UDS Communication Model

UDS communication follows the Client–Server model.

Client

The client role in UDS communication is typically performed by a Diagnostic Tester (also called a diagnostic tool). It initiates communication by sending request messages and then receives one or more diagnostic responses from servers.

In some cases, a request may be forwarded by a Gateway ECU to another ECU. When this happens, the Gateway ECU temporarily assumes the role of a client within that subnetwork.

Performance and Error Handling

Time parameters defined by ISO standards on the client side:

• P2Client

• P2*Client

• P3Client_Phys

• P3Client_Func

• P6Client

• P6*Client

Server

The server role in UDS communication is always performed by Electronic Control Units (ECUs). A server receives diagnostic requests and provides the corresponding diagnostic responses.

Performance and Error Handling

Time parameters defined by ISO standards on the server side:

• P2Server

• P2*Server

• P4Server