Describes the categories of vswitches.

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Describes the categories of vswitches.

Because a vswitch has many advantages, its application and development speed is much higher than that of a hub. There are various types of vswitches, mainly to meet the needs of different application environments. This article will introduce some mainstream categories of switches.

I. Division from network coverage

1. WAN switches

WAN switches are mainly used in wide-area networks in areas such as the interconnection of telecom man networks and Internet access. They provide basic communication platforms,

2. LAN switches

This type of switch is our common switch and also our learning focus. LAN switches are used in local networks to connect terminal devices, such as servers, workstations, hubs, routers, network printers, and other network devices. They provide high-speed independent communication channels.

In fact, LAN switches can be divided into multiple different types of switches. Next we will continue to introduce the main classification standards for LAN switches,

Ii. Division based on transmission media and transmission speed

Depending on the network transmission media used by the switch and the transmission speed, we can generally divide the LAN switch into Ethernet switch, Fast Ethernet switch, Gigabit (G bit) Ethernet switch, 10 Gigabit (10G bit) ethernet switch, FDDI switch, ATM switch, and ring switch.

1. Ethernet Switch

The first thing to note is that the "Ethernet switch" here refers to the Ethernet switch with bandwidth below Mbps, in fact, we will also talk about a "Fast Ethernet switch", "Gigabit Ethernet switch" and "10 Gigabit Ethernet switch" which are actually Ethernet switches, however, they adopt different protocol standards or transmission media, and their interface forms may also be different.

The swap switch is the most common and cheap. It has a complete range of grades and a wide range of applications. It can be seen in large and small LAN networks. Ethernet includes three network interfaces: RJ-45, BNC and AuI, the transmission media used are: twisted pair wire, thin coaxial cable and coarse coaxial cable. Do not think that Ethernet is a RJ-45 interface, but twisted pair cable type RJ-45 interface in the network equipment is very common. Of course, the current vswitches cannot be all BNC or AuI interfaces, because currently, the networks using coaxial cables as transmission media are seldom seen, generally, on the basis of RJ-45 interface, BNC or AuI interface is provided to balance the network connection of coaxial cable media. 1 shows a diagram of an Ethernet switch with RJ-45 and AuI interfaces.

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2. Fast Ethernet Switch

This type of switch is used for Mbps Fast Ethernet. Fast Ethernet is a network technology that implements Mbps transmission bandwidth on common twisted pair wires or optical fiber cables. It should be noted that fast Ethernet is regarded as a pure port with 10/100 MPs bandwidth. In fact, it is basically Mbps adaptive. In general, this type of Fast Ethernet switch usually uses a pair of wires. Some Fast Ethernet switches may leave a few fiber interfaces "SC" in order to ensure network interconnection with other optical transmission media ". Figure 2 shows a diagram of a fast Ethernet switch.

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3. Gigabit Ethernet Switch

A ge Ethernet switch is a new type of network, which is also called a "gigabit (GB) Ethernet ", that's because its bandwidth can reach 1000 Mbps. It is generally used for the backbone network segment of a large network, the transmission medium has two kinds of optical fiber, twisted pair wire, the corresponding interface is "SC" and "RJ-45" interface. Figure 3 shows two Gigabit Ethernet switch products.

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4. 10 Gigabit Ethernet Switch

The 10 Gigabit Ethernet switch is mainly used to adapt to the access of the 10 Gigabit Ethernet network. It is generally used on the backbone network segment and uses the optical fiber as the transmission medium. The interface method is also the optical fiber interface. This type of switch is also called a 10G Ethernet switch. At present, 10G Ethernet technology is still in the initial stage of research and development, and the price is very expensive (generally 2-9 US $). Therefore, the practical application of 10G Ethernet in various users is not very common, most enterprise users have already adopted a mature Gigabit Ethernet technology, and believe that this speed can meet enterprises' data exchange needs. Figure 4 shows a 10 Gigabit Ethernet switch. It can be seen that it uses all optical interfaces.

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5. ATM Switch

An ATM switch is a product used in an ATM network. Due to its unique technical characteristics, ATM networks are currently only widely used in backbone network segments of China Telecom and postal network. Therefore, its switch products are rarely seen in the market. For example, if we use the pppoa protocol in the ADSL Broadband Access method described below, we need to configure an ATM switch on the local terminal (NSP, the cable modem Internet access method of cable TV also uses an ATM switch at the local end. Its transmission medium generally uses optical fiber, interface type also has two kinds: Ethernet RJ-45 interface and optical fiber interface, these two kinds of interface is suitable for different types of network interconnection. Figure 5 is such an ATM switch. Compared with the inexpensive Ethernet switch, the price of the ATM switch is very high, so it cannot be found in the general area network.

