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Top2. Rpl Specification
RPL is a distance vector routing protocol for the LLNs which describes a method of construction of a logical topology called DODAG (Destination Oriented Directed Acyclic Graph) (Mardini, Ebrahim & Al-Rudaini, 2017) which use an objective function and a set of metrics and constraints seen Figure 1. The objective function is based on a combination of metrics and constraints to calculate the “better acceptable path” (Zhao, Kumar, Chong, & Rongxing, 2017). The RPL messages generation is based on a timer. Additionally, nodes configure transmission intervals messages using the Trickle algorithm (Lamaazi & Benamar, 2018). Trickle is a timer that allows nodes sharing the transmission medium with high rates of loss as the case of LLNs, exchanging information and data, scalable, saving energy, and ensuring successful transmission. This timer reduces the frequency of control messages transmission, while maintaining coherent information within the network (Barcelo, Correa, Vicario & Morell, 2016). The basic idea of a Trickle timer is to send frequently more DIOs message when detecting inconsistency in a DODADG. As long as node receives consistent information, it will increase exponentially its transmission interval until a predetermined minimum frequency (Yassein, Aljawarneh, & Masadeh, 2017). RPL uses the following controls messages (Tripathi, D’Oliveira, & Vasseur, 2010):