We should only include Cluster-scoped traffic features in the `BackendCluster`.

[zhaohuabing]

We should only include Cluster-scoped traffic features in the BackendCluster.

	Traffic *ClusterTrafficFeatures `json:"traffic,omitempty" yaml:"traffic,omitempty"`

// ClusterTrafficFeatures holds the TrafficFeatures fields that translate to Envoy cluster (CDS)
// configuration - the ones applyTraffic consumes. These are the only fields safe to bake into a
// merged BackendCluster shared across routes; route/HCM-scoped features (rate limit, fault
// injection, etc.) live directly on TrafficFeatures instead.
//
// +k8s:deepcopy-gen=true
type ClusterTrafficFeatures struct {
	// load balancer policy to use when routing to the backend endpoints.
	LoadBalancer *LoadBalancer `json:"loadBalancer,omitempty" yaml:"loadBalancer,omitempty"`
	// Proxy Protocol Settings
	ProxyProtocol *ProxyProtocol `json:"proxyProtocol,omitempty" yaml:"proxyProtocol,omitempty"`
	// HealthCheck defines the configuration for health checking on the upstream.
	HealthCheck *HealthCheck `json:"healthCheck,omitempty" yaml:"healthCheck,omitempty"`
	// AdmissionControl defines the schema for admission control based on success rate.
	AdmissionControl *AdmissionControl `json:"admissionControl,omitempty" yaml:"admissionControl,omitempty"`
	// Circuit Breaker Settings
	CircuitBreaker *CircuitBreaker `json:"circuitBreaker,omitempty" yaml:"circuitBreaker,omitempty"`
	// Request and connection timeout settings
	Timeout *Timeout `json:"timeout,omitempty" yaml:"timeout,omitempty"`
	// TcpKeepalive settings associated with the upstream client connection.
	TCPKeepalive *TCPKeepalive `json:"tcpKeepalive,omitempty" yaml:"tcpKeepalive,omitempty"`
	// settings of upstream connection
	BackendConnection *BackendConnection `json:"backendConnection,omitempty" yaml:"backendConnection,omitempty"`
	// HTTP2 provides HTTP/2 configuration for clusters
	// +optional
	HTTP2 *HTTP2Settings `json:"http2,omitempty" yaml:"http2,omitempty"`
	// DNS is used to configure how DNS resolution is handled by the Envoy Proxy cluster
	DNS *DNS `json:"dns,omitempty" yaml:"dns,omitempty"`
}

// TrafficFeatures holds the information associated with the Backend Traffic Policy.
// +k8s:deepcopy-gen=true
type TrafficFeatures struct {
	// ClusterTrafficFeatures holds the cluster (CDS) scoped fields. Inlined, so serialization and
	// promoted field access (e.g. tf.CircuitBreaker) are unchanged.
	ClusterTrafficFeatures `json:",inline" yaml:",inline"`
	// RateLimit defines the more specific match conditions as well as limits for ratelimiting
	// the requests on this route.
	RateLimit *RateLimit `json:"rateLimit,omitempty" yaml:"rateLimit,omitempty"`
	// BandwidthLimit defines bandwidth limiting for the backend.
	BandwidthLimit *BandwidthLimit `json:"bandwidthLimit,omitempty" yaml:"bandwidthLimit,omitempty"`
	// FaultInjection defines the schema for injecting faults into HTTP requests.
	FaultInjection *FaultInjection `json:"faultInjection,omitempty" yaml:"faultInjection,omitempty"`
	// Retry settings
	Retry *Retry `json:"retry,omitempty" yaml:"retry,omitempty"`
	// ResponseOverride defines the schema for overriding the response.
	ResponseOverride *ResponseOverride `json:"responseOverride,omitempty" yaml:"responseOverride,omitempty"`
	// Compression settings for HTTP Response
	Compression []*Compression `json:"compression,omitempty" yaml:"compression,omitempty"`
	// HTTPUpgrade defines the schema for upgrading the HTTP protocol.
	HTTPUpgrade []HTTPUpgradeConfig `json:"httpUpgrade,omitempty" yaml:"httpUpgrade,omitempty"`
	// Telemetry defines the schema for telemetry configuration.
	Telemetry *BackendTelemetry `json:"telemetry,omitempty" yaml:"telemetry,omitempty"`
	// RequestBuffer defines the schema for enabling buffered requests
	RequestBuffer *RequestBuffer `json:"requestBuffer,omitempty" yaml:"requestBuffer,omitempty"`
}

Originally posted by @zhaohuabing in #9477 (comment)