?The principle of switch is what?Switches, what does it do?
what is the
Switch (English: Switch, meaning "Switch ")Is a kind of network equipment for the electrical signal forward.It can provide access switches of any two nodes of electrical signal pathway.The most common switch Ethernet switches.Other common and telephone voice, optical switch, etc.
exchange (switching) is based on the needs of information communication on both ends of the transmission, using artificial or equipment automatically, to transfer the information to meet the requirements on the corresponding routing technology.According to the working position is different, can be divided into the wan and LAN switch.Wide-area switch (switch) is a complete the function of information exchange in communication system equipment, its application in data link layer.Switches have multiple ports, each port has the function of the bridge, can connect a local area network (LAN) or a high performance server or workstation.In fact, the switch is sometimes referred to as multiple port Bridges.
in a computer network system, the exchange of the concept is put forward to improve the Shared work mode.And HUB HUB is A Shared equipment, the HUB itself does not recognize the destination address, host A to host B when the same local area network data transmission, data packets in with the architecture of the HUB is broadcast on the network mode of transmission, by every one terminal via validation data in baotou address information to determine whether to accept.That is to say, in this way of working, the same time can only transmit a set of data frames on the network of communication, if a collision have to try again.This way is Shared network bandwidth.Popular said, ordinary switch is not with the function of management, a root into line, other interface from the computer.
switches transfer mode has full duplex, half duplex, full duplex/half duplex adaptive.
of full duplex refers to switch in sending data will also be able to receive data at the same time, both synchronized, we usually call it seems, also can hear each other voice of speech.Full duplex switches are currently supported.Full duplex delay is small, the benefits of fast.
work in data link layer, the principle of switch has a very high bandwidth of the back of the bus and internal exchange matrix.All switch ports are articulated in the back on the bus, the control circuit receives packets, deal with port looks for in memory in order to determine the destination MAC address table (network adapter hardware address) of the NIC (NIC) articulated in which port, through internal exchange matrix quickly to send the packet to the destination port, if the destination MAC does not exist, broadcast to all ports, exchange opportunities & after receiving port to respond to otherLearning "New address, and put it as a supplement to internal MAC address table.Using switches can also keep the network "Piecewise "By contrast the IP address table, only allows the necessary network traffic through the switch.Through switches filtering and forwarding, can effectively reduce the collision domain, but it can't be divided radio network layer, namely the broadcast domain.Switches can be carried out at the same time between multiple ports for data transfer.Each port can be regarded as independent of the physical network segment (note: the IP network segment), connected to the network device alone enjoy full bandwidth, do not need to compete with other equipment to use.When the node A to node D send data, node B can send data to the node C at the same time, and it all has two transmission network bandwidth, have their own virtual connection.If used here is 10 MBPS Ethernet switch, the switch at this moment in circulation is equal to 2 ×10 MBPS = 20 MBPS, while using 10 MBPS Shared HUB, a HUB in circulation will not exceed 10 MBPS.To sum up, switch is a kind of based on MAC address identification, can finish the packaging forward data frames function of network equipment.Switches can "Learning "MAC address, and keep it in the internal address table, through between the originator of a data frame and target receivers to establish a temporary switching path, make the data frame directly by the source address to reach the destination address.
switch of main functions, including physical addressing, network topology, error checking, frame series, and flow control.Switches also has some new features, such as the support of VLAN (virtual local area network), support for link together, and even some still have the function of the firewall.
study: Ethernet switches to understand each port connected device's MAC address, and will address together with the corresponding port mapping in switches in the cache MAC address table.
forward/filter: when the purpose of a data frame address mapping in the MAC address table, it is forwarded to connect the port of destination node instead of all ports, such as the data frame is broadcast/multicast frame is forwarded to all ports).
eliminate loop: when the switch includes a redundant circuit, Ethernet switch by avoiding loop of spanning tree protocol, while allowing existing backup path.
switch in addition to able to connect to the same type of network, also can be in different types of network (such as Ethernet and fast Ethernet) between the interconnection.Today many switches are able to provide support fast Ethernet and FDDI high speed connection, used to connect to other switches in the network or the key server bandwidth consumption big provide additional bandwidth.Every port
in general, switches used to link a separate network segments, but sometimes in order to provide faster access speed, we can put some important network computer directly connected to the switch port.In this way, the key of the network server and important users have faster access speed, support more information flow.
finally the basic function of a brief summarize of switches:
1. Like hubs, switches, provides a large number of available for cable connection port, it can be used in a star topology wiring.
2. Such as Repeaters, hubs and bridge, when the frame forwarding, exchange opportunities to produce a distortionless square electrical signals.
3. Like Bridges, switches, all use the same on each port forwarding or filtering logic.
4. Like Bridges, switches, local area network can be divided into multiple collision domains, each collision domain is independent of the broadband, thus greatly improving the bandwidth of local area network (LAN).
5. In addition to the function of Bridges, hubs and Repeaters, switches also provides a more advanced features, such as virtual local area network (VLAN) and higher performance.