Discover the Basic Components and Working Principles of Network Cards

Network cards play a crucial role in computer networking as hardware components, facilitating data transfer between computers and networks. This article delves into network cards' fundamental components and working principles, shedding light on their significance in computer networks.

Network cards comprise several key functional modules, including the Control Unit (CU), Output Buffer (OB), Input Buffer (IB), Line Coder (LC), Line Decoder (LD), Transmitter (TX), and Receiver (RX). These modules work in tandem to ensure seamless data transfer and communication management.

In addition, the network card also includes several key components such as interfaces, connectors, control chips, processors, memory and buffers. Among them, interfaces and connectors provide the physical connection that enables the network card to communicate with the computer system. The control chip and processor are responsible for the control logic and data processing functions of the network card. Memory and buffers are used to temporarily store data for efficient processing and transmission. For more details about network cards, please refer to What Is a Network Interface Card - NIC Definition, Function & Types.

Working Principles of Network Cards

A network card (network adapter) is a type of computer hardware used to manage data transmission between a computer and a computer network. The process of sending and receiving data involves the following steps:

Data Transmission

• 1. Data Encapsulation

• The application generates data and passes it to the transport layer (typically TCP or UDP), which adds port information and encapsulates it into segments. 

• The transport layer sends these segments to the network layer (usually the IP layer in TCP/IP models), where they are packed with source and destination IP addresses into packets.

• The network layer passes these data packets down to the control unit of the network card one by one. After CU receives data packets from the network layer, it encapsulates each data packet into a frame. The data frame encapsulated in Ethernet is the Ethernet Frame.

• 2. Digital Signal Conversion

• Data usually exists in the form of digital signals. Converters within the NIC transform these digital signals into a form suitable for the transmission medium, such as electrical signals, optical signals, or wireless signals.

• 3. Data Sending

• After transmitter receives the physical signal from line coder, it adjusts the power and other characteristics of the physical signal, and then sends the adjusted physical signal through the line. This might involve coordinating communication with other network devices, like switches or routers.

• In Ethernet technology, network cards typically use Carrier Sense Multiple Access with Collision Detection (CSMA/CD) protocol to avoid collisions on the network.

Data Reception

• 1. Signal Detection

• The network card monitors the transmission medium for signals. Upon detecting the appropriate signal (e.g., electrical for Ethernet or radio for wireless networks), the NIC begins to receive data. 

• 2. Analog to Digital Signal Conversion

• If the signal is analog (as in some wireless transmissions), an Analog-to-Digital Converter (ADC) within the network adapter converts it to a digital signal.

• 3. Frame Verification and Processing

• The network card checks the received frame for integrity, verifying the Frame Check Sequence (FCS) to ensure data integrity.

• The network adapter also checks the MAC address to determine if the frame is indeed intended for the machine, or if it's a broadcast or multicast that should be ignored.

• 4. Data Separation

• Once the frame is confirmed for the machine, link layer software extracts the packet from the frame and passes it up to the network layer.

• The network layer parses the IP information and forwards the packet to the correct transport layer protocol (TCP or UDP) as necessary.

• 5. Delivery to Application

• Data is eventually handed off from the transport layer to the respective application, often involving the process of passing data through the operating system kernel to the user-space application.

The process takes place within the framework of the TCP/IP protocol suite and represents typical data transmission in computer networks. In practical operation, network cards may also handle conflict avoidance, traffic control, error handling, and other network management functionalities. Moreover, advanced configurations such as Virtual Local Area Networks (VLANs) and Quality of Service (QoS) might involve additional processing by the network adapter.

Understanding the basic composition and working principles of network cards is crucial for comprehending the intricate processes behind efficient data transmission in computer networks. Network adapters, with their collaborative operations, enable seamless communication and data transfer. By grasping the underlying mechanisms of network cards, network administrators and enthusiasts can optimize network performance and troubleshoot potential issues effectively.