Implements the SDAP Protocol.

For PDUs received from the PDCP layer, extracts SDAP headers (if present), restores the associated QoS Flow based on QFI, and forwards the resulting SDUs to the upper layer (IP, Ethernet, or application for unstructured sessions).

For SDUs received from the upper layer, performs QFI-to-DRB mapping, encapsulates the data with SDAP headers if needed, and forwards the packets to the PDCP layer. On the gNB DL path, the QFI is always taken from the QfiReq tag (set by GtpUser). On the UE UL path two sources may answer: the classified QFI (the QfiReq tag, stamped by QosFlowClassifier's rules or set by the application directly) and a reflective QoS match, the rule derived from observed downlink traffic. When both answer, reflectiveQosOverridesQfi says which wins; one alone is used as-is; a packet with neither joins the default QoS flow (QFI 0, the default DRB).

Whether a bearer's packets carry an SDAP header is the control plane's decision, delivered per bearer in the pushed configuration (computed by BearerConfigurator: a header is needed exactly when the QFI could not be recovered from the DRB alone on the RX side, unless the configuration suppresses it -- see the suppressSdapHeader entry field there). On a headerless bearer both ends agree on the one QFI it carries -- its sole mapped QFI, or QFI 0 when none is mapped: RX assigns that value to every packet, and TX verifies each packet against it, stopping with an error when another QoS flow shows up.

Flows of the D2D machinery are outside SDAP and pass through this module untouched in both directions: their bearers are peer-keyed, carry no QoS flows, and Ip2Nic assigns them (3GPP sidelink has its own SL-SDAP over PC5, which is not modeled). This holds in either mode -- a D2D-capable pair's flow keeps its ownership while in infrastructure mode, since the mode switch tears down and re-establishes within that machinery.

Supports all 3GPP PDU session types (IPv4, IPv6, Ethernet, Unstructured) via the pduSessionType field of the bearer configuration.

SDAP does not author its own configuration: the QFI-to-DRB mapping and the per-bearer SDAP settings are authored network-wide (see the staticDrbs parameter of BearerConfigurator), delivered to RRC, and pushed into this module from there at initialization.

Gates:

• upperLayerIn/upperLayerOut: connects to the upper layer (Ip2Nic or app).
• pdcpIn/pdcpOut: connects to the PDCP layer.

Inheritance diagram

The following diagram shows inheritance relationships for this type. Unresolved types are missing from the diagram.

Parameters

Name	Type	Default value	Description
nodeRole	string		Node role: "UE" or "gNB" - determines reflective QoS behavior
bearerConfiguratorModule	string	"bearerConfigurator"
establishBearersOnDemand	bool	true	When false, a packet that finds no established bearer raises an error instead of establishing one (static bearers are established up front; see the staticDrbs parameter of BearerConfigurator)
reflectiveQosTableModule	string	""	UE only: path to ReflectiveQosTable module (empty = disabled)
useReflectiveQos	bool	false	UE only
reflectiveQosOverridesQfi	bool	false	UE only: when a packet has both a classified QFI (QfiReq tag) and a reflective QoS match, true = the reflective QFI wins, false = the classified one; a packet with only one of the two always uses it

Properties

Name	Value	Description
display	i=block/layer

Gates

Name	Direction	Size	Description
upperLayerIn	input		From upper layer (Ip2Nic or app)
upperLayerOut	output		To upper layer (Ip2Nic or app)
pdcpIn	input		From PDCP layer
pdcpOut	output		To PDCP layer

Source code

//
// Implements the SDAP Protocol.
//
// For PDUs received from the PDCP layer, extracts SDAP headers (if present),
// restores the associated QoS Flow based on QFI, and forwards the resulting SDUs
// to the upper layer (IP, Ethernet, or application for unstructured sessions).
//
// For SDUs received from the upper layer, performs QFI-to-DRB mapping,
// encapsulates the data with SDAP headers if needed, and forwards the packets
// to the PDCP layer. On the gNB DL path, the QFI is always taken from the
// QfiReq tag (set by GtpUser). On the UE UL path two sources may answer: the
// classified QFI (the QfiReq tag, stamped by ~QosFlowClassifier's rules or set
// by the application directly) and a reflective QoS match, the rule derived
// from observed downlink traffic. When both answer, reflectiveQosOverridesQfi
// says which wins; one alone is used as-is; a packet with neither joins the
// default QoS flow (QFI 0, the default DRB).
//
// Whether a bearer's packets carry an SDAP header is the control plane's
// decision, delivered per bearer in the pushed configuration (computed by
// ~BearerConfigurator: a header is needed exactly when the QFI could not be
// recovered from the DRB alone on the RX side, unless the configuration
// suppresses it -- see the suppressSdapHeader entry field there). On a
// headerless bearer both ends agree on the one QFI it carries -- its sole
// mapped QFI, or QFI 0 when none is mapped: RX assigns that value to every
// packet, and TX verifies each packet against it, stopping with an error when
// another QoS flow shows up.
//
// Flows of the D2D machinery are outside SDAP and pass through this module
// untouched in both directions: their bearers are peer-keyed, carry no QoS
// flows, and ~Ip2Nic assigns them (3GPP sidelink has its own SL-SDAP over
// PC5, which is not modeled). This holds in either mode -- a D2D-capable
// pair's flow keeps its ownership while in infrastructure mode, since the
// mode switch tears down and re-establishes within that machinery.
//
// Supports all 3GPP PDU session types (IPv4, IPv6, Ethernet, Unstructured)
// via the pduSessionType field of the bearer configuration.
//
// SDAP does not author its own configuration: the QFI-to-DRB mapping and the
// per-bearer SDAP settings are authored network-wide (see the staticDrbs
// parameter of ~BearerConfigurator), delivered to RRC, and pushed into this module from
// there at initialization.
//
// Gates:
//  - upperLayerIn/upperLayerOut: connects to the upper layer (Ip2Nic or app).
//  - pdcpIn/pdcpOut: connects to the PDCP layer.
//
simple NrSdap like INrSdap
{
    parameters:
        string nodeRole @enum("UE","gNB");  // Node role: "UE" or "gNB" - determines reflective QoS behavior
        string bearerConfiguratorModule = default("bearerConfigurator");
        bool establishBearersOnDemand = default(true);  // When false, a packet that finds no established bearer raises an error instead of establishing one (static bearers are established up front; see the staticDrbs parameter of ~BearerConfigurator)
        string reflectiveQosTableModule = default("");  // UE only: path to ReflectiveQosTable module (empty = disabled)
        bool useReflectiveQos = default(false); // UE only
        bool reflectiveQosOverridesQfi = default(false);  // UE only: when a packet has both a classified QFI (QfiReq tag) and a reflective QoS match, true = the reflective QFI wins, false = the classified one; a packet with only one of the two always uses it
        @display("i=block/layer");
    gates:
        input upperLayerIn;     // From upper layer (Ip2Nic or app)
        output upperLayerOut;   // To upper layer (Ip2Nic or app)
        input pdcpIn;           // From PDCP layer
        output pdcpOut;         // To PDCP layer
}

File: src/simu5g/stack/sdap/NrSdap.ned

---

This documentation is released under the Creative Commons license