Comprehensive Explanation of Common Terminologies Related to Switches: Essential Knowledge for the Low - Voltage Electrical Industry
In the low - voltage electrical industry, switches are undoubtedly one of the most core and common devices. Whether it is building enterprise networks, campus networks, or data center networks, switches play a crucial role. However, to truly understand and utilize switches in depth, mastering the relevant professional terminologies is indispensable. Today, let's delve into the common and key terminologies related to switches to help you take your expertise in the low - voltage electrical field to the next level.
Switch
A switch is a key device used to implement switched networks. In the ISO OSI model, it is located at the second layer, the Data Link Layer. Its main function is to operate on frames and possesses intelligent processing capabilities. Unlike traditional hubs, switches can accurately forward data frames to the target port based on the destination MAC address, greatly improving network transmission efficiency and security.
Data Link Layer
The Data Link Layer is located at the second layer of the ISO/OSI reference model. It is responsible for the error - free transmission of data in frames over the lines between nodes. Through a series of means such as detection, flow control, and retransmission, it ensures that from the perspective of the Network Layer, the link appears error - free. This layer provides a reliable transmission foundation for the upper - layer network protocols, enabling data to be transmitted accurately and efficiently across the network.
IEEE 802.3
This is the basic standard for Ethernet, which defines the specifications for the Physical Layer and the Data Link Layer of Ethernet. It lays the foundation for the development of Ethernet technology. It specifies the frame format, transmission media, signal encoding, and other key elements of Ethernet, allowing Ethernet devices from different manufacturers to be compatible and communicate with each other.
IEEE 802.3u
The Fast Ethernet standard, which increases the transmission rate of Ethernet from 10 Mbps to 100 Mbps. It adopts a frame format and protocol similar to IEEE 802.3 but achieves higher transmission speeds by improving Physical Layer technologies, meeting the growing demand for network bandwidth.
IEEE 802.3ab
The Gigabit Ethernet (Unshielded Twisted Pair) standard, which allows Gigabit Ethernet transmission over ordinary Category 5 or Category 5e unshielded twisted pairs. The emergence of this standard makes it more convenient to deploy Gigabit Ethernet in existing network environments, reducing the cost of network upgrades.
IEEE 802.3z
The Gigabit Ethernet (Fiber and Copper Cable) standard, which not only supports fiber - optic media but also some high - performance copper media, such as Category 6 twisted pairs. It provides a wider range of transmission media options for Gigabit Ethernet, meeting the deployment needs of different scenarios.
IEEE 802.3x
The flow control standard, which aims to solve the problem of network congestion. When the network is congested, network devices can use predefined Pause frames for flow control, notifying the sender to pause data transmission, thus preventing further degradation of network performance.
IEEE 802.1X
The port - based access control standard, which provides a secure access control mechanism for the network. Through a three - part architecture consisting of a client, an authentication system, and an authentication server, it performs identity authentication on devices connected to the switch ports. Only authenticated devices can access network resources, effectively preventing the connection of unauthorized devices.
IEEE 802.1q
The VLAN standard, which allows a physical network to be divided into multiple logical Virtual Local Area Networks. Only hosts (switch ports) within the same VLAN can communicate with each other, while communication between different VLANs requires a router or a Layer 3 switch. VLAN technology improves network security and management flexibility.
IEEE 802.1p
The traffic priority control standard, which is used to classify the priority of data traffic in the network. By assigning different priorities to different types of traffic, it ensures that critical business traffic (such as voice and video) can be transmitted preferentially, improving the Quality of Service (QoS) of the network.
IEEE 802.1d
The Spanning Tree Protocol (STP), which is used to detect and eliminate loops in the network. When there are multiple connections between switches, STP automatically selects the most important connection as the active path and blocks the other connections as backup paths. When the main connection fails, STP can automatically activate the backup connection to ensure network connectivity without manual intervention.
Full - Duplex and Half - Duplex
In network transmission, full - duplex and half - duplex are two different communication modes. Full - duplex means that receiving and sending use two independent channels and can occur simultaneously without interference. Switches we usually refer to are typically full - duplex devices, capable of simultaneous bidirectional data transmission. Half - duplex, on the other hand, means that receiving and sending share a single channel, and only sending or receiving can occur at the same time. Therefore, conflicts may occur in half - duplex mode. Hubs are typical half - duplex devices.