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6. FDDI Switch

The FDDI technology was developed before the rapid Ethernet technology was developed. It mainly aims to solve the limitations of 10 Mbps Ethernet and 16 Mbps token network speed at that time, because its transmission speed can reach 100 Mbps, which is much higher than the first two speeds at that time, there was still a certain market at that time. However, it used optical fiber as the transmission medium at the time, which is much higher than the network cost of Dual-line transmission media. Therefore, with the successful development of the Fast Ethernet technology, FDDI technology also loses its market. Because of this, FDDI devices, such as FDDI switches, are rare. FDDI switches are used in the fast data exchange networks of small and medium-sized enterprises in the old age. Their interfaces are all optical interfaces, figure 6 shows a 3com FDDI switch.

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Iii. Application hierarchy

Based on the network layer applied by the vswitch, we can divide the network switch into five types: enterprise-level switch, campus network switch, department-level switch, Working Group switch, and table model switch.

1. enterprise-level switches

Enterprise-level switches are a type of high-end switches. They generally adopt a modular structure and can be used as the backbone of an Enterprise Network to build a high-speed LAN. Therefore, they are usually used at the top layer of an enterprise network.

Enterprise-level switches can provide customized services, priority queue services, and network security control, and quickly adapt to the needs of data growth and change, so as to meet user needs. For networks with more requirements, enterprise-level switches can not only transmit massive data and control information, but also provide hardware redundancy and software scalability to ensure reliable network operation. This type of switch clearly shows its own requirements from its location. At least the bandwidth and transmission rate are much higher than the average backplane capacity, therefore, enterprise-level switches are generally Ethernet switches over 1 Gigabit. Enterprise-level switches generally use fiber-optic ports to ensure high transmission rates. So what kind of switch can be called an enterprise-level switch? To be honest, there is no clear standard, but we usually think that if it is a backbone switch of an enterprise, the switch that can support more than 500 information points is an enterprise-level switch, 7 shows youxun's modular Gigabit Ethernet switch, which belongs to the enterprise-level switch category.

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Enterprise switches can also be connected to a large chassis. This chassis product usually supports many different types of components, such as fast Ethernet and large network relay, FDDI concentrator, licensing ring Mau and router. Enterprise switches are very useful in building enterprise-level networks, especially for networks that need to support some network technologies and previous systems. Based on the chassis equipment usually has very powerful management features, so it is very suitable for the environment of the enterprise network. However, the cost of chassis-based equipment is very high, and few small and medium-sized enterprises can afford it.

2. Campus Network Switch

Campus network switches, which are rarely used in large networks and are generally used as backbone switches of networks. This type of switch provides fast data exchange capability and full duplex capability, provides intelligent features such as fault tolerance, and supports expansion options and other functions such as VLAN in layer-3 switching.

This type of switch is usually used for the name of a scattered campus network. In fact, it does not have to be applied to a campus network, but only indicates that it is mainly used in a large network with scattered physical distance. Because the campus network is relatively scattered and the transmission distance is relatively long, in the backbone network segment, such switches usually use fiber or coaxial cable as the transmission medium, of course, the switch also needs to provide SC Optical Fiber port and BNC or AuI coaxial cable interface.

3. Department-level switches

A department-level switch is a switch for a department-level network. It is much smaller than the network scale that can be followed by the first two types. This type of switch can be fixed or module configuration. Generally, in addition to the common RJ-45 twisted pair interface, it also has an optical fiber interface. Department-level switches generally have outstanding smart features. They support port-based VLAN (Virtual LAN), which enables port management and can use full dual-or half-duplex transmission modes at will, you can control traffic and manage the network. You can configure, monitor, and test switches through the serial port of a PC or through the network. If it is used as a backbone switch, it is generally considered that the switch of medium-sized enterprises that support the following 300 information points is a department-level switch, as shown in Figure 8 is a department-level switch product.

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4. workgroup switches

The work group switch is an ideal replacement product for traditional hubs. It is generally fixed and has a certain number of 10base-t or 100base-tx Ethernet ports. The switch simply decides to forward information based on the MAC address of each packet. This forwarding decision generally does not consider the deeper information hidden in the packet. Different from a hub, the forwarding latency of A vswitch is very small, and the operation is similar to the performance of a single LAN, far exceeding the forwarding performance between common Bridging networks.

