Non-adaptive routing algorithms, also known as static routing algorithms, do not change the selected routing decisions for transferring data packets from the source to the destination. They construct a static routing table in advance to determine the path through which packets are to be sent.
The static routing table is constructed based upon the routing information stored in the routers when the network is booted up. Once the static paths are available to all the routers, they transmit the data packets along these paths. The changing network topology and traffic conditions do not affect the routing decisions.
Types of Non − adaptive Routing Algorithms
Flooding − In flooding, when a data packet arrives at a router, it is sent to all the outgoing links except the one it has arrived on. Flooding may be of three types−
Uncontrolled flooding − Here, each router unconditionally transmits the incoming data packets to all its neighbours.
Controlled flooding − They use some methods to control the transmission of packets to the neighbouring nodes. The two popular algorithms for controlled flooding are Sequence Number Controlled Flooding (SNCF) and Reverse Path Forwarding (RPF).
Selective flooding − Here, the routers don't transmit the incoming packets only along those paths which are heading towards approximately in the right direction, instead of every available paths.
Random walks (RW) − This is a probabilistic algorithm where a data packet is sent by a router to any one of its neighbours randomly. The transmission path thereby formed is a random walk. RW can explore the alternative routes very efficiently. RW is very simple to implement, requires small memory footprints, does not topology information of the network and has inherent load balancing property. RW is suitable for very small devices and for dynamic networks.