peer to peer ad-hoc networks csi 5148 wireless ad hoc networking

Download Peer to peer ad-hoc  networks CSI 5148 Wireless Ad Hoc  Networking

Post on 24-Feb-2016




0 download

Embed Size (px)


Peer to peer ad-hoc networks CSI 5148 Wireless Ad Hoc Networking. By: Margi Fumtiwala (5781941). Agenda. Introduction Peer to Peer Network P2P vs. Client/Server architecture Structured P2P overlay network Unstructured P2P overlay network Gnutella P2P Architecture Comparison - PowerPoint PPT Presentation


Slide 1

Peer to peer ad-hoc networks

CSI 5148 Wireless Ad Hoc Networking

By: Margi Fumtiwala (5781941)Peer to Peer Ad Hoc Networks1AgendaIntroductionPeer to Peer NetworkP2P vs. Client/Server architectureStructured P2P overlay networkUnstructured P2P overlay networkGnutellaP2P Architecture ComparisonAd Hoc NetworkTypes of Ad Hoc NetworkAd Hoc Routing AlgorithmsDynamic Source Routing (DSR)Research ProblemSolutionDynamic P2P Source Routing (DPSR)Conclusion

2Peer to Peer Ad Hoc NetworksIntroductionPeer to peer (P2P) overlay networks are built at application layer

Used for indexing and peer discoveryContents are directly exchanged between the underlying Internet Protocol (IP) networks

3Peer to Peer Ad Hoc Networks

Figure 1. Schematic network topology of a Peer to Peer network[R. Shollmeier, Routing in Mobile Ad Hoc Networks and Peer-to-Peer Networks, a Comparison, Inter. Workshop on Peer-to-Peer Computing, Pisa, Italy, May 2002]Peer to Peer networkP2P architecture works in distributed mannerSelf-organizing, decentralized overlay networksParticipating nodes contribute resources and cooperate to provide a service

Differs from client/server network architecture

Peer node is called SERVENT i.e. acts as server and client simultaneously4Peer to Peer Ad Hoc Networks4Peer to Peer Ad Hoc NetworksP2P vs. Client-Server architectureAdvantages over client/server network architecturePeer nodes are similar and mostly have same propertiesNo central body like serverTransfer is not delayed because no server entityIf a peer leaves, neighbouring peers sense it and update their records accordinglyResource present at multiple nodes No fear of central point of failure

5Peer to Peer Ad Hoc Networks5Peer to Peer Ad Hoc NetworksP2P vs. Client-Server architecture (Cont.)

6Peer to Peer Ad Hoc Networks[]Structured P2P overlay networkP2P overlay networks classification: Structured and UnstructuredStructured P2P overlay network: Tightly controlled networkScalable and do not required floodingAlso referred as Distributed Hash Table (DHT) with two main operations like Put (key, value) and Get (key)DHT stores information about the nodes using Put functionKey = Node IP # Hash function, Value = Key (Corresponding node containing File or directory) # functionAdvantage: messages correctly reach the destination even if large number of nodes crashesExample: Chord

7Peer to Peer Ad Hoc NetworksPeer to Peer Ad Hoc Networks7Unstructured P2P Overlay NetworkUnstructured P2P overlay network:No prior knowledge about the topology of the networkHighly dynamic and peers connect in an arbitrary mannerSearch operation takes time due to floodingAdvantages: Easy implementation, simplicity, keyword search and dynamic environmentsDrawback: Scalability8Peer to Peer Ad Hoc NetworksPeer to Peer Ad Hoc Networks8Unstructured P2P ArchitectureNode stores information about N random nodesChecks its table whether location of requested item is present or notPresent: sends request for that content to that node Not Present: broadcasts the requestNode receives the request, checks its table whether it has relevant content or notIf any present node leaves the network, its entry in the table is replaced by randomly selected node containing some relevant informationDrawback: Costly Node does not contain complete picture of the network in routing table, so floods requestEx: Gnutella

9Peer to Peer Ad Hoc NetworksGnutellaUtilizes a set of messages to help communication between servants Ping: (hello) used to check the servantsPong: Back propagated to the node who sent PingContains the address of the node and the data it shares with networkQuery: Flooded in the network by servant to find the location of the content it is looking forUpon receiving Query message: Servant checks if contains relevant information in its local data setIf yes: Back propagates QueryHit messageQueryHit: Back-propagated by the node where requested item is presentPush: Contains some relevant data from the server to the client10Peer to Peer Ad Hoc NetworksGnutella: Example11Peer to Peer Ad Hoc NetworksACEDBDataDataACEDBDataDataACEDBDataDataACEDBDataDataACEDBDataDataACEDBDataData143256P2P Architecture: A ComparisonTaxonomyUnstructuredStructuredArchitectureFlat and ad hoc network of servants.Flooding request and peers download directlyUnidirectional and circular NodeId spaceScalabilityNoYesReliabilityYesNoSearching OperationBlind SearchIndex SearchExampleGnutellaChord12Peer to Peer Ad Hoc NetworksAd Hoc NetworkCollection of autonomous devices communicating using wireless links without any pre-existing infrastructureIndependent from any stationary infrastructure and no central administrationRapidly deploying and self configuring

