What Is a Fiber-Optic Switch?

Fiber switch is a kind of high-speed network transmission relay equipment, also known as Fibre Channel switch and SAN switch. Compared with ordinary switches, it uses fiber optic cable as the transmission medium. The advantages of optical fiber transmission are fast speed and strong anti-interference ability. There are two main types of fiber switches. One is the FC switch used to connect to the storage. The other is an Ethernet switch. The port is a fiber-optic interface. It has the same appearance as an ordinary electrical interface, but the interface type is different.

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1. In the description and 6 access switches, it can adapt to the scale of 120 to 150 networks.

Switch (Switch) means "switch" is a kind of network equipment used for electrical (optical) signal forwarding. It can provide an exclusive electrical signal path for any two network nodes of the access switch. The most common switch is an Ethernet switch. Other common ones are telephone voice switches and fiber switches. Switching is a collective term for technologies that send information to be transmitted to the corresponding routing that meets the requirements according to the needs of the two ends of the communication to transmit information, either manually or automatically. The switches can be divided into WAN switches and LAN switches according to different working positions. A wide-area switch is a device that performs information exchange functions in a communication system. It is applied at the data link layer. The switch has multiple ports, each of which has a bridging function, and can be connected to a LAN or a high-performance server or workstation. In fact, switches are sometimes referred to as multi-port bridges.

The Layer 2 switch works at the second layer of the OSI reference model, the data link layer. The CPU inside the switch will form a MAC table by mapping the MAC address to the port when each port is successfully connected. In future communications, packets destined for this MAC address will only be sent to its corresponding port, not all ports. Therefore, the switch can be used to divide the data link layer broadcast, that is, the collision domain; but it cannot divide the network layer broadcast, that is, the broadcast domain. The switching technology operates in the second layer of the OSI seven-layer network model, the data link layer. Therefore, the switch forwards data packets based on the MAC (Media Access Control) address--the physical address. For the IP network protocol, it is transparent, that is, the switch does not know or need to know the IP addresses of the source machine and the sink machine when it forwards the data packets. It only needs to know its physical address, which is the MAC address. During the operation of the switch, the switch will continuously collect data to create its own address table. This table is quite simple. It shows on which port a MAC address is found. Therefore, when the switch receives a TCP / IP data, When the packet is received, it will look at the destination MAC address of the packet, and check its address table to confirm which port the packet should be sent from. Because this process is relatively simple, and this function is performed by a brand new hardware-ASIC (Application Specific Integrated Circuit), it is quite fast. Generally it only takes tens of microseconds. The switch can decide where an IP data packet should be sent. . It is worth mentioning: In case the switch receives an unknown packet, that is, if the destination MAC address cannot be found in the address table, the switch will "spread" the IP data packet, that is, it will send it from every Submitted in the port, just as the switch is processing a received broadcast packet. The weakness of a Layer 2 switch is that it is not very effective in processing broadcast packets. For example, when a switch receives a broadcast packet from a TCP / IP workstation, it will pass the packet to All other ports, even if some ports are connected to IPX or DECnet workstations. In this way, the bandwidth of non-TCP / IP nodes will be negatively affected. Even if the same TCP / IP nodes have the same subnet as the subnet of the workstation sending the broadcast packet, they will have no original source. If they receive network broadcasts that have nothing to do with them for no reason, the efficiency of the entire network will be greatly reduced. Since the 90's, LAN switching devices have appeared. From the perspective of network switching products, there are roughly three types of switching products: port switching, frame switching, and cell switching.

Port switching technology first appeared in slot-type hubs. The backplane of such a hub is usually divided into multiple Ethernet segments (each network segment is a broadcast domain), and each network segment is connected through a bridge or router. After the Ethernet module is inserted, it is usually assigned to a certain network segment on the backplane. Port switching is suitable for assigning the ports of the Ethernet module among multiple network segments on the backplane. In this way, network management personnel can allocate users between different network segments according to the load of the network. This switching technology is based on the first layer (physical layer) of OSI. It does not change the characteristics of the shared transmission medium, so it is not a real exchange.

Frame switching is currently the most widely used LAN switching technology. It provides a mechanism for parallel transmission by segmenting traditional transmission media, reducing the collision domain of the network, and thus obtaining higher bandwidth. There are differences in the technologies used by different manufacturers to implement frame exchanges, but generally there are two ways of processing network frames: store-and-forward and straight-through. Store-and-Forward: When a data packet enters a switch with this technology, the switch will read enough information to not only determine which port will be used to send the packet, but also Decide whether to send the packet. This can effectively exclude those defective network segments. Although this method is not as fast as the exchange rate using straight-through products, they can eliminate the often harmful consequences caused by corrupted data packets. Cut-Through: When a data packet enters a switch using this technique, its address will be read. It will then be sent regardless of whether the packet is in the wrong format. Since only the first few bytes of a data packet are read, this method provides a greater number of exchanges. However, all packets, even those that may be corrupted, will be sent. Until the receiving station can detect these corrupted packets and ask the sender to resend. But if the network interface card fails, or the cable is defective, or if there is an external signal source that can cause data packet corruption, errors will be very frequent. With the development of technology, the straight-through exchange will be gradually phased out. In the "straight-through" switching method, the switch reads only the first few bytes of the network frame, and then transmits the network frame to the corresponding port. Although the switching speed is fast, it lacks advanced control of the network frame and has no intelligence. At the same time, it can not support the exchange of ports with different speeds; the "store and forward" exchange method uses error detection and control on the reading of network frames.

The basic idea of cell switching is to use fixed-length cells for switching, so that hardware can be used for switching, which greatly improves the switching speed, and is especially suitable for the effective transmission of multimedia signals such as voice and video. At present, the actual application standard of cell switching is ATM (Asynchronous Transmission Mode), but the ATM equipment is more expensive to manufacture, and its application in the local area network has been gradually replaced by the Ethernet frame switching technology.