# Context-Aware Pending Interest Table Management Scheme for NDN-Based VANETs
## 5 Context-Aware Pending Information Table Entry Management (CPITEM) Scheme  
Packet drop and delay in VANETs is common and can lead to a maximum number of stale PIT entries. Chances of Data packet loss are higher because of their size. The most important challenge in PIT management is to decide which \(PITE\) to be replaced, or life decreased in case of PIT overload. Removing a \(PITE\) might disrupt some critical \begin{table}
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Table 1: \(Cont.\)services. Demand for safety and non-safety information in VANETs is increasing significantly. Drivers and passengers have a higher demand for traffic-related information, popular content as well as road entertainment applications, such as weather information, breaking news, streaming live videos, and downloading multimedia content. Different delivery priorities may be required. For example, video delivery to a vehicle required for safe driving (to raise awareness related to an area of interest under bad weather) should take precedence over the delivery of a recent cartoon for a child. The later video is less critical. This in turn requires that the \(PITE\) for safety content be given priority over the \(PITE\) for non-safety content. In the event of \(PITSize>threshold(\theta)\), \(PITE\) related to a safety application must not be replaced. PIT management is critical for effective content distribution. To meet the latency requirements of VANET applications and effective management of PIT, PITEs must be prioritised. Furthermore, allocating priorities will aid in decision-making regarding \(PITE\) replacement in the event of PIT overload. Considering VANET applications' QoS requirements, assigning priority to \(PITE\) is critical. However, the question is which components of information should be considered to prioritize PITEs. The CPITEM scheme, therefore, provides the mechanisms for the context-aware \(PITE\) replacement in case of \(PITSize>threshold(\theta)\). In the VANETs, different applications have different QoS needs. In the proposed CPITEM scheme, the \(PITE\) priority is calculated using the following information components: (i) Content type (safety/non-safety), (ii) Application popularity (demand of application), (iii) \(PITE\) lifetime (PEL), (iv) \(PITE\) size in terms of InRecords associated with PITE, and (v) duration of time \(PITE\) stays in PIT (termed resting time in PIT). When a vehicle receives an Interest packet, it first checks the PIT. If it is valid message and there is a space in the PIT store, the \(PITE\) will be stored directly. Otherwise, the CPITEM scheme computes the priority based on aforementioned components. If the received Interest priority is greater than the \(PITE\) in the PIT with lowest priority, the \(PITE\) in the PIT with lowest priority will be replaced with the \(PITE\) for the received Interest. Otherwise, if the upcoming Interest has a lower priority than the \(PITE\) in the PIT with the lowest priority, the newly received Interest will be dropped. Likewise, the original NDN forwarding daemon, the consumer vehicle, sends an Interest message containing the default attributes including Nonce, \(InterestLifetime\), and hop count. Only the Data name is constructed based on our previously proposed context-aware content-naming scheme [9]. The CACN Data-naming scheme allows for the identification of both safety and non-safety contents. Furthermore, the CACN features a coding scheme that represents the majority of the content name components, allowing for addressing communication and storage complexity [9]. The CACN scheme allows for representing Content Type (CT), Content Scope (CS), and Application ID (AppID) information in the content name along with other information components. The CACN is divided into two partitions: (i) obligatory and (ii) supplementary. The information about the content is stored in the obligatory part.