Improving Performance in the Gnutella Protocol Jonathan Hess
- Slides: 22
Improving Performance in the Gnutella Protocol Jonathan Hess Benjamin Poon University of California at Berkeley Department of Computer Science Cs 294 -4 Peer-to-Peer Systems 1
Outline n n n Background Motivation Solution n n Mirroring Directed Search Results Possible Future Work Cs 294 -4 Jonathan Hess | Benjamin Poon 2
Background n Gnutella n n Protocol for distributed search No centralization Searches through query flooding Opponents n Cs 294 -4 Censorship + threatening of Gnutella users Jonathan Hess | Benjamin Poon 3
Motivation Opponents cause participation causes replication of shared files 1. 2. Same files being shared, but not as many copies n replication causes 3. n n è Cs 294 -4 workload for sharing peers Need for deeper query depths Overall decrease in performance Jonathan Hess | Benjamin Poon 4
Solution n Improve performance given decreased participation n n Cs 294 -4 Mirroring Directed Search Jonathan Hess | Benjamin Poon 5
Mirroring – Main Idea Achieve more replication by copying file to a willing peer (a mirror) Only replicate on demand Preserve blame on original sharer of file n n Cs 294 -4 i. e. , mirrors should retain plausible deniability despite sharing the file Jonathan Hess | Benjamin Poon 6
Mirroring Request Messages n Mirror requestor (originator) sends Mirroring Request Message (MRM) to find a client to act as mirror n n No need to flood n n Clients pass MRM’s only on one randomly chosen outgoing connection MRMTTL should be relatively high n n MRM(header, listening. Port, file. Index) Prevents people from intercepting query traffic to see what file is Con: originator must stay in network in order for mirroring to occur Cs 294 -4 Jonathan Hess | Benjamin Poon 7
Mirroring – Sending MRMs Procedure per client sharing n files F 1…Fn n 1. 2. Record demand Di (# uploads) for locally shared file Fi When Di > mirror. Threshi, request a mirror n 3. Having a new mirror means we shouldn’t create additional mirror as readily n Cs 294 -4 Send MRM on one random outbound connection mirror. Threshi += thresh. Increment Jonathan Hess | Benjamin Poon 8
Mirroring – Receiving MRMs Mirror M sends file transfer request for MRM. file. Index to originator O O receives request for file. Index O adds M to its list of mirrors of file. Index O sends M encrypted file associated with 1. 2. 3. 4. file. Index n n Cs 294 -4 Preserves plausible deniability for mirror Con: still a possibility for a client to figure out what original file was – how? Jonathan Hess | Benjamin Poon 9
Mirroring – Using Mirrors Procedure for originator of MRMs n n If originator has enough bandwidth n n If not enough bandwidth n n Check if there are mirrors for file. Index If no mirrors n n Serve files Proceed according to original Gnutella protocol If has mirrors n Multiplex requests over set of mirrors M 1. . . Mx n Cs 294 -4 Send Query. Hits as if they were from Mi (1 <= i <= x) containing the decryption key Jonathan Hess | Benjamin Poon 10
Directed Search – Motivation n As the ratio of free-loaders to serving peers increases, search moves towards needle-in-a -haystack n n n Cs 294 -4 Flood excels at finding piles of hay Much research effort has gone into successive deepening and file indexing Directed search is not as well understood Jonathan Hess | Benjamin Poon 11
Directed Search – Main Idea n n Pay a one time up front cost for a bloom filter broadcast Nodes within N hops merge filter into a collection associated with each edge n n Collection is depth aware Upon receiving a query, forward message to n edges with highest scores Cs 294 -4 Jonathan Hess | Benjamin Poon 12
Directed Search n n Query reaches nquery nodes n may be much smaller than out-degree and query. TTL can be larger than normal TTLs n n n Cs 294 -4 nquery. TTL < out-degree. TTL Reach more and better users Avoid free-loaders Jonathan Hess | Benjamin Poon 13
Results n Simulation: Bloom. Net n Models real-world Gnutella network as close as possible n n Uses statistics from many previous measurement studies of Gnutella networks File sharing/requesting n n n Cs 294 -4 Master filename list of 5072 files Each client chooses to share certain number of files from master list Queries generated by taking a random filename at most once from master list according to modified Zipf distribution (à la Efficient search in peer-to-peer networks, B. Yang, H. Garcia-Molina) Jonathan Hess | Benjamin Poon 14
Results – Overview n Advantages n Bloom. Net finds hits better than Gnutella n n Uses approximately 3 x less query bandwidth As network size increases n n Bloom. Net achieves higher % successful queries than Gnutella n n Gap in performance increases Uses approximately 3 x less query bandwidth Disadvantages n 20% more total bandwidth used to run Bloom. Net n Cs 294 -4 Can be improved using different Bloom parameters Jonathan Hess | Benjamin Poon 15
Results – Query Success Cs 294 -4 Jonathan Hess | Benjamin Poon 16
Results – Query Bandwidth Cs 294 -4 Jonathan Hess | Benjamin Poon 17
Results – Total Bandwidth Cs 294 -4 Jonathan Hess | Benjamin Poon 18
Possible Future Work n Mirroring n n More sophisticated demand realization techniques – gossiping protocols? Directed Search n n n Cs 294 -4 Only highly-connected peers exchange Bloom Filters Better score functions for edge selection Better understanding of filter merging Jonathan Hess | Benjamin Poon 19
Questions Cs 294 -4 Jonathan Hess | Benjamin Poon 20
Cs 294 -4 Jonathan Hess | Benjamin Poon 21
Simulation Parameters n n n Clients Bloom Depth Bloom Size Ping TTL Query TTL Mirror TTL Cs 294 -4 1024 3 -4 384 -3072 5 5 -7 15 Jonathan Hess | Benjamin Poon 22
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