These will be a bunch of articles written with the purpose of giving you the reader, an overview of the different roles that Microsoft Lync Server 2010 contains. This article is about the Front-end server and its purpose.

The Front-End service themselves have a lot of different objectives. The voice and video services is hosted here. Also the conferencing part is hosted here. The conferencing service could be a potential service to move away from the front-end servers if this service is used a lot or if the front-end servers are loaded from voice and video activity. The Mediation service or Public Switched Telephony service (PSTN) access can be collocated on every Front-End server as well. This gives flexibility and redundancy on your PSTN connections or SIP trunks.

The Mobility service is integrated on the front-end server as well. If you choose to implement this service, all requests from mobile clients will end up here.

Now the heart of Microsoft Lync is known as the Front-End server comes in 2 license versions.

1. Standard Edition

2. Enterprise Edition

Standard Edition

This is an all in one solution. With this installation you have both the Front-End and Back-end databases on the same server. It takes advantage of Microsoft’s own free product Microsoft SQL express installation, and stores the data locally on the server. This solution is great if redundancy and high availability is not a concern of your company. This server hosts up to 5000 simultaneously users and can have access to Public Switched Telephony services if you mediation server is collocated.

Enterprise Edition

The Enterprise edition of Microsoft Lync is a much more scalable version. As the Standard edition, this server hosts up to 5000 per server, and doing a bit of math, this can scale up to huge multinational companies with more than 100.000 users. But how does it work?

In short terms the Front-End services are now talking to a back-end database. This could be any Microsoft SQL servers as long as they are in versions of 2005, 2008 or 2008 R2. If you choose this solution, it would be obvious to install the back-end databases on a clustered Microsoft SQL server farm to make the backend redundant as well.

Using the Enterprise Edition you also need to implement hardware load-balancers to direct and alternate the traffic between the Front-End servers. This traffic has the option to be divided further and can include DNS load balancing, but that is beyond the scope of this article.

About licensing it is a good rule of thumb is that the Enterprise licenses cost about 4-5 times the Standard edition ones. But this is peanuts compared to the feature set you get, and next to nothing compared to the license structures you see within other vendors who can provide the same or close to the same feature set.

I hope this has been informative for you, and that you are excited about the next articles to come.