Hi, I have had no response to this, so I will modify the registrar module in my outbound branch to contain a new parameter for flow timer. When this parameter is set: * The registrar module will reject REGISTER requests without the outbound option-tag in a Supported: or Require: header with a 421 response containing a Require: header with the outbound option-tag. * When a REGISTER request does contain the outbound option-tag and the registration is successful the 200 response will contain a Requires: header with the outbound options-tag and a Flow-Timer: header with the parameter value. When this parameter is not set: * The registrar module will reject REGISTER requests with a 420 response containing a Require: header with the outbound option-tag. Regards, Peter -- Peter Dunkley Technical Director Crocodile RCS Ltd