What is the relation between SDF and TFT at PGW/PCEF ?

Question

I read that when PGW's packet handler process maps an IP packet to a EPS bearer, it do DSCP marking.
And I also read DSCP marking is associated QCI of a bearer. How DSCP marking will help out to get maintained QoS of a bearer.

Answer 1

TFT stands for "Traffic flow template" and SDF stands for "Service data flow". At PGW/PCEF, each bearer has its own (Qos) requirements like ARP, QCI, bitrate.And each bearer can carry data of many applications.

One bearer has one TFT and multiple packet filters. But packet filter are in the order like.
Bearer 1 has packet filter 1 and packet filter 2.
Then bearer 2 will have packet filter 3.

When a packet receives at PGW. PGW cross checks this packet with all the packet filters with the evaluation order. when a particular packet filter matched then it pick the TFT and data send through the bearer to which TFT is associated.
Each packet filter is a SDF.

Answer 2

TFT (Traffic Flow template) is a filter or a template that is used to guide different packet Flows belonging to a particular service (SDFs) to be flowing through different EPS bearers using proper QoS.
In other words, A TFT maps/helps/guides SDFs to use the proper EPS bearers as a part QoS treatment.