Analysis of Middlebox Interactions for Signaling Protocol Communication along the Media Path

Document Type Expired Internet-Draft (mmusic WG)
Authors Brian Stucker  , Hannes Tschofenig  , Gonzalo Salgueiro 
Last updated 2013-12-01 (latest revision 2013-05-30)
Replaces draft-sipping-stucker-media-path-middleboxes
Stream Internet Engineering Task Force (IETF)
Expired & archived
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Stream WG state Dead WG Document
Document shepherd Ari Keränen
IESG IESG state Expired
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


Middleboxes are defined as any intermediary box performing functions apart from normal, standard functions of an IP router on the data path between a source host and destination host. Two such functions are network address translation and firewalling. When Application Layer Gateways, such as SIP entities, interact with NATs and firewalls, as described in the MIDCOM architecture, then problems may occur in the transport of media traffic when signaling protocol interaction takes place along the media path, as it is the case for recent key exchange proposals (such as DTLS-SRTP). This document highlights problems that may arise. Unfortunately, it is difficult for the end points to detect or predict problematic behavior and to determine whether the media path is reliably available for packet exchange. This document aims to summarize the various sources and effects of NAT and firewall control, the reasons that they exist, and possible means of improving their behavior to allow protocols that rely upon signaling along the media path to operate effectively.


Brian Stucker (
Hannes Tschofenig (
Gonzalo Salgueiro (

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