What speed do the UbiSwitch baseboard SFPs support?

BotBlox Hardware
1

– Copied from customer query –

Q1: What speeds does the 10Gbit ports on the UbiSwitch Baseboard support? 10G, 5G, 2.5G, 1G?

Q2: Does the SFP module only forward the speed that the baseboard support? Or does it do any conversion.

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There are two communication planes to consider when working with an SFP.

The first communication plane is between the SFP module and the device it is plugged into (in this case, UbiSwitch and the baseboard). This plane is referred to as the MAC plane. The second plane is between the SFP and the physical media that connects it to the other devices in your system. This plane is referred to as the PHY plane.

In most cases the speed of the MAC plane must match the speed of the PHY plane. As an example, take a 1000BASE-LX SFP like this. The PHY plane here is a 1000BASE-LX optical fiber; at 1000Mbps. For this, the MAC plane (that is, the plane that UbiSwitch Baseboard expects) needs to be 1000BASE-X.

The difference is, however, in using a 10GBASE-T SFP like this. The PHY plane here can vary from 100BASE-T, 1GBASE-T, 2.5GBASE-T and 10GBASE-T, which allows it to connect to a vast array of devices. The question here is, what should the MAC plane be? In this case, the MAC plane is fixed at 10GBASE-R.

This makes sense for a PHY plane that is 10GBASE-T, but what about when the PHY plane is, say, 1GBASE-T? In this case, data is interspersed on the MAC plane, meaning that even though the MAC plane is technically 10Gbps, data is only actually coming through at 1Gbps. The same thing happens at the other PHY speeds.

This protocol is all handled automatically when using a 10GBASE-T SFP with UbiSwitch + Baseboard. If you plug a 10GBASE-T SFP into the baseboard, you can then connect any speed device on the PHY plane, and it will work without and configuration. This is because, by default, those SFP ports on UbiSwitch + Baseboard are configured in 10GBASE-R mode, allowing it to work with any 10G SFP.

However, if you are using a different type of SFP (ie, not a 10G SFP), you will need to tell UbiSwitch to change the MAC speed. This is done using the command line interface on the 3.3V serial port on UbiSwitch. Here is a guide to using that serial port.