notes/docs/lectures/acn/05_DTN_advanced_protocols.md

DTN Protocols - Advanced

Rate control - addresses easing network congestion by controlling the rate of traffic on the network.

Adaptive forwarding - to direct traffic away from congestion hot spots.

Spray and Focus

• Spray and focus replicates an allowable number of messages from source in the spray phase.
• The focus phase allows each node to forward a copy of its messages to other potential nodes until the messages gets to its destination.
• The protocol uses a single-copy utility based routing scheme to forward a copy of the message further.
• Forwarding decisions are made based on timers which record the times nodes come in communication range of each other.
• 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.

SimBet

• 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.
  • A central node has the ease of connecting other nodes in a network.
  • This is known as centrality a measure of the structural importance of a node in a network.
• A central node uses similarity and betweenness centrality to avoid unnecessary information exchange in the entire network.
• SimBet maintains a single copy of each message in the network to reduce resource overheads.

Replication Management

Replication Management refers to easing network congestion by managing the amount and frequency that messages are replicated.

• 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.

Café

• Congestion Aware Forwarding Algorithm (Café)
  • Single-copy
  • Adaptive forwarding techniques - to reduce network congestion by directing traffic away from nodes experiencing congestion to less congested areas of the network.
  • Uses Contact Manager and Congestion Manager

Contact Manager - deals with nodes forwarding heuristics, updating statistics for each contact such as frequency and duration's.

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.

CafREP

• Congestion Aware Forwarding and Replication (CafREP)
  • replication-based
  • builds on Cafe protocol by coalescing the proposed adaptive forwarding algorithm with an adaptive replication management technique