Brief introduction and application analysis of switch technology

Classification and function of switch

The switch is the "cornerstone" of the network platform, also known as the network switch. It is also a kind of hub, but it is quite different from the common hub function. A common hub only acts as a data-receiving transmission, while a switch can intelligently analyze packets and send them selectively. For example: We send out a batch of packets that are dedicated to someone, and if they are in a network environment that uses a common hub, everyone can see the packet. In a network environment where the switch is used, the switch will analyze who the packet is sent to and then pack and encrypt it, at which point only the recipient of the packet can receive it.

Broadly speaking, switches are divided into two types: WAN switches and LAN switches. The wide area network switch is mainly used in the telecommunication field and provides the basic platform for communication. The LAN switch is applied to local area network, which can be used to connect terminal equipment, such as PC and network printer. From transmission media and transmission speed can be divided into Ethernet switches, Fast Ethernet switches, Gigabit Ethernet switches, FDDI switches, ATM switches and Token ring switches. From the scale application can be divided into enterprise-class switches, departmental switches and workgroup switches. The scale of the vendors is not exactly the same, generally speaking, the enterprise switches are racks, departmental switches can be rack (fewer slots), or fixed profiles, and workgroup-level switches are fixed profiles (simpler). On the other hand, from the size of the application, as a backbone switch, the switch that supports more than 500 information points for large enterprise applications is a class switch, and the switches that support the 300 information points for the following midsize enterprises are departmental switches, while the switches that support 100 information points are team-level switches. If not specified below, the switch referred to is a LAN switch.

As we all know, the switch works on the second layer of the OSI Reference Model-the data link layer, the main functions include physical address, network topology, error checking, frame sequence and flow control. Physical address (corresponding to the network address) defines the device in the data link layer of the way of addressing; The network topology includes the description of the data link layer, defines the physical connection mode of the equipment, such as the star topology or the bus topology, and so on. The upper-level protocol alarm with error check to transmit error The data frame sequence collates and transmits frames other than sequences, and the streaming control slows down the transmission of the data so that the receiving device does not crash because it receives more information than it can handle at a given moment. At present, the switch also has some new features, such as the VLAN support, support for the link convergence, and even some of the features of the firewall, which is the third layer of the function of the switch. The so-called third-tier switch is to increase the routing function when VLAN partitioning is based on protocol.

Current situation and trend analysis of switch technology

The third tier exchange is the key to adopting an intranet, which combines the advantages of a second-tier switch and a third-tier router into a flexible solution that delivers wire-speed performance at all levels. This integrated architecture also introduces policy management attributes that not only associate the second tier with the third tier, but also provide traffic prioritization, security, and a variety of other flexible features such as link aggregation, VLAN, and dynamic deployment of the intranet. The third layer switches are divided into interface layer, switching layer and routing layer.

The interface layer contains all the important LAN interfaces: 10/100m Ethernet, Gigabit Ethernet, FDDI, and ATM. The switching layer integrates a variety of LAN interfaces, supplemented by policy management, and provides link pooling, VLAN, and tagging mechanisms. The routing layer provides the primary LAN routing protocol: IP, IPX, and AppleTalk, and provides a third-tier forwarding technology for traditional routing or passthrough through policy management. Policy Management and administration enables network administrators to tailor the network to the specific needs of the enterprise.

Relative to the third layer, the level of the second layer is decided by the so-called network control classification, a pure second-tier solution, is the cheapest solution, but it in the division subnet and broadcast restrictions, such as the least control. Third-tier switches provide dynamic integration support for all levels in the classification. Traditional general-purpose routers can do the same with external switches, but the third tier switches require less configuration, smaller space, less cabling, cheaper prices, and higher and more reliable performance than the solution.-----

The third layer switch basically has all the functions of the traditional switch, with the third layer switch as the standard, the switch specific technology realization includes:

1. Programmable ASIC

ASIC is dedicated to optimize the second layer of processing of the dedicated integrated circuit, is the core of today's networking solution, it integrates a number of functions on a chip, with simple design, high reliability, low power consumption, higher performance and lower cost advantages.

2. Distributed pipeline

With distributed pipelining, multiple distributed forwarding engines can transmit packets independently and quickly. In a single pipeline, multiple ASIC chips handle multiple frames at the same time. This concurrency and pipelining improves forwarding performance to a new level: Unicast, Broadcast (broadcast), and multicast (multicast) line-speed performance on all ports.