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draft-sparks-sipping-max-breadth-00 Robert Sparks Estacado Systems

Max-Breadth Limiting Amplification Attack Damage Controlling the Impact of a Request on the Network. draft-sparks-sipping-max-breadth-00 Robert Sparks Estacado Systems. Max-Breadth. Discussed in depth at SIPit 17.

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draft-sparks-sipping-max-breadth-00 Robert Sparks Estacado Systems

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  1. Max-BreadthLimiting Amplification Attack DamageControlling the Impact of a Request on the Network draft-sparks-sipping-max-breadth-00 Robert Sparks Estacado Systems

  2. Max-Breadth • Discussed in depth at SIPit 17. • Concept explored in maxforward-problems by apportioning remaining Max-Forwards values among branches • Feedback: would break existing deployments • New proposal: A separate, complementary mechanism to Max-Forwards

  3. Max-Breadth Mechanism • New Max-Breadth header carries # of concurrent branches that can be added downstream from recipient. • Value apportioned among branches • As branches finish, their value can be reclaimed and applied to new branches • Small values push forking towards serial (1==serial) where that makes sense • For applications where restricting the branching this way doesn’t make sense, an element would return a new 4xx Max-Breadth exceeded response

  4. Impact of Mechanism • Requests generally traverse the same graph, but only a bounded number of edges are active (each edge is a SIP transaction) at any given time. • In existing and currently anticipated deployments, mechanism would not perturb processing at all unless something was going wrong.

  5. Why is this important? • The loop-detection fix to the known amplification attack helps, but isn’t perfect. • With loop-detection, attack reduces to O(2^M) where M is the number of AORs involved. Minor changes render O(2^MlogM) amplification • Depletion of Max-Breadth can be monitored, providing early warning and better diagnostics for emerging problems.

  6. Going Forward • List discussion • Before SIPit is better • Analyze the mechanism • Can we identify a concrete application where this approach causes harm? If not, this should be passed to SIP soon.

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