Problems with Max-Forwards Processing (and Potential Solutions)

Document Type Expired Internet-Draft (individual)
Author Scott Lawrence 
Last updated 2005-10-18
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


This document describes an attack against SIP networks where a small number of legitimate, even authorized, SIP requests can stimulate massive amounts of proxy-to-proxy traffic. The document analysis ways to limit the impact of this kind of attack, and proposes changes to the SIP protocol to help mitigate the risk. The document also proposes ways to improve diagnosis of failures caused by the hop limit being reached. The purpose of this document is to stimulate discussion of the identified problem and proposed solutions. Much of the proposed solution language appears normative, but implementors should not treat the current document as such. Comments are solicited, and should be directed to the SIPPING working group list at ''.


Scott Lawrence (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)