6.1 Overview

Subversion was designed with an abstract network layer. This means that a repository can be programmatically accessed by any sort of server process, and the client repository access API allows programmers to write plugins that speak relevant network protocols. In theory, Subversion can sport an infinite number of network implementations. In practice, there are only two servers at the time of writing.

Apache is an extremely popular webserver; using the mod_dav_svn module, Apache can access a repository and make it available to clients via WebDAV/DeltaV protocol, which is an extension of HTTP. In the other corner is svnserve: a small, standalone server program that speaks a custom protocol with clients. Table 6-1 presents a comparison of the two servers.

Note that Subversion, as an open-source project, does not officially endorse any server as primary or official. Neither network implementation is treated as a second-class citizen; each server has distinct advantages and disadvantages. In fact, it's possible for different servers to run in parallel, each accessing your repositories in its own way, and each without hindering the other (see Section 6.5 later in this chapter). Here's a brief overview and comparison of the two available Subversion servers as an administrator, it's up to you to choose whatever works best for you and your users.

Table 6-1. Network server comparison

Feature	Apache + mod_dav_svn	svnserve
Authentication options	HTTP(S) basic auth, X.509 certificates, LDAP, NTLM, or any other mechanism available to Apache httpd	CRAM-MD5 or SSH
User account options	private "users" file	private "users" file, or existing system (SSH) accounts
Authorization options	blanket read/write access, or per-directory access control	blanket read/write access
Encryption	via optional SSL	via optional SSH tunnel
Interoperability	partially usable by other WebDAV clients	not interoperable
Web viewing	limited built-in support, or via 3rd-party tools such as ViewCVS	via 3rd-party tools such as ViewCVS
Speed	somewhat slower	somewhat faster
Initial setup	somewhat complex	fairly simple