inet: internet network architectures - matthias petschick · 2016-08-31 · the p2p oracle matthias...

The P2P Oracle

Matthias Petschick

Seminar Internet Routing,TU-Berlin

Wintersemester 2007/2008

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Orientation

● Introduction● The problem – motivation● Possible solution - The Oracle Service● Metrics & Simulations● Results & Open questions

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Introduction

● P2P usage is on the rise nowadays– Up to 83% of all Internet traffic in some regions

– Not only file sharing, also voice/video communication, entertainment and more

– Demand increasing

● This is both good and bad news for ISPs+ Increased revenue from broadband connection sales

– More complex traffic routing required● Why?

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Orientation


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Routing in the Internetand how P2P affects it

● Internet consists of Autonomous Systems (ASes), owned by Internet Service Providers (ISPs)

● Traffic between two ASes usually incurs additional costs (customer <-> provider)

● ISPs have established policies to ensure cost-effective and efficient routing➔ P2P networks ignore these policies to create

independent, uncorrelated overlay network● Expensive paths, which do not necessarily have the

capacity for the additional traffic may be chosen ➔ An issue for both user and ISP

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The Problem...

● ISP Point of View:– P2P traffic costs ISPs money and resources

● Some ISPs take action against P2P, e.g. blocking ports or prioritizing other traffic, endangering the net neutrality

➔ Users try to disguise their traffic, which in turn increases the routing problem

● User Point of View:– Download rates suffer from using non-optimal routes

– High latency

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...and how it could be solved

● ISP provides all information to the user✗ Internal network structure is corporate secret

● P2P application performs measurements✗ Additional traffic from measurements

✗ Inaccurate, routing can change at any time

● ISPs and users can work together to overcome this✔ ISP uses knowledge about internal network to suggest

alternative paths to users

✔ Users benefit from suggestions through faster download speed and better latency

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Orientation


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The Oracle Service

● Focus on the Gnutella network

● P2P nodes choose from a list of IPs where to connect to or download content from

● ISPs can influence this by providing a service to sort this list in a way that's beneficial for both parties

● User point of view:– Improved performance– Participation voluntary, no private information leaked directly from

list of IPs

● ISP point of view:– No additional network information is revealed than publicly known– Returns control of where traffic flows to the ISP

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P2P without Oracle

● P2P nodes in two ASes

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P2P without Oracle


● P2P node in AS 1 searches file

– Node in AS 1 has file


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P2P without Oracle





● The node in AS 2 may be chosen

➔ Data crossing AS boundaries

➔ Possibly slower connection than to node in local AS 1

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P2P with Oracle





● Oracle service is queried instead of randomly choosing a node

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P2P with Oracle





● Oracle service is queried instead of randomly choosing a node

● Oracle suggests node in local AS

➔ Traffic remains within AS boundary

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Interests & Concerns

● ISP perspective– Widespread Oracle usage

● User perspective– Does the Oracle

● negatively affect the connectivity within the P2P network?● degrade the number of search results?

➔ Users wouldn't use Oracle!

● 3 different simulations to test effects on P2P network– Graph based with Subjects Environment

– Protocol based with SSFNet

– The actual Gnutella client in Testlab

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Orientation


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Network topology as a graph

● Underlay (AS) network:– ASes represented through nodes

– Connections between ASes corresponding to edges

– Edges have a cost defined as weight

● Overlay (P2P) network:– P2P nodes equal graph nodes

– Connections between P2P nodes are edges

● Message between two overlay nodes needs to traverse underlay graph

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The Internet & P2P as a graph

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Metrics

● To measure the effectiveness of the oracle, the following metrics were used:– Degree: A node's number of connections

● Connections should preferrably be local within the AS

– Hop count diameter: Maximum (#edges) of the shortest paths from one to every other node of the overlay graph

● Should be low for the overlay graph

– AS diameter: Maximum cost of the cheapest paths between any 2 nodes of the overlay graph

● Costs accumulate from routing data over underlay graph edges

– Flow conductance: Measurement of how well a network can withstand faults and congestions, like faulty peers

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Graph simulations

● Biased graph (with Oracle) vs. unbiased graph (without Oracle) – Only small difference in

connectivity and mean degree

– Hop count and AS diameter not negatively affected

– Locality improved considerably

➔ No negative side effects on the overlay graph

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SSFNet Simulations

● Gnutella protocol implemented in SSFNet

● Modified for Oracle usage

● Results:

– Marginal decrease of mean node degree➔ Gnutella network structure not negatively affected

– Slight increase in overlay graph diameter

– Verly low average AS distance, most nodes connected within local AS

➔ Lower costs for ISP and faster download rates for user

– Decrease of negotiation traffic by a factor of 2

➔ Oracle works with real P2P network equally well as with simulated graph

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SSFNet SimulationsWithout Oracle With Oracle

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Gnutella in Testlab

● Controlled environment, consisting of switches, routers and computers, running Gnutella client– Forms various AS topologies (ring, star, tree, random mesh)

● Special focus on effect on search queries✔ Number of search results only slightly reduced

✔ Searches that yielded results without Oracle always returned results with Oracle usage as well

✔ Negotiation traffic reduced by 50%

✔ No adverse effects detected

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Orientation


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Summary of Simulation results

✔ All in all, no negative effect on P2P network's structural properties by Oracle

✔ Improved, i.e. shorter, AS distance➔ Better locality➔ Beneficial for both ISP and user

✔ Number of search results not affected

✔ Reduction of negotiation traffic

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Open questions and concerns

● Applicability for newer P2P clients, e.g. Bittorrent– Downloads from many sources at once– Usually less nodes to choose from➔ Can locality be maintained?

● Privacy– Is it possible to draw conclusions (user profiles) from list of IPs submitted

to the Oracle?– Would copyright holders call for storing queries to the Oracle for later

use in court?

● User behaviour– Users often throttle their upstream bandwidth– Oracle bases suggestion on ISP information, no info about user settings

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Literature

● Vinay Aggarwal, Anja Feldmann, Christian Scheideler, ”Can ISPs and P2P Users Cooperate for Improved Performance?” in ACM SIGCOMM Computer Communication Review, 37(3), 2007

● Vinay Aggarwal, Anja Feldmann, ”Locality-Aware P2P Query Search with ISP Collaboration” in Networks and Heterogeneous Media Journal

● Matei Ripeanu, Ian Foster, Adriana Iamnitchi, ”Mapping the Gnutella Network: Properties of Large-Scale Peer-to-Peer Systems and Implications for System Design”, in IEEE Internet Computing Journal special issue on peer-to-peer networking, vol.6(1) 2002

● Tim Lohman, ”Most ISPs to limit P2P traffic”, http://www.itnews.com.au/News/NewsStory.aspx?story=30821

● ipoque GmbH, ”Internet Study 2007”,http://www.ipoque.de/media/Internet studies/Internet study 2007

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Questions?

inet: internet network architectures - matthias petschick · 2016-08-31 · the p2p oracle matthias...

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