EPS Bearer ID is similar to NSAPI from GTPv1. There is not much of a difference. I tried to capture the EBI;s in the below call flow. Its pretty much self explanatory. EBI values are always assigned by MME. So MME sets a EBI value for default bearer and sends it to SGW in Create Session request. In the same way MME again assigns the EBI value to dedicated bearer in Create Bearer Response.
One thing to note is LBI, which is Linked Bearer Id. This is the default bearer ID. It used to link dedicated bearers with the default bearer. Bearer Context : EBI mean that EBI value is sent in Bearer Context IE. EBI Id is of 4 bits, which mean we can have 16 bearers. But there are 5 reserved values which I could never find out. So we will have altogether 11 bearers.
PTI is procedure transaction ID. PTI, LBI and TAD will give us a unique combination to create/delete a dedicated bearer.
Correct me if I am wrong. Comments are welcome.
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