Nodes connected by multihop wireless pathsFree to move arbitrarily which results in frequent and unpredictable changes in the network topologyCommunicating nodes may be out of range so the participating nodes must be able to relay traffic13Peer to Peer Ad Hoc NetworksTypes of Ad Hoc NetworkTypes: Mobile Ad Hoc NetworksWireless Sensor networksWireless Mesh networks

14Peer to Peer Ad Hoc NetworksAd Hoc Routing AlgorithmTwo categories: Proactive and Reactive routing algorithmProactive or table driven routing algorithm: Node has full network view at every time ex. routerTopology updates are broadcasted immediately to all other nodesRoute establishment can take place very fastDisadvantage: Number of required topology updates within a time periodNot feasible for nodes rising over certain thresholdEx: Destination Sequenced Distance Vector Routing (DSDV)

15Peer to Peer Ad Hoc NetworksAd Hoc Routing Algorithm (Cont.)Reactive or on demand routing algorithmNode does not send any kind of topology updates to its neighboursTo set up a route, source floods route discovery (short) message Destination node replies back to source upon receiving discovery message using memorized pathsSource sends full message using recorded pathRoute discovery message may contain accumulated delay, congestion, power, cost etc. along paths; best path selected at destinationEx: Dynamic Source Routing (DSR)

16Peer to Peer Ad Hoc Networks

Dynamic Source Routing (DSR)

Two major phases: Route discovery and Route maintenanceRoute discovery: Starts when a mobile node tries to send a packet to a destinationNode checks its own routing cacheCache contains a valid route: Route is used to forward the packetCache does not contain a route: Broadcasts a route request to neighbours containing its own address, the destination address and a unique sequence number for loop detectionReceiving node checks its cacheCache does not contain a route: Adds its own address to the packet and forwardsNode receives multiple copies: Forwards the first request, and discards the following copies

17Peer to Peer Ad Hoc NetworksDSR (Cont.)Route reply : If a node has route to the destination, or the route request reaches the destinationNode is not destination: Adds its cached route to the route reply messageEvery data packet contains full path with the addresses of all intermediate nodesAdvantage: Intermediate nodes do not have to cache the path and can save memoryDisadvantage: size of every packet is increased as it contains the full route information

Route maintenance is fulfilled by route error packetsSent back to the source when an intermediate node or the destination is not reachableNode forwarding an error packet, deletes the broken hop and all routes relying on that broken hop

18Peer to Peer Ad Hoc NetworksDSR: ExamplePeer to Peer Ad Hoc Networks19

[Bahr2002, Dynamic Source Routing]DSR: Example (Cont.)Peer to Peer Ad Hoc Networks20

[Bahr2002, Dynamic Source Routing]Research Problem:Routing in P2P overlay with Underlying Ad hoc networksP2p overlay networks and underlying ad hoc networks (connecting mobile nodes communicating with each other via multi-hop wireless links) share key characteristics of selforganization and decentralization Problem: Connectivity

Dynamic P2P Source Routing (DPSR), exploits the synergy between p2p and Ad Hoc for increased scalabilityIntegration of PASTRY (Proximity-Aware STructured p2p overlay Routing protocol) and DSRDPSR limits the number of the source routes that each node has to discover21Peer to Peer Ad Hoc Networks21Peer to Peer Ad Hoc NetworksSolution:DPSRNodeId Assignment:DPSR assigns each node a unique, uniform, randomly assigned nodeIdsNodeIds (128-bit) = Node IP # hash function (using SHA-1)

22Peer to Peer Ad Hoc NetworksDPSR (Cont.)Routing Table and Leaf Set:Each entry in DPSR leaf set and routing table stores the route to reach the designated nodeId and the IP address of the destination node

Each node maintains a leaf set, consisting of L/2 nodes with numerically closest larger nodeIds, and L/2 nodes with numerically closest smaller nodeIds, relative to the present nodes nodeIdL is an even integer parameter with typical value 16

23Peer to Peer Ad Hoc Networks[Y. Hu, Exploiting the synergy between peer-to-peer and mobile ad-hoc networks. In Hot-OS IX, May 2003]DPSR (Cont.)Routing:Message key (128-bit) = Destination IP # hash functionCurrent node forwards message to a node whose nodeId shares with the key a prefix that is at least one digit (or b bits) longer than the prefix that the key shares with the current nodeIdIf no such node is found in the routing table, message is forwarded to a node whose nodeId shares a prefix with the key as long as the current node, but is numerically closer to the key than the current nodeIdMessage will be delivered to the destination node whose nodeId matches the message keyEach hop in the DPSR network is a multihop s


View more >