Getting started with Ethernet Switches

In actual use, an Ethernet switch generally does not require both parties to send and receive data at the same time. One-way transmission devices such as printers can be used in half-duplex or even single-ticket mode, and do not need to switch back, one-way transmission devices such as printers can be used in half-duplex mode or even in a single ticket, and do not need to be reversed.

In actual use, it is generally not necessary for both parties to send and receive data at the same time. One-way transmission devices such as printers can be used for half-duplex or even one-time work, and do not need to switch back. The switch can "Learn" the MAC address and store it in the internal address table. By creating a temporary exchange path between the initiator of the data frame and the Target receiver, the data frame can directly reach the destination address from the source address. The vswitch has a high-bandwidth back bus and an internal switching matrix.

All the ports of the vswitch are attached to the back bus. After the control circuit receives the data packet, the processing port searches for the address table in the memory to determine the hardware address of the target MAC Nic) NIC is mounted to which port, and data packets are quickly transmitted to the destination port through the internal switching matrix. If the destination MAC does not exist, the packets are broadcast to all ports, after receiving the port response, the switch "learns" the new address and adds it to the internal address table.

A vswitch can transmit data between multiple port pairs at the same time. Each port can be considered as an independent network segment, and the network devices connected to it enjoy all the bandwidth alone, so they do not need to compete with other devices. When node A sends data to node D.

Node B can send data to node C at the same time, and both transmission enjoy all the bandwidth of the network and all have their own virtual connections. A little different from the HUB. If we use a 10 Mbps Ethernet switch, the total traffic of the switch is 2 × 10 Mbps = 20 Mbps, when a 10 Mbps shared HUB is used, the total traffic of a HUB will not exceed 10 Mbps.

A hub is A shared device. The HUB itself cannot identify the destination address. When A host A in the same LAN transmits data to host B, data packets are transmitted in a HUB-based network in broadcast mode. Each terminal verifies the address information of the data packet header to determine whether to receive the data packets. That is to say, in this way, only a group of data frames can be transmitted over the network at the same time. If a collision occurs, retry. This is shared network bandwidth.

In a broad sense, there are two types of switches: WAN switches and LAN switches. WAN switches are mainly used in the telecom field to provide basic communication platforms. LAN switches are used in local networks to connect terminal devices, such as PCs and network printers.

The transmission media and transmission speed can be divided into Ethernet switches, Fast Ethernet switches, Gigabit Ethernet switches, FDDI switches, ATM switches, and wildcard ring switches. Large-scale applications can be divided into enterprise-level switches, department-level switches, and working group switches.

Generally, enterprise-level switches are rack-mounted, and department-level switches can have fewer rack-mounted slots) or fixed configurations, the working group-level switch is relatively simple with fixed configurations ).

On the other hand, from the perspective of application scale, enterprise-level switches support large enterprise applications with more than 500 information points as enterprise-level switches, and department-level switches support Switches of medium enterprises with less than 300 information points, switches that support less than 100 information points are working group-level switches.

The main functions of a vswitch include physical addressing, network topology, error verification, frame sequence, and traffic control. At present, the switch also has some new functions, such as support for VLAN Virtual LAN), support for Link aggregation, and even some also have firewall functions.

In addition to connecting to the same type of network, a vswitch can also interconnect different types of networks, such as Ethernet and Fast Ethernet. Nowadays, many vswitches can provide high-speed connection ports that support fast Ethernet or FDDI. These ports are used to connect other vswitches in the network or provide additional bandwidth for key servers with high bandwidth usage.

FDDI (Fiber Distributed Data Interface, Optical Fiber Distributed Data Interface) refers to the LAN standard defined by ANSI X3T9.5, which specifies the use of the token transmission network of the optical Fiber cable 1 0 0-M B p s, the maximum transmission distance is 2 kilometers. F d I uses a double ring structure to provide redundancy.

Compared with c d I and f d I Ⅱ, each port of the switch is used to connect an independent network segment, but sometimes to provide faster access speed, we can directly connect some important network computers to the port of the switch.

In this way, the key servers and important users of the network have a faster access speed and support greater information traffic. Switch switching mode:

Switches are switched in the following three ways:

1. pass-through:
A straight-through Ethernet switch can be understood as a line matrix telephone switch that is crossly And crossly between ports. When a packet is detected on the input port, it checks the packet header, obtains the destination address of the packet, and starts the internal dynamic search table to convert it to the corresponding output port, connect data packets at the intersection of input and output to the corresponding port to implement the switching function.

Because it does not need to be stored, the latency is very small and the exchange is very fast, which is its advantage. Its disadvantage is that because the data packet content is not saved by the Ethernet switch, you cannot check whether the transmitted data packet is incorrect and the error detection capability cannot be provided. Because there is no cache, the input/output ports with different rates cannot be directly connected, and packet loss is easy.

2. Storage forwarding:
Storage Forwarding is the most widely used method in the computer network field. It stores the data packets on the input port first, and then performs CRC cyclic verification) checks to obtain the destination address of the data packet after processing the error packet, convert a search table to an output port to send packets.

Because of this, the storage and forwarding method is insufficient when the data processing latency is large, but it can detect errors of data packets entering the switch, effectively improving network performance. In particular, it supports switching between ports at different speeds to ensure collaboration between high-speed ports and low-speed ports.

3. Fragment isolation:
This is a solution between the first two. It checks whether the length of the packet is 64 bytes. If it is smaller than 64 bytes, it indicates a false packet, the packet is discarded; if it is larger than 64 bytes, the packet is sent. This method does not provide data verification. It processes data faster than the storage and forwarding method, but is slower than the pass-through method.

Ethernet Switch Applications if your Ethernet has a large number of users, busy applications, and a variety of servers, and you have not made any adjustments to the network structure, the performance of the entire network may be very low. One solution is to add a 10/100 Mbps switch over Ethernet.

• Summary of test layer-3 switches
• In-depth analysis of vswitch MAC Address Access Control Problems
• Analyze the relationship between a wireless switch and a hub
• Can a smart switch replace a hub?
• Why does a wireless switch replace a hub?

It not only supports 10 Mbps of conventional Ethernet data streams, but also supports Mbps of Fast Ethernet connections. If the network usage exceeds 40% and the collision rate exceeds 10%, the switch can help you solve some problems. Vswitches with Mbps Fast Ethernet and 10 Mbps Ethernet ports can run in full duplex mode and can establish dedicated 20 Mbps to Mbps connections.