71 lines
3.4 KiB
Markdown
71 lines
3.4 KiB
Markdown
# Mobile Ad Hoc Networks (MANETs)
|
|
|
|
* An infrastructure-less network formed by mobile wireless nodes
|
|
* Nodes in MANET can communicate via single or multi-hop approach (due to absence of centralised network infrastructure)
|
|
* Nodes operate as clients, routers and servers at the same time to forward packets
|
|
* The mobility of nodes results in frequent and unpredictable changes in network topology
|
|
|
|
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.
|
|
|
|
|
|
#### MANET Routing
|
|
|
|
* Mobile wireless nodes create a temporary connection between them to forward data
|
|
* Because some nodes may not be cooperative or faulty, they may drop/compromise packets
|
|
* Typically routing is split into **route discovery** and **actual data transmission**.
|
|
* Nodes have to self organise in order to route.
|
|
|
|
|
|
|
|
(green boxes is route chosen)
|
|
|
|
The source has a limited range of nodes it can detect, it cannot send it direct to the destination as it doesn't know where the destination is. Hops are decided by communication protocols.
|
|
|
|
#### Proactive MANETs
|
|
|
|
* Also known as table driven routing protocol
|
|
* Nodes in the network maintain a comprehensive routing information of the network
|
|
* This is done by spreading network status information to nodes and tracking changes in network topology - think the network is constantly pinged
|
|
* These status updates can slow the network with the traffic
|
|
* Useful if the network is not that large
|
|
|
|
#### Reactive MANETs
|
|
|
|
* Also known as on-demand routing
|
|
* Network nodes only store information of paths to destination nodes
|
|
* Nodes delay the search for routes to new destinations in order to reduce communication overheads
|
|
* i.e. if a route is found between A and B, this route will be stored and not recalculated
|
|
* May be slower, as a shorter path may not be used
|
|
|
|
#### Hybrid MANETs
|
|
|
|
* Hybrid protocols combine the advantages of proactive and reactive protocols to reduce traffic overheads and route discovery delays
|
|
|
|
Table showing all different protocols of MANETs
|
|
|
|
|
|
|
|
### Delay/Disconnection Tolerance
|
|
|
|
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.
|
|
|
|
* Messages get dropped at intermediate nodes when the link to the next hop is none existent in MANETs
|
|
* DTNs expand MANETs to allow more intermittent and sparse connections of nodes caused by node mobility or low transmission range.
|
|
|
|
#### Store-carry-forward Paradigm
|
|
|
|
* DTN routing protocols allow forwarding of messages by using a 'store-carry-forward' approach.
|
|
* messages are stored by nodes and moved in hops throughout the network until messages reach their destination
|
|
* This approach is used by DTN routing protocols to increase the probability of message delivery.
|
|
|
|
#### DTN Protocol Classifications
|
|
|
|
##### Flooding based
|
|
|
|
* Flooding based routing protocols spread a message and have multiple copies of the message in the network.
|
|
* This is done to increase the probability of messages reaching their destination and also decrease the time of delivery
|
|
|
|
##### Forwarding based
|
|
|
|
* 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 networks with limited resources.
|