[rfc-dist] RFC 5393 on Addressing an Amplification Vulnerability in Session Initiation Protocol (SIP) Forking Proxies

rfc-editor@rfc-editor.org rfc-editor at rfc-editor.org
Fri Dec 12 13:27:45 PST 2008

A new Request for Comments is now available in online RFC libraries.

        RFC 5393

        Title:      Addressing an Amplification Vulnerability in 
                    Session Initiation Protocol (SIP) Forking Proxies 
        Author:     R. Sparks, Ed., S. Lawrence, 
                    A. Hawrylyshen, B. Campen
        Status:     Standards Track
        Date:       December 2008 
        Mailbox:    RjS at nostrum.com, 
                    scott.lawrence at nortel.com, 
                    alan.ietf at polyphase.ca,
                    bcampen at estacado.net
        Pages:      20
        Characters: 48722
        Updates:    RFC3261

        I-D Tag:    draft-ietf-sip-fork-loop-fix-08.txt

        URL:        http://www.rfc-editor.org/rfc/rfc5393.txt

This document normatively updates RFC 3261, the Session Initiation
Protocol (SIP), to address a security vulnerability identified in SIP
proxy behavior.  This vulnerability enables an attack against SIP
networks where a small number of legitimate, even authorized, SIP
requests can stimulate massive amounts of proxy-to-proxy traffic.

This 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

This document is a product of the Session Initiation Protocol Working Group of the IETF.

This is now a Proposed Standard Protocol.

STANDARDS TRACK: This document specifies an Internet standards track
protocol for the Internet community,and requests discussion and suggestions
for improvements.  Please refer to the current edition of the Internet
Official Protocol Standards (STD 1) for the standardization state and
status of this protocol.  Distribution of this memo is unlimited.

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