For these computers, you do not need to purchase a network card if you plan on using a wired connection. Whether you're upgrading a workstation, scaling a small business network, or building out a hyperscale data center, a fiber network card (NIC, network interface card) is one of the most critical components for connectivity. Copper Ethernet NICs still have their place, but when bandwidth, distance. NIC → the technical term for a network interface card, usually PCIe or onboard. Answer first: choose a NIC or adapter by the required medium, link modes, port and connector, host bus bandwidth and slot wiring, driver and operating-system support, offloads, queues, timing or RDMA needs, thermals. Small Form-factor Pluggable, or SFP, is a hot-swappable optical communication transceiver. This can be over Ethernet (RJ45) or Wi-Fi, and different cards might have different hardware on board to support different use cases. At this point, I have internet from Orange (in Poland) via optical fiber.
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