Service Principal Name is a unique identifier of a service instance and is used by Kerberos Authentication to link a service instance with a service logon account.
SPNs have the format of serviceclass/host:port servicename
For example HTTP/www.treyresearch.net:8080
Serviceclass is required and identifies the general class of service such as SQL
Host is required and is the name of the computer the service is running on. This may be FQDN or netbios
Port is optional and only specified if the default port is not used
The default SPNs are registered by the NetLogon service. They are refreshed every 22 minutes after startup.
Command line create a SPN