Default Bearer Request

Question 1

Create Default Bearer Request: MME —-> S-GW

Answer 1

1. MME selects a S-GW and allocates an EPS bearer identity for default bearer associated with UE.
2. MME sends a “create default bearer request.”
   This message provides a subscribed APN AMBR for the APN. MSISDN is included if the attach type indicates handover. Then, selection mode indicates that a subscribed APN was selected. Charging characteristics indicates which kind of charging the bearer context is liable for.
3. MME sends Create Default Bearer Request with following IEs:
   IMSI, MSISDN, MME TEID for Control Plane, PDN GW address, PDN Address, APN, RAT Type, Default EPS bearer QoS, PDN Type, APN-AMBR, EPS Bearer Identity (EBI), Protocol COnfiguration Options, Handover Indication, ME identity, User Location Information (ECGI), MS Info Change Reporting Support Indication, Selection Mode, Charging Characteristics, Trace Reference, Trace Type, Trigger ID, OMC identity, Maximum APN Restriction, Dual Address Bearer Flag, Protocol over S5/S8.

Question 2

Create Default Bearer Response : S-GW ——> PDN-GW

Answer 2

1. S-GW creates a new entry in its EPS bearer table
2. S-GW sends a create default bearer request message to PDN GW, indicated by the PDN GW address received in the previous step.
   This message contains the following information:
   IMSI, MSISDN, APN, S-GW address for User Plane, S-GW TEID of the User Plane, S-GW TEID of the Control plane, RAT Type, Default EPS bearer QoS, PDN Type, PDN Address, Subscribed APN-AMBR, EPS bearer identity, Protocol Configuration Options, Handover Indication, ME Identity, user Location Information (ECGI), MS Info change Reporting SUpport Indication, Selection Mode, Charging Characteristics, Trace Reference, Trace Type, Trigger ID, OMC Identity, Max APN Restriction
   Dual Address Bearer Flag.

Question 3

Create Default Bearer Response : PDN-GW ——> S-GW

Answer 3

1. P-GW creates a new entry in its EPS bearer context table
2. P-GW generates a charging ID.
   This new entry allows the P-GW to route user plane PDU’s between the S-GW and the packet data network, allowing them to start charging.
3. PDN-GW returns a create default bearer response with following IE’s:
   PDN-GW address for the user plane, PDN GW TEID of the user plane, PDN GW TEID of the control plane, PDN Type, PDN address, EPS Bearer Identity, EPS bearer QoS, Protocol Configuration Options, Charging ID, Prohibit payload compression, APN Restriction Cause, MS Info Change Reporting Action, APN AMBR.

Question 4

Create Default Bearer Response : S-GW ——–> MME

Answer 4

1. S-GW returns a create default bearer response to MME.