Flooding is used in computer networks

routing algorithm Routing is the process of selecting a path for traffic in a Network theory, network or between or across multiple networks. Broadly, routing is performed in many types of networks, including circuit switching, circuit-switched networks, such as ...

in which every incoming packet is sent through every outgoing link except the one it arrived on. Flooding is used in bridging and in systems such as

Usenet Usenet () is a worldwide distributed discussion system available on computers. It was developed from the general-purpose Unix-to-Unix Copy (UUCP) dial-up network architecture. Tom Truscott and Jim Ellis conceived the idea in 1979, and it was ...

and

peer-to-peer file sharing Peer-to-peer file sharing is the distribution and sharing of digital media using peer-to-peer (P2P) networking technology. P2P file sharing allows users to access media files such as books, music, movies, and games using a P2P software program tha ...

and as part of some

routing protocol A routing protocol specifies how routers communicate with each other to distribute information that enables them to select routes between nodes on a computer network. Routers perform the traffic directing functions on the Internet; data packets ...

s, including OSPF,

DVMRP The Distance Vector Multicast Routing Protocol (DVMRP), defined in , is a routing protocol used to share information between routers to facilitate the transportation of IP multicast packets among networks. It formed the basis of the Internet's hist ...

, and those used in ad-hoc wireless networks (WANETs).

Types

There are generally two types of flooding available, uncontrolled flooding and controlled flooding. In ''uncontrolled flooding'' each node unconditionally distributes packets to each of its neighbors. Without conditional logic to prevent indefinite recirculation of the same packet,

broadcast storm A broadcast storm or broadcast radiation is the accumulation of broadcast and multicast traffic on a computer network. Extreme amounts of broadcast traffic constitute a "broadcast storm". It can consume sufficient network resources so as to render ...

s are a hazard. ''Controlled flooding'' has its own two algorithms to make it reliable, SNCF ( Sequence Number Controlled Flooding) and RPF (

reverse-path forwarding Reverse-path forwarding (RPF) is a technique used in modern routers for the purposes of ensuring loop-free forwarding of multicast packets in multicast routing and to help prevent IP address spoofing in unicast routing. In standard unicast IP r ...

). In SNCF, the node attaches its own address and sequence number to the packet, since every node has a memory of addresses and sequence numbers. If it receives a packet in memory, it drops it immediately while in RPF, the node will only send the packet forward. If it is received from the next node, it sends it back to the sender.

Algorithms

There are several variants of flooding algorithms. Most work roughly as follows: #Each node acts as both a transmitter and a receiver. #Each node tries to forward every message to every one of its neighbors except the source node. This results in every message eventually being delivered to all reachable parts of the network. Algorithms may need to be more complex than this, since, in some case, precautions have to be taken to avoid wasted duplicate deliveries and infinite loops, and to allow messages to eventually expire from the system.

Selective flooding

A variant of flooding called selective flooding partially addresses these issues by only sending packets to routers in the same direction. In selective flooding, the routers don't send every incoming packet on every line but only on those lines which are going approximately in the right direction.

Advantages

The advantages of this method are that it is very simple to implement, if a packet can be delivered then it will (probably multiple times), and since flooding naturally utilizes every path through the network it will also use the shortest path.

Disadvantages

Flooding can be costly in terms of wasted bandwidth. While a message may only have one destination it has to be sent to every host. In the case of a

ping flood A ping flood is a simple denial-of-service attack where the attacker overwhelms the victim with ICMP "echo request" (ping) packets. This is most effective by using the flood option of ping which sends ICMP packets as fast as possible without wait ...

or a

denial of service attack In computing, a denial-of-service attack (DoS attack) is a cyber-attack in which the perpetrator seeks to make a machine or network resource unavailable to its intended users by temporarily or indefinitely disrupting services of a host connect ...

, it can be harmful to the reliability of a

computer network A computer network is a set of computers sharing resources located on or provided by network nodes. The computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are ...

. Messages can become duplicated in the network further increasing the load on the network as well as requiring an increase in processing complexity to disregard duplicate messages. Duplicate packets may circulate forever, unless certain precautions are taken: * Use a

hop count In wired computer networking, including the Internet, a hop occurs when a packet is passed from one network segment to the next. Data packets pass through routers as they travel between source and destination. The hop count refers to the numbe ...

or a

time to live Time to live (TTL) or hop limit is a mechanism which limits the lifespan or lifetime of data in a computer or network. TTL may be implemented as a counter or timestamp attached to or embedded in the data. Once the prescribed event count or timesp ...

(TTL) count and include it with each packet. This value should take into account the number of nodes that a packet may have to pass through on the way to its destination. * Have each node keep track of every packet seen and only forward each packet once. * Enforce a network topology without

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Examples

In Open Shortest Path First (OSPF), flooding is used for transferring updates to the topology ( LSAs). In low data rate communications, flooding can achieve fast and robust data communications in dedicated protocols such as VEmesh,virtual-extension.com which operates in the Sub-1 GHz frequency band and

Bluetooth mesh networking Bluetooth Mesh is a computer mesh networking standard based on Bluetooth Low Energy that allows for many-to-many communication over Bluetooth radio. The Bluetooth Mesh specifications were defined in the Mesh Profile and Mesh Model specifications ...

, which operates in the 2.4 GHz frequency band. Both these protocols serve as underlying technologies in the

Digital Addressable Lighting Interface Digital Addressable Lighting Interface (DALI) is a trademark for network-based products that control lighting. The underlying technology was established by a consortium of lighting equipment manufacturers as a successor for 1-10 V/ lighting ...

in use in professional and commercial lighting control.

References

{{reflist, refs= {{cite book , author-first1=Andrew S. , author-last1=Tanenbaum , author-link1=Andrew S. Tanenbaum , author-first2=David J. , author-last2=Wetherall , title=Computer Networks , edition=5th , date=2010-03-23 , publisher=

Pearson Education Pearson Education is a British-owned education publishing and assessment service to schools and corporations, as well for students directly. Pearson owns educational media brands including Addison–Wesley, Peachpit, Prentice Hall, eCollege, ...

, isbn=978-0-13-212695-3 , pages=368–370 {{cite web , title=Controlled Flooding in Wireless Ad-hoc Networks , author-first1=Ashikur , author-last1=Rahman , author-first2=Wlodek , author-last2=Olesinski , author-first3=Pawel , author-last3=Gburzynski , publisher=

University of Alberta The University of Alberta, also known as U of A or UAlberta, is a public research university located in Edmonton, Alberta, Canada. It was founded in 1908 by Alexander Cameron Rutherford,"A Gentleman of Strathcona – Alexander Cameron Rutherfor ...

, Department of Computing Science , location=Edmonton, Alberta, Canada , date=2004 , work=International Workshop on Wireless Ad-Hoc Networks , url=http://www.senserf.com/pg/PAPERS/tarp1.pdf , access-date=2015-10-15 , url-status=live , archive-url=https://web.archive.org/web/20170210205207/http://www.senserf.com/pg/PAPERS/tarp1.pdf , archive-date=2017-02-10 Routing algorithms Flooding algorithms