How asterisks open up new possibilities for lync PSTN connectivity

Favad Qaisar 22 March 2012 2

Asterisk is an open source Voice over IP (VoIP) server that can serve as a gateway for Lync Server. However, Asterisk is not a supported Lync Server gateway. It is a great private branch exchange (PBX) for testing voice connectivity and features with Lync Server. Asterisk comes with high-end features like interactive voice response (IVR), voice mail, or automatic call distribution (ACD). It is highly programmable and able to handle VoIP calls over multiple protocols.
Asterisks allow you to integrate Lync Server with PBXs that are not certified for direct Session Initiation Protocol (SIP) with Lync Server 2010 or it helps you integrate Lync with other third-party telephony systems for example, Skype and Google Talk.
Skype uses a proprietary protocol based on a peer-to-peer architecture. Asterisk developed a channel driver for the Skype network that enables Asterisk to interface with the closed Skype network. Skype also released Skype SIP, which enables IP-PBXs that support SIP to interface with the Skype network. On the other hand Google Talk uses the Jabber protocol. This does not lend itself to integrate with most VoIP platforms because most other platforms do not offer Extensible Messaging and Presence Protocol (XMPP) along with SIP as communication platform. Although the Lync Server 2010 XMPP gateway server provides instant messaging (IM) and presence interoperability with Lync Server, it does not provide direct SIP integration for voice (that is, telephony). For voice integration with Google Talk, Asterisk provides a Google Talk channel driver that uses the Jabber protocol to communicate with Google and other Jabber-based servers.
As it is clear by now that Asterisk can interoperate with Skype, it can serve as the gateway interconnecting Lync Server to Skype. The following configuration options are available to connect Asterisk to Skype:
Skype for SIP This solution is provided by Skype and enables SIP clients to directly register to a SIP server on the Skype network.
Skype for Asterisk This solution is provided by Digium, the company that created Asterisk, and enables the Asterisk server to connect directly to the Skype network.
By using these services, the Asterisk server (that is, as the SIP server) can receive incoming calls from any Skype user. Skype users can call your company by using one or more of your Skype business account’s names. One can also receive calls from any public switched telephone network (PSTN) user if they have purchased a Skype “online number” from Skype Manager. The ability to accept PSTN calls through Skype are included in your monthly “online number” charge.
To configure Google Talk you need to configure two additional files, gtalk.conf and jabber.conf, which located in the folder /etc/asterisk. After that the first thing that needs to be done is to create a Google Talk account to finish the jabber and gtalk configuration files. After completing the configuration, restart Asterisk, the Google Talk account should automatically register with the Google Talk network. This shall complete the Asterisk registration process with Google talk.
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Favad Qaisar (51 Posts)

I am a Unified Communications Engineer. Over the last 3 years, I have been working dedicatedly on OCS/LYNC and Exchange 2007/2010. I was responsible for getting my Company Microsoft’s Unified Communication Voice Certified Partner status. Occasionally, I like to share my experiences on the latest developments in the Unified Communications industry.


  1. Tell1000 9 October 2012 at 4:36 am - Reply

    Can Asterisk integrate with Lync’s API to upate a user’s pressence information if they are on a call?

  2. Favad Q 9 October 2012 at 7:29 pm - Reply


    It should practically be able to, Lync API can do all this stuff, a Dot Net developer should be able to guide you better though.


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