The FreeSWITCH team is excited to announce that FreeSWITCH is the first telephony application to support the new SIP 4.1 protocol specification.
Unlike its predecessors, SIP 4.1 has been created with the collaboration of both the jabber foundation and the IETF. With this match made in heaven, one can now encapsulate an xml representation of a sip message, which in turn can encapsulate a standard SIP 2.0 message making it possible to do more than ever before.
Other exciting features include:*) RFC 4109 support: (SIP over SMTP), allowing packets to traverse NAT with ease.
*) Full circle presence: endpoints must subscribe to each character in the printable ASCII range that may be used to indicate presence and the server will send an xml notification to the client for each character that is enabled whenever a call takes place which in turn can be used to build a SIP 4.1 FYI packet that can be sent to all the neighboring SIP devices so they may send themselves a NOTIFY telling them that the light should blink if the same packet happens to be sent from a neighbor. Then when the neighbor wants to send a presence packet it establishes a dialog with the Third Party Presence Agent TPPA and leaves the message there. Then it sends the server a PRESENCE packet, which is then, relayed to the subscribers with the TPPA id so all the subscribers can connect to the TPPA server to make the little light blink.
*) Retirement of SDP: SDP is deprecated in favor of a list of URL’s describing the desired codec. The UA can then request this URL and get the full details of the media requirements. The media port is negotiated through trial and error where the calling UA asks the called UA if the port it has guessed randomly is correct via direct TCP connection and an exchange of XML PORT MARKUP LANGUGE XPML
INVITE bob@alice.com SIP 4.1
Content-type: sip-xml-encapsulated
<SIP version=”4.1”>
<content type=”SIP-INVITE”>
<INVITE recipient=”bob@alice.com”>
<data type=”sip-2/0”/>
<![CDATA[INVITE bob@alice.com SIP 2.0
To: bob@alice.com
From: alice@bob.com
Subject: SIP Rocks
]]>
</data>
</INVITE>
</content>
</SIP>
--
Anthony Minessale II
FreeSWITCH http://www.freeswitch.org/
ClueCon http://www.cluecon.com/
AIM: anthm
MSN:anthony_minessale@hotmail.com
GTALK/JABBER/PAYPAL:anthony.minessale@gmail.com
IRC: irc.freenode.net #freeswitch
FreeSWITCH Developer Conference
sip:888@conference.freeswitch.org
iax:guest@conference.freeswitch.org/888
googletalk:conf+888@conference.freeswitch.org
pstn:213-799-1400
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