Short description
(English)
|
This project will investigate the feasibility of content-centric networks in the context of mobile ad hoc networks. The investigation comprises efficient caching strategies for resource constraint devices, energy-efficient operation as well as reliable content discovery and delivery. The mechanisms proposed in this work will be evaluated by simulations and emulations based on existing CCN implementations.
|
Partners and International Organizations
(English)
|
BE, CH, CY, CZ, DE, DK, EL, ES, FI, FR, HR, IE, IT, LV, MK, NL, NO, PT, RS, SE, SI, TR, UK
|
Abstract
(English)
|
Opportunistic networking defines communication in challenged networks, where connectivity and contact durations between devices are unpredictable and intermittent. Content-centric communication (CCN) can support opportunistic networking. In this project, we focus our work on communication via the IEEE 802.11 standard. The main topics of this project are divided into three areas: memory management, energy efficient operation and content discovery/delivery. We have implemented a communication scheme based on broadcast and unicast communication. Since connectivity between devices is unknown in opportunistic networks, discovery can only be performed via broadcast. If an answer is received, the content source can be addressed directly via unicast. Forwarding strategies switch back to broadcast if content sources disappear and are not reachable anymore via unicast. Evaluations have shown that adaptive unicast transmissions can significantly reduce the number of transmitted duplicates and decrease the required time for content retrieval. If multiple concurrent unicast flows are identified, a content source can switch back to broadcast. To discover namespaces, we combined Regular Interest Discovery (RID) and Enumeration Request Discovery (ERD) discovery, developed within the first year, to increase discovery efficiency exploiting the advantages of both approaches. CCN content names in a content object cannot be changed without resigning the content. To support flexible location-based discovery, we have also designed and implemented an alias mapping approach that locally maps temporary names to unique static names. After an alias discovery, content retrieval is performed using the unique content name enabling the identification of identical content for duplicate suppression and caching. If a requester never meets a suitable content source, Interests need to be forwarded. We investigated multi-hop forwarding based on overhearing and improved multi-hop forwarding by limiting Interest forwarding. We have also implemented algorithms to dynamically adapt Interest lifetimes based on current round trip times between requesters and content source. This enables faster retransmissions in case of collisions resulting in higher throughput. If connectivity to other nodes is intermittent, multi-hop forwarding does not work because CCN requires symmetric content retrieval, i.e., content is returned on the same path back to the requesters. Therefore, we implemented and evaluated agent-based content retrieval on Android smart phones and in hybrid emulation environments. Evaluations have shown that it is advantageous even in case of continuous connectivity but different link capacities. Caching can be extended to persistent storage on repositories. To avoid memory depletion, old content needs to be deleted. We designed and implemented an automatic storage replacement strategy for CCN repositories based on content popularity and age.
|
