If you want to use subversion(svn) behind a proxy then you have to do the following.
1. Go to servers file of subversion ~/.subversion/servers
2. In the servers file edit the settings under [global] tag according to your proxy settings appropriate values.
[global] http-proxy-host = proxy-server.example.com http-proxy-port = your-port-value(eg-3120)
3. Save and you are Done!