Switch

Switch is a used for signal transmitted network equipment. It can be for the two random access switches provide exclusive network nodes signal pathways. The most common switches is Ethernet switches. Other common speech and telephone switches, optical switch etc.

Switching is according to the need of both ends to transfer information communication, use manual or automatic equipment complete method to the information transmitted to comply with the requirements of the corresponding technical routing collectively. The generalized switches (switch) it is a kind of complete information exchange communication system function of equipment. In computer networks [1] systems, exchange concept of improved sharing work mode. We've been introduced to the HUB on A Shared equipment is, on itself cannot identify the