This article provides a brief overview of the server roles and the general features they provide:

  • Front End Server and Back End Server
  • A/V Conferencing Server
  • Edge Server
  • Director
  • Mediation Server
  • Monitoring Server
  • Archiving Server

Let us go with Key points:

Front End Server and Back End Server

Front End Server:
The Front End server is the central server role in Lync Server 2010. It runs on a single server in Lync server 2010 Standard Edition and is collocated with the Back End Server configuration. In the Enterprise Edition, the Front End Server as a separate server from the Back End Server. The Front End Server role:

• Provides SIP registrar and Presence aggregation for handling client regisration and publishing aggregated user presence to other users
• Provide conferencing services such as audio/video conderencing, Web conferencing, Application sharing, IM conferencing and dial-in Conferencing.
• Manages the Central Management Database that deploy the configuration data to all other Lync Server 2010 servers. If multiple Lync Server pools are deployed, only the first deployed pool will contain Front End Server that maintain the CMS.
• Provides device and client updates for Lync Server 2010 phone devices and Lync Server 2010 clients.

Back End Server
The Back End Servers are database servers running Microsoft SQL Server that provide the database services for the Front End pool. The Back End Servers serve as backup stores for the pool’s user and conference data, and are the primary stores for other databases such as the Response Group database. Information stored in the Back End Server databases includes presence information, users' Contacts lists, conferencing data, including persistent data about the state of all current conferences, and conference scheduling data.

A/V Conferencing Server
The A/V Conferencing Server role can now be in a separate pool to enhance scalability. It is usually collocated with the Front End Server. This collocation is central processing unit (CPU)-intensice in large installations that heavily use audio/video conferencing. Therefore, it may be necessary to seperate the A/V conferencing server role from all the other functions that a Front End Server Manages.

The Audio/Video conferencing enables real-time audio and video communication among users, if they have required client devices, such as headsers for audio conferences and webcams for video conferences. When you deploy conferencing, you can enable users to use both Web conferencing and A/V conferencing or just Web conferencing

Edge Server
The Edge Server in Lync Server 2010 should be placed on the perimeter network, and it manages all external connections from remote users, federated users, Public IM network users, or external users, who have been invited to join Web conferences. The main functions of the Edge Server role are to:
• Provide access edge services by handling both inbound and outbound SIP signaling, Presence, and IM exchange.
• Provide Web conferencing edge services by enabling external access to Web conferences that are running on the internal server.
• Provide audio/video edge services by ensuring that audio and video can securely traverse not only within the company firewall, but also beyond the firewall where remote, federated, or anonymous users may be located.
• Facilitate remote desktop sharing and file transfers.

The Director authenticates internal and remote users, and redirects them to the correct server pool, if you have deployed several server pools in the organization. The Director:
• Authenticates internal users and redirects them to the appropriate pool; and it is not involved in the rest of the user session.
• Authenticates external users and stays in the signaling path for the rest of the user session.
• Provides users with their Backup Registrar address before redirecting them to the appropriate pool if a Back Registrar is configured.

Mediation Server
The Mediation Server role can be collocated with the Front End Server, run as a single server, or run as a pool of servers. The primary role of the Mediation Server is to translate and add additional services to third-party internet protocol (IP) private branch exchange (PBXs) or SIP-PSTN Gateways. The other tasks are to:
• Strip or add encryption on signaling and media.
• Transcode the codec that the PBX or gateway uses, for example, G.711, to a Microsoft-supported codec, for example, RTAudio or Siren, which is licensed by Microsoft from Polycom for audio conferencing. Note that Siren is only used in backwards compatibility scenarios.
• Add firewall traversal capabilities or interactive connectivity establishment (ICE) support for calls between PBX and Gateways that do not support these capabilities.

Monitoring Server
The two main functions of the Monitoring Server are to collect Quality of Experience (QOE) monitoring information and Call Details Records (CDR) information. The QOE reports are sent to Lync Server 2010 whenever an audio or video session has ended. However, for CDR records, any session such as peer-topeer,audio/video conferencing, instant messaging, desktop sharing, or Web conferencing, is collected. For organizations where you are planning to deploy Lync Server 2010, you should recommend the use of the Monitoring Server because it is a key troubleshooting tool where users utilize audio/video in either an Enterprise Voice, PC Audio only and/or conferencing scenario.

Archiving Server
The plan for deploying the Archiving Server is for legal compliance reasons to archive instant messaging and conferencing information. Lync Server 2010 allows organizations to archive Web conferences also. However, Lync Server 2010 does not archive the video and audio portions of conversations or conferences.