Title: Efficient Content Location Using Interest-based Locality in Peer-to-Peer Systems
1Efficient Content Location Using Interest-based
Locality in Peer-to-Peer Systems
- Presented by Lin Wing Kai
2Outline
- Background
- Design of Interest-based Locality
- Simulation of Interest-based Locality
- Enhancement of Interest-based Locality
- Understanding the scheme
3Background
- 3 types of P2P systems
- Centralized P2P Napster
- Decentralized Unstructured Gnutella
- Decentralized Structured Distributed Hash Table
(DHT)
4Background
- Each peer is connected randomly, and searching is
done by flooding. - Allow keyword search
Example of searching a mp3 file in Gnutella
network. The query is flooded across the network.
5Background
- DHT (Chord)
- Given a key, Chord will map the key to the node.
- Each node need to maintain O(log N) information
- Each query use O(log N) messages.
- Key search means searching by exact name
6Outline
- Background
- Design of Interest-based Locality
- Simulation of Interest-based Locality
- Enhancement of Interest-based Locality
- Understanding the scheme
7Interest-based Locality
- Peers have similar interest will share similar
contents
8Architecture
- Shortcuts are modular.
- Shortcuts are performance enhancement hints.
9Creation of shortcuts
- The peer use the underlying topology (e.g.
Gnutella) for the first few searches. - One of the return peers is selected from random
and added to the shortcut lists. - Each shortcut will be ordered by the metric, e.g.
success rate, path latency. - Subsequent queries go through the shortcut lists
first. - If fail, lookup through underlying topology.
10Outline
- Background
- Design of Interest-based Locality
- Simulation of Interest-based Locality
- Enhancement of Interest-based Locality
- Understanding the scheme
11Performance Evaluation
- Performance metric
- success rate
- load characteristics (query packets per peers
process in the system) - query scope (the fraction of peers in each query)
- minimum reply path length
- additional state kept in each node
12Methodology query workload
- Create traffic trace from the real application
traffic - Boeing firewall proxies
- Microsoft firewall proxies
- Passively collect the web traffic between CMU and
the Internet - Passively collect typical P2P traffic (Kazza,
Gnutella) - Use exact matching rather than keyword matching
in the simulation. - song.mp3 and my artist song.mp3 will be
treated as different.
13Methodology Underlying peers topology
- Based on the Gnutella connectivity graph in 2001,
with 95 nodes about 7 hops away. - Searching TTL is set to 7.
- For each kind of traffic (Boeing, Microsoft
etc), run 8 times simulations, each with 1 hour.
14Methodology Storage and replication modeling
(web)
- The first peer make the web request will be
modeled as first node containing the web pages. - Subsequent search from other peers will search
from this peer and replicate the page.
15Methodology Storage and replication modeling
(P2P)
- From the traffic trace collected, if a file is
downloaded for download at t0. - The file should also be available for download
before t0. - However, if the file isnt downloaded during the
sampled trace, - There is no information to indicate the existence
of the file.
16Simulation Results success rate
17Simulation Results load, scope and path length
-- Query load for Boeing and Microsoft Traffic
-- Query scope for shortcut scheme is about 0.3,
where in Gnutella is about 100.
-- Average path length of the traces
18Outline
- Background
- Design of Interest-based Locality
- Simulation of Interest-based Locality
- Enhancement of Interest-based Locality
- Understanding the scheme
19Increase Number of Shortcuts
20Using Shortcuts Shortcuts
Add the shortcuts shortcut
Performance gain of 7 on average
21Outline
- Background
- Design of Interest-based Locality
- Simulation
- Enhancement of Interest-based Locality
- Understanding the scheme
22Interest-based Structures
- When viewed as an undirected graph
- In the first 10 minutes, there are many connected
components, each component has a few peers in
between. - At the end of simulation, there are few connected
components, each component has several hundred
peers. Each component is well connected. - The clustering coefficient is about 0.6 0.7,
which is higher than that in Web graph.
23Web Objects Locality
- Webpage contains several web objects, locality
should exists in between these objects.
24Locality Across Publishers
- Same publisher exhibit low interest locality,
peer actually may interest different publishers
content.
Same publisher shortcuts means shortcuts that are
originally created as accessing the same content
from the same publisher for the current request.
25Sensitivity of Shortcuts
- Run Interest based shortcuts over DHT (Chord)
instead of Gnutella.
Query load is reduced by a factor 2 4. Query
scope is reduced from 7/N to 1.5/N
26Conclusion
- Interest based shortcuts are modular and
performance enhancement hints over existing P2P
topology. - Shortcuts are proven can enhance the searching
efficiencies. - Shortcuts form clusters within a P2P topology,
and the clusters are well connected.