Initial Attach on E-UTRAN with Diameter Interfaces
A UE needs to register with the network to receive services that require registration.
The following figure shows the call flow derived from the 3GPP reference for initial attach on E-UTRAN with Diameter interfaces Gx and Gy.

Step | Description | ||
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1 |
MME sends Create Session Request to S-GW. |
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2 |
S-GW sends Create Session Request to SMF. |
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3 |
SMF sends RADIUS Access-Request to AAA server for authentication. |
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4 |
AAA Server sends Access-Accept to SMF. |
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5 |
SMF sends Gx Credit Control Request Initial to PCRF server requesting for policy. |
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6 |
PCRF Server sends Gx Credit Control Answer Initial to SMF. |
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7 |
SMF sends Gy Credit Control Request Initial to the OCS server requesting for quota.
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8 |
OCS server sends Gy Credit Control Answer Initial to SMF. |
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9 |
SMF sends Radius Accounting request start to AAA Server. |
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10 |
AAA Server sends Radius Accounting Response to SMF. |
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11 |
SMF sends N4 PFCP Session Establishment Request to UPF to create PDRs/FARs/QERs/URRs. |
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12 |
UPF sends N4 PFCP Session Establishment response to SMF. |
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13 |
SMF sends Create Session Response to S-GW. |
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14 |
S-GW sends Create Session Response to MME |
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15 |
MME sends Router solicitation to S-GW for IPv6 call. |
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16 |
S-GW sends Router Solicitation to UPF for IPv6 call. |
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17 |
UPF sends Router Advertisement to S-GW for IPv6 call. |
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18 |
S-GW sends Router Advertisement to MME for IPv6 call. |