Acronyms and Abbreviations

• AutoSar: Automotive Open System Architecture
• SWC: Software Component
• BSW: Basic Software
• SOME/IP(SOMEIP): Scalable service-Oriented MiddlewarE over IP
• IPC: Inter Process Communication

Overview

SOME/IP:

• SOMEIP middleware has been proposed to solve the problem of service unification and remote invocation within a network. This middleware is loacated at the application layer.
• Each SWC can use the SOMEIP interface to interact whit other SWCs through someipd(SOMEIP-Deamon).

IPC:

• IPC refers to communication or information exchange between different processes. The methods include Pipline, FIFO, Semaphore, Socket, Streams and so on.
• In Autosar, IPC uses the protocol of SOME/IP and the CM implements the communication stack in BSW.

SOCAL:

• CM implements SOCAL, and the communication protocol is unified using SOME/IP protocol. So that either SWCs on the same ECU or SWCs on different ECUs can communicate via SOCAL without having to care the underlying communication method.

SOME/IP protocol

Applications can use SOME/IP to offer or acquire certain types of services. SOME/IP defines several service interface types:

Method

Methods are used for request/response communication patterns. They can be categorized into:

• Methods with return values: Client sends a request and expects a response
  • Synchronous calls: Client waits for response
  • Asynchronous calls: Client continues execution and handles response later
• Methods without return values (Fire & Forget): Client sends request without expecting response

Event

Events implement the publish/subscribe pattern:

• A consumer can subscribe to event messages from a provider
• The provider sends messages either:
  • Periodically at configured intervals
  • When event data changes
• Events are unidirectional (provider to subscriber)
• Multiple subscribers can receive the same event

Fields

Fields represent data elements that can be accessed remotely. They combine getter/setter methods with notifications:

1. Getter: Read access to field value

   • Client requests current value
   • Server responds with value

2. Setter: Write access to field value

   • Client sends new value
   • Server updates field
   • Optional response confirms update

3. Notification: Change notification for field value

   • Similar to events
   • Subscribers receive updates when field value changes
   • Can be configured for periodic updates

Message Structure

SOME/IP messages consist of:

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+---------------+----------------+----------------+----------------+
| Message Header| Request ID    | Protocol Ver   | Interface Ver  |
+---------------+----------------+----------------+----------------+
| Message Type  | Return Code   | Payload Length | Payload        |
+---------------+----------------+----------------+----------------+

• Message Header: Contains routing information
• Request ID: Identifies service and method
• Protocol Version: SOME/IP protocol version
• Interface Version: Service interface version
• Message Type: Request/Response/Notification/Error
• Return Code: Success/Error indication
• Payload: Actual data being transmitted

Service Discovery

SOME/IP includes a Service Discovery (SD) protocol that:

• Announces available services
• Handles service instance finding
• Manages subscribe/unsubscribe for events
• Supports service availability monitoring

Communication Patterns

SOME/IP supports multiple communication patterns:

1. Client/Server (Request/Response)
2. Publish/Subscribe (Events)
3. Fire & Forget (One-way messages)

These patterns can be used over various transport protocols:

• TCP for reliable communication
• UDP for efficient broadcast/multicast
• IPC for local communication