Two users have IP phones running SCCP phone loads. Which purpose does the SCCP protocol server during the call?

Digitizing and sampling analog voice is performed by the IP phone's onboard DSP, and the resulting audio is transmitted via RTP/UDP, not through SCCP to CUCM.

Voice media travels directly between IP phones using RTP/UDP; SCCP carries only signaling messages and never transports audio streams.

SCCP (Skinny Client Control Protocol) operates exclusively as a signaling protocol between a Cisco IP phone and CUCM, exchanging call setup, hold, transfer, and teardown messages - voice media is carried separately by RTP directly between endpoints, making CUCM the central signaling point for all SCCP phone calls.

SCCP is a client-server protocol where each phone communicates individually with CUCM, not with the other phone directly - peer-to-peer signaling between phones is not part of how SCCP functions.