[Asterisk-Dev] 487 message in response to CANCEL

[Tom Schroer]

I was hoping someone may have come across this and have some input or
interpretation.  On SIP to SIP calls with asterisk set up with
canreinvite=yes, when an incoming call reaches *, but * has not sent
back final response and the Calling party sends a CANCEL, asterisk will
respond back with OK to the CANCEL, send a CANCEL to the called party,
receive an OK back from the called party as well as a 487 message which
it then ACKs.  However, asterisk does not send a 487 message to the
calling party.  I wanted to get others' opinions on whether this last
issue, where no 487 message is sent to the calling party, is consistent
with 3261.  Here is the call flow of what is occurring.  

Party A        Asterisk          Party B
  |---INVITE------>|                |
  |<--TRYING-------|                |
  |                |---INVITE------>|
  |                |---TRYING-------| 
  |                |<--180 RINGING--|
  |<--180 RINGING--|                |
  |                |<--180 RINGING--|
  |                |<--180 RINGING--|
  |                |<--180 RINGING--|
  |----CANCEL----->|                |
  |<---200 OK------|                |
  |                |-----CANCEL---->|
  |                |<----200 OK-----|
  |                |<-----487-------|
  |                |------ACK------>|

Technically, should the asterisk be sending a 487 message to the Calling
Party?  Is there a configuration parameter that is or is not set that
could be causing asterisk not to forward that on?  I just downloaded the
latest CVS version to confirm and I am still seeing this behavior.  Any
help would be appreciated.
Thanks
Tom Schroer