FYI
We found some SIP widely used implementations don't like loose-routing parameter (";lr") without any value (which is the currently documented use of loose-routing) and break. We will probably introduce a workaround option which will allow to use lr with value (e.g., ";lr=true").
In particular, we learned that Windows Messenger, rejects loose-record-routed requests and replies with "400 BAD Request" to INVITES with ";lr" in it.
Cisco IOS strips all RR parameters without value away, including ";lr" from Route header fields in subsequent requests.
-Jiri
-- Jiri Kuthan http://iptel.org/~jiri/