Project Manager: Susan S. Bradley Content Architect

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Contributors

Project Manager: Susan S. Bradley

Content Architect: Rui Maximo

Chapter Lead: Geoff Clark

Writers: Geoff Clark, Paul Adams

Technical Reviewers: Jamie Stark, Mahendra Sekaran

Lead Editor: Kate Gleeson

Art Manager: Jim Bradley

Production Editor: Kelly Fuller Blue

Table of Contents

Contributors 4

Introduction 7

Scenarios 7

Asterisk Integration with Lync Server 2010 7

Basic Call Flow 9

Asterisk with Skype 10

Skype for SIP 11

Skype for Asterisk 11

Asterisk with Google Talk 13

Asterisk Direct SIP Internals 14

Installation of Asterisk 20

Configuration 22

Configure Asterisk 22

Configure sip.conf 22

Configure extensions.conf 24

Configuring the X-Lite Client 30

Troubleshooting Asterisk 31

Configure Asterisk for Skype 32

Skype for SIP 32

Skype for Asterisk 37

Testing Calls from Skype for Asterisk to Lync Server 39

Testing calls from Lync Server to Skype for Asterisk 39

Configure Asterisk for Google Talk 39

jabber.conf 41

gtalk.conf 42

extensions.conf 42

sip.conf 43

Sample Jabber Interactive Voice Response (IVR) 44

Extension Dial Plan Configuration 44

[from-gtalk] 46

Outbound Calls 48

Summary 49

Additional Resources 49

Introduction

This chapter introduces how to integrate Lync Server 2010 with Asterisk. 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.

If you need to integrate Lync Server with PBXs that are not certified for direct Session Initiation Protocol (SIP) with Lync Server 2010 or integrate with other third-party telephony systems (for example, Skype and Google Talk), 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.

Asterisk supports the following protocols: H.323, Skinny Call Control Protocol (SCCP), Media Gateway Control Protocol (MGCP), Google Talk, Skype, SIP, and traditional time division multiplexing (TDM) interfaces.

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.

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.

By integrating Asterisk directly with Lync Server (that is, by using direct SIP), it is possible to interoperate Lync Server with other proprietary telephony systems such as Skype and Google Talk. This chapter covers how you configure direct SIP with Skype and Google Talk.

Scenarios

Bob and Alice both work for Contoso, Ltd. in the Messaging and Voice team. They are tasked with testing all of the Enterprise Voice features in Lync Server. The organization has an existing voice infrastructure based on a PBX system. However, they are not permitted to make any changes to the existing PBX system.

The Messaging and Voice team decides to use Asterisk to integrate all Enterprise Voice features (for example, dial-in conferencing, response groups, inbound and outbound calling, and call park) in Lync Server with their PBX system.

The team also decided that they want to integrate Skype and Google Talk with Asterisk. Bob knows that Asterisk has developed a Skype and Jabber Channel driver and wants to offer these alternate solutions for connecting Lync client and Office Communicator endpoints to these VoIP networks.

In this chapter, Bob and Alice use Asterisk to integrate with Lync Server 2010. They also setup connectivity to Skype and Google Talk using Asterisk. Call flows are outlined for these configurations. This chapter includes detailed configuration steps for deploying these features and integrating with Lync Server 2010.