You administer a UCM environment that contains only Cisco IP phones with factoryinstalled firmware.
Which of the following messages will not be sent or received by the IP phones? (Select 2 choices.)
A.
486 Busy here
B.
Connected
C.
INVITE
D.
Off Hook
E.
On Hook
Explanation:
Cisco IP phones with factory firmware will not send or receive 486 Busy here messages. In addition, these IP
phones will not send INVITE messages. Both the 486 Busy here message and the INVITE message are call
signaling messages that are sent and received by Session Initiation Protocol (SIP) endpoints. By default, Cisco
IP phones use Skinny Control Client Protocol (SCCP), which is a Ciscoproprietary client/ server call signaling
protocol. Although Cisco IP phones can be configured to use SIP when installed with a firmware replacement,
the Cisco IP phones in this scenario are using factoryinstalled firmware.
SIP is an Internet Engineering Task Force (IETF)standard call signaling protocol that is supported by a wide
variety of IP telephony vendors. A call signaling protocol is responsible for the setup, maintenance, and
teardown of a voice call. For example, call signaling protocols can detect and report when a phone is off-hook.
SIP uses a textbased signaling method, which is easier to understand and troubleshoot than the binary method
used by other protocols, such as SCCP and H.323.
SIP is most commonly used by Internet telephony service providers (ITSPs). Therefore, many nonCisco IP
phones and video phones are SIP phones. Because Cisco Unified Communications Manager (UCM) supports
SIP, it is possible for nonCisco IP phones to be registered with UCM and function on a Voice over IP (VoIP)
network that otherwise contains SCCP endpoints.
Connected, Off Hook, and On Hook are all call signaling state messages that are sent to SCCP endpoints in a
UCM environment. SCCP typically represents each of these call states with a callstate identifier number. For
example, a callstate of 1 indicates a call state of Off Hook. A callstate of 2 indicates a call state of On Hook.https://www.cisco.com/en/US/tech/tk652/tk701/
technologies_configuration_guide_chapter09186a00800eadfa.html#xtocid2
https://www.cisco.com/c/en/us/support/docs/voice-unified-communications/unified-communications-managercallmanager/69267-callstates-sccp-endpoints.html#callstates