Working group switches generally do not have the network management function. If they are used as backbone switches, they are generally considered to support switches within 100 information points as working group-level switches. 9 shows a Fast Ethernet workgroup switch.

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5. desktop switches

A table-based switch, which is the most common low-end switch, is different from other switches. It supports a small number of MAC addresses per port and usually has a small number of ports (within 12 ports, but it is not absolute), only has the most basic switch features, of course, the price is also the cheapest.

Although this type of switch is the lowest in the entire switch, it still has the general superiority of the switch compared with the hub, and many application environments only need these basic performance, therefore, it is widely used. It is mainly used for office desktops of small or medium-sized enterprises. In terms of transmission speed, most desktop switches currently provide multiple ports with 10/100 Mbps adaptive capability. Figure 10 shows two desktop switches of different brands.

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4. Switch structure division

Based on the port structure of the vswitch, The vswitch can be roughly divided into two different structures: fixed port switch and modular switch. In fact, there is also a balance between the two, that is, a certain number of expansion slots or modules are provided on the basis of providing basic fixed ports.

1. Fixed port switch

As the name implies, the fixed port is fixed. If it is port 8, it can only have eight ports and cannot be added. 16 ports can only have 16 ports and cannot be expanded. Currently, vswitches with fixed ports are common and there is no clear rule on the number of ports. Generally, port 8, port 16, and port 24 are standard ports. But now the manufacturers have their own opinions. They think that the number of ports can be produced in the market. Currently, vswitch ports are relatively complex. The number of non-standard ports mainly includes four ports, five ports, 10 ports, 12 ports, 20 Ports, 22 ports, and 32 ports.

Although fixed port switches are relatively cheaper, they can only provide limited ports and fixed interfaces. Therefore, regardless of the number of users that can be connected, it also has certain limitations in terms of available transmission media. However, this type of switch is widely used in working groups and is generally applicable to small networks and Desktop Exchange environments. 11. Figure 12 shows the intention of a vswitch with port 16 and port 24 respectively.

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Fixed port switches are divided into desktop switches and rack-mounted switches due to their installation architecture. Like hubs, rack-mounted switches are easier to manage and more suitable for large-scale networks. Their structures must comply with 19 inch international standards, it is used to install in a Cabinet together with other switching devices, routers, servers, and so on. Table-based switches can only provide a small number of ports and cannot be installed in cabinets. Therefore, they are generally used only for small networks. Figure 13 and Figure 14 show a desktop fixed port switch and a rack-mounted fixed port switch.

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2. modular Switch

Modular switches are much more expensive, but with greater flexibility and scalability, users can choose a number of modules with different speeds and different interface types at will, to meet ever-changing network needs. In addition, most chassis switches have strong fault tolerance capabilities, support redundant backup of switching modules, and often have hot swappable dual power supply to ensure the power supply of switches. When selecting a vswitch, you should select the chassis or fixed mode based on the needs and funding considerations. Generally, enterprise-level switches should consider their scalability, compatibility, and troubleshooting. Therefore, chassis switches should be selected, while backbone switches and working group switches should have a single task, therefore, a simple and clear fixed switch can be used. 15 is a modular, Fast Ethernet switch with four pluggable modules, which can be flexibly configured as needed.

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5. Division based on the protocol layer of the switch

We know that all network devices work at a certain level of the OSI/RM open model. The higher the working level, the higher the technical level of the devices and the better the performance, the higher the grade. Also, with the development of the exchange technology, the switch has evolved from the second layer that originally worked in OSI/RM to the fourth switch that can work now, therefore, the protocol layer switches can be divided into Layer 2 switches, Layer 3 switches, and Layer 4 switches.

1. Layer 2 Switch

The L2 Switch is defined at the second protocol layer of OSI/RM, because it can only work at the layer-data link layer of the OSI/RM open system model. Layer 2 switches rely on link layer information (such as MAC addresses) to exchange the line rate between data on different ports. The main functions include physical addressing, error verification, frame sequence, and data flow control. This is the most primitive exchange technology product. Currently, table-based switches generally belong to this type, because table-based switches generally do not have a very complex job and are at the most basic layer of the network, therefore, you only need to provide the most basic data link function. Currently, Layer 2 vswitches are the most widely used (mainly for low prices and meeting the actual application requirements of small and medium-sized enterprises). They are generally used at the desktop level of small or medium-sized enterprises. As shown in Figure 16, it is a second-layer switch product. It should be noted that all switches are backward compatible at the protocol level, that is, all switches can work on the second layer.

