The document discusses SIP conferencing capabilities provided by SylkServer, an open source SIP application server. It describes how SylkServer supports features like HD audio conferencing, multiparty chat using MSRP, sharing files and screens, and providing information on conference participants. The document outlines SylkServer's evolution over time to add these features and its use of standards like MSRP and RFC4575 to enable advanced conferencing functionality.

1. Saúl Ibarra Corretgé

2. AG Projects SIP Conferencing Reloaded
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AG Projects
● SIP infrastructure for providers
● SIPThor: horizontal scalability without user limit
● Software projects:
● Blink
● SIPSIMPLE SDK
● SylkServer
● MediaProxy
● OpenXCAP
● MSRPRelay

3. AG Projects SIP Conferencing Reloaded
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Current state
of the art

4. AG Projects SIP Conferencing Reloaded
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5. AG Projects SIP Conferencing Reloaded
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Conferencing today
● Usually mere RTP mixers
● Conference calls need a context
● Lack of multiplexed information
● Different media types
● Session information
● Participants information
● Shared resources
● There is sometimes a nice website with information

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SylkServer

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SylkServer
● Open Source SIP application server
● Conferencing
● HD audio
● Chat
● File transfer
● Screen sharing
http://sylkserver.com

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SIP Chatserver
● Chat server using
MSRP
● Ad-hoc rooms
● Join using SIP
2009 2010 2011 2012

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● SIP chatserver no
longer worked with
our latest APIs
● Needed a rewrite
2009 2010 2011 2012

10. AG Projects SIP Conferencing Reloaded
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Less than a
week later...

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SIP Chatserver Reloaded
● HD audio
● Multiparty chat
● Conference event
package
2009 2010 2011 2012

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SylkServer 1.0.0
● HD audio conferencing
● Multiparty chat
● Participants information
2009 2010 2011 2012

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Blink 0.24.0 + SylkServer 1.1.0
● HD audio
conferencing
● Multiparty chat
● Participants
information
● Add / remove
participants
2009 2010 2011 2012

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Blink Pro 1.1.0 + SylkServer 1.2.0
● HD audio
conferencing
● Multiparty chat
● Participants
information
● Add / remove
participants
● File transfers (push
and pull)
2009 2010 2011 2012

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Blink Pro 1.6.0 + SylkServer 1.3.0
● HD audio
conferencing
● Multiparty chat
● Participants
information
● Add / remove
participants
● File transfers (push
and pull)
● Screensharing
2009 2010 2011 2012

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How does it
actually work?

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MSRP
● Message Session Relay Protocol
● Real IM (session based) for SIP
● RFC 3428 (SIP MESSAGE) is not real IM
● Very simple, just a couple of RFCs (4975 and 4976)
● TLS is mandatory

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MSRP
● MSRP allows us to negotiate a TCP connection
between 2 SIP endpoints
● Instant Messaging
● File transfer (RFC 5547)
● Screen sharing
– VNC over MSRP (expired draft)
– Stream images

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MSRP
v=0
o=- 3519532764 3519532764 IN IP4 192.168.1.43
s=Blink Pro 1.1.2 (MacOSX)
c=IN IP4 192.168.1.43
t=0 0
m=message 2855 TCP/TLS/MSRP *
a=path:msrps://192.168.1.43:2855/fd5a5fbfe517e6c2ed76;tcp
a=accept-types:message/cpim text/* application/im-iscomposing+xml
a=accept-wrapped-types:*
a=setup:active

20. AG Projects SIP Conferencing Reloaded
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MSRP
v=0
o=- 3519533090 3519533090 IN IP4 192.168.1.43
s=Blink Pro 1.1.2 (MacOSX)
c=IN IP4 192.168.1.43
t=0 0
m=message 2855 TCP/TLS/MSRP *
a=path:msrps://192.168.1.43:2855/15be969db481aaa26f35;tcp
a=sendonly
a=accept-types:*
a=accept-wrapped-types:*
a=setup:active
a=file-selector:name:"clever_algorithms.pdf" type:application/pdf size:3133774
hash:sha1:87:F7:A7:5A:F5:48:0F:8A:DD:3F:D8:49:F0:86:51:93:A2:9B:89:19

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A SIP conference server

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Contact: <sip:test@81.23.228.139:5060>;isfocus

