摘要:Any node can receive a lot of information about the network by placing its interface into promiscuous mode. The information the node can receive can be used to build trust levels for different modes.
messages on a per interface basis.
To avoid radio collisions due to synchronized forwarding, a jitter is introduced to the message forwarding. This is a random small time interval for which the message is to be cached in the node before forwarding it. When using forwarding-jitter, piggybacking of messages will often occur since multiple messages that are to be forwarded might arrive within the buffer period. When this happens, messages are stacked within the same OLSR packet.
3.4.3 Link set optimization
Due to the nature of the MPR selection, only nodes which are chosen as MPRs by one or more neighbors, needs to declare their link-state. In fact, these nodes need only declare the MPR selectors in the link state messages. When this information is flooded to all nodes in the MANET, all nodes will have enough information to calculate shortest path routes to all hosts. The default OLSR setting is that a node only floods link-state messages if it is chosen as MPR by at least one neighbor, and it only announces its MPR selectors in these messages. In a topology as illustrated in figure 3-6 only the nodes selected as MPRs (gray nodes) by one or more neighbors will transmit link-state messages. One can easily see that this information, in addition to some neighbor-sensing scheme, will be sufficient to create a full understanding of the topology.
3.5 Neighbor discovery:
OLSR requires a system which can detect neighbors and the communication lines to them. On a regular interval, HELLO messages are sent out. Figure 3-7, illustrates a simplified form of neighbor discovery using HELLO messages.
First, an empty HELLO message is sent by A and that message is been received by B, hence registering A as an asymmetric neighbor; because in the HELLO message, B is unable to locate its own address. Now B sends a HELLO message in order to declare A as an asymmetric neighbor. As soon as A receives this message from B, it will find its own address and in this way B is set to be a symmetric neighbor. At the end, when B receives HELLO message from A, where A has already included B in that message, B will register A as a symmetric neighbor.
3.5.1 Link sensing
To keep up-to-date information on what links exist between a node and its neighbors, the link set is maintained. In HELLO messages a node emits all information about the links to neighbors from the interface on which the HELLO is transmitted. When declaring links, the IP addresses of the actual interfaces making up the link is used. When declaring the neighbor state of neighbors not reachable on the interface on which the HELLO is transmitted, the main address of the neighbor node is used.
In a scenario like the one depicted in figure 3-8, A would send the following information in its HELLO message on interface a1:
Its current link and neighbor state for d1.
Its current link and neighbor state for c1.
Its current neighbor state for the main address of node B which is b1.
When building a HELLO to be transmitted on a2, node A will include the following information:
Its current neighbor state for d1.
Its current neighbor state for c1.
Its current link and neighbor state for b2.
Upon receiving a HELLO from a neighbor, a node checks to see if the HELLO message contains the IP address of the interface the message本论文由英语论文网提供整理,提供论文代写,英语论文代写,代写论文,代写英语论文,代写留学生论文,代写英文论文,留学生论文代写相关核心关键词搜索。