Information Technology Reference
In-Depth Information
directory/line numbers, ring tones, softkey layout (on-screen buttons), and so on. Al-
though the TFTP server configuration is sent using the TFTP protocol, the operating con-
figuration is sent using SIP or SCCP.
These protocols (SIP or SCCP) are then used for the vast majority of the phone functional-
ity following the registration. For example, as soon as a user picks up the handset of the
phone, it sends a SCCP or SIP message to the call processing server indicating an off-hook
condition. The server quickly replies with a SCCP or SIP message to play dial tone and
collect digits. As the user dials, digits are transmitted to the call processing server using
SCCP or SIP; call progress tones, such as ringback or busy, are delivered from the call pro-
cessing server to the phone using SCCP or SIP. Hopefully, you get the idea: The Cisco IP
Phone and call processing server have a dumb terminal and mainframe style of relation-
ship, and the “language of love” between them is SCCP or SIP.
