1. Ad Hoc Network

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

3. 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

4. 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.

5. 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

6. 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 )

7. 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

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

9. Benefits Easy to deployment Fast deployment
No dependence on infrastructure

10. 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

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

12. Military use

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

14. An ad-hoc network as a graph

15. 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

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

23. Ad-hoc routing protocols

24. 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.

25. 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.