Default EPS Bearer Context activation
Procedure
- Default EPS Bearer Context activation Procedure is an ESM procedure initiated by network.
- This procedure is used to establish a default EPS bearer context between the UE and EPC.
- Initiated by network in response to PDN connectivity request from UE.
- The default bearer context activation can be part of attach procedure. If attach procedure fails default bearer context establish also fails.
- Default EPS bearer context doesn’t have any TFT assigned during activation, but network may anytime assign a TFT after establishment and may modify the TFT or packet filter of this default bearer.
- Default bearer context activation procedure initiated by MME by sending Active Default EPS Bearer Context Request.
- In case initial attach if default bearer is activated , the Activate default EPS bearer context request is sent in attach accept message.
- If Activate default EPS bearer context request is sent in response to PDN connectivity request from UE, MME will start T3485.
- MME will assign an EPS bearer identity in ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST.
- MME will retrieve the PTI from PDN CONNECTIVITY request sent in the activate request from UE.
- UE should verify the PTI (procedure transaction id) received in the message from network with the PTI sent from UE.
- UE shall send a reject message with one of the following reject causes
o
#26 Insuffiencent
Resources
o
#31
Request rejected, Unspecified
o
#95-111 protocol error
- If UE provided APN in PDN connection request and received ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST UE shall stop T3396 if it is running for APN provided by UE.
- If the PDN request is for emergency UE should not stop T3396 if it is running.
·
EPS
BEARER :
o
Established between UE to P-GW( E-RAB +S8
bearer)
o
E-RAB is established between UE and S-GW(Radio
bearer +S1 bearer)
o
S8 bearer is established between S-GW to P-GW
o
Radio bearer is established between UE and
eNodeB.
o
S1 bearer is established between eNodeB to S-GW
·
Default Bearer :
o
Established while attach. Per PDN connection one
default bearer will be established. Allocates IP address to UE.
o
No QOS, TFT or Guaranteed bit rate.
·
Dedicated
Bearer :
o
Dedicated bearer will be linked to a default
bearer.
o
QOS can be Guaranteed bit rate or Non-Guaranteed
bit rate.
o
If default bearer is deactivated dedicated
bearer will also be deactivated.