What is flooding in networking?

Answer 1

Flooding most often occurs when a large enough number of packets (the droplets in a stream of data) are flowing through the network that regular data cannot be sent in a normal speed and fashion. Generally it a packet/response of syn/ack or synpackets: the intialization of connections between 2 tcp/ip hosts requires a set of back and forth responses eg. "hey, are you there?" "yes, I'm here." "Are you ready to receive data?" "yes I am, go."

A synflood consists of something like that horrible Verizon Mobile commercial - "Can you hear me now? Can you hear me now? Can you hear me now? Can you hear me now? Can you hear me now? Can you hear me now? Can you hear me now?....." you get the idea. Synflood hosts don't respond to the "yes" back from destination, they keep just asking over and over. The faster the flood, the slower the network and computers on the network will run. There are people who take remote control of a large number of pcs (a zombienet or bot-net) and use these to flood the victim with even larger numbers of syn packets. They get control usually by malware (viruses or trojans) and often can't be traced.

Innocent flooding can occur when a router is given a circular route to some of the hosts on the network - the router asks for the response from a certain host and another router says 'I know where that is.. it's (another interface on the first router)' and passes the requst to router 1, who then passes it again to router 2, who sends it to router 1, who sends it to router 2 ..... using protocols to test for and close internal loops in a network will most often stop flooding.

Answer 2

Flooding is large streams of packets focused at a target causing services on that host to shut down.