I had several ADFS and Single Sign On (SSO) questions from a large university in northern California proceeding with Office 365 for Education for faculty, staff and students.
What servers do I need to accommodate single sign on (SSO) aka Federated ID?
The following on premises servers are needed to accommodate SSO with Office 365:
Do we require ADFS proxies or can I just deploy an ADFS internal server?
Technically, you can get away with just ADFS servers and no proxy servers for Federated ID, we recommend you deploy ADFS proxies to protect your ADFS servers and to allow for client access restriction capabilities such as denying access to email when off campus or IP filtering.
Can I use TMG or UAG instead of an ADFS proxy server?
Currently, it is slated to be supported however the documentation is still being developed. In some cases, such as IP filtering, an ADFS proxy is still required in conjunction with UAG or TMG There is some initial documentation here.
Is there an order they need to be installed?
Yes, configure ADFS and federated ID first and then Directory Sync Server. You would think it is the other way however things run better when ADFS is configured prior to Dirsync.
Do I need full blown SQL Server with ADFS?
It depends on how you are going to implement ADFS and the total number of ADFS servers deployed. If you require stretched ADFS this requires full blown SQL to accommodate this scenario or if you require more than 5 ADFS servers WID cannot scale beyond that number of ADFS servers. See here for the differences between WID and SQL with ADFS or here for topology choices for ADFS.
What versions of SQL are supported?
WID, SQL 2005 and SQL 2008.
How many ADFS servers do I need for Federated ID?
Each ADFS server scale varies depending on load frequency such as will everyone be logging within a 15 minute interval or spread over an hour. This answer can range from 2 ADFS servers for 10,000 users with high availability with high load or many more users depending on your load frequency.
See the ADFS sizing calculator here to help narrow it down.
Can I enable geo-redundancy with ADFS?
Yes, it is possible to enable this with SQL mirroring/Replication to an alternate datacenter along with geoaware load balancers.
What happens if ADFS is unavailable?
ADFS is required to access Office 365 when using Federated ID (SSO). You want to ensure you have redundant ADFS proxies and ADFS servers to reduce any downtime to the cloud.
What type of hardware do I need for ADFS?
Make sure you do not underspec your ADFS servers as it does require some horsepower to run effectively:
Federation Service Server
· Dual Quad Core 2.27GHz (8 cores)
· 16GB RAM
· Gigabit Network
Federation Service Proxy Server
· Quad Core 2.24GHz (4 cores)
· 4GB RAM
Where can I get more information on deploying ADFS?
There is a good ADFS deployment guide here and a O365 ADFS deployment checklist here.