Interest packets retransmission in lossy CCN networks and its impact on network performance

Abstract

When both interest packets and data chunks can be dropped on the way, due to network impairments, deciding who, the CCN router or the end-system, sets the timeout duration and retransmits the interest packet after a timeout are two key issues that affect the performance of the network. More specifically, they impact directly the occupancy of the pending interest table (PIT). The standard does not address these issues clearly and the typical CCN implementations (like CCNx) address them naively leaving room for further improvements. In lossy networks, if the router does not retransmit pending interests (no-rtx) the average PIT entry lifetime increases dramatically. Conversely, if the CCN router retransmits pending interests (rtx) periodically, it is not clear how frequently it should do so. In this paper we investigate the performance of the two types of routers in lossy networks, in the presence of both caching and interest aggregation. The study aims at shedding some light on how much performance improvement is achieved by one type of routers over the other. We also introduce a new method for estimating the PIT entry timeout that is shown to perform better than the currently used default method in CCN.