What is an in-vehicle Ethernet switch?

An in-vehicle Ethernet switch is a device that has multiple ports for connecting to ECUs, sensors, cameras, etc., and builds a network by interconnecting these devices.
It is designed to communicate or control transfers using MAC FRAMES for interconnection and ensure the communication quality required for automobiles. The Automotive Ethernet Switch fulfills the role of Layer 2 of the OSI reference model, and handles the layer one level higher than the Automotive Ethernet PHY.

The main function of an in-vehicle Ethernet switch is to check the received FRAMES and then forward it according to the FRAMES type.

The in-vehicle Ethernet switch checks the contents of the Ethernet FRAMES and forwards it accordingly.
The FRAMES configuration for this transfer process is as follows:
*For details on FRAMES structure, please refer to Ethernet FRAMES (Technical Column).

• Ethernet FRAMES (Technical Column)

• Preamble

Leading signal for synchronization

• SFD

Area indicating the start of FRAMES

• TPID

Area showing whether or not a tag is present

• TCI

Area for storing priority and VLAN number

• Type

Areas that control protocols (such as IPv4)

• FCS

Area used for error checking

The number of communication partners varies depending on the type of data being communicated, so different transfer methods are used.

• Unicast

A method of transferring data by specifying one destination.

• Multicast

A method of transferring data by specifying multiple destinations.

• broadcast

A method of transferring data to an unspecified number of recipients (all destinations).
Executed when the destination MAC address is FF:FF:FF:FF:FF:FF.
*MAC address is a unique identifier for network-connected devices.

In-vehicle Ethernet switches have functions called "VLAN," "QoS," and "ACL" to improve communication quality.

• VLAN

It virtually separates or combines physically connected networks.
This increases the security level of the network and reduces congestion.

• QoS

QoS (Quality of Service) performs priority control and bandwidth control according to packet priority.

• ACL

An ACL (Access Control List) is a list for controlling communication Access.
Decide to pass/discard any FRAMES.