Next: How SOMEIP and SOMEIP-SD Work

SOMEIP and SOMEIP-SD developed by 宝马 at 2011, to over come the issue of "static data path" and "static data length" in Legacy Network Architecture as we said before.

Imagine we have two ECUs: one provides a service, while the other requires it.

The ECU that offers the service is referred to as the "Server" and the one that requests the service is called the "Client."

This network architecture is called Service-Oriented Architecture (SOA) because each ECU that holds information provides a service. Any other ECU that needs this service will communicate with the server to obtain the information it requires.

Remember that this architecture must support dynamic data paths and dynamic data lengths. Let's explore how SOMEIP and SOMEIP-SD facilitate these requirements!

How SOMEIP works:

1. Dynamic Path through "SOMEIP-Service Discover"

First, the server joins a multicast group using a specific multicast address.

Next, the server sends multicast messages to the network switch via this multicast address. If you’re unsure what this means, I will explain it in the next article.

The multicast address of the server looks like this (as captured through Wireshark):

These multicast messages include the SOMEIP-SD frame, allowing the server to offer all its available services, each identified by a unique Service ID.

On the other hand, the client joins the same multicast group using the same multicast address.

Then, the client sends multicast messages through this address to the network switch.

The multicast address of the client looks like this (as captured through Wireshark):

These multicast messages include the SOMEIP-SD frame, allowing the client to search for specific services using their respective Service IDs.

Because both the client and the server are in the same multicast group, they can discover each other. This process creates a dynamic path between the two ECUs at runtime!

As highlighted in the picture above, we can see that both ECUs have found each other, and the SOMEIP protocol comes into play!

I understand that this may seem challenging in a text format, but don't worry! In the next article, we’ll go through the same example together. ??

2. Dynamic Length through "SOMEIP":

After the two ECUs discover each other through SOMEIP-SD, they communicate using SOMEIP. The dynamic length feature is implemented through a serialize/de-serialize mechanism.

In the picture above, you can see the frame structure of a SOMEIP packet, including its length.

For more information about serialize/de-serialize, please refer to the AUTOSAR documentation for SOMEIP through this link: AUTOSAR DOCUMENT

Now, let’s have some fun! In the next article, I will provide you with hands-on experience on how to set up your machine to support VSOMEIP, which is the implementation of the SOMEIP protocol.

Prev: Look Inside ECU Next: Practicing on VSOMEIP