[Serusers] PRACK on forked response

Hi all, I'm using SER purely for testing purposes just now. Currently testing our handling of forked responses and hit upon the following situation: My outgoing INVITE is forked to two UASs (also our own SIP endpoint), one of which sends a reliable 180 and the other an unreliable 180. The UAC sends a PRACK on the dialog ID of the reliable response but SER forwards this response on to both UASs the result being the UAS that sent the unreliable 180 responds to the PRACK with a 481 (the PRACK contains a To-tag that part defines a dialog unknown to that UAS). I confess I can't find anything describing this scenario in any RFC but it strikes me as incorrect behaviour on SERs part. Does SER support PRACK? If not then no matter, I can live with it - it doesn't affect the outcome of any call. If it does, does anyone have any thoughts on this? Cheers Steve Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) P Please consider the environment and don't print this e-mail unless you really need to