Content search and routing under custodian unavailability in information-centric networks

Dealing with the sudden unavailability of content custodians (origin servers) in a network has received limited attention in information-centric networks (ICN). We consider a scenario where the content custodians in an ICN are temporarily unavailable, possibly due to reasons such as device malfunctioning, power outage or Denial of Service (DoS) attacks. In contrast to the traditional host-centric Internet, users can still be served in an ICN as content is cached at in-network nodes. We begin by making the observation that if caches continue to operate using their native cache insertion and eviction policies after the content custodians become unavailable, over time the network content diversity decreases. Therefore, we recommend freezing network caches once the custodians become unavailable. We then propose a routing and search algorithm, Content Exploration under Server Unavailability (CESU), that uses breadcrumbs to effectively locate content cached at in-network nodes and serve user requests when the custodians are unavailable. We perform extensive simulations on real Internet topologies in the Icarus simulator and demonstrate that CESU can efficiently locate content cached in the network. CESU outperforms shortest path routing in terms of content requests served by 56% on average, and achieves up to 98.5% of the total request serving potential.