On The Latency of BFS Interval Cooperation Web Caching

1. On The Latency of BFS Interval Cooperation Web Caching Arwa Zabian Maurizio Bonuccelli Department of Computer Science University of Pisa / Italy Arwa zabian

2. Talk overview • Give a brief introduction of the problem • The presentation of our algorithm • Our results • Conclusion and future works Arwa zabian

3. Web caching Client Client Arwa zabian

4. Problems of Web Caching • Limited cache size • Cosistency problem • Caching dynamic content Solutions • Prefetching • Cooperative Web Caching Arwa zabian

5. Cooperative web caching Arwa zabian

6. Problems in cooperative web caching • Where the request must be forwarded? • How it can be retrieved? Arwa zabian

7. Goal • The goal is the reduction of the latency perceived by the web client . • Delay analysis in a cooperative web caching: • Network factors • System factors System factors Arwa zabian

8. Delay motivations: SearchingDefining the topology • Finding the proxy that have the request, it depends on the topology of the system. • The proxy cache in our system are organized in a tree. • The tree construction is done using NDA (Neighbour Discovering Algorithm). • NDA is based on BFS, it visits the tree by levels. Arwa zabian

9. Defining the topology NDA (Neighbours Discovering Algorithm) Arwa zabian

10. Delay motivation: SeachingFinding the request • When NDA runs in a given graph it constructs a tree called Child-Tree, in which each node reports its parent label. • The maximum length of label assigned to n nodes is 2logn+1 bits. • Based on the information collected each node constructs a routing table that is a data structure in which is inserted the node labels and their Interval of documents. • The documents are organized in intervals of their URL based on the interval routing scheme proposed by Santoro and Khatib[82]. N. Santoro, R. Khatib: Routing Without Routing Table. Tech. Rep, SCS-TR-6 School of Computer Science, Carleton University. Ottawa 1982 Arwa zabian

11. Searching : Complexity analysis • NDA is asymptotically optimum as search graph algorithm. • Time complexity is O(|E|+|V|). • Message complexity in construction Child-Tree is O(|E|+|V|). Arwa zabian

12. Delay motivation Routing and fault tolerance NDA contribues in the routing process in two factors they are: • Routing decision. • Address solution at each hop. • Fault tolerance: it maintains a backup links used in the case of nodes and links faulty. Arwa zabian

13. Routing : Complexity analysis • The size of data structure constructed by the information collected during the NDA discovering process is logarithmic with the number of nodes of the graph. • The number of nodes travelled by each message, in Child-Tree is O(log n). Arwa zabian

14. Simulation Results • All our simulation were run on top of NS2. • The goal was the reduction of the searching and routing time. • Our simulation results confirm that the searching time is fixed in all the conditions studied and varied only in the case of miss. • The routing time is strictely related to the size of the document and to the number of hops between proxy and server Arwa zabian

15. Simulation Results: factors influenced in the latency • Type of the document: static or dynamic. • Page popularity. • Number of request. • Number of hops. • Page size Arwa zabian

16. Type of the document : static or dynamic Dynamic Static Arwa zabian

17. Page Popularity Static and less popular page Static and popular page Arwa zabian

18. Number of request • The latency is decreased when the number of requests is increased between two modification. Arwa zabian

19. Simulation Results: Number of hops • The retrieving process R R R Arwa zabian

20. Simulation Results: Number of hops • The latency is increased linearly with the number of hops Arwa zabian

21. Simulation Results : Page size • The simulation results show that the most important factor that influences in the latency variation is the page size. • The latency is increased linearly with the page size. Hierarchical Randomized Arwa zabian

22. Simulation Results: Page size • The hit ratio is influenced by the page size. 82% 82% 18% 100% Arwa zabian

23. Simulation Results: Page size The transmission time is strictly related to the page size that affect the latency. The transmission time is increased linearly with the page size. Arwa zabian

24. Simulation Results : Transmission Time hierarchical randomised T.T Arwa zabian

25. Results: • Scalability: the latency is independent on the network size. Arwa zabian

26. Results : Scalability Arwa zabian

27. Results: • Reliability : the system ensures that the client receives the request in the presence of some links faults with some additional delay penalty. Arwa zabian

28. Related works • Riptide is a peer-to-peer web caching system built on top of OceanStore that uses a routing mechanism called Tapestry. • The comparison of our system with that for Riptide show that : our system perform well for small documents . Both systems give a similar results for medium document. When Riptide performs better than our system for large documents Arwa zabian

29. Related works • Comparison results in term of latency Arwa zabian

30. Related work • Comparison results in term of hit Riptide NDA 82% 100% 100% Arwa zabian

31. Conclusion • We proposed an algorithm based on BFS that reduces the searching time by reducing the size of the data structure used rapresenting the documents in intervals based on their URL’s. • Our algorithm was proposed to reduce the routing time by reducing the address resolution in each node. • We obtained a reliable system that allow the client to receive the request with the presence of some faulty link in the system. It is scalable in which the latency perceived by the client is independent on the system size. Arwa zabian

32. Future work • Utilizing the document division method in developing a technique for the request prefetching between proxy and proxy. • Modelling the system to include the dynamic case ( insertion and deletion of nodes). • Performs some additional simulations to include the cases not covered in our previous work. Arwa zabian

33. Questions? Arwa zabian

34. References [1] A. Zabian, M. Bonuccelli ``BFS Based Algorithm for Routing and Fault Tolerance in a Cluster of Web Caching''. Technical Report, ``http:\\www.di.unipi.it\ ~ bonucce''. [2] B. Zaho, A.Joseph and J. Kubiatowicz, ''Tapestry: Infrastructure For Fault-tolerance Wide Area Location and Routing''. Technical Report UCB//CSD-01-1141, U.C. Berckley 2001. [3] C. Wells. ``The Oceanstore Archive: Goal, Structure and self Repair'', Master thesis, University of California, Berkeley.May2001 [4] Duane Wessels.``Internet Cache Protocol(ICP)'', version 2. RFC 2186 . [5] E. Zegura, K. Calvert and S. Bhattacharjee. ''How to model an Internetwork''. In Proc. of INFOCOM, 1999. [6] L.Fan, P. Cao, J. Almedia, A.Z. Border,``Summary-Cache a scalable Wide Area Web Cache sharing Protocol'', IEEE/ACM Transactions on Networking. Vol 8. No 3,pp: 281-293. June 2000. [7] Martin Hamilton, Alex Rousskov, Duane Wessels, ``Cache Digest'', National Laboratory for Applied Network Research, Aprile1998. “http:\\Squid.nlanr.net\Squid\cachedigest'' [8] Patrick R .Eaton ``Caching the web with OceanStore'‘ . Technique report UCB/CSD/021212.U.C.Berkely. November 2002. Arwa zabian