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P2P-ISP Cooperation: Risks and Mitigation in Multiple-ISP Networks
Mung Chiang,Princeton University
Aliye Özge Kaya, Wade TrappeWINLAB,
Rutgers University{ozgekaya, trappe}@winlab.rutgers.edu
WINLAB
Overview
Recent P2P-ISP cooperation proposals and their risks Possible outcomes of P2P-ISP cooperation Framework to model the interaction between ISPs and P2P
providers Risk Mitigation
WINLAB
Current P2P-ISP Interaction:No Cooperation: Lose-lose situation for all!
P2P Providers: -Limited capability to infer network topology-Network oblivious peering-Randomize the traffic to prevent filtering P2P traffic by ISP
ISPs: -Increased cost and backbone traffic because of the P2P traffic-Incentives to filter and limit P2P traffic
End-Users
•Poor P2P experience( lower rates, higher delay)
•Incentives to change the ISP and P2P provider
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P2P-ISP Cooperation: Win-Win for all?
Peering decisions avoiding bottlenecks, costly connections.
Reduced costs for ISPsImproved performance for P2Ps
P2P takes into account
ISP’s preferences
P2P Provider discloses
peer locations
ISP discloses network related
Information
End-Users
Better P2P performance:
Download from the closer peers
Higher download rates, reduced delay
Satisfied customer
WINLAB
Does P2P-ISP Cooperation bring only benefits in multi-ISP case?
The benefits have been demonstrated in the single ISP case but potential risks have been not well examined for the multiple ISP case
We first look to the existing cooperation proposals, and identify possible risks.
ISP P2PISP P2P
ISP
ISPISP
ISP
P2P
P2P
WINLAB
Recent Proposals for P2P-ISP Cooperation:Approach A: ISP supported oracle [Aggarwal08]
P2P provider suggests the P2P users possible peers
• Preferential Treatment: P2P can manipulate the list such that to promote the peers in some ISP’s more than the others
ISP ranks the peers for the P2P user
• ISP has the full freedom to manipulate P2P-traffic
• P2P provider can use this ISP oracle to infer sensitive Information
P2P users chooses the peers accordingly
• Choices made by ISPs are not always in the interest of the end user
• Worse Performance?
WINLAB
Recent Proposals for P2P-ISP Cooperation:Approach B: CDN supported Oracle [Choffnes08]
Monitor CDN redirection properties
• Peers redirected to the same CDN server are assumed to close to each other
Assign the peers with the similar redirection properties
• Localized traffic might not yield always the best performance for ISPs or P2P providers.
Peer Assignment without any direct involvement of ISP
• What if the ISP reveals the CDN servers in its network or P2P infers it?
WINLAB
Recent Proposals for P2P-ISP Cooperation: Approach C: P4P [Xie08]
ISP reveals the network topology, P2P reveals peer locations
• Exchange inacccuratetopology, misleading information ( e.g. unexistingcongestion).
iTracker assigns each peer to a cluster called PID
• Computes the metric p4p distance between the PIDs
• Peering suggestion to theAppTracker in form of of p4p distances between the clusters
AppTracker assigns peers close in terms of p4p distance to each other
• P2P provider or ISP can reverse engineer the topology by clustering PID’s with similar preferences.
• Ignore hints from the iTracker
WINLAB
Comparison of Approaches A, B,CA: ISP Oracle B : CDN Oracle C: P4P
Manipulation of Traffic by ISP alone
ISP has fullfreedom tomanipulatetraffic.
not possible partially (mightmisrepresent itsown network)
Can the P2Pprovider infernetworktopology?
partially (useISP oracleas trafficmonitor)
partially (CDNsreplica servesas identifiers ofISPs)
partially (clusterPID’s with similarpreferences,iTracker as trafficmonitors)
Preferential Treatment by P2P (hiding-promoting peers)
possible(manipulatethe list ofthe suggestedpeers)
possible (useCDN Replicaservers asidentifiers forthe preferredISPs)
possible(misrepresentlocation of thepeers, ignorehints fromiTracker)
Manipulation of Traffic by ISP alone
Can the P2Pprovider infernetworktopology?
Preferential Treatment by P2P (hiding-promoting peers)
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Outcomes of P2P-ISP Cooperation
Benefit Drawback Counter-Intuitive
P2P Efficiency(Higher rates, lessdelay)
Lose privacy and sensitive information like topology
Unfairness (betterbenefits for non-cooperatingISP)
Reduced inter-ISPcost
Difficult to verify theexchanged information
Selfish behaviorleading degradationof the benefits
Reduced bandwidthconsumption
Benefit Drawback Counter-intuitive
WINLAB
Drawbacks of Cooperation
Use “No Valley and Prefer Customer Policy” of routing also as giving preference for the destination– Customer ISPs will be forced to
send much more content to the provider ISPs
Exchanging Misleading Information– Inaccurate topology, nonexisting
congestion etc. Preferential Treatment
– ISPs or P2Ps selectively release information in a way to favor some P2P providers or ISPs over others.
