# An Efficient Framework Model for Optimizing Routing Performance in VANETs
## 3 Framework Components
### OLSR Protocols and Parameter Overview  
A link state routing protocol was proposed in [25] for discovering the shortest path. This protocol has an efficient mechanism that can be adapted to sensing and collecting information about its neighbors and immediately create a route based on the number of hops. Each node generates a different type of message in order to sense its neighbor nodes [24]. Basically, the nodes exchange recent knowledge periodically based on HELLO-interval and Topology Control (TC) messages in order to declare all the links. Then, each node collects links' information of one and two-hop neighborhood in order to update their routing tables and look for the candidate nodes that have a high probability to become a MPR node.  
In OLSR, the MPRs are selected using the HELLO-interval messages and are only responsible for forwarding TC messages to special nodes in the network. This feature ensures a minimum level of packet broadcasting over the whole network. Therefore, the performance of OLSR is greatly influenced by the number of HELLO-interval and TC messages and their interval time. Furthermore, increasing the rate of Hello-interval and TC messages leads to more frequent updates in the topology table thereby resulting in more routing overhead [27]. The HELLO-interval represents the time interval in seconds needed to exchanged information about neighbor nodes, where each node knows the expected time of each link. Accordingly, the REFRESH-interval minimizes the routing overhead by controlling the number of HELLO-interval messages. Thus, the adjustment of the OLSR message interval should be taken into consideration to reduce the overhead and to enhance network scalability.  
This work tunes the most important configuration parameters, which have a great impact on network performance as proposed in the ordinary OLSR. Table 1 summarizes the main configuration parameters of OLSR RFC-3626. For this purpose, it is necessary to declare all the links with all neighbors at least once within the scope of the updated REFRESH-interval. Consequently, the HELLO-interval must be smaller than or equal to the REFRESH-interval. The TC-interval represents the volume of information that may be involved in the periodic HELLO-interval message. By exchanging HELLO-interval messages, each node can receive information from the broadcast of the TC-intervalmessages throughout the whole network. The messages contain a set of fully advertised links between nodes, which must be compiled to determine the routing table. The NEIGHB HOLD TIME parameter refers to the time validity of the information through the hello default configuration, which should be equal to 3 HELLO-interval. The TOP HOLD TIME is the parameter that indicates how much time is required as a validity period for the information in the TC interval message. The default configuration is equal to 3 TC-interval. Nodes in OLSR-RFC network determine its willingness value between 0 to 7 to act as a MPR and participate in forwarding based on their optimal mode of source destination. DUP HOLD TIME value of (30 s) was calculated according to the time that node needs to process the information about forwarded packets. Therefore, we choose this value because it is more compatible with the other BOLSR-PSO configuration parameters.  
As a result, these parameters define the degree of time allocated, which can be selected from a ready-made group of eight levels for re-routing message information that is equal to 3 by default. The interesting features of OLSR [25] made it the best candidate to tune the configuration of VANETs environment. The simple operation and the MPR set concept allow this protocol to offer very competitive delays which is an important factor in VANET application.