DELAY TOLERANT NETWORK

DELAY TOLERANT NETWORKPRESENTATION BY ANDIMA GEOFREY AND NANSAMBA MOREENDelay Tolerant NetworkDelay tolerant networks are categories of sparse wireless networks. Sparse networks have no complete network from source to destination in intermediately connected mobile networks.Examples; wildlife tracking sensor networks, military networks and interplanetary networks .INTRODUCTIONDTNs use store-and-forward message switching to overcome the problems associated with intermittent connectivity, long or variable delay, asymmetric data rates and high error rates.Messages are forwarded from a storage place on one node to a storage place on another node along a path that eventually reaches the destination.

INTRODUCTION Figure 1: store carry and forward mechanism INTRODUCTIONThe DTN architecture implements store-and-forward message switching by overlaying a new protocol layer called the bundle layer on top of heterogeneous region-specific lower layers.

The bundle layer ties together the region specific lower layers so that application programs can communicate across all regions that make up a DTN.INTRODUCTIONAll regions that make up a DTN use a single bundle layer.The layers below the bundle layer e.g transport layer are chosen for their appropriateness to the communication environment of each region.In DTN, there is no preexisting complete path provided. To route a packet from source to destination Intermediate nodes take part in process. When the transmitting node comes into range of intermediate node, it simply forwards the message to that intermediate node and this way the message reaches to the destination.

INTRODUCTIONSPRAY AND WAIT ROUTING SCHEMEContains two phases;Spray phase: source node forwards the message or packet to intermediate node.Wait phase: if destination is not found in spray phase, each node carry the message and whenever the destination is encountered, the node itself will forward the message to destination.

PROPERTIES OF DTNLow date rate and high latency- due to frequent change of network topology and nodes mobility.Disconnection- created from unexpected fault and network partition.Long queuing delay-In DTN source node initiate the transmission that may be expensive because of the limited number of transmission opportunity. Combine this issue suggest that message need to be stored for long period of time in message buffer. PROPERTIES OF DTNLimited longevity-the end to end delay from the sensor node to the destination node is larger than the surviving time of the node which stores the data temporarily because of environmental dangers or hostile action Limited resources- nodes are mobile and battery operated, limited memory space will restrict the data buffering.

ROUTING PROTOCOLS

ROUTING PROTOCOLSCategories of routing protocols:Deterministic routingStochastic routing

ROUTING PROTOCOLSDETERMINISTIC ROUTING Assumes knowledge of network topology and its characteristics for computing the optimal route from source to destination.Classified into ;Oracle based routingLink state based routingSpace time based routing

ROUTING PROTOCOLSSTOCHASTIC ROUTINGNetwork topology and its characteristics are not known.classified into;Active protocol routingPassive protocol routing

ROUTING PROTOCOLSTYPES OF ACTIVE ROUTING PROTOCOLSMeet and visit (MV)Message Ferrying (MF)TYPES OF PASSIVE ROUTING PROTOCOLSEpidemic routingSpray and wait

CONCLUSIONIn DTN, a node is an entity with a bundle layer which is the heart of DTN, and it supports node to node retransmission by means of custody transfer. REFERENCES1] Delay tolerant networking research group. http://www.dtnrg.org.

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