Pending Interest Lifetime Mechanism for Vehicular Named Data Networks

Named Data Networking (NDN) is a future Internet architecture, which locates the requested content using unique content names for effective content distribution. The very nature of Vehicular Adhoc Networks (VANETs), where the nodes are constantly mobile, has a high influence on the process of connection establishment, making it a challenging task. Hence, the attributes of NDN have been adapted into VANETs and is termed as Vehicular Named Data Networks (VNDN). VNDN locates the requested content within the vehicular network domain using the content name instead of its locale. Every node that requires a specific content sends out an Interest packet as a means of request and keeps waiting for the corresponding Data packet. A Time To Live (TTL) field is maintained in every Interest packet to restrict its broadcast scope. A record of each incoming Interest that is yet to be fulfilled is maintained as a Pending Interest Table (PIT). Each PIT record is kept for a specific period of time, termed as PIT Entry Lifetime (PEL). The PIT entry is removed when the Data packet arrives at the node or if the lifetime of an entry expires. The loss of Interest and Data packets are frequent due to the dynamic topology of VANETs causing an increase in PIT size depending on the PEL. A fixed PEL value of 4 seconds in Vanilla NDN does not seem to reduce the PIT size, thereby leading to packet drops, which in turn would affect the overall efficiency of VNDN. In this work, a hop limit based PEL estimation mechanism is proposed, where each vehicle that forwards the Interest estimates the PEL and reduces the PIT size.