MAC Address
The MAC address is the address used at the Media Access Control Layer, that is, the physical address of a network interface card (NIC, a local area network node). In the physical transmission process at the network bottom layer, hosts (local area network nodes) are identified by their physical addresses. MAC addresses are generally represented by 6 bytes (48 bits) and are usually globally unique, providing a unique identifier for network devices.
IP Address
An IP address is a 32 - bit address assigned to each host connected to the Internet. Through an IP address, we can access each host and realize communication in the network. IP addresses are divided into two versions, IPv4 and IPv6. With the development of the Internet, IPv6 is gradually becoming the mainstream to solve the problem of IPv4 address depletion.
Auto - Negotiation
The Auto - Negotiation standard allows switches to adapt to the working rate and mode in a certain order, which is 100M full - duplex, 100M half - duplex, 10M full - duplex, and 10M half - duplex. This function enables switches to automatically negotiate the best working parameters with connected devices, improving network compatibility and ease of use.
Full - Duplex Flow Control
Following the IEEE 802.3x standard, when the network is congested, network devices use predefined Pause frames for flow control. The sender will pause data transmission for a certain period after receiving a Pause frame, thus alleviating network congestion and ensuring stable network operation.
Half - Duplex Flow Control (Backpressure Technology)
Based on the IEEE 802.3x standard, when the processor detects that the buffer is about to fill up, it sends a fake collision signal to the source station, causing it to delay for a random time and then continue sending. This technology can alleviate and eliminate congestion, but its efficiency may be lower compared to full - duplex flow control.
Wire - Speed
Wire - speed refers to the theoretical maximum value of data forwarding by a switch, which reflects the data processing capability of the switch. In practical applications, the actual forwarding rate of a switch may be affected by various factors, such as network congestion and device performance.
Broadcast Storm Control
A broadcast storm is an abnormal phenomenon where the number of broadcast frames on the network (due to being forwarded) increases sharply, affecting normal network communication. Broadcast storms occupy a large amount of network bandwidth, causing the entire network to malfunction. The broadcast storm control function allows ports to filter broadcast storms on the network. When the number of broadcast frames received by a port reaches a predetermined threshold, the port will automatically discard the received broadcast frames, thus ensuring the normal operation of the network.
TRUNK (Port Aggregation)
TRUNK is usually used to aggregate multiple ports together to form a high - bandwidth data transmission channel. The switch treats all aggregated ports as a single logical port. Through port aggregation technology, network bandwidth and reliability can be improved, and load balancing and link redundancy can be achieved.
VLAN (Virtual Local Area Network)
A VLAN is a broadcast domain composed of a group of terminal workstations. Only hosts (switch ports) within the same VLAN can communicate with each other. VLAN technology can establish logical workgroups without considering the specific wiring structure, with advantages such as flexible configuration and increased system security. By using VLANs, devices from different departments or with different business functions can be divided into different virtual networks for isolation and management.
Port VLAN
A Port - based VLAN, where only ports within the same VLAN can communicate with each other. This VLAN division method is simple and intuitive and is suitable for scenarios with relatively fixed network structures.
Tag VLAN
Based on IEEE 802.1Q, it uses VIDs to divide different VLANs. A VLAN tag (Tag) is inserted into the data frame, and the VID in the tag is used to identify different VLANs, enabling data frames to be transmitted and exchanged between different VLANs.
VID (VLAN ID)
A VID is an identifier for a VLAN, used to represent a certain Tag VLAN. Through the VID, switches can identify and process data frames from different VLANs, realizing VLAN isolation and communication.
MTU VLAN
In the VLAN settings of a switch, each user's occupied port and the uplink port are divided into a separate VLAN. This VLAN division method can realize independent management and control of each user, improving network security and service quality.
MAC Address Aging Time
Switches' ports have the function of automatically learning addresses. The source addresses (source MAC addresses and switch port numbers) of frames sent and received through the ports are stored in the address table. The aging time is a parameter that affects the learning process of the switch. Timing starts from the moment an address record is added to the address table. If no frames with the source address of this MAC address are received by any ports within the aging time, these addresses will be deleted from the dynamic forwarding address table. Static MAC address tables are not affected by the address aging time.
Static Address Table
Static MAC addresses are different from dynamically learned MAC addresses. Once a static address is added, it will remain valid until it is deleted and is not subject to the maximum aging time. The static address table records the static addresses of ports, with one MAC address corresponding to one port. If set, all data sent to this address will only be forwarded to the corresponding port. This is also known as MAC address binding.
MAC Address Filtering
MAC address filtering is achieved by configuring filter addresses, allowing switches to filter data frames that are not expected to be forwarded. When a restricted MAC address is connected to the switch, the switch will automatically filter out frames with this address as the destination address to achieve security purposes. Addresses in the filter address table are valid for all switch ports. Addresses that have been added to the filter address table cannot be added to the static address table or dynamically bound to ports.
Dynamic MAC Address Binding
In the dynamic address binding state, a switch's port can dynamically learn MAC addresses, but the number of learnable addresses is limited. When the port learns a MAC address, it is immediately bound, and then the next address is learned. Bound addresses are not subject to the aging time and will remain valid. When the port learns a certain number of addresses, it will stop learning and binding. Bound MAC addresses will only be deleted when the port's address binding function is disabled or the switch is restarted.
Port Security
When port security is enabled on a certain port, the port will not learn new MAC addresses and will only forward data frames from learned MAC addresses. Other data frames will be discarded. The judgment condition is that for frames sent to the switch, if their source address is a member of the MAC address table of the port, they are allowed to be forwarded; otherwise, they will be discarded. When port security is set to "Disabled", the port will resume automatically learning new MAC addresses and forwarding received frames. The port security function can effectively prevent the connection of unauthorized devices and ensure network security.
Port Bandwidth Control
The input and output data transmission rates of each port (except module ports) can be limited through bandwidth control. Through port bandwidth control, network bandwidth can be reasonably allocated to prevent certain users or devices from occupying too much bandwidth and affecting the normal use of other users.
Port Monitoring
Port monitoring involves copying the packets from the monitored port to the monitoring port. A host with packet analysis software installed is connected to the monitoring port. Network administrators can analyze the collected data packets to perform network monitoring and troubleshoot network problems. The port monitoring function provides network administrators with a means to monitor network traffic in real - time and troubleshoot issues.
Cable Testing
When a suitable twisted - pair cable is connected to a switch port, the state of the twisted - pair cable can be tested through the switch to confirm whether there are any problems and where they occur. The cable testing function can help network administrators detect cable faults in a timely manner, quickly locate problems, and improve network maintenance efficiency.
SNMP
The Simple Network Management Protocol (SNMP) is an application - layer (Layer 7 of the OSI model) protocol used for remote monitoring and configuration of network devices. SNMP enables network management stations to read and modify the settings of gateways, routers, switches, and other network devices. Through SNMP, network administrators can realize centralized management and monitoring of network devices, promptly detect and solve network problems.
IGMP (Internet Group Management Protocol)
IP uses switches, multicast routers, and hosts that support IGMP to manage multicast communication. A group of hosts, routers (or switches), and members belonging to the same multicast group exchange multicast data streams, and all devices in the group use the same multicast group address. The IGMP Snooping technology significantly improves network utilization for applications such as video - on - demand. In the network, when performing IP multicast communication for various multimedia applications, unnecessary bandwidth usage can be reduced by setting IGMP on each port of the switch.
IEEE 802.1D/STP
The IEEE 802.1D Spanning Tree Protocol (STP) automatically disconnects loop connections when it detects loops on the network. When there are multiple connections between switches, only the most important connection is activated as the active path, and the other connections are blocked as backup paths. When the main connection fails, the Spanning Tree Protocol will automatically activate the backup connection to take over the work of the main connection without any manual intervention. The STP protocol ensures the reliability and stability of the network and avoids problems such as broadcast storms caused by loops.
IEEE 802.1X Authentication Protocol
The port - based network access control protocol. The architecture of this protocol is divided into three parts: the client, the authentication system, and the authentication server. Through the IEEE 802.1X authentication protocol, identity authentication of devices accessing the network can be realized. Only authenticated devices can access network resources, effectively improving network security.
Mastering these terminologies related to switches is of great importance for technicians engaged in the low - voltage electrical industry. They not only help us better understand and use switches but also play a crucial role in network planning, design, and maintenance. I hope that through this introduction, you can gain a deeper understanding of switches and provide strong support for your work in the low - voltage electrical field.
