The name "rsyslog" stems back to the planned support for syslog-reliable. Ironically, the initial release of rsyslog did NEITHER support syslog-reliable NOR tcp based syslog. Instead, it contains enhanced configurability and other enhancements (like database support). The reason for this is that full support for RFC 3195 would require even more changes and especially fundamental architectural changes. Also, questions asked on the loganalysis list and at other places indicated that RFC3195 is NOT a prime priority for users, but rather better control over the output format. So here we are, with a rsyslod that covers a lot of enhancements, but not a single one of these that made its name ;) Since version 0.9.2, receiving syslog messages via plain tcp is finally supported, a bit later sending via TCP, too. Starting with 1.11.0, RFC 3195 is finally support at the receiving side (a.k.a. "listener"). Support for sending via RFC 3195 is still due. Anyhow, rsyslog has come much closer to what it name promises.
The next enhancement scheduled is support for the new syslog-protocol internet draft format, not the least to see how easy/complicated it is to implement. We already know that some subleties of syslog-protocol will require at least one considerable architectural change to the syslogd and this might delay things a little. Our immediate goal is to receive feedback and get the bugs out of the current release. Only after that we intend to advance the code and introduce new features.
The database support was included so that our web-based syslog interface can be used. This is another open source project which can be found under http://www.phplogcon.org. We highly recommend having a look at it. It might not work for you if you expect thousands of messages per second (because your database won't be able to provide adequate performance), but in many cases it is a very handy analysis and troubleshooting tool.
Rsyslogd supports an enhanced syslog.conf file format, and also works with the standard syslog.conf. In theory, it should be possible to simply replace the syslogd binary with the one that comes with rsyslog. Of course, in order to use any of the new features, you must re-write your syslog.conf. To learn how to do this, please review our commented sample.conf file. It outlines the enhancements over stock syslogd.
If you are interested in the IHE environment, you might be interested to hear that rsyslog supports message with sizes of 32k and more. This feature has been tested, but by default is turned off (as it has some memory footprint that we didn't want to put on users not actually requiring it). Search the file syslogd.c and search for "IHE" - you will find easy and precise instructions on what you need to change (it's just one line of code!). Please note that RFC 3195/COOKED supports 1K message sizes only. It'll probably support longer messages in the future, but it is our believe that using larger messages with current RFC 3195 is a violation of the standard.
Be sure to visit Rainer's syslog block to get some more insight into the development of rsyslog and syslog in general.