1. Deployment Model: Dapr and Linkerd have different deployment models. Dapr is designed to be a runtime that is embedded within the application, enabling developers to write their applications without being tightly coupled to any specific infrastructure or platform. On the other hand, Linkerd is a service mesh that operates as a separate layer in the infrastructure, intercepting network traffic between services and providing observability, security, and reliability features.

2. Service Discovery: Dapr and Linkerd differ in their approaches to service discovery. Dapr relies on external service discovery mechanisms, such as Kubernetes' DNS-based discovery or Consul, to locate and connect to other services. Linkerd, on the other hand, has its own integrated service discovery mechanism that automatically generates a registry of services based on the Kubernetes API, simplifying the service-to-service communication.

3. Traffic Routing: Dapr and Linkerd handle traffic routing differently. Dapr relies on sidecar proxies to handle inbound and outbound traffic, allowing developers to define routing rules and policies using service invocation patterns. Linkerd, on the other hand, uses its own data plane proxy to transparently route traffic between services based on a set of predefined rules and policies configured in the control plane.

4. Protocol Support: Dapr and Linkerd have different levels of protocol support. Dapr provides a pluggable model that allows developers to use various protocols for communication between services, including HTTP, gRPC, and Pub/Sub. Linkerd, on the other hand, primarily focuses on HTTP-based protocols and provides features such as HTTP/2 and WebSocket support, while also working with gRPC.

5. Fault Injection: Dapr and Linkerd differ in their fault injection capabilities. Dapr provides built-in support for injecting faults, such as delays, retries, and failures, into service interactions, allowing developers to test the resilience of their application. Linkerd, on the other hand, offers more advanced fault injection capabilities through its traffic control policies, allowing operators to simulate latency, errors, and timeouts at the network layer.

6. Security: Dapr and Linkerd also differ in their security features. Dapr provides a secure communication model by default, using mutual TLS authentication between services, while also offering encryption at rest for state management. Linkerd, on the other hand, provides security features such as mutual TLS authentication, access controls, and request-level encryption for securing communication within the service mesh.

In summary, Dapr and Linkerd differ in their deployment models, service discovery approaches, traffic routing mechanisms, protocol support, fault injection capabilities, and security features.