Refer to the exhibit. An engineer is troubleshooting an issue with the caller not hearing a PSTN announcement before the SIP call has completed setup. How must the engineer resolve this issue using th

Question

Options

• Avoice service voip sip send 180 sdp
• Bvoice service voip sip rehxx require 100rel
• Csip-ua disable-early-media 180
• Dvoice service voip sip no reMxx

• A
  3% (1)
• B
  81% (26)
• C
  6% (2)
• D
  9% (3)

Explanation

When a PSTN carrier sends early media announcements (ringback, congestion tones, recorded messages) before the call is answered, they are delivered in provisional responses such as 180 Ringing or 183 Session Progress with SDP. Without reliable provisional responses, these messages may be dropped or ignored because standard SIP provisionals (1xx) are not retransmitted. RFC 3262 defines the '100rel' extension and the PRACK method to make provisional responses reliable - the recipient must acknowledge them with PRACK, ensuring early media SDP is not lost. The IOS command 'voice service voip > sip > rel1xx require 100rel' (represented as 'rehxx' in the question due to formatting) enables this. Option A sends SDP in 180 but without reliability guarantees. Option C disables early media for 180, which would worsen the problem. Option D disables reliable response handling.

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