Optimized Link State Routing Protocol
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Optimized Link State Routing short OLSR is a routing protocol for mobile ad hoc networks, which is adapted to the requirements of a mobile wireless LANs version of the link state routing. The protocol is described in RFC 3626.
In this distributed flexible routing process all nodes ( routers ) is known, the complete network topology, so that they can determine the shortest path to the goal from case to case. As a proactive routing protocol, it provides the necessary information ready for it at any time.
Operation
The topology discovery is performed at OLSR two types of messages: HELLO and Topology Control ( TC) messages. HELLO messages are used for link sensing, neighbor discovery and to the communication from the multipoint relay selection. The TC messages are used to distribute the information obtained about possible links in the network.
A participating in the network device (node ) discovered its 1 -hop and 2 -hop neighbors about the periodically sent HELLO messages. These include the IP addresses of the already known 1 -hop neighbors as well as the status of the connection to them and are not forwarded. From its one -hop neighbors, each node Multipoint Relays selected ( MPRs ), so that it can reach over it every its 2- hop neighbors. The MPRs are the nodes that forward broadcast messages, which makes flooding more efficient. They are the ones that create the TC messages that contain a list of at least the nodes from which they were selected as MPRs, so that for each node is at least one way of knowing how it can be achieved. This TC messages are distributed throughout the network. In this way, each node obtains an idea of the network and can create routing tables.
In OLSR protocol, Dijkstra's algorithm is employed.
Optimizations
OLSR is an optimized link-state routing protocol that was adapted to the requirements of mobile ad hoc networks, but is also used in other structures. There are the following main approaches to the further development and optimization:
Auto- Assignment of IP addresses
Critical to the OLSR Protocol is currently no auto- assignment of IP addresses is possible. To avoid that the IP addresses of the wireless clients are assigned twice ( eg laptops ), they are allocated centrally in some projects or the router firmware. To ensure that the internet access is possible only after registration. It would also be possible, the IP assignment decentralized to organize and orient to the MAC address of the WLAN card. For this purpose, it needs an update of the OLSR software. In some Freifunk initiatives ( immobile ) OLSR nodes are hierarchically assigned pools of IP addresses to a central, which in turn assign them via DHCP to the surrounding (mobile) nodes.
End-to -end encryption
Currently, each node can see what conduct by the other nodes in the network, or what websites they request or files they upload. If a route is found first, the proposed optimization is this secure with end-to -end encryption.
Hybrid access
Meshed networks require OLSR node. Nevertheless, the wireless access through the normal radio range to the users, who no OLSR installed on the laptop or PC, to be made possible. This would require an OLSR node not only packets of OLSR nodes to forward, but also of normal configured wireless cards in the defined area of the node. A OLSR node would assign it an IP address from a centrally allocated to him by DHCP pool to a non- OLSR - enabled nodes and serve this as a gateway into the OLSR network. However, such a mass is attached to the tailed client DHCP lease of the node and therefore of limited capable of roaming. Every movement in the catchment area of another node performs when you run the DHCP lease to a different IP address, so that for example streaming applications are suspended. This problem would be solved, if an auto- assignment would be introduced.
Bandwidth Management
Goal in the future is if the software is operational for both wireless chip in the laptop and the router to implement bandwidth management such as the log SrcRR à la Netlimiter, when divided the available bandwidth and can be dynamically used can be used for the three groups of users: Owner, OLSR nodes a few hops away and finally the non- OLSR nodes in the immediate vicinity of the wireless router. Thus there would be a broadband management for the operator of the node: His private, non-shared bandwidth forwarded bandwidth for other OLSR nodes and a bandwidth for normal nodes in the immediate vicinity of the access points that do not use OLSR.
Operate wireless cards as a router
Currently, for example, a router and a laptop with wireless chip each other software necessary. Elegant, if the OLSR installation software could be loaded on both a router as well as on the laptop with a wireless chip would be. There are first approaches that want to regulate on the software that each wireless chip simulates a router that is supported on the then OLSR.
Transition to IPv6
Is currently being discussed.
Fine-tuning for
- Not every node generates Link State Advertisements ( LSAs ), but only marked as Multipoint Relay (MPR ).
- It will be sent as little as possible control messages over the network.
- MPRs can choose to send only information about the nodes between itself and the MPRs, they have selected.
Application
OLSR finds out in the next BATMAN research in free radio networks application.
Other ad-hoc routing protocols
- Ad hoc routing protocol list ( s)
- AODV
- B.A.T.M.A.N.