Structured P2P over Wireless Multi-hop Networks

Transkript

1 Structured P2P over Wireless Multi-hop Networks Marcel C. Castro Karlstad University, Sweden 1

2 Outline Background and motivation Structured P2P Overlay in MANETs Performance evaluation Conclusion and future work 2

3 Need for P2P in MANET P2P model can be an attractive approach in MANETsin order to provide distributed services such as: Data sharing( file, video, music) Mobility Management Security (Anonymity) P2PSIP INVITE Contact: P2P overlay columbia.edu REGISTER => REGISTER Alice s Alice host Client-server maintenance, configuration, controlled infrastructure No central server as in MANET, search latency 3

4 Similarities between P2P and MANETs Same paradigm Resource (e.g., files) Discovery vs. Route Discovery Self-organizing network Lack of managing and centralizing units 4

5 Challenges in supporting P2P over MANETs P2P Networks MANET Motivation for creating the network Logical infrastructure to provide a service A physical infrastructure to provide connectivity Connection between two nodes Fixed medium and direct Wireless and indirect Connection confidence High ( physical connections) Low ( wireless connections) Peer location Any Internet point Restricted area Structure Routing Peer Mobility Broadcast Physical apart from logical structure Proactive, reactive, hybrid Fixed/Limited Virtual, multiple unicasts Physical structure corresponding to logical structure Proactive, reactive, hybrid Mobile Physical, to all nodes in transmission range area 5

6 Understanding Structured P2P Also known as Distributed Hash Table (DHT) Idea: Route a packet based on a key to the node in the network that is currently responsible for the packet's key. This process is referred to as indirect or key-based routing. 6

7 Structured P2P Overlay in MANETs A B Overlay B IP A 7

8 Structured P2P Overlay in MANETs A B Overlay B IP A 8

9 Bamboo DHT (1/3) 64 0 (6 bits) N1 K6 N8 Large id space N51 NodeIds picked randomly from space N48 K46 N42 N38 root node for key id space K36 N32 N21 N14 nodeid key Hash[ ] = N1 Keys picked randomly from space Hash[picture.jpg] = K46 Key is managed by its root node: Live node with id closest to the key location of object or actual object 9

10 Bamboo DHT (2/3) O(N) messages on avgto resolve query I am N1 N8 Who s resp for file K46 N51 N48 K46 file K46 stored here N14 N42 N21 N38 N32 nodeid key 10

11 Based on Pastry routing logic LeafsetTable: Bamboo DHT (3/3) List of successors and predecessors that are the numerically closest in key space Routing Table: List of nodes that share a common prefix Proactive Management Overlay Neighbor ping: Keepalive message to one-hop neighbors and RTT estimation. Leafset update: A random node is selected from its leafset followed by a leafset table synchronization. Routing update: Exchange routing table information based on node prefix level inorder to optimize routing entries. Data storage update: A random node is selected from its leafsetfollowed by a data storage table synchronization. 11

12 Simulation Setup Modules in ns-2 Bamboo DHT 1 (see table 1) AODV-UU 2 using default settings Settings IEEE b (11Mbit/s transmission and 1Mbit/s broadcast) in DCF Mode RTS/CTS disabled TwoRayGround propagation model Standard AODV-UU settings No replicas Traffic Generation Topology Metrics No bootstrap period 500 bytes of put message every 2 sec 32 bytes of get messages every 2 sec Static Mesh Nodes (4, 9, 16, 25, 49 nodes) TX range of 250m and 500m carrier sense NodeIDs of nodes are generated randomly No node movement Management Overhead Success rate Lookup delay NO Standard Custom Leafset update Local routing update Global routing update Data Storage update Neighbor Ping Tab. 1: Bamboo Management Periods(secs) 1- O. Rensfelt, Tools and methods for evaluation of overlay networks, IT Licentiate Theses, Uppsala University, B. Wiberg, Porting aodv-uuimplementation to ns2 and enabling tracebased simulation, Master s thesis, Uppsala University,

13 Results (1/3) Setup Compare total bamboo management traffic Results Bamboo overhead increases with number of nodes; Standard management is much more aggressive compared to custom and no management; Custom management imposes less overhead compared to standard management due to less frequent leafsetand routing table updates. Total Overlay Traffic (Kbytes) NO management CUSTOM management STANDARD management Number of Nodes Fig. 1: : Impact of Bamboo Management traffic 13

14 Results (2/3) Setup Request Success rate. Dropped packets reason Results The ability to find the destination nodes which are responsible for the specific keys degrades as management overhead increases network contention; Higher network contention induces higher amount of dropped packet in standard management compared to custom and no management. Success Ratio (%) 100,00 90,00 80,00 70,00 60,00 50,00 40,00 30,00 20,00 10,00 0, Number of Nodes NO management CUSTOM management STANDARD management Fig. 2: Request Success rate NO Custom Standard Route Timeout (TOUT) Route TTL (TTL) No route (NRTE ) Node Queue Full (IFQ) Total Dropped Tab. 2: Number of dropped packets and correspondent reason in the 36 nodes topology 14

15 Results (3/3) 1 0,9 0,8 Probability (lookup delay > x) 0,7 0,6 0,5 0,4 0,3 Results 0,2 0, Lookup delay (sec) Fig. 3: CDF of lookup delay in the 36 nodes topology NO management CUSTOM management Standard management Custom and standard management maintain lower lookup delays if compared to no management due to the optimized leafsetand routing table, guaranteed via periodic tables updates; Some lookups take shorter time to complete for standard than for custom due to the aggressiveness of standard timeouts. 15

16 Conclusion and Future Work Conclusion: Many key characteristics between P2P and MANETs Aggressiveness of standard Bamboo management over Multihop networks A balance between lookup efficiency and management traffic overhead can be found. Current/Future work: Real user traffic modelling Different network topologies (e.g. mobility) Performance evaluation with other proximity aware technique (number of hops) 16

17 Thank you! Marcel C. Castro 17