SgNB Addition Request — the point of this capture (EN-DC bearer setup, "with DRB-ID"). This is X2AP procedure id-sgNBAdditionPreparation (27): the MeNB (LTE anchor) asks the secondary gNB to allocate NR radio resources so the UE can run in dual connectivity (EN-DC / NSA Option 3). The MeNB owns the UE here — note the identifier is the MeNB-UE-X2AP-ID = 1 (the gNB will mint its own SgNB-UE-X2AP-ID in the Acknowledge that never comes).

The bearer being added, decoded from the E-RABs-ToBeAdded list (exactly one item):

E-RAB-ID 11, mapped to DRB-ID 1 — the explicit Data Radio Bearer identity this capture is named for. Carrying the DRB-ID in the request lets the MeNB pin the NR DRB identity rather than leaving it to the SgNB.
en-DC-ResourceConfiguration: pDCPatSgNB, mCGresources and sCGresources all present — i.e. this bearer uses both Master and Secondary Cell Group lower-layer resources (a split-bearer shape).
resource-configuration: sgNBPDCPnotpresent — the PDCP anchor stays at the MeNB; the SgNB contributes NR RLC/MAC/PHY only. So this is an MCG-anchored split bearer, not an SCG bearer with SgNB-terminated PDCP.
Requested SCG E-RAB QoS: QCI 16, ARP priority = highest (1), shall-not-trigger-pre-emption, not-pre-emptable.
meNB-UL-GTP-TEIDatPDCP: the MeNB's uplink GTP-U endpoint for the split bearer — here 0.0.0.0 / TEID 0x00000000 (placeholder), and rlc-Mode is Unknown. Real values would point the SgNB's uplink X2-U traffic back at the MeNB's PDCP.

Security context IEs are present but carry placeholder patterns: the SgNBSecurityKey (S-KgNB) is all zeros (256-bit), and the NR UE security capabilities advertise no standard algorithms (nRencryptionAlgorithms=0x0001, nRintegrityProtectionAlgorithms=0x0002 — the 128-NEA1/2/3 and 128-NIA1/2/3 bits all decode as Not supported). An opaque MeNBtoSgNBContainer (the RRC CG-ConfigInfo) is also included as a short stub (f0f1f2…). In a live add the gNB would use S-KgNB and these caps to configure NR security and reply with a SgNBAdditionRequestAcknowledge carrying the SCG RRCReconfiguration.

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