A Traffic Flow Template (TFT) is always associated with an EPS Bearer of a particular QCI.
Multiple SDF templates can be associated with the same bearer. One SDF template can be linked with one SDF or multiple SDFs. A SDF is nothing but an IP packet filter which works based on tuple of (source IP address, source port, destination address, destination port and protocol)
In the downlink direction, when PGW receives an IP packet destined to UE, it is processed against the available service data flows to decide the relevant EPS bearer which will carry the downlink IP packet. Once one SDF is matched, associated SDF template knows which EPS bearer this packet should be forwarded.
When a bearer modification happen, one more TFT is assigned to same bearer which already has one TFT. In scenario is known as TFT aggregation where multiple TFTs are associated with same EPS bearer. This usually happen when UE want to send by using a particular dedicated bearer rather than using default bearer. Default bearer may or many not have TFT.
