45 lines
2.6 KiB
Markdown
45 lines
2.6 KiB
Markdown
# DTN Protocols - Advanced
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**Rate control** - addresses easing network congestion by controlling the rate of traffic on the network.
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**Adaptive forwarding** - to direct traffic away from congestion hot spots.
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#### Spray and Focus
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* Spray and focus replicates an allowable number of messages from source in the spray phase.
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* **The focus phase allows** each node to forward a copy of its messages to other potential nodes until the messages gets to its destination.
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* The protocol uses a single-copy utility based routing scheme to forward a copy of the message further.
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* Forwarding decisions are made based on **timers** which record the times nodes come in communication range of each other.
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* Node $$A$$ forwards message with destination $$D$$ to node $$B$$ , **if and only if** $$B$$ has a higher potential of delivering the message to $$D$$.
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#### SimBet
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* A source node with no prior knowledge of the destination node will forward a message to a more central node that has the potential of finding a suitable relay node.
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* A central node has the ease of connecting other nodes in a network.
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* This is known as **centrality** a measure of the **structural importance** of a node in a network.
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* A central node uses **similarity and betweenness centrality** to avoid unnecessary information exchange in the entire network.
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* SimBet maintains a single copy of each message in the network to reduce resource overheads.
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### Replication Management
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Replication Management refers to easing network congestion by managing the amount and frequency that messages are replicated.
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* This is particularly notable concern as it is often the replication of messages that leads to congestion in DTNs, with surplus and redundant messages causing wastage within node message buffers.
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#### Café
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* Congestion Aware Forwarding Algorithm (Café)
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* Single-copy
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* Adaptive forwarding techniques - to reduce network congestion by directing traffic away from nodes experiencing congestion to less congested areas of the network.
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* Uses **Contact Manager** and **Congestion Manager**
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**Contact Manager** - deals with nodes forwarding heuristics, updating statistics for each contact such as frequency and duration's.
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**Congestion Manager** - focuses on calculating the availability of nodes, keeping and updating a record of information such as the amount of available buffer and delays expected from each contacted node.
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#### CafREP
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* Congestion Aware Forwarding and Replication (CafREP)
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* replication-based
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* builds on Cafe protocol by coalescing the proposed **adaptive forwarding algorithm with an adaptive replication management technique**
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