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210-060 · Question #109

The IP phone of user A is registered with Cisco Unified Communications Manager subscriber1 while the IP phone of user B is registered with subscriber2. User A is speaking to user B on an active…

The correct answer is D. This action does not affect the call. Once an IP call is established, the RTP media stream flows directly between phones peer-to-peer and is independent of the CUCM subscriber that handled call setup.

Call Control

Question

The IP phone of user A is registered with Cisco Unified Communications Manager subscriber1 while the IP phone of user B is registered with subscriber2. User A is speaking to user B on an active call. A junior network engineer mistakenly reboots subscriber1. What effect does this have on the call?

Options

  • AUser A can hear B, but B cannot hear A.
  • BUser A cannot hear B, but B can hear A.
  • CThis action drops the call.
  • DThis action does not affect the call.
  • EThe call remains active, but quality may suffer.

How the community answered

(27 responses)
  • A
    15% (4)
  • B
    4% (1)
  • C
    4% (1)
  • D
    52% (14)
  • E
    26% (7)

Why each option

Once an IP call is established, the RTP media stream flows directly between phones peer-to-peer and is independent of the CUCM subscriber that handled call setup.

AUser A can hear B, but B cannot hear A.

RTP audio is a bidirectional stream between the two endpoints; a CUCM reboot does not affect the media plane, so it is impossible for only one direction to be silenced.

BUser A cannot hear B, but B can hear A.

Like choice A, unidirectional audio loss implies a media-plane problem such as a firewall or NAT issue, not a CUCM server reboot, because the RTP stream does not traverse CUCM.

CThis action drops the call.

The call does not drop because CUCM is not in the RTP media path; an existing call only drops if a CUCM-initiated re-INVITE or keepalive is specifically required and fails.

DThis action does not affect the call.Correct

In Cisco Unified Communications Manager, call signaling (SCCP or SIP) is handled by CUCM subscribers, but the actual RTP audio stream flows directly between the two IP phones once the call is established. Rebooting subscriber1 removes it from handling new signaling requests, but the active RTP path between user A and user B does not pass through CUCM, so the in-progress call is unaffected.

EThe call remains active, but quality may suffer.

Call quality is determined by the network path between the two phones, not by CUCM server availability, so rebooting a subscriber has no effect on jitter, delay, or packet loss for an active call.

Concept tested: CUCM media path independence from call signaling servers

Source: https://www.cisco.com/c/en/us/support/docs/voice/h323/14201-callsetup-failover.html

Topics

#CUCM redundancy#call survivability#subscriber node#call processing

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