Get a demo board from chipset vendor to see if it meets your product requirement such as performance, compatibility, OS support, …etc.
Let’s use Realtek RTL8125BG/RTL8125BGS 10/100/1000M/2.5G Ethernet controller as one example. It combines a four-speed IEEE 802.3 compatible Media Access Controller (MAC) with a four-speed Ethernet transceiver, PCI
Express 2.1 bus controller, and embedded memory. It already has MAC and PHY hence we can make it in a small form factor using PCIe x1 slot. It supports ACPI, Vlan, and industry standard features, etc. As to OS support, it supports Windows and Linux.
– Bandwidth consideration: The transfer rate of 2.5G Ethernet is about 312.5MB/s(no deduction of header/protocol overhead). RTL8125 supports PCIe Gen2 x1 which is 0.5GB/s. Apparently, PCIe gen2 x1 slot is sufficient to accommodate transfer rate of 2.5G Ethernet.
-Connection:
RJ45(on the NIC) – RTL8125(on the NIC) – PCIe 2.1(on the NIC connects to PCIe x1 slot)
-Chipset/controller :
Realtek RTL8125BG/RTL8125BGS 10/100/1000M/2.5G Ethernet controller
-Physical interface specification:
RJ45 supports 10/100/1000M/2.5G
PCIe 2.1 x1
-PCB design: Get reference design and recommended AVL from chipset vendor to design your NIC.
-PCIe bracket: Full length, Low profile or both.
-Validation: SI, Reliability, shock & vibe, thermal, functionality, performance, system/OS compatibility, PXE boot, wake on lan,…etc.
-Driver support: Base on the driver from chipset vendor to modify to your own driver or leave it as is(simply using vendor’s drivers).