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Conference event package
SUBSCRIBE sip:test@conference.sip2sip.info SIP/2.0
Via: SIP/2.0/UDP 192.168.1.43:60530;rport;branch=z9hG4bKPjEgakb...
Max-Forwards: 70
From: "Saúl" <sip:31208005163@ag-projects.com>;tag=I3OcER0qmkv...
To: <sip:test@conference.sip2sip.info>
Contact: <sip:cmugnheo@192.168.1.43:60530>
Call-ID: cv8.LQxG4qjcDZSxOZKoOhQr0OF7lz-Z
CSeq: 26852 SUBSCRIBE
Event: conference
Expires: 3600
Accept: application/conference-info+xml
Allow-Events: conference, message-summary, presence, presence.winfo, xcap-diff, refer
User-Agent: Blink Pro 1.1.2 (MacOSX)
Content-Length: 0

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RFC4575 payload
<conference-description>
<display-text>Ad-hoc conference</display-text>
<free-text>Hosted by SylkServer-1.2.1</free-text>
</conference-description>
<host-info>
<web-page>http://sylkserver.com</web-page>
</host-info>
<conference-state>
<user-count>1</user-count>
<active>true</active>
</conference-state>

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RFC4575 payload
<users state="full">
<user entity="sip:31208005163@ag-projects.com" state="full">
<display-text>Saúl</display-text>
<endpoint entity="sip:cmugnheo@83.43.224.233:60530" state="full">
<display-text>Saúl</display-text>
<status>connected</status>
<joining-info><when>2011-07-13T23:39:07+02:00</when></joining-info>
<media id="152141036"><type>message</type></media>
</endpoint>
</user>
</users>

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RFC4575 payload
<agp-conf:resources>
<agp-conf:files>
<agp-conf:file name="fry.png"
hash="sha1:E1:FA:5C:C2:0A:95:DC:3C:C0:7E:AD:F6:25:50:BB:62:D9:F5:B8:3B"
size="177533" sender="Saul <sip:31208005163@ag-projects.com>" status="OK"/>
</agp-conf:files>
</agp-conf:resources>

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Adding / removing participants
REFER sip:agp@conference.sip2sip.info SIP/2.0
Via: SIP/2.0/UDP 192.168.99.36:65017;rport;branch=z9hG4bKPjjao...
Max-Forwards: 70
From: "Saúl" <sip:31208005163@ag-projects.com>;tag=7HXkWbL...
To: <sip:agp@conference.sip2sip.info>
Contact: <sip:yoreqcfd@192.168.99.36:65017>
Call-ID: oiXv9JpNLp9f8GbRLDYw6dVrEnhU7On0
CSeq: 15438 REFER
Event: refer
Accept: message/sipfrag;version=2.0
Allow-Events: conference, message-summary, presence, presence.winfo, xcap-diff, refer
Refer-To: <saghul@sip2sip.info>;method=INVITE
Referred-By: sip:31208005163@ag-projects.com
User-Agent: Blink Pro 1.3.0 (MacOSX)
Content-Length: 0

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What about
Asterisk?

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Basic conference info with Asterisk (idea)

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BYE

31. 1. Everything should be a
building block

32. 2. Our customers need help

33. 3. Use Open Standards

34. 4. “Let's build it before
we're too old to enjoy it”
Carl G. Fisher

35. 5. “Skate to where the
puck is going to be, not
where it has been”
Wayne Gretzky

36. AG Projects SIP Conferencing Reloaded
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37. AG Projects SIP Conferencing Reloaded
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BYE sip:audience@itexpo SIP/2.0
Via: SIP/2.0/UDP 192.168.99.23:49919;rport;branch=z9hG4bKPjDb30Dx0sH-ozn9QB.cCCboyU.atR97aM
Max-Forwards: 70
From: "saghul" <sip:saul@ag-projects.com>;tag=UCpGKVZbQQx7BUKYtiuPEX668oa9jaU7
To: <sip:audience@itexpo>;tag=as59aef35c
Call-ID: DEWDfu63OACwYeQk7MrhmRhRq.1cqqis
CSeq: 10633 BYE
Route: <sip:81.23.228.129;lr;ftag=UCpGKVZbQQx7BUKYtiuPEX668oa9jaU7;did=641.a8a9c553>
User-Agent: blink-0.20.2
Content-Length: 0
@saghul
saul@ag-projects.com
sip:saul@ag-projects.com

38. AG Projects SIP Conferencing Reloaded
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References
● MSRP protocol (RFC4575, RFC4576)
● MSRP file transfer (RFC5547)
● MSRP switch (draft-ietf-simple-chat)
● Conference event package (RFC4575)
● A framework for conferencing with SIP (RFC4353)
● Conferencing for User Agents (RFC4579)