Why would RTP traffic that is sent from the originating endpoint fail to be received on the far endpoint?

Question

Options

• AThe far end connection data (c=) in the SDP was overwritten by deep packet inspection in the call signaling path.
• BCisco Unified Communications Manager invoked media termination point resources.
• CThe RTP traffic is arriving beyond the jitter buffer on the receiving end.
• DA firewall in the media path is blocking TCP ports 16384-32768.

• A
  91% (42)
• B
  2% (1)
• C
  2% (1)
• D
  4% (2)

Explanation

The most common cause of RTP not being received on the far end is that the c= (connection data) line in the SDP has been overwritten by a device performing deep packet inspection (DPI) - such as a NAT device, firewall, or session border controller - along the signaling path. The c= line tells the originating endpoint where to send its RTP stream. If a DPI device incorrectly rewrites this IP address (e.g., replacing a valid public IP with a private/incorrect address), the originating endpoint sends RTP to the wrong destination and the far endpoint never receives it. Option B (MTP invocation) would change the media path but not cause complete failure. Option C (jitter buffer overflow) causes audio quality degradation, not total loss. Option D is incorrect because RTP uses UDP, not TCP, and the standard RTP port range is 16384–32767.

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