Research On Routing Algorithm Based History Contact Characterizationin Delay Tolerant Networks

The highly successful architecture and protocols of today'sInternet may operate poorly in environments characterized by verylong delay paths and frequent network partitions.These problemsare exacerbated by end nodes with limited power or memoryresources.Often deployed in mobile and extreme environmentslacking continuous connectivity,many such networks have theirown specialized protocols,and do not utilize IP.Kevin Fall proposed the delay tolerant network(DTN)in 2003.DTN contains a network architectureand application interface structured around optionally-reliableasynchronous message forwarding,with limited expectations ofend-to-end connectivity and node resources.The architectureoperates as an overlay above the transport layers of the networks itinter-connects,and provides key services such as in-network datastorage and retransmission,authenticatedforwarding,etc.The research of routing in delay tolerant network has become a fundamental challenge.Many researchers have investigated this fundamental challenge,particularly over the past five years.In this paper,we focus on the history-based routing in DTN.Most existing history-based routing protocols for delay tolerant networks resort to coarse-grained encounter informationfor making message forwarding decisions.However,this coarse-grained information can not give precise expression of the contact patterns between nodes in the network,thereby leading to inaccurate forwarding decisions.In this paper,we present a kind of improved probabilistic routing protocol using history of encounters and transitivity in delay tolerant networks(I-PRoPHET),a probabilistic routing scheme based on fine-grained contact characterization.Each node in I-PRoPHET uses a slotted sliding window mechanism to maintain the information of historical contacts,by which new contact information can be quickly incorporated and outdated history data can be easily removed.The granularity of collected history data can be controlled by adjusting the size of the sliding window to reflect the contact patterns.Based on the fine-grained contact statistics,a greedy forwarding scheme is designed by combining the advantages of contact duration based forwarding and quota based routing.First,we calculate the delivery prediction which present the probability that two nodes meet in the future based the contact length.Secondly,we built a candidate forwarders list with fixed capacity for every message that a node hold.Finally,a node will forward a copy of a message if the encounter node in the candidate forwarders list of the message.The performance of I-PRoPHET was evaluated through extensive simulations,and results show that,compared with existing schemes,I-PRoPHET can significantly enhance message delivery rate with very low communication overhead.