70 lines
3.4 KiB
Markdown
70 lines
3.4 KiB
Markdown
# Mobile Ad Hoc Networks (MANETs)
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- An infrastructure-less network formed by mobile wireless nodes
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- Nodes in a MANET can communicate via a single- or multi-hop approach (due to the absence of centralised network infrastructure)
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- Nodes operate as clients, routers and servers at the same time to forward packets
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- The mobility of nodes results in frequent and unpredictable changes in network topology
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One of the core features of a MANET node is the ability to autonomously connect to other nodes and configure itself for data transmission over the network.
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#### MANET Routing
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- Mobile wireless nodes create a temporary connection between them to forward data
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- Because some nodes may be uncooperative or faulty, they may drop or compromise packets
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- Typically routing is split into **route discovery** and **actual data transmission**.
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- Nodes have to self-organise in order to route.
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(The green boxes show the chosen route.)
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The source has a limited range of nodes it can detect. It cannot send data directly to the destination as it doesn't know where the destination is. Hops are decided by communication protocols.
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#### Proactive MANETs
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- Also known as table-driven routing protocols
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- Nodes in the network maintain comprehensive routing information about the network
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- This is done by spreading network status information to nodes and tracking changes in network topology - think the network is constantly pinged
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- These status updates can slow the network with the traffic
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- Useful if the network is not that large
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#### Reactive MANETs
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- Also known as on-demand routing
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- Network nodes only store information about paths to destination nodes
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- Nodes delay the search for routes to new destinations in order to reduce communication overheads
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- i.e. if a route is found between A and B, this route will be stored and not recalculated
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- May be slower, as a shorter path may not be used
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#### Hybrid MANETs
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- Hybrid protocols combine the advantages of proactive and reactive protocols to reduce traffic overheads and route discovery delays
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Table showing the different MANET protocols:
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### Delay/Disconnection Tolerance
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Traditional MANET routing protocols like DSR and AODV (both reactive) cannot work in intermittent infrastructure-less environments because they require a complete path from source to destination for communication.
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- Messages get dropped at intermediate nodes when the link to the next hop is non-existent in MANETs
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- DTNs expand MANETs to allow more intermittent and sparse connections between nodes caused by node mobility or low transmission range.
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#### Store-carry-forward Paradigm
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- DTN routing protocols allow forwarding of messages by using a 'store-carry-forward' approach.
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- Messages are stored by nodes and moved in hops throughout the network until they reach their destination
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- This approach is used by DTN routing protocols to increase the probability of message delivery.
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#### DTN Protocol Classifications
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##### Flooding-Based
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- Flooding-based routing protocols spread a message and have multiple copies of the message in the network.
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- This is done to increase the probability of messages reaching their destination and also decrease the time of delivery
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##### Forwarding-Based
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- Forwarding-based routing protocols gather information about the nodes in a network to select the best path to forward messages, with the aim of enhancing message delivery in networks with limited resources.
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