The Subversion client spends most of its time managing working copies. When it needs information from a repository, however, it makes a network request, and the server responds with an appropriate answer. The details of the network protocol are hidden from the user; the client attempts to access a URL, and depending on the URL schema, a particular protocol is used to contact the server (see Repository URLs). Users can run svn --version to see which URL schemas and protocols the client knows how to use.

When the server process receives a client request, it typically demands that the client identify itself. It issues an authentication challenge to the client, and the client responds by providing credentials back to the server. Once authentication is complete, the server responds with the original information the client asked for. Notice that this system is different from systems like CVS, where the client pre-emptively offers credentials (“logs in”) to the server before ever making a request. In Subversion, the server “pulls” credentials by challenging the client at the appropriate moment, rather than the client “pushing” them. This makes certain operations more elegant. For example, if a server is configured to allow anyone in the world to read a repository, then the server will never issue an authentication challenge when a client attempts to svn checkout .

If the client's network request writes new data to the repository (e.g. svn commit ), then a new revision tree is created. If the client's request was authenticated, then the authenticated user's name is stored as the value of the svn:author property on the new revision (see the section called “Unversioned Properties”). If the client was not authenticated (in other words, the server never issued an authentication challenge), then the revision's svn:author property is empty. ^[22]