A method for traffic forwarding in communication networks, the method comprising: receiving, by a base station of a communication network, a PDU session establishment request from a user equipment, UE, wherein the PDU session establishment request comprises a single network slice selection assistance information, NSSAI, a quality of service, QoS, indicator and an allocation and retention priority, ARP; mapping, by the base station, the single NSSAI to a flow label field of a header based on the QoS indicator and the ARP; transmitting (323, 331), by the base station, the PDU session establishment request along with the flow label field to a session management function, SMF, via an access and mobility function, AMF, of the communication network; selecting, by the SMF, a specific slice link function, SLF, based on the flow label field received in the PDU session establishment request; transmitting, by the SMF, the PDU session establishment request along with the flow label field to the specific SLF; transmitting, by the specific SLF, the single NSSAI of the PDU session establishment request to a data plane application function, DPAF, of the communication network; converting, by the DPAF, network slice information of the single NSSAI of the PDU session establishment request into QoS transport characteristics; comparing, by the DPAF, the QoS transport characteristics of the single NSSAI with QoS transport characteristics of NSSAIs in the DPAF of the communication network; transmitting, by the DPAF, a PDU session establishment response via the SMF and the AMF to the UE for establishing data flow using the single NSSAI in response to the QoS transport characteristics of the single NSSAI matching the QoS transport characteristics of the NSSAI in the DPAF of the communication network; and transmitting, by the DPAF, the PDU session establishment response via the SMF and the AMF to the UE for establishing data flow using a new NSSAI in response that the QoS transport characteristics of the single NSSAI not matching the QoS transport characteristics of the NSSAI in the DPAF of the communication network. receiving, by a base station of a communication network, a PDU session establishment request from a user equipment, UE, wherein the PDU session establishment request comprises a single network slice selection assistance information, NSSAI, a quality of service, QoS, indicator and an allocation and retention priority, ARP; mapping, by the base station, the single NSSAI to a flow label field of a header based on the QoS indicator and the ARP; transmitting (323, 331), by the base station, the PDU session establishment request along with the flow label field to a session management function, SMF, via an access and mobility function, AMF, of the communication network; selecting, by the SMF, a specific slice link function, SLF, based on the flow label field received in the PDU session establishment request; transmitting, by the SMF, the PDU session establishment request along with the flow label field to the specific SLF; transmitting, by the specific SLF, the single NSSAI of the PDU session establishment request to a data plane application function, DPAF, of the communication network; converting, by the DPAF, network slice information of the single NSSAI of the PDU session establishment request into QoS transport characteristics; comparing, by the DPAF, the QoS transport characteristics of the single NSSAI with QoS transport characteristics of NSSAIs in the DPAF of the communication network; transmitting, by the DPAF, a PDU session establishment response via the SMF and the AMF to the UE for establishing data flow using the single NSSAI in response to the QoS transport characteristics of the single NSSAI matching the QoS transport characteristics of the NSSAI in the DPAF of the communication network; and transmitting, by the DPAF, the PDU session establishment response via the SMF and the AMF to the UE for establishing data flow using a new NSSAI in response that the QoS transport characteristics of the single NSSAI not matching the QoS transport characteristics of the NSSAI in the DPAF of the communication network.