3.2.5.1.9 Tunnel-Type
A RADIUS server MUST process the Tunnel-Type RADIUS attribute as specified in [RFC2868], with one additional enhancement: if the value of the Tunnel-Type RADIUS attribute is 0x00013701, it SHOULD be taken as a hint to the RADIUS server that the tunneling protocol supported by the tunnel endpoint is [MS-SSTP].<7>
When the RADIUS server receives this attribute, it checks the policy that has been configured by the server administrator. If configured to do so, the RADIUS server uses the value of this attribute to authorize the request.
For more details about this vendor-specific value for the Tunnel-Type RADIUS attribute, see section 2.2.2.1.