...
- Upload the file either manually to /var/sipxdata/configserver/phone/profile/tftproot/ or through the Admin Portal -> Devices -> Device files
- Apply this configuration files to the desired devices: Devices -> Phones -> <MAC> -> Custom configuration and fill in the name of the file (e.g: gruu.cfg)
- Send profiles
Note: This will be improved as to be configurable from Admin Portal per device
Documentation on GRUU :http://tools.ietf.org/html/draft-ietf-sip-gruu-15