Shield in connectors

[Freshman]

This is regarding the purpose of what is called as "shield" in connectors?

I want to understand why do we need "shield" in connectors and why is it required?

I happen to go through ethernet and saw the RJ45 connectors which has shield.

I read that the shield is just the outer metal casing of the RJ45 connector. But how it is connected to the chassis ground, I am not sure. Also, why it is required?

[selcuk]

The shield is the chassis part closest to the conductors inside the connector. Of course, you should bond it to the chassis to make it its part. It helps redirecting transient fault currents to the chassis ground. It decreases the emissions from the circuit by providing a good bonding with the chassis and the connector.

Some ethernet connectors have flexible fingers. Those are for making a reliable bond with the chassis. You may also connect the shield to the PCB ground via its leads. But using only PCB leads doesn't result in a reliable 360 degree bonding.

If you want to know about connecting the ethernet shield to the circuit ground, you may refer to Figure 17 and Table 5 on the below document. It shows EMC measurements for direct ground connections vs. capacitor, resistor, varistor etc.
https://www.we-online.com/catalog/media/o721297v410%20ANP116_Gigabit-Ethernet__EN.pdf