Normally, Windows servers running Microsoft Terminal Services can use a session broker (known as Terminal Services Session Directory in Windows Server 2003 and TS Session Broker in Windows Server 2008) to ensure that user sessions are assigned to specific servers. If a client initiates a connection request to the wrong terminal server, that server redirects the client to the appropriate server.
When you have a BIG-IP system, however, the incorrect server needs to redirect the client to the BIG-IP system virtual server, rather than to an individual server in the load balancing pool. To ensure that this happens, you can configure an MSRDP profile. With an MSRDP profile, Local Traffic Manager uses a token that the session broker provides to maintain persistence records. If a user initiates a session for which no session broker token exists, Local Traffic Manager makes load balancing decisions according to whichever load balancing method is configured for the pool.
In summary, using Local Traffic Manager with an MSRDP persistence profile, in conjunction with a session broker, allows for higher scalability and a greater range and flexibility of load balancing options than when using a session broker alone.

Server platform issues

By default, Local Traffic Manager with MSRDP persistence enabled load balances connections according to the way that the user has configured Local Traffic Manager for load balancing, as long as the session broker is configured on each server in the pool. Terminal Services Session Directory and TS Session Broker are features that are only available on Windows Server 2003 or Windows Server 2008, 2012 respectively. Therefore, each server in the pool must be a Windows Server 2003 or Windows Server 2008 server, if you want to use MSRDP persistence in default mode. Also, each client system must be running the remote desktop client software that is included with any Windows Server 2003 or Windows Server 2008, 2012 system.
If, however, you want to enable MSRDP persistence but your server platforms are running older versions of Windows (on which Session Directory or TS Session Broker is not available), you can enable MSRDP persistence in non-default mode. This causes Local Traffic Manager to connect a client to the same Windows server by way of the user name that the client provides. Note that enabling MSRDP persistence in non-default mode (that is, with no session broker available on the servers) is less preferable than the default mode, because it provides limited load-balancing and redirection capabilities.