‘Many-to-one’ routing

A common scenario in a wireless network is the need for most network nodes to communicate with a single node that performs some centralized function, for example, a gateway. This node is often referred to as a concentrator.

In order to establish communication with the concentrator, each remote node may initiate a ‘route discovery’, resulting in a corresponding entry in the Routing table of each routing node along the way. If most network nodes need to communicate with the concentrator, many such route discoveries may be initiated. Where the resulting routes have a common leg, the relevant Routing table entries will not be duplicated but shared. However, a large number of simultaneous route discoveries may require significant memory space in the nodes near the concentrator for the temporary storage of route discovery information, and possibly result in memory overflow and traffic congestion.

A more efficient method of establishing routes to a concentrator is for the concentrator to initiate a ‘many-to-one’ route discovery for routes from all other network nodes to itself. To do this, the concentrator broadcasts a route discovery request and the Routing tables are updated as the broadcast propagates through the network. Since no responses are generated, the temporary storage of route discovery information is not required and network traffic congestion is minimized.

Many-to-one route discovery is illustrated in the figure below.

‘Many to one’ routing

In order to avoid the storage of return routes (from the concentrator) in the Routing tables of intermediate nodes, the technique of source routing is used - the outward route taken by a message to the concentrator is remembered by the concentrator and embedded in the response message. In this case, the response message must carry up to 30 addresses of the nodes along the return route (maximum number of hops allowed is 30).

Parent topic:Network routing