WINLAB
The cooperating ISPs may not be willing to send content to the peers in non-cooperating ISPs
Counter-Intuitive Outcomes:Better benefits for the non-cooperating ISPs
Average Rate [R]
ISP A ISP B ISP C
No Cooperation 0.6 0.6 0.6
All Cooperating 0.75 0.75 0.75
ISP C not coperating (Enough Peers) 0.75 0.75 1
ISP C not cooperating (Not enough peers)
0.75 0.75 0.5
• Cooperating ISP : Downloads content with probability ½ and rate R within the network with probability ¼ from any other network at rate ½ R • Non cooperating ISP: Downloads content with probability 1/3 from any network
No Cooperation
All Cooperating
ISP C not cooperating (Enough Peers)ISP C not cooperating (Not enough peers)
WINLAB
What do the P2P-ISP cooperation frameworks have in common? Can we investigate the risks in unified framework?
The common entity in all approaches is an oracle which gives hints to the P2P provider. The main difference is whether ISP gets individual and indirect involvement (Approach A) No involvement (Approach B) Direct Involvement (Approach C)
in oracle P2P does the peering assignments based on the hints from the
oracles ISP downloads content more from some ISPs than the others as
a result of these peering assignments.
WINLAB
Overview of our framework:
Consider ISP j request a traffic volume V, each ISP i supplies of it.
We model the hints given by the oracle to the P2P provider by a metric called .
We model the manipulations by the P2P provider by a metric . P2P provider determines which ISP provides what fraction of V
to the ISP j based on and
βα
α β
Vijθ
WINLAB
Modeling hints from oracles
: Willingness of ISP i to send content to ISP j : Willingness of ISP i to receiver content from ISP j : Joint preference of ISP i to send content to ISP j
(Compromise by oracle)
ISP i ISP j5.0=ijβ
1=sijβ 0=r
ijβsijβrijβ
ijβ
WINLAB
P2P has the freedom to ignore or enforce preferences of some ISPs (captured by metric ) more than others.
The metric assigned by the P2P provider to manipulate the traffic flow from ISP i to ISP j.
Modeling manipulations of P2P providers
ijβ
ijα
WINLAB
Traffic Allocation by the P2P provider for ISP j
Let be the fraction of the traffic demand V of ISP j supplied by ISP i
P2P provider does the traffic allocation by solving:
Solution mathematically equivalent to the water filling
ijθ
WINLAB
Manipulations by the P2P provider
ISP 9 is less preferred P2P provider manipulates traffic
from ISP 7 and ISP 8 to ISP 9 We set
equal to We vary between 0 and 2.
98899779 ,,, αααα
)(1 jiij ≠=β2=iiβ
αα
WINLAB
Net Income versus α• As P2P provider observes the preference of ISP 7 and ISP 8 to send much more content to ISP 9, ISP 9 is enforced to download from ISP 8 and ISP 9.
The P2P provider puts more weight to the preferences of ISP 7 and ISP 8
As the P2P observes the preferences of ISP 7 and ISP 8 more the cost for
ISP 9 increases
WINLAB
When ISP joins the cooperation the ISP lets the P2P provider know the minimum fairness levels to continue the cooperation.
Rate Fairness and Cost Fairness: P2P can raise the fairness level for that ISP by reallocating
some of the traffic at a higher rate or lower cost. If the P2P provider reallocates using the strategy
that results in average rate then fairness level will be raised to . .The P2P provider determines from:
Risk mitigation by enforcing fairness
WINLAB
Rate fairness
As the P2P observes the preferences of ISP 7 and ISP 8 to send and receive more content from ISP 9 the rate
fairness decreases for ISP-9
WINLAB
Guideline Principles for P2P-ISP Cooperation
Avoid ISP owned oracles for inter-ISP peering decisions Enforce fairness between ISPs and P2P providers by auditing
by third parties or punishment strategies Observe the hints from the oracles partially, make some
portions of the peering assignments based randomly or some other inferred metric like delay.
WINLAB
Concluding Remarks
We focus this work on the risks of cooperation, especially when multiple ISPs co-exist and form their own peering relationships.
We built a mathematical model for the three recent approaches of cooperation, classifying the potential risks and metrics, and construct numerical examples and analytical results on some of the major unintended or counter-intuitive behaviors.
We believe that P2P-ISP cooperation is generally helpful to all parties involved, and can have significantly good practical impact after their risks are discovered and bounded.
Quantifying of the guideline principles is an interesting next step in fully understanding the best P2P-ISP collaboration mechanism
