This part will cover the overall architecture of Microsoft's Unified Communications platform.
One of the reasons I appreciate working with this platform is the truely unified nature of the application stack. We're dealing with two server products (for the most part) when it comes to Microsoft UC; Office Communications Server 2007 R2 and Exchange Server 2007.
Office Communications Server 2007 R2 is available in two versions; Standard and Enterprise. The same goes for Exchange Server. So the first question is:
Q: What is the difference between Standard and Enterprise for OCS and Exchange?
A: It has to do mostly with your requirement for High Availability. Do you need HA? If so, then use Enterprise for both platforms.
The Standard Edition of both OCS and Exchange do not support high availability at all. In fact with OCS you don't get the choice of where to install the database and shared components; it will install SQL Express locally.
It should be worth mentioning that the server edition software is independent of the client licensing platform. For example, you can have an Enterprise OCS and Exchange CAL for your users who connect to a Standard Edition OCS/Exchange environment (and vice versa).
Q: What is the difference between the Standard OCS CAL and Enterprise?
A: The Microsoft web site has a great page which talks about this.
Q: What is the difference between the Standard Exchange CAL and Enterprise?
A: Again the Microsoft web site explains this well.
When you license both Exchange and OCS with 'all the trimmings' you get the following high-level features:
- Presence/Instant Messaging
- Web Conferencing (Live Meeting)
- PC to PC and voice/video
- IP Telephony (VoIP)
- Audio dial-in conferencing
- Group chat
Exchange UM features
- Unified Messaging
- Outlook Voice Access
- Auto Attendant
As a best practice I like to design OCS solutions so they include some additional Microsoft UC platforms such as:
- Microsoft OCS Monitoring Server (for QoE/CDR)
- Microsoft OCS Archiving Server (for IM logging)
- Microsoft OCS Edge Server (for remote IM/Voice/Video/Federation/etc)
- Microsoft OCS Mediation Server (for VoIP/PSTN features)
- Microsoft OCS Communicator Web Access (for dial-in conferencing and web-based IM)
Q: When do you need a Monitoring Server?
A: I like to include the Monitoring Server role in just about every implementation for two reasons. First, the Quality of Experience technology is key to understanding the Mean Opinion Score (MOS) of your voice conversations. The MOS score is given to a voice call and is a simulated subjective analysis of voice quality on a per call basis. The QoE data is invaluable when troubleshooting voice quality issues and has improved significantly from the R1 release. Second, the CDR data rolled up into the SQL reports contains excellent information when it comes to determining how many IM conversations, PC to PC calls, or conferences were conducted in a certain time frame. You can use this data to gauge relative interest in the technology or for capacity planning.
Q: When do you need an Archiving Server?
A: If you have a requirement to log Instant Message conversations.
Q: When do you need an Edge Server?
A: If you have a requirement to communicate with other companies running OCS (Federation), you want to enable users to have public IM capability (Yahoo!/AOL/MSN), or you simply want to enable remote access (anonymous or authenticated). One of the primary reasons for an Edge Server is to permit people to join your hosted Live Meeting sessions.
Q: When do you need a Mediation Server?
A: If you wish to enable Voice over IP and use OCS to place phone calls. The Mediation server performs a few tasks. First, it does basic protocol conversion from Microsoft's "RTAudio" codec to a more industry standard "G7.11" codec. Second, it performs encryption or decryption on voice traffic. Many vendors today offer this server in an appliance configuration where the Mediation Server is combined with a voice gateway; this is often called a "Hybrid Gateway". One vendor called "NET" www.net.com has a gateway called the VX1200 which can perform both tasks without the need for a Windows operating system. The conversion is performed "on chip" and the integration with AD means you can implement OCS voice with one less server! Last, the Mediation Server performs inbound number normalization for PSTN calls (more on this later).
Q: When do I need a CWA Server?
A: If you want to provide dial-in audio conferencing or web-based IM.
That pretty much covers the high level components for now.