What is TFT (traffic flow template)

In the realm of cellular networks adhering to 3GPP (3rd Generation Partnership Project) standards like LTE (Long-Term Evolution) and 5G NR (New Radio), TFT stands for Traffic Flow Template. It's a crucial element within the Packet Data Convergence Protocol (PDCP) layer, acting as a filter that maps incoming data flows onto specific EPS bearers (Evolved Packet System bearers) within the network.

Understanding EPS Bearers:

• EPS bearers are logical data channels established within the core network to carry user data traffic (e.g., internet browsing, video streaming) between the user equipment (UE) and the core network.
• Different EPS bearers can be configured with specific QoS (Quality of Service) parameters like priority and guaranteed bit rate to cater to the varying needs of different data traffic types.

The Role of TFT:

• A TFT acts as a set of packet filters that define the criteria for assigning incoming data packets from the UE to appropriate EPS bearers. These filters are based on various packet characteristics, including:
  • IP Addresses: Source and/or destination IP addresses can be used to identify specific traffic flows.
  • Port Numbers: Source and/or destination port numbers can be used to differentiate between different applications or services generating the data traffic.
  • Protocol Identifiers: Protocol identifiers within the packet header can be used to filter specific types of traffic (e.g., TCP, UDP).

Benefits of Using TFTs:

• Traffic Prioritization: By mapping specific traffic types to dedicated EPS bearers with appropriate QoS settings, TFTs enable network operators to prioritize critical traffic (e.g., voice calls, video conferencing) over less time-sensitive traffic (e.g., email, file downloads).
• Efficient Resource Allocation: TFTs help ensure efficient utilization of network resources by assigning data flows to EPS bearers that match their specific requirements.
• Improved User Experience: By prioritizing critical traffic and efficiently managing resource allocation, TFTs contribute to a smoother and more responsive user experience for various applications and services on the mobile network.

Dynamic TFT Management:

• TFTs are typically configured and managed by the network operator.
• The specific filters and mappings within a TFT can be dynamically adjusted based on real-time network conditions and user needs.
• Additionally, some network deployments might utilize pre-defined TFT templates for specific traffic types, simplifying configuration and ensuring consistent handling of common traffic categories.

Complementary Roles with TFC (Transport Format Combination):

• While TFTs operate at the PDCP layer for traffic flow mapping, TFC (Transport Format Combination) operates within the physical layer, defining how data is encoded and transmitted on the radio channel. Both concepts play crucial roles in optimizing data flow within cellular networks.

Conclusion:

TFTs are essential components for managing data traffic flow within 3GPP cellular networks. By acting as filters that map data to appropriate EPS bearers, TFTs enable network operators to prioritize traffic, allocate resources efficiently, and contribute to an improved user experience for various mobile data services. Understanding TFTs is vital for grasping the mechanisms employed by cellular networks to manage and optimize data traffic flow.