Q17On-Premises Call Control
An administrator uses the Cisco Unified Real-Time Monitoring Tool to investigate recent calls on a Cisco UCM cluster. The SIP trace for an on-net direct-media call shows two **180 Ringing** messages and two **BYE** messages. Why do multiples of each message type appear in the trace?
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Community votes
Discussion · 11
C 12
Selected Answer: C
the source phone doesn't "ring". it gets a "ringing" packet from the CUCM which gets it from the destination phone. that's why there are 2 messages.
4
C is the correct one
B 3
Selected Answer: B
B. The source phone has to signal to the destination phone that it is ringing, and the destination phone signals back with a 180 Ringing message. The same process applies to 11 BYE messages.
When a call is made, the source phone sends a SIP INVITE message to the Cisco UCM, which sends a SIP INVITE message to the destination phone. The destination phone signals back with a 180 Ringing message to the Cisco UCM, which signals back with a 180 Ringing message to the source phone. This happens twice, resulting in two 180 Ringing messages in the SIP trace. Similarly, when the call ends, both phones send a BYE message to the Cisco UCM, resulting in two BYE messages in the SIP trace.
3
C is the correct one
C 3
Selected Answer: C
The device that sends the 180 Ringing signal is the phone you're calling, the "destination" phone, not the source phone (when you call somebody, their phone rings, not yours).
A 2
Selected Answer: A
Docs for how to analyze a SIP call point to A
https://www.cisco.com/c/en/us/support/docs/unified-communications/unified-communications-manager-callmanager/213583-procedure-to-analyse-call-flow-of-sip-ca.html
A 2
Selected Answer: A
Seems like A:
https://www.cisco.com/c/en/us/support/docs/unified-communications/unified-communications-manager-callmanager/213583-procedure-to-analyse-call-flow-of-sip-ca.html
C 2
Selected Answer: C
It's C. If you've ever checked a SIP trace for a call, you'd see this. The first packet you see comes from the destination phone, which sends a "180 Ringing" to CUCM to let it know the phone is physically ringing. The second one is from CUCM forwarding it to the source phone that placed the call, so it can play Ringback tone to the calling user.
B 1
Selected Answer: B
The correct answer is B
1
Answer B is wrong but the explanation is correct (Answer is C)
D 1
Selected Answer: D
When you look at a SIP trace in the Real-Time Monitoring Tool (RTMT) that seems to "double up" on messages like 180 Ringing or BYE, it is a strong sign that the call is not a single end-to-end signaling path, but is instead being split by a Media Termination Point (MTP).