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Published byJunior Sims Modified over 9 years ago
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Fairness Attacks in the eXplicit Control Protocol Christo Wilson Christopher Coakley Ben Y. Zhao University of California Santa Barbara
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Motivation Heavy research in recent years into explicit feedback protocols Demonstrate desirable qualities ◦Fairness between flows ◦High utilization ◦Few drops ◦No slow start Not security aware “Honesty is for the most part less profitable than dishonesty” -- Plato, The Republic Our work: quantifying the impact of attackers through detailed experiments
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Table of Contents Background and Attack Model Experimental Setup Sender-side Attacker ◦Congestion controlled ◦Fully Unresponsive Receiver-side Attacker Proposed Defenses Conclusion
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Background – Explicit Feedback Bottleneck Explicit Feedback Enabled Internet Feedback = -42 Throughput = -42 Throughput = 1000
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Attack Model Feedback mechanism abuse enables attacks: ◦Selective compliance with feedback ◦Falsified feedback Two attack types: ◦Sender-side ignores feedback ◦Receiver-side falsifies header information Attacker goals: ◦Control as much bandwidth as possible ◦Denial of Service (DoS) remote hosts
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Experimental Setup Attacker models implemented using XCP Tests performed in ns2 ◦10ms latency ◦1KB packets ◦Drop-tail queues ◦20 Mbit bottleneck link ◦
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Sender-side Attacker Explicit Feedback Enabled Internet Feedback = -42 Throughput = 1000 Throughput = -42
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Sender-side Attacker Two types of attackers implemented: ◦Congestion controlled TCP like behavior Continuous additive c_wnd growth Multiplicative c_wnd back off after packet drop ◦Fully unresponsive Only probes for bandwidth once (1 packet drop) Locks c_wnd at 50% of current size Trumps congestion controlled attackers Resumes probing in response to: ◦ positive feedback ◦ 25% reduction in RTT
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Sender-side Attacker (Congestion Controlled) 9 Sender-Side Attackers w/ 1 Normal Flow Normal FlowUtilization
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Sender-side Attacker Two types of attackers implemented: ◦Congestion controlled TCP like behavior Continuous additive c_wnd growth Multiplicative c_wnd back off after packet drop ◦Fully unresponsive Only probes for bandwidth once (1 packet drop) Locks c_wnd at 50% of current size Trumps congestion controlled attackers Resumes probing in response to: ◦ positive feedback ◦ 25% reduction in RTT
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Sender-side Attacker (Fully Unresponsive) 1 Sender-Side Attacker w/ 49 Normal Flows A +10 B +35 Total Flows = 5Total Flows = 15Total Flows = 50
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Sender-side Attacker (Fully Unresponsive) 4 Sender-Side Attackers w/ 1 Normal Flow A +1 B +1 C +1 D Normal Flow
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Receiver-side Attacker Explicit Feedback Enabled Internet Feedback = 9999 Throughput = 1000 Throughput = -42
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Receiver-side Attacker 1 Receiver-Side Attacker w/ 49 Normal Flows
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Proposed Defenses: Edge Monitors Edge monitors ◦Must be ubiquitous ◦Requires per flow monitoring/state Sender-side attacks detected by monitoring actual versus expected throughput Receiver-side attacks are trivially detected Issues: ◦Ubiquity of monitors can not be guaranteed ◦Unfeasible router overhead ◦Network edge does not exist
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Proposed Defenses: Attack Severity Sender-side attacks are tractable problem ◦Elephant flow monitors exist ◦Detectable anywhere in network path ◦Motivation for attack is lacking ◦Can not be used to DoS Receiver-side attacks represent difficult challenge ◦Can target/break well behaved hosts ◦DoS potential ◦Motivation for attack is much stronger
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Proposed Defenses: Nonce Feedback Injection Explicit Feedback Enabled Internet Feedback = -H4X0R3D Throughput = -H4X0R3D
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Proposed Defenses: Nonce Feedback Injection Explicit Feedback Enabled Internet Feedback = 9999 Throughput = -H4X0R3D
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Conclusion Existing explicit feedback protocols are vulnerable to exploitation ◦Sender-side attacks ◦Receiver-side attacks Attacks are highly effective Applies to existing explicit feedback protocols ◦XCP, RCP, MaxNet, JetMax, etc Proposed solutions are inadequate ◦Potential solution: nonce feedback injection
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