Subject: [MMUSIC] new draft on media routing with ALGs

From: "Ejzak, Richard P \(Richard\)" <[email-masked]>
Date: Mon, 26 Jan 2009 16:51:02 -0600

Hello,
Please comment on the following draft, which was submitted to improve
media routing when interconnecting SIP networks using ALGs.  Work on
this draft was triggered by a 3GPP Release 9 work item on "optimal media
routing", which is documented in 3GPP TR 23.894.
 
http://www.ietf.org/internet-drafts/draft-ejzak-mmusic-bg-bypass-00.txt
 
This is the abstract from the draft:
 
"This document describes an extension to the Session Description
Protocol (SDP) that can be used by systems of cooperating networks using
Application Level Gateways (ALG) to insert border gateways performing as
Network Address Port Translators (NAPT) between their IP realms to
identify when border gateways can be bypassed for more efficient media
flow.  This extension can be used by networks based on a protocol using
the SDP offer/answer model, such as the IP Multimedia Subsystem (IMS) of
the Third Generation Partnership Project (3GPP), which is based on the
Session Initiation Protocol (SIP).  ALGs using this extension can
determine within a single SDP offer/answer transaction when the
insertion of a new border gateway would cause the media path to re-enter
an IP realm visited elsewhere within the media path, and to bypass one
or more border gateways that would otherwise be included in the media
path.  This extension also works with hosted NAPT traversal schemes to
establish a direct media path between endpoints within the same IP
realm.  Optional procedures provide additional means to improve media
flow."
 
BR, Richard Ejzak
Alcatel-Lucent
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