1 / 29

Grid vs. Peer-to-Peer

Grid vs. Peer-to-Peer. Yin Chen s0231189@sms.ed.ac.uk 25 June 2003. Content. Grid vs. P2P What’s the request Why P2P architecture Issues of P2P P2P case study- Freenet Design. Grid vs. P2P. Grid. Standards- based Persistent Addresses security issues

Download Presentation

Grid vs. Peer-to-Peer

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Grid vs. Peer-to-Peer Yin Chen s0231189@sms.ed.ac.uk 25 June 2003

  2. Content • Grid vs. P2P • What’s the request • Why P2P architecture • Issues of P2P • P2P case study- Freenet • Design

  3. Grid vs. P2P Grid Standards- based Persistent Addresses security issues Resources are more powerful,more diverse, better connected Data intensive Facing problems of autonomic configuration and management Not much scalable

  4. Grid vs. P2P • P2P Much scalability Fault tolerance Self-configuration Automatic problem determination Higher variable behaviour But lack of infrastructure Security problems Less concerned with qualities of service

  5. What’s the request • A user requests the car service, and keeps logs recording if the request success or fail • The user may asks all other users about history request records. By statistic, we can know particular service responding ability. • Which can also gives prediction of further request.

  6. Why P2P • Not run-time information • Better fault tolerance, • Pull model efficient and less network traffic

  7. Issues of P2P - Topology

  8. Issues of P2P - Response Modes

  9. Issues of P2P … It turns to be problem of query from distributed data stores, which is different from central database query …

  10. Issues of P2P - Query Processing Recursively Partitionable Query

  11. Issues of P2P - Abort Timeout (1) • Problems - User no longer interested in query results - Query will forever roaming the network without stop it - The query should be fade away after sometime - Static timeout remains unchanging across hops • Solution ->Dynamic Abort Timeout - Nodes further away from the originator timeout earlier than nodes closer to the originator. - Decrease the timeout at each hop - Exponential decay with halving

  12. Issues of P2P - Abort Timeout (2)

  13. Issues of P2P - Query Scope (1) • Problems -No necessary to search the whole net - Broadcast model will flooding the network. • Solutions ->Select a neighbour subset - Search only a specific domain, host, owner - Random select half of the neighbours - In a tree-like topology, select all child and ignore all parent - Only find a single result. - Specify the maximum number of result (maxResults) and bytes(maxResultBytes) to be returned.

  14. Issues of P2P - Query Scope (2) • Maintain a statisticsabout its neighbours. Only select neighbours that meet minimum requirements in term of latency, bandwidth or historic (maxLatency, minBandwidth, minHistoricResult) • Neighbour Selection Query • Radius of a query - is a measure of path length. - Set the maximum number of hops a query is allowed to travel - The radius is decreased by one at each hop. - The roaming query and response fade away when a radius of less than zero.

  15. Issues of P2P - Routing • Random forwarding(random walk) • Learning: nodes record the requests answered by other nodes. A request is forwarded to the peer that answered similar requests previously or randomly. • Best neighbour: records the number of answers received from each peer. A request is forwarded to the peer who answered the largest number of requests. • Learning + best neighbour: identical with the learning, when no relevant experience exists, the request is forwarded to the best neighbour.

  16. P2P Case Study - Freenet • Freenet provides a file-storage service • The network is entirely decentralised • Information publishers and consumers are anonymous • Communications are encrypted • Files in the data store are encrypted

  17. Adding New File • A user assigns the file a GUID key, sends an insert message, containing file identifier(GUID) and a time-to-live(TTL)value. • GUID is location-independent globally unique identifier. By hashing the contents of the file. • On receiving an insert, the node checks if the key already exist. If not, stores it, creates a routing entry for it, looks up the closest key, and forwards the message to the related node. • If TTL expires, the final node returns an “all clear” message. The user then sends the data alone the path.

  18. Requesting File • Every node maintains a routing table, listing addresses of other nodes and GUID keys. • On receiving a query, it first checks its own store. If it finds the file, it announces itself as the holder. Otherwise, it forwards the query to the node with the closest key. • If the file is found, each node passes the file alone the chain, and creates a new entry in its routing table. • Each node might also cache a copy locally. • The query maintains a TTL, decreased at each hop. • If a node runs out of candidates, it reports failure and back the its predecessor, which then tries its second choice

  19. Adding New Node • New node sends a announcement to an existing node, with a TTL. • The receiving node forwards the announcement to another node chosen randomly from its routing table. • The announcement continues to propagate until its TTL runs out.

  20. Training Routes • Nodes that reliably answer queries will be added to more routing tables. • Well-known nodes tend to see more requests and become better connected. • Similar keys tend to cluster in the nodes along the same path, because requests will be for similar files which have similar keys.

  21. Managing Storage • Given finite disk space, sometime need to decide which file to keep. • Freenet decides by the frequency of requests per file, keeps the more popular files. • Frequently requested files have more copies in the network. Treegrows in that direction • Unrequested files are subjected to delete. Treeshrinks in that direction.

  22. Design Tree Topology Each node maintains a Log File Each node also maintains a Local Data Store for storing the queries result.

  23. Design • Adding New Node - When a new node adds to the network, it connects itself to only one existing node. • Adding LogRecord - When a user accesses services, a log record will be created - Log records should provide information about service name, service accessing time, success/fail flag

  24. Design - Query • Query - When a node sets up a query, it first looks up its local data store to see if the same query exists. - If it is a new query , the node multicasts a query message to all connecting nodes. The query message contains Query Conditions, Maximum Data Volume value and a Dynamic Abort Timeout(DAT) value. - Query Condition may contains time period which user concerns, services name etc.

  25. Query - On receiving the query message, a node first looks up its own local data store, if there is no same query, it multicasts the query to all connecting nodes. - When DAT expires, the final node begins to return data along the chain. - Response using Routed Response mode

  26. Design - Query - To reduce network traffic, calculation will operate at each node. Using Recurisively Query Plan. The calculation result will propagate up along the chain.

  27. Design - Query - To avoid data flooding, only necessary volume data will be calculated, that is specified by Maximum Data Volume - Each chain will return zero or one result - Dynamic Abort Time (DAT) using Exponential decay with halving model. DAT will decrease at each hop.

  28. Design • Calculation - By particular statistics methodology • Showing Result - Final result will be shown in graph style - The query result will also be saved in the Local Data Store • Deleting log records - To save disk space, early log records should be deleted after period of time

  29. Grid vs. P2R Thanks !

More Related