Microsoft Lync Server
Microsoft Lync Server (previously Microsoft Office Communications Server) is an enterprise real-time communications server software, providing the infrastructure for enterprise instant messaging, presence, VoIP, ad hoc and structured conferences (audio, video and web conferencing) and PSTN connectivity through a third-party gateway or SIP trunk. These features are available within an organization, between organizations and with external users on the public internet or standard phones (on the PSTN as well as SIP trunking).
One basic use of Lync Server is instant messaging (IM) and presence within a single organization. This includes support for rich presence information, file transfer and voice and video communication. Lync uses Interactive Connectivity Establishment for NAT traversal and TLS encryption to enable secure voice and video both inside and outside the corporate network.
Lync Server also supports remote users, both corporate users on the Internet (e.g. mobile or home workers) as well as users in partner companies. Lync supports identity federation, enabling interoperability with other corporate IM networks. Federation can be configured either manually (where each partner manually configures the relevant edge servers in the other organization) or automatically (using the appropriate SRV records in the DNS).
Microsoft Lync Server uses Session Initiation Protocol (SIP) for signaling along with the SIMPLE extensions to SIP for IM and presence. Media is transferred using RTP and SRTP. The live meeting client uses Persistent Shared Object Model (PSOM) to download meeting content. The communicator client also uses HTTPS to connect with the web components server to download address books and expand distribution lists. By default, Supported combinations includes encrypted communications using SIP over TLS and SRTP as well unencrypted SIP over TCP and RTP. Microsoft has published details of supported configuration for qualified vendors through Unified Communications Open Interoperability Program (UCOIP).
IM is only one portion of the Lync suite. The other major components are VoIP telephony and video conferencing through the desktop communicator client. Remote access is possible using the desktop, mobile and web clients.
When Microsoft Office Live Communications Server was originally launched on 29 December 2003, it replaced the Exchange Instant Messenger Service that had been included in Exchange 2000, but which was removed from the Exchange 2003 feature set. Holders of Exchange 2000 licenses which include Software Assurance are entitled to receive Live Communications Server as an upgrade, along with Exchange 2003; however, Live Communications Server Client Access Licenses must be purchased as normal for new users.
OCS R2 was announced at VoiceCon in Amsterdam in October 2008, just 364 days after releasing Office Communications Server 2007. This version has major advantages over the original solution and positioned Microsoft firmly in place to be a major player in IP telephony and video (telepresence).
New call management capabilities let receptionists and team assistants take a large volume of incoming calls and quickly route them to the intended recipients with a simple click, while delegation features allow executives to completely hand over the management of their phone calls to their assistants. New desktop-sharing capabilities allow users on Windows, Macintosh, and Linux platforms to collaborate with one another at the same time they talk to each other using enhanced audio conferencing features. The Group Chat feature lets organizations set up searchable, topic-based chat rooms that persist over time, allowing geographically distributed teams to better collaborate with one another while preserving organizational knowledge.
Interestingly, all of these features are covered under a single license per user through the Enterprise Client Access License (ECAL) from Microsoft. This is dramatically different than traditional telephony and VoIP vendors who charge for additional clients, endpoints, and interfaces into the communications system.
The improved on-premises audioconferencing capability puts enterprises in control of their audioconferencing infrastructure while saving money on audioconferencing costs over hosted bridges. The Single Number Reach feature allows IT to log business calls placed by users from cellular phones for accounting purposes while helping to ensure that the same dialing rules that apply to calls made by users from their work phone also extend to their cellular calls. The new video monitoring capabilities allow IT to surveil video calls and conferences on their network, while support for SIP-trunking does away with the need to manage expensive on-premises gateways. Video in OCS is also interoperable with third party solutions such as Tandberg and PolyCom systems as well (Polycom has not yet provided its connector with new Microsoft Lync 2010). This means that customers can keep their existing investment in these systems, but extend video to the desktop via Office Communications Server.
One of the biggest advantages of having a software-based communications infrastructure is that businesses can embed communications capabilities into existing line-of-business applications and use communications and workflow capabilities to automate business processes, which saves money, saves time, and improves customer service. Office Communications Server 2007 R2 delivers an extensible communications platform that works with an organization’s existing messaging and telephony infrastructure and can adapt to changing business needs. This extensibility is one of the major reasons that Gartner has placed Microsoft at the top of their Unified Communications Magic Quadrant for 2007, 2008 and 2009.
- Dial-in audioconferencing
- Desktop sharing
- Persistent Group Chat
- Attendant console and delegation
- Session Initiation Protocol trunking
- Mobility and single-number reach
Microsoft Lync Server 2010 reached general availability in November 2010. Microsoft Lync 2013 is released to manufacturing in October 2012. The general availability date is still to be announced.
- 2012 - Lync Server 2013 (RTM October 11th, 2012)
- 2010 - Lync Server 2010
- 2009 - Office Communications Server 2007 R2
- 2007 - Office Communications Server 2007
- 2006 - Live Communications Server 2005 with SP1
- 2005 - Live Communications Server 2005, codenamed Vienna
- 2003 - Live Communications Server 2003
Client software and devices 
Microsoft Lync is the primary client application released with Lync Server. This client is used for IM, presence, voice and video calls, desktop sharing, file transfer and ad hoc conferences. With Lync 2013 there will be a release of Lync Light Client with less features. Microsoft also ships the Microsoft Attendant Console. This is a version of the Lync more oriented towards receptionists or delegates / secretaries or others who get a large volume of inbound calls.
