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What is traffic flow aggregate and traffic flow template ?? How those two are related ?

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What is traffic flow aggregate and traffic flow template ?? How those two are related ?
posted Aug 24, 2016 by Lavanya L

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1 Answer

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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.

answer Aug 25, 2016 by Harshita
thanks harshita
Similar Questions
0 votes

I am not sure whether my understanding is correct or not. As per my knowledge, UL-TFT at UE side takes care of IP packet to bearer mapping. I have seen many reference of LTE UE stack for user plane and found IP layer is just above the PDCP layer.
Packet filters are communicated to UE from the network using NAS signalling.
I just want to know where exactly/which layer is responsible to do bearer mapping at UE side.

+1 vote

Few doubts about TFT -
1. What is the role of TFT in LTE is it just limited at PGW or more then that.
2. How this is applied at PGW.

+3 votes

Lets say UE has two bearers established - default and dedicated. Each has its own APN
How is traffic differentiated between these two bearer and on what basis?

Say APN = A for default bearer
APN = B for dedicated bearer

Say APN A has default bandwidth of 200 kbps

Say UE is sending packets beyond bandwidth of 200 kbps, will it use dedicated bearer? Who decides this?

Thanks.

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