http://www.rfc-editor.org/rfc/rfc5393.txt
RFC 5393: Addressing an Amplification Vulnerability in Session Initiation Protocol (SIP) Forking Proxies, R. Sparks, S. Lawrence, A. Hawrylyshen, B. Campen2008-12-01T23:00:00-00:00This document strengthens loop-detection requirements on SIP proxies when they fork requests (that is, forward a request to more than one destination). It also corrects and clarifies the description of the loop-detection algorithm such proxies are required to implement. Additionally, this document defines a Max-Breadth mechanism for limiting the number of concurrent branches pursued for any given request. [STANDARDS-TRACK]