Do we establish a PDP context during Attach procedure? Is this context kept while Attached?

Question

Why in LTE we establish a PDP context during Attach procedure but in UMTS it is not. Any pointers, it will also be good if someone can describe the Attach procedure in detail (though there are so many blogs but don't know which one is to follow)

Answer 1

The attach procedure is finished with the allocation of the IP address to the UE and establishment of a default bearer (basic IP connectivity). This bearer is alive during all the time the UE is registered/attached in the network (“the always on concept”). The default bearer can be considered/mapped to a PDP context from UMTS/GPRS network. However it is described by Rel. 8 QoS parameters.