Other client software and devices include:
- Lync Mobile is a Mobile edition of the Lync Server 2010 client and designed to offer similar functionality including voice calls via the GSM Network , instant messaging, presence and single number reachability. Clients for Lync Mobile includes the IPhone, Ipad, Android, Windows Phone 7 and 8.
New releases of Lync Mobile 2013 (Wave 2) are anticipated - bringing along features such as collaboration as well as Voice and Video over IP
- Microsoft RoundTable is an audio and video conferencing device that provides a 360-degree view of the conference room and tracks the various speakers. This device is now produced and sold via Polycom under the product name CX5000.
There are in the documentation of Lync 2013 references to Lync Room Edition Devices - that are anticipated to provide close to Immersive Experience.
- LG-Nortel and Polycom also make IP phones in a traditional phone form factor that operate an embedded edition of Office Communicator 2007. The physical plastic phones as referred by Microsoft are also named Tanjay Phones.
- IP Desk Phones 'Optimized for Lync': Powered by Lync Phone Edition these phones have full support to PBX functionalities, access to calendar and contacts, rich conferencing, extended functionalities when connected to the PC, and integrated security and manageability. Built from the ground up for Lync, these phones come in different models designed to meet specific business needs, including a rich information worker experience, a basic desk phone, common area phone, or conference room phone. Aastra and other vendors offer IP Desk Phones Optimized for Microsoft Lync. 
- Damaka has Lync clients for Android, iOS (iPhone/iPad), BlackBerry, Symbian, Windows 8, Mac OS X, Ubuntu Linux. It provides chat, voice, file transfer, video, and desktop sharing functions.
- Fisil has Lync clients for Android, iPhone, Windows, Linux, Mac
It should be noted that contrary to the last two bullet points, there is no available, supported Linux client for Lync  as of May 2013. The unifiedme.co.uk reference does list a Pidgin-based workaround, but according to the information at CERN , it has important limitations. The Damaka reference leads to the Google+ main page and has no information on a Linux client that I could find. The Fisil reference goes to a project management company that can write custom software.
Lync Server also has the capability to log and archive all instant message traffic passing through the server and to create Call Detail Records for conferences and voice. These features can help provide compliance with legal requirements for many organizations. The Archiving server is not an overall end-to-end compliance solution, as archiving requires you to install the Archiving Server and to configure front end servers accordingly.
Public IM Connectivity (PIC) 
Lync Server also enables organizations to interoperate with four external IM services: AOL Instant Messenger, Microsoft Messenger service, Yahoo! Messenger, and Google Talk. PIC was first introduced with Service Pack 1 for Live Communications Server 2005, PIC is licensed separately for Yahoo, but is free for AOL and Messenger service for customers with Software Assurance. See the external user access capabilities by user type in Microsoft Lync
With Lync Server 2013 - XMPP is natively part of the product
Pidgin supports OCS for Linux clients 
As of 2012[update] The Sipe plugin enables clients such as Pidgin, a multi-protocol instant messenger client which runs under Microsoft Windows as well as on Linux, to support MS Lync Servers with some limitation (Audio but no SRTP, No Video) via the extended version of SIP/SIMPLE.
Competitors to Lync Server include:
- 3CX Phone System; 3CX Phone System for Windows is a software-based IP PBX
- Alceo's BCS Communicator
- Asterisk (PBX) Platform - SIP, ISDN, IAX, SMS, open source telephone system
- AT&T UC and SIP Services
- Avaya Aura (tm) Presence Services (with Messaging) and one-X software
- Bopup Communication Server; Based on private and secure IM protocol
- Cisco's Unified Presence Server and Unified Personal Communicator
- Elastix; Elastix PBX, VoIP email, IM, faxing and collaboration functionality
- eZuce openUC Enterprise
- IBM's Lotus Sametime
- iChat Server (see Mac OS X Server)
- Jabber XCP (from Jabber, Inc., not to be confused with the IETF open standard XMPP)
- NEC's UCB and UCE
- Siemens' OpenScape
- Sun Java System Instant Messaging (see Sun Java Communications Suite)
In instant messaging, the free public instant messaging networks (Google, Live Messenger, Yahoo and AOL) are widely used and represent a degree of competition. There have been attempts by other vendors at providing solutions such as Yahoo!'s Enterprise Instant Messenger; however these attempts have been largely unsuccessful. An ICQ corporate client and server option once existed, but it is no longer supported or developed.
Products such as Cisco Unified Presence Server (Version 6.0.2+) support federation with Microsoft Office Communication Server 2007 to provide presence of Cisco IP phones and remote call control of the IP phone from the Microsoft Office Communicator client.
The Siemens OpenScape solution offers a federation with the Office communicator, and also an integration into the office communicator, allowing to use the standard functionalities of the office communication suite together with the SIP based voice functionalities of the Siemens platform.
The Asterisk telephone platform supports SIP, IAX, and ISDN connections. Most telephones that support these protocols may be used with Asterisk, including software phone clients.
See also 
- Similar products
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- Official website
- Lync Dev Center
- Inside OCS blog
- Alex Lewis, Tom Pacyk, David Ross, Randy Wintle (2013). "Microsoft Lync Server 2013 Unleashed, 2nd Edition". Sams Publishing. ISBN 978-0-672-33615-7.