A very high level topic to finish 2015, but one it is always useful to cover as a reference for more complex understanding of Skype for Business Server, what are the Skype for Business Server 2015 (SfBS) roles and what functions do they perform?
The Front-End Server role is the core role in any SfBS deployment and hosts delivers most core functions for your Skype for Business clients. You can configure a pool of Front-End servers for high availability.
- User authentication and registration.
- Presence information and contact card exchange.
- Address book services and distribution list expansion.
- IM functionality, including multiparty IM conferences.
- Web conferencing, PSTN dial-in conferencing and A/V conferencing (if deployed).
- Application hosting, for both applications included with Skype for Business Server (i.e. Conferencing Attendant and Response Group application) and third-party applications.
- Web components to supported web-based tasks such as web scheduler and join launcher.
- Archiving, to archive IM communications and meeting content for compliance reasons.
- If Persistent chat is enabled, Persistent Chat Web Services for Chat Room Management and Persistent Chat Web Services for File Upload/Download.
- Front-end pools are also the primary store for user and conference data. Information about each user is replicated among three front-end servers in the pool, and backed up on the back-end servers.
Finally, one Front-End Server will also run the Central Management Server which manages and deploys configuration to all Skype for Business Servers in the deployment.
The Back-End server runs SQL databases to provide database services for the Front-End server/Front-End Pool. It can host backup stores for pool users, conferencing data. The Back-End servers also host several primary stores, such as Response Group database. Although a single Back-End server is supported it is recommended that you configure high availability using either SQL Server Mirroring, a SQL Server Cluster, or SQL Server Always On.
A Back-End server does not run any SfBS software/services.
The Edge Server role is required to enable communication and collaboration with external users (users who are not members of the SfBS organisation). The Edge Server role is also used to provide connectivity to Public IM services such as Skype.
The Mediation Server role is required for Enterprise Voice and Dial-In Conferencing functionality. The Mediation Server translates signalling and media traffic between the Skype for Business clients and a PSTN Gateway/IPBX/SIP Trunk.
You can co-locate the Mediation Server role with the Front-End Server role.
The Director role is used to provide additional security for external users signing into the SfBS organisation. It does not host any user accounts or presence data, neither does it provide any conferencing services.
The Director server authenticates user requests before forwarding to the internal SfBS servers. This ensures that should a Denial of Service (DoS) attack be directed at your SfBS organisation it will only affect the Director server and therefore external authentication, but your internal services will remain uninterrupted.
Persistent Chat Server Roles
The Persistent Chat server role enables groups of people to hold ongoing conversations in an environment similar to an online “chat room” where the conversation continuity is not lost when the users log off/end the chat.
This role service is hosted on the Front-End servers and the chat history data and the information about categories and chat rooms are stored on the Back-End servers.
There is an additional Persistent Chat Compliance Server role which stores compliance information for organisations where this is a concern.
Video Interoperability Server
The Video Interoperability Server (VIS) is used to integrate your SfBS deployment with Third Party video conferencing solutions. This functionality is currently only available on-premises.
The VIS role is currently on focussed on Cisco and Tandberg systems, however, Microsoft is looking to expand this in the future.