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210-060 · Question #114

Client A in X site uses an IP phone to call client B in Y site. Engineers have selected SCCP as the default VoIP signaling protocol. Which network path will the call signaling take when client A…

The correct answer is B. IP phone X > CUCM subscriber > IP phone Y using TCP port 2000. In SCCP deployments, all call signaling flows through CUCM using TCP port 2000, never directly between endpoints.

Call Control

Question

Client A in X site uses an IP phone to call client B in Y site. Engineers have selected SCCP as the default VoIP signaling protocol. Which network path will the call signaling take when client A calls client B?

Options

  • AIP phone X > CUCM subscriber > IP phone Y using TCP port 1000
  • BIP phone X > CUCM subscriber > IP phone Y using TCP port 2000
  • CIP phone X > CUCM subscriber > IP phone Y using UDP port 1000
  • DIP phone X > IP phone Y using TCP port 2000
  • EIP phone X > IP phone Y using TCP port 1000

How the community answered

(32 responses)
  • A
    3% (1)
  • B
    88% (28)
  • C
    6% (2)
  • D
    3% (1)

Why each option

In SCCP deployments, all call signaling flows through CUCM using TCP port 2000, never directly between endpoints.

AIP phone X > CUCM subscriber > IP phone Y using TCP port 1000

TCP port 1000 is not assigned to SCCP; the correct port is TCP 2000 (or TCP 2443 for encrypted SCCP).

BIP phone X > CUCM subscriber > IP phone Y using TCP port 2000Correct

SCCP uses TCP port 2000 as its registered well-known port for signaling between IP phones and Cisco Unified Communications Manager. Because SCCP is a client-server protocol, all call control messages from the originating phone travel to the CUCM subscriber, which then instructs the destination phone - making CUCM the mandatory intermediary in the signaling path.

CIP phone X > CUCM subscriber > IP phone Y using UDP port 1000

SCCP signaling is transported over TCP, not UDP; UDP is used by RTP for the actual voice media stream, not for call control.

DIP phone X > IP phone Y using TCP port 2000

SCCP does not support direct phone-to-phone signaling; the protocol requires CUCM to mediate all call setup and teardown between endpoints.

EIP phone X > IP phone Y using TCP port 1000

SCCP uses TCP port 2000, not port 1000, and the signaling path must always traverse CUCM - a direct endpoint-to-endpoint path is not possible with SCCP.

Concept tested: SCCP signaling path through CUCM and TCP port 2000

Source: https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/port/cucm_b_port-usage-guide.html

Topics

#SCCP#signaling path#TCP port 2000#call signaling

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