ADHOC NETWORKADHOC NETWORK

By. By. P. Victer PaulP. Victer Paul

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Wireless NetworkWireless Network

Wireless networks use some sort of radio Wireless networks use some sort of radio frequencies in air to transmit and receive frequencies in air to transmit and receive data instead of using some physical data instead of using some physical cables. cables.

Wireless Networking devices can operate Wireless Networking devices can operate in one of the two modes: in one of the two modes: Infrastructure modeInfrastructure mode Ad hoc modesAd hoc modes

Infrastructure modeInfrastructure mode Infrastructure modeInfrastructure mode wireless networking wireless networking

bridges (joins) a wireless network to a wired bridges (joins) a wireless network to a wired Ethernet network. Ethernet network.

A wireless access point (AP) is required for A wireless access point (AP) is required for infrastructure mode wireless networking. infrastructure mode wireless networking.

To join the WLAN, the AP and all wireless clients To join the WLAN, the AP and all wireless clients must be configured to use the same SSID must be configured to use the same SSID ((Service Set Identifier, the name of the wireless Service Set Identifier, the name of the wireless network that you wish to join).network that you wish to join).

The AP is then cabled to the wired network to The AP is then cabled to the wired network to allow wireless clients access to, for example, allow wireless clients access to, for example, Internet connections or printers. Internet connections or printers.

Infrastructure modeInfrastructure mode

Ad-Hoc ModeAd-Hoc Mode

ad-hocad-hoc mode is a method for wireless devices to mode is a method for wireless devices to directly communicate with each other. directly communicate with each other.

Operating in ad-hoc mode allows all wireless Operating in ad-hoc mode allows all wireless devices within range of each other to discover devices within range of each other to discover and communicate in peer-to-peer fashion and communicate in peer-to-peer fashion without involving central access points.without involving central access points.

To set up an ad-hoc wireless network, each To set up an ad-hoc wireless network, each wireless adapter must be configured for ad-hoc wireless adapter must be configured for ad-hoc mode and must use the same SSID. mode and must use the same SSID.

Ad-Hoc ModeAd-Hoc Mode

Ad hoc NetworkAd hoc Network Ad hoc Ad hoc has two definitions—the has two definitions—the

first can be either “impromptu” first can be either “impromptu” or “using what is on hand,” or “using what is on hand,” while the other is “for one while the other is “for one specific purpose.”specific purpose.”

Ad hoc networks, which are Ad hoc networks, which are also called also called mesh networksmesh networks, are , are defined by the manner in which defined by the manner in which the network nodes are the network nodes are organized to provide pathways organized to provide pathways for data to be routed from the for data to be routed from the user to and from the desired user to and from the desired destination. destination.

All available nodes are aware All available nodes are aware of all other nodes within range. of all other nodes within range.

Routing Protocols Routing Protocols

Routing protocols between any pair of Routing protocols between any pair of nodes within an ad hoc network can be nodes within an ad hoc network can be difficult because the nodes can move difficult because the nodes can move randomly and can also join or leave the randomly and can also join or leave the network network

Three categories that existing ad-hoc Three categories that existing ad-hoc network routing protocols fall into: network routing protocols fall into: 1. Table Driven Protocols 1. Table Driven Protocols 2. On Demand Protocols 2. On Demand Protocols 3. Hybrid Protocols 3. Hybrid Protocols

Ad-hoc Mobile Routing ProtocolsAd-hoc Mobile Routing Protocols

Table Driven Routing ProtocolsTable Driven Routing Protocols also known as Proactive Protocols also known as Proactive Protocols work out routes in the background independent work out routes in the background independent

of traffic demands.of traffic demands. Each node uses routing information to store the Each node uses routing information to store the

location information of other nodes in the location information of other nodes in the network and this information is then used to network and this information is then used to move data among different nodes in the move data among different nodes in the network. network.

This type of protocol is slow to converge and This type of protocol is slow to converge and may be prone to routing loops. may be prone to routing loops.

Fisheye State Routing is an example of a Table Fisheye State Routing is an example of a Table Driven Protocol. Driven Protocol.

On Demand Routing Protocols On Demand Routing Protocols also known as Reactive Protocols also known as Reactive Protocols establish routes between nodes only when they are establish routes between nodes only when they are

required to route data packets. required to route data packets. When a route is required by a source node to a When a route is required by a source node to a

destination for which it does not have route destination for which it does not have route information, it starts a route discovery process information, it starts a route discovery process which goes from one node to the other until it which goes from one node to the other until it arrives at the destination or a node in-between has arrives at the destination or a node in-between has a route to the destination. a route to the destination.