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2. layer-3 Switch

The third layer is also defined by the network layer, which corresponds to the OSI/RM open system model. That is to say, this type of switch can work at the network layer, which is more advanced than the second layer switch, enhanced functions. Because the layer-3 Switch works at the network layer of the OSI/RM model, it has the routing function. It provides IP address information to the network path selection and implements line rate exchange of data between different network segments. When the network specification is large, it can be divided into small independent VLAN network segments based on special application requirements to reduce the impact of broadcast. Generally, these switches adopt a modular structure to meet the needs of flexible configuration. In large and medium-sized networks, layer-3 switches have become basic configuration devices. Figure 17 shows that 3Com is a layer-3 switch.

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3. layer-4 Switch

The layer-4 switch is a switch product developed using the layer-4 switch technology. Of course, it works on the layer-4 of the OSI/RM model, that is, the transport layer, directly facing specific applications. The layer-4 switch supports various protocols, such as HTTP, FTP, telnet, and SSL. Set up a virtual IP address (VIP) for each server group for search in the layer-4 switch. Each group of servers supports some application. Each application server address stored in the Domain Name Server (DNS) is a VIP address, rather than a real server address. When a user applies for an application, a VIP Connection Request (such as a tcpsyn packet) with the target server group is sent to the server switch. The server switch selects the best server in the group, replaces the VIP in the terminal address with the actual Server IP address, and sends the connection request to the server. In this way, all packets in the same range are mapped by the server switch and transmitted between the user and the same server. Shown in 18 is a layer-4 switch product. It can be seen that it also uses a module structure.

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The layer-4 exchange technology has obvious advantages over the original layer-2 and layer-3 exchange technologies. From the operational perspective, the layer-4 exchange technology is stable, because it controls the packet in the range from the source end to the destination end. On the other hand, a vro or layer-3 Switch only processes a single package. It is unclear where the previous package came from or where the next package came from. They only detect the TCP port numbers in the packet header, establish a priority queue based on the application, and the router determines the packet route based on the links and available nodes of the Network; the layer-4 switch determines the interval based on the available servers and performance. Currently, because this switching technology is not yet mature and expensive, layer-4 switches are rare in practical applications.

6. Based on whether the network management function is supported

If a vswitch supports network management, we can divide it into two categories: "Network Management" and "non-network management.

The task of a vswitch is to keep all the network resources in good state. Vswitch provides various network management methods based on the console, web pages, and telnet remote logon network. Therefore, the network administrator can perform local or remote real-time monitoring on the switch's working status and network running status, and manage the working status and working mode of all switch ports globally. The Network-managed switch supports the SNMP protocol. The SNMP protocol is composed of a set of simple network communication specifications. It can complete all basic network management tasks and has less demand for network resources, provides some security mechanisms ,. The working mechanism of the NMP protocol is very simple, and network information is exchanged mainly through various types of messages, namely, PDUS (protocol data units. However, vswitches are much more expensive than non-vswitches described below.

Vswitches use the embedded remote monitoring (rmon) standard to track traffic and sessions, which is effective for determining network bottlenecks and congestion points. The software agent supports four rmon groups (history, statistics, alarms, and events), enhancing traffic management, monitoring, and analysis. Statistics are general network traffic statistics, and historical statistics are network traffic statistics within a certain period of time. Alarms can be triggered when the preset limit value of network parameters is exceeded. Time indicates management events.

There are also vswitches that provide policy-based QoS (Quality of Service ). A policy is a rule that controls the behavior of a vswitch. The Network Administrator uses the policy to allocate bandwidth, priority, and control network access to the application stream, the focus is on the bandwidth management policies required to meet the service level agreement and the method of publishing policies to the switch. Multiple light emitting diodes (LEDs) that indicate port status, half duplex/full duplex, and 10 BaseT/100baset at each port of the vswitch, as well as systems and redundant power supplies (RPS) A comprehensive and convenient visual management system is formed by switching status LEDs with bandwidth utilization. Currently, most department-level switches are non-Network-managed. Only enterprise-level and a few department-level switches support the network management function. Figure 19 shows two network-managed switch products.

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We have introduced several mainstream classification methods of vswitches one by one. I believe you will have a basic and comprehensive understanding of the main types of vswitches.

 

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