- A broker to manage and direct user connections
- A portal for users to select where they want to connect
- A method to deliver the user's profile and data (such as roaming profiles, UE-V and folder redirection)
- A method to deliver the user's applications (such as App-V of published applications from RDS)
- A secure means to enable the connection from external parties without VPN (such as RD Gateway which encapsulates RDP in HTTPS packets)
- A protocol for the communication between the client and the virtualized desktop (Remote Desktop Protocol for Microsoft solutions)
- A client on the endpoint device that supports the protocol used
The in-box virtualized desktop solution in supports both VDI and session virtualization and has all of the items above, delivering a complete solution. However, regarding the last point, the client for endpoint devices, Microsoft only provides RDP clients for Windows-based devices and doesn't provide an RDP client for iOS or Android platforms.
Third parties do provide RDP clients for those platforms. This means just because Microsoft doesn't provide a client for iOS or Android, doesn't mean you can't leverage a Microsoft virtualized desktop from those devices. You would just need to use a third-party RDP client-- for example Wyse has an iOS RDP client in the Apple Store.
Citrix does provide clients for their protocol for many types of devices and has advantages in terms of handling slower speed, higher latency links and some other features. But just because you have iOS devices or Android doesn't mean you can't use the Microsoft virtualized desktop solution.