How the Switch works

Switching technology is a simplified, low-cost, high-performance and high-end port-intensive exchange products, reflecting the bridging technology of the complex switching technology in the OSI Reference Model of the second layer of operation. Unlike the bridge, the switch forwarding delay is very small, the operation is close to the single LAN performance, far more than the normal bridge between the Internet forwarding performance.

The switching technology allows the bandwidth adjustment of the shared-type LAN segment to reduce the bottleneck of information flow between local area networks. There are now Ethernet, Fast Ethernet, FDDI and ATM technology exchange products.

Three kinds of switching technology

Port Exchange

Port switching technology first appeared in slot-type hubs, this type of hub backplane is usually divided into more than one Ethernet segment, without network bridge or router connection, the network is not connected. After the etheric main module is inserted, it is usually assigned to the network segment of a backplane, and the port exchange is used to distribute and balance the Ethernet module's port between the multiple network segments of the back bench. Depending on the level of support, the port can also be subdivided into:

* Module Exchange: The entire module for the network segment migration

* Port Group Exchange: Usually the ports on the module are divided into several groups, each set of ports allow network segment migration.

* Port level Exchange: Supports each port to migrate between different network segments. This switching technology is based on the first layer of OSI, and has the advantages of flexibility and load balancing. If properly configured, it can also be a certain degree of fault tolerance, but does not change the characteristics of the shared transport media, so it can not be called a real exchange.

Frame switching

Frame switching is the most widely used LAN Exchange technology, it provides the mechanism of parallel transmission through the differential segment of the traditional transmission medium, in order to reduce the conflict domain and obtain high bandwidth. Generally speaking, each company's products de implementation technology are migratory differences, but the network frame processing methods have a few:

* True Exchange: Provide wire speed processing capacity, the switch read only the first 14 bytes of the network frame, the network frame will be transferred to the corresponding fracture.

* Store Forwarding: Error and control by reading the network frame.

The former method is very fast, but lacks more advanced control over the network frame, lacks intelligence and security, and cannot support the exchange of ports with different rates. Therefore, the latter technology is the focus of the vendors.

The exchange of the letter element

ATM technology represents a dose of "medicine" for many of the problems in networks and communications. ATM uses a fixed-length 53-byte exchange of bytes. Because of the fixed length, it is easy to implement with hardware. ATM uses a dedicated, differential connection, running in parallel, that can be set up multiple nodes at the same time through a switch, but does not affect the communication capabilities between each node. ATM also allows communication between the source node and the target node. ATM uses the statistical time Division circuit to reuse, thus can greatly improve the utilization of the moral. ATM bandwidth can reach 25M, 155M, 622M, or even gigabytes of power.

Types and selection of LAN switches

LAN switches can be classified according to the network technology used:

* Ethernet Switch

* Token Ring Switch

*fddi switch

*ATM switch

* Fast Ethernet Switch switch

If the switch is divided according to the field of application, it can be divided into:

* Desktop Switch

* Workgroup Switch

* Trunk Switch

* Enterprise-Class Switches

* Segmented switch

* Port Switches

* Network switch