On Demand Protocols more suited to large On Demand Protocols more suited to large networks with light traffic and low mobility.networks with light traffic and low mobility.

An example of an On Demand Protocol is Dynamic An example of an On Demand Protocol is Dynamic Source Routing. Source Routing.

Hybrid Routing Protocols Hybrid Routing Protocols Combine Table Based Routing Protocols with Combine Table Based Routing Protocols with

On Demand Routing Protocols. On Demand Routing Protocols. Each node in the network has its own routing Each node in the network has its own routing

zone, the size of which is defined by a zone zone, the size of which is defined by a zone radius, which is defined by a metric such as radius, which is defined by a metric such as the number of hops. the number of hops.

Zone Routing Protocol (ZRP) is an example Zone Routing Protocol (ZRP) is an example of a Hybrid routing protocol.of a Hybrid routing protocol.

ad hoc wireless setup in a home ad hoc wireless setup in a home networknetwork

diagram illustrates use of a so-called diagram illustrates use of a so-called ad hoc wireless setup in a home ad hoc wireless setup in a home networknetwork

Ad-Hoc Networking FeaturesAd-Hoc Networking Features

Regardless of the application, there are Regardless of the application, there are certain critical features that can determine certain critical features that can determine the efficiency and effectiveness of an ad-the efficiency and effectiveness of an ad-hoc network. hoc network.

These features can be categorized into These features can be categorized into quantitative features andquantitative features and qualitative featuresqualitative features

Quantitative Critical FeaturesQuantitative Critical Features

Network Settling Time Network Settling Time Network Join Network Join Network Depart Network Depart Network Recovery Time Network Recovery Time Frequency of Updates Frequency of Updates Memory Byte Requirement Memory Byte Requirement Network Scalability NumberNetwork Scalability Number

Qualitative Critical FeaturesQualitative Critical Features

Knowledge of Nodal Locations Knowledge of Nodal Locations Effect to Topology ChangesEffect to Topology Changes Power Consciousness Power Consciousness Single or MultichannelSingle or Multichannel Preservation of Network SecurityPreservation of Network Security QoS Routing and Handling of Priority QoS Routing and Handling of Priority

MessagesMessages Real-time Voice ServicesReal-time Voice Services Real-time Video ServicesReal-time Video Services

Security in Ad-hoc NetworksSecurity in Ad-hoc Networks

Security GoalsSecurity Goals AvailabilityAvailability ConfidentialityConfidentiality IntegrityIntegrity AuthenticationAuthentication

Components of an ad hoc Components of an ad hoc networknetwork

Wireless PCI cardsWireless PCI cards Wireless USB NIC PCMCIAWireless USB NIC PCMCIA

HOW TO SETUP WIRELESS HOW TO SETUP WIRELESS ADHOC NETWORKADHOC NETWORK

Troubleshoot problems finding Troubleshoot problems finding wirelesswireless

If Nodes does not detect a network that If Nodes does not detect a network that you think is in range of your computer, it you think is in range of your computer, it could be because of one the following could be because of one the following reasons:reasons: There is interference from other devicesThere is interference from other devices The network you are looking for is set to The network you are looking for is set to

not broadcast its network name (SSID)not broadcast its network name (SSID) Verify the SSIDVerify the SSID

Advantages of Ad Hoc NetworksAdvantages of Ad Hoc Networks

The principal advantages of an ad hoc network The principal advantages of an ad hoc network include the following:include the following: Independence from central network administrationIndependence from central network administration Self-configuring, nodes are also routersSelf-configuring, nodes are also routers Self-healing through continuous re-configurationSelf-healing through continuous re-configuration Scalable—accommodates the addition of more nodes Scalable—accommodates the addition of more nodes Flexible—similar to being able to access the Internet Flexible—similar to being able to access the Internet

from many different locationsfrom many different locations

Limitations of Ad Hoc NetworksLimitations of Ad Hoc Networks

While ad hoc networks are typically used where While ad hoc networks are typically used where they have the greatest emphasis on its they have the greatest emphasis on its advantages, there are some limitations:advantages, there are some limitations: Each node must have full performanceEach node must have full performance Throughput is affected by system loadingThroughput is affected by system loading Reliability requires a sufficient number of available Reliability requires a sufficient number of available

nodes. Sparse networks can have problemsnodes. Sparse networks can have problems Large networks can have excessive latency (time Large networks can have excessive latency (time

delay), which affects some applicationsdelay), which affects some applications

ApplicationsApplications

Applications of Ad hoc networks.Applications of Ad hoc networks. Military battlefield networksMilitary battlefield networks Personal Area Networks (PAN)Personal Area Networks (PAN) Disaster and rescue operation Disaster and rescue operation Peer to peer networksPeer to peer networks