Application viewpoint: Development and Evolution of switches and bridges

There are many things worth learning about switches and bridges. Here we mainly introduce the development and evolution of switches and bridges, also known as bridges, which are storage and forwarding devices connected to two local networks, it can be used to connect a network system with identical or similar architecture. This not only expands the distance or range of the network, but also improves the performance, reliability, and security of the network.

The bridge works at the data link layer, connects two LANs, and forwards Frames Based on the MAC address. It can be seen as a "low-layer Router" working at the network layer, based on Network addresses such as IP addresses ).

Vswitch

A switch is a set-line device that leads the network system. Most switches and bridges operate on Layer 2 of the data link layer of the OSI reference model. If the hub is regarded as a built-in Ethernet bus, the switch can be regarded as an interconnected system consisting of multiple Bus switches. Each vswitch port corresponds to a backboard bandwidth Bus Core Bus that is an order of magnitude higher), and the backboard Bus is connected to a Switch Engining engine. Data Packets between different ports are transferred to the switching engine through the backplane bus, and are exchanged through the storage forwarding, pass-through forwarding, and quasi-pass-through forwarding modes.

Development and Evolution of switches and bridges

In the middle of 1980s, the first LAN bridge entered the market. In the initial stage, the bridge is mainly used for LAN segmentation, transmission distance extension, and application devices. In addition, the LAN breaks through the limit of shared network bandwidth. To enable LAN to meet the current application requirements, you need to expand the LAN system. To make the network system more reliable, a LAN system is divided into several independent physical network segments. The need to connect physical network segments and expand LAN systems leads to the development of bridges. It can be said that at that time, the bridge was successfully used.

With the rapid development of microelectronics ASIC, processor and storage technology, the chip technology of bridge is becoming more and more advanced, and the technology and product of bridge have been continuously developed and upgraded. The network system design requires that high-performance bridges have multiple ports. With the simultaneous development of requirements and microelectronics technology, the design and manufacturing of multi-port bridges with 8, 12, 16, and 24 ports will become possible after 1990s. It is worth noting that the difference between the bridge and the switch lies in the market, not the technology. A switch performs network segmentation in the same way as a bridge. A switch is a multi-port bridge. Specifically, bridges with high port density are called LAN switches. The real difference between a switch and a bridge lies in the difference between a switch and an old bridge.

Differences between a vswitch and a bridge

The basic functions of a LAN switch are the same as those of a bridge. It supports Frame Forwarding, frame filtering, and Tree Algorithm generation. However, the switch and the bridge still have the following differences:

1. When a vswitch is working, it actually allows the channel between many group ports to work simultaneously. Therefore, the functions of switches and bridges are not only a bridge function, but also a set of functions of multiple bridges. That is, the bridge generally has two ports, and the switch has a high-density port.

2. Differences in Segmentation

Because the vswitch supports multiple ports, you can divide the network system into more physical network segments, so that the entire network system has higher bandwidth. The bridge only supports two ports. Therefore, the physical network segments of the bridge are quite limited.

3. Differences in transmission rates

The data transmission rate of A vswitch is faster than that of a bridge.

4. Differences in data Frame Forwarding Methods

Before a bridge sends a data frame, it usually receives the complete data frame and executes the frame detection sequence (FCS) before forwarding the data frame. The vswitch and the bridge have two Frame Forwarding modes: storage forwarding and direct forwarding. Before sending data, direct forwarding does not require waiting time after receiving the complete data frame and the 32-bit Cyclic Redundancy checksum CRC calculation check.