[OpenAFS] service principal question

[Jiann-Ming Su]

I'm trying to deploy my OpenAFS cell on a Kerberos realm that doesn't
match the cell name -- I don't control the Kerberos realm.  On the
README.servers.gz file that's distributed with the Debian packages, it
says:

      If your Kerberos realm name does not match your AFS cell name (if,
      for instance, you have one Kerberos realm with multiple AFS cells),
      use "afs/cell.name" as the name of the principal above instead of
      just "afs", where cell.name is the name of your new AFS cell.

Is it absolutely necessary to create the service principal as
"afs/cell.name"?  That is, does it need the "/"?  Can it be
"afs_cell.name"?  Thanks for any tips and clarifications.
--
Jiann-Ming Su
"I have to decide between two equally frightening options.
 If I wanted to do that, I'd vote." --Duckman