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Verify VoLTE ↔ VoWiFi handover keeps the same call alive.

IMS is a good example of a shared APN: VoLTE and VoWiFi traffic for the same subscriber both ride the operator's ims APN, just over different access — LTE via S5/S8, Wi‑Fi calling via ePDG on S2b. Blaze emulates both sides of a handover and asserts the PGW anchors the session correctly instead of dropping the call, while GTP Proxy carries both access paths natively in production.

# Blaze scenario — illustrative syntax
procedure "VoLTE → VoWiFi handover (S5/S8 → S2b)":
  role: server               # emulate the PGW under test

  step "anchor over LTE":
    expect CreateSessionRequest from SGW on S5S8:
      IMSI: "901700000000001"
      APN: "ims"
      RAT-Type: EUTRAN
    reply CreateSessionResponse:
      Cause: "Request Accepted"
      PAA: "10.64.12.7"       # UE IP allocated on LTE

  step "handover onto Wi-Fi":
    expect CreateSessionRequest from ePDG on S2b:
      IMSI: "901700000000001"
      APN: "ims"
      RAT-Type: WLAN
      Indication.HI: true       # Handover Indication
    reply CreateSessionResponse:
      Cause: "Request Accepted"
      assert PAA == "10.64.12.7"   # same IP == same call, no drop

  step "old LTE path torn down":
    expect DeleteSessionRequest from SGW on S5S8
    reply DeleteSessionResponse: Cause: "Request Accepted"

Result

LTE anchor accepted, PAA 10.64.12.7
S2b handover accepted, same PAA
Old S5/S8 session cleanly deleted
Zero-second IP change = no dropped call

PASS — 4/4 assertions · 3 procedure steps

Illustrative output. Native support for LTE ↔ Wi‑Fi calling handover means Blaze can emulate the SGW/MME side and the ePDG side of the same subscriber in one scripted procedure.

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