Ad Hoc Network

Outline Introduction Benefits Applications Security Issues Routing protocols in Ad-hoc network

Introduction Ad Hoc network is a collection of wireless mobile hosts forming a temporary network without the aid of any established infrastructure or centralized administration Machines may join and leave the network at any time Machines are mobile; movement is entirely unrestricted Each machine forwards data packets for other machines in the network

Introduction The transmission of a host is received by all hosts within its transmission range due to the broadcast nature of wireless communication and omni-directional antennae. If two wireless hosts are out of their transmission ranges in the ad hoc networks, other hosts located between them can forward their messages, which effectively builds connected networks among the mobile hosts in the deployed area.

Introduction C A B C is out of the wireless transmission range of A A Simple Ad Hoc Wireless Network C is out of the wireless transmission range of A A and C need the help of B to exchange packets

Introduction Ad Hoc Network Consists of mobile hosts (or nodes) which communicate with other nodes through wireless medium without any fixed infrastructure( like AP in 802.11)

Introduction Dynamic network topology The mobile nodes are free to move randomly and organize themselves arbitrarily; thus, the network's wireless topology may change rapidly and unpredictably. move

Characteristics and tradeoffs Self-organized Self-deployed Decentralized Dynamic network topology Tradeoffs Limited Bandwidth Need Multi-hop router Energy consumption problem Security problem

Benefits Easy to deployment Fast deployment No dependence on infrastructure

Applications Personal area networking Emergency operations Cell phone, laptop, PDA , tablet pc Emergency operations Search and rescue Policing and fire fighting Civilian environments Taxi cab network Boats, aircrafts Military use On the battle field

Personal area networking Cell phone, laptop, PDA , tablet pc

Military use

Civilian Applications Disaster Recovery (flood, fire, earthquakes etc) Homeland defense Search and rescue in remote areas Environment monitoring (sensors) Space/planet exploration

An ad-hoc network as a graph

Critical issues in ad hoc networking Routing: Efficient: minimize control update O/H and redundant forwarding robust, QoS enabled routing route security, covert operations Security: Multicast: congestion controlled; reliable

Security Issues Security is an important issue for ad hoc networks, especially for those security-sensitive applications. we consider the following attributes: Availability Confidentiality Integrity Authentication Non-repudiation.

Availability Keep the network alive against denial of service attacks. A denial of service attack could be launched at any layer of an ad hoc network. physical and media access control layers Jamming the wireless channel network layer disrupt the routing protocol and disconnect the network. higher layers bring down high-level services. One such target is the key management service, an essential service for any security framework.

Confidentiality Some sensitive information requires confidentiality Ex. Strategic or tactical military information Leakage of such information could be dangerous , therefore we need to protect these information Routing information must also remain confidential in some cases, because the information might be used to track any node by an adversary.

Integrity Guarantees that a message being transferred is never corrupted. A message could be corrupted because of radio propagation impairment, or because of malicious attacks on the network.

Authentication Enables a node to ensure the identity of the peer node it is communicating with. Without authentication, an adversary could masquerade a node, thus gaining unauthorized access to resource and sensitive information and interfering with the operation of other nodes.

Non-repudiation Ensures that the origin of a message cannot deny having sent the message. Non-repudiation is useful for detection and isolation of compromised nodes. When a node A receives an erroneous message from a node B, non-repudiation allows A to accuse B using this message and to convince other nodes that B is compromised by an adversary.

Ad-hoc routing protocols

Source-Initiated On-Demand routing protocols AODV: Ad-hoc On-Demand Distance Vector Routing DSR: Dynamic Source Routing Generate routes when desired by the source node. Packet on source node must wait until a route is discovered. Periodic route updates are not required.

Table-Driven routing protocols DSDV: Destination-sequenced Distance-vector Routing Every node need to maintain a table to store routing information. Require mechanisms to update the routing table periodically Cause signaling traffic and power consumption problems Packets on source can be forwarded immediately since the routes are always available.