In SRVCC scenarios, what media plane adjustment is done?

Interview
1

Q. In SRVCC scenarios, what media plane adjustment is done?

a) MEGACO reassigns IP addresses
b) PCRF creates a new bearer
c) RTP flows are redirected from IMS to CS domain
d) SIP is re-negotiated mid-call

Check 🔎

:arrow_right: Correct answer: Letter c.

In SRVCC (Single Radio Voice Call Continuity) scenarios, when a VoLTE call is handed over from LTE (IMS) to a legacy CS (Circuit Switched) domain like 2G/3G, the RTP (Real-time Transport Protocol) media stream is redirected from the IMS core to the CS network.

  • The ATCF/ATGW handles this media redirection.
  • This allows the ongoing voice session to continue seamlessly despite the radio access technology change.

Q. In SRVCC scenarios, what media plane adjustment is done?

a) :x: MEGACO reassigns IP addresses
→ Incorrect. MEGACO (H.248) is used for control between MGC and MGW but does not reassign IPs in SRVCC context.

b) :x: PCRF creates a new bearer
→ Incorrect. PCRF (Policy and Charging Rules Function) deals with policy enforcement and QoS but isn’t responsible for the media path redirection during SRVCC.

c) :white_check_mark: RTP flows are redirected from IMS to CS domain
→ Correct. The core media path shifts from IMS (VoIP over LTE) to CS (circuit-based voice) during SRVCC.

d) :x: SIP is re-negotiated mid-call
→ Incorrect. SIP re-negotiation is not performed; instead, SRVCC triggers control and media redirection procedures without a SIP UPDATE or re-INVITE.