Need some guide on user permission

I'm trying to set up svn repository using in my department. I would like
to have several repositories categorized by access levels. I'm trying to
follow the way in the manual that is setup the repository own by someone
and let him to start the server. Then I want to use the existing user unix
accounts and authorize them one by one to the repositories. I wonder if
this can be achieved by svn://, or should I use svn+ssh://. Which method
should I use to set the account. Thank you.

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Thone M.