# Context-Aware Pending Interest Table Management Scheme for NDN-Based VANETs
## 5 Context-Aware Pending Information Table Entry Management (CPITEM) Scheme
### Non-Safety PITE Priority
#### 5.2.4. PITE Priority
In Non-Safety Content Application (NSCA) scenarios, the consumers are sending Interest messages to request non-safety content related to applications such as NSCAIA (multimedia file sharing), NSCAIB (multimedia file sharing), NSCAII (commercial advertisement), NSCAIII (navigation map), and NSCAIII (parking availability). Considering our proposed CACN scheme, the five different non-safety content names considered for experimental evaluation are as follows: (i) \(NSCAIA\) (\(Non-Safety/Global/Audio/Multimediafile\)\(sharing:Music/\dots\)), (ii) \(NSCAIB\) (\(Non-Safety/Global/Video/Multimedia\)\(filesharing:Drama/\dots\)), (iii) \(NSCAII\) (\(Non-Safety/Local/Text/Commercial\)\(Advertisement:Hotel/\dots\)), (iv) \(NSCAIII\) (\(Non-Safety/Local/Pictorial/Navigation\)\(Map:City/\dots\)), and (v) \(NSCAIV\) (\(Non-Safety/Local/text/Parking\ availability:/\dots\)). There are eight consumers who are requesting content at the same rate. In the case of the multimedia file sharing application, three consumers are sending Interests for two types of content (NSCAIA, NSCAIB). Two consumers are showing interest in NSCAIA content, and one consumer is interested in NSCAIB content. The multimedia file sharing application is the most popular application in the simulation scenario. The reason is that two different multimedia content types are demanded by a group of three different consumers. One of the other five consumers is interested in SCAI content; the second is interested in SCAII; the third in NSCAIII; the fourth in NSCAIII; and the fifth in NSCAIV content. After every time \(t^{\prime}\), the consumer vehicle sends the Interest packet for the different content related to similar applications. Like HLLR, the NDN default forwarding (Interest broadcast) scheme is used as a forwarding strategy in our experimental demonstration. Experiment 1: Total Number of Drop Interest Messages Due to PIT Size as a Function of Growth in Interest Messages

This experiment is carried out to demonstrate the total number of dropped messages due to PIT overflow as a function of growth in Interest messages. The network comprises 130 vehicles, 8 of which are consumers, and 7 are producers. The PIT size, which represents the amount of available space in each vehicle in terms of PIT entries, is set at 30 entries. In Experiment 1, for the first point on the x-axis, the message generation rate is four messages/s. For the second, third, fourth, and fifth points, the message generation rate is five, six, seven, and eight messages per second, respectively. The number of messages transmitted varies from 1600 to 3200. When the number of messages transmitted is 1600, 400 messages are related to safety, 600 messages are related to popular non-safety, and 600 messages are related to non-popular non-safety content. Upon receiving the Interest, each vehicle creates a \(PITE\) if it is a valid Interest, and the \(PITE\) does not already exist. Furthermore, only vehicles with matching PIT entries forward the Data message. Unsolicited messages are simply dropped. Figure 1 depicts how the implemented \(PITE\) replacement schemes (HLLR [11], CPITEM) behave as the number of Interest messages in the network increases. Figure 1a depicts the overall number of dropped Interest messages as the number of Interest messages in the network increases. The number of dropped Interest messages for safety content is depicted in Figure 1b as a function of Interest message growth in the network. Figure 1c depicts the number of dropped non-safety Interest messages as a function of Interest message growth in the network. Figure 1d depicts the number of dropped non-safety, popular Interest messages in the network as a function of Interest message growth. The number of dropped Interest messages for non-safety, non-popular content is depicted in Figure 1e as a function of Interest message growth in the network. Figure 1f illustrates the average interest satisfaction delay of HLLR and CPITEM schemes in a VANET highway scenario as a function of Interest message growth in the network.