring Service  
Our method of defense, DMP, focuses on achieving smooth communication directly after attack detection in the presence of a jammer. Thus, we assume the existence of detection and mapping mechanism for the victim area such as optimal detection policy against sophisticated jammer [3] and mapping service of the jamming area [8]. We will explain DMP with the following terms:  
* _Victim/Jamming zone_: Zone including victim nodes against jamming attacks
* _Neighbor zone_: Adjacent zones of each zone
* _Destination zone_: Zone including a destination node
* _Detour node_: As the boundary node of the victim zone, it performs the algorithm shown in Table 2, thus it detours normal traffic with the determined multiple paths. * _Forward node_: The first foothold nodes are used to detour normal traffic. After the detour nodes determine these nodes, they forward normal traffic to them. * _Forward zone_: Zone determined by a detour node for detouring normal traffic  
After mapping the victim zone and selecting the detour nodes, our method of defense provides new paths to the destination node. For efficiently detouring normal traffic, we divide the network into rectangular zones. We assume that each node knows its zone ID and neighbor zones, and can know the zone ID of a node through the node ID and calculate the distance between two zones. However, our method of defense can be adjusted to zones with other shapes such as a hexagonal zone or an arbitrary shaped zone. We will discuss the extension of this basic detouring service in subsection 3.2. For our detouring service via multiple paths, each node has forward nodes included in each neighbor zone. When jamming attacks are detected, each detour node performs the algorithm shown in Table 2. If the next-hop of normal traffic is a node in the jamming area (line 1), it composes the set of forward nodes. In order to construct the proper set, it initially gathers the suitable forward zones among neighbor zones according to the distance from destination zone. If forward nodes in the neighbor zones are included in the set of jamming nodes, the zone is excluded from the set of forward zones (line 4). Moreover, if normal traffic has already been forwarded from a previous detour node, a zone including the previous node is excluded (\(\emph{z}\
eq\emph{dz}\)). Then, the forward nodes in the set of forward zones are sorted according to the distance of the included forward zone from the destination zone, and \(\emph{a}\) nodes in the sorted list are chosen (line 10-13). Finally, the detour node detours normal traffic evenly to the determined forward nodes. However, if the next-hop of traffic is not included in the jamming area, the detour node simply routes the traffic according to the normal routing protocol. Figure 3 depicts an example of forward zones as victim zones. The nodes in zone 33 have neighbor zones 22, 23, 24, 32, 34, 42, 43 and 44. On general routing, the possible cases in which the next-hop of normal traffic is a node in the jamming area are as follows: jamming zone 22, 23 and 32, as shown in Figure 3. Thus, the forward zones determined by line 4 of the algorithm shown in Table 2 are zones, except for each jamming zone among 22, 23, 24, 32 and 42. For example, if each node has a forward node in each neighbor zone and \(\mathbf{\alpha}\) is equal to 2, then the detour nodes in zone 33 consist of two forward nodes in zone 23/32, zone 22/32 and zone 22/23 in the respective cases.