A Network Interface Card (NIC) is a hardware component that enables a computer or device to connect to a network. It provides the physical and logical interface for sending and receiving data over LANs (Local Area Networks), WANs (Wide Area Networks), or the internet. The network interface card (NIC) grew out of Ethernet, invented by Robert Metcalfe at Xerox PARC in 1973.
🧩 1. Types of NICs
| Type | Description | Use Case |
|---|---|---|
| Ethernet NIC | Wired connection via RJ-45 port; supports 10/100/1000 Mbps or 2.5G/5G/10G+ | Desktops, servers, routers |
| Wireless NIC (Wi-Fi) | Connects to wireless networks (802.11a/b/g/n/ac/ax/be) | Laptops, tablets, mobile devices |
| Fiber NIC | Uses SFP/SFP+ or QSFP ports for fiber-optic links | Data centers, high-speed servers |
| Virtual NIC | Software-defined NICs in virtual machines | Cloud computing, virtualization |
| Thunderbolt/USB NIC | External NICs via USB or Thunderbolt | Laptops without built-in Ethernet |
⚙️ 2. Key Specifications
- Speed: 10 Mbps → 100 Mbps → 1 Gbps → 2.5G/5G/10G/25G/40G/100G+
- Interface: PCIe (internal), USB/Thunderbolt (external), M.2 (laptops), or integrated on motherboard
- MAC Address: Unique hardware identifier for each NIC
- Duplex Mode: Full-duplex (send/receive simultaneously) vs half-duplex
- Offloading Features: TCP checksum offload, segmentation offload, etc. to reduce CPU load
🧠 3. Integrated vs Dedicated NICs
- Integrated NICs: Built into the motherboard (common in laptops and desktops)
- Dedicated NICs: Add-in cards (PCIe) for higher performance, redundancy, or specialized networking (e.g., 10GbE, RDMA)
🛠️ 4. NIC in System Architecture
- Connects to the CPU via PCIe bus
- Communicates with network stack in the OS
- Uses DMA (Direct Memory Access) to transfer data to/from RAM
- Works with switches, routers, and firewalls in the network
🔒 5. NIC Features in Modern Systems
- Wake-on-LAN (WoL): Power on a system remotely
- PXE Boot: Boot from network (used in enterprise deployments)
- VLAN Tagging: Supports virtual LANs for traffic segmentation
- QoS Support: Prioritizes traffic types (e.g., VoIP, video)
- SR-IOV: Virtual NICs for VMs with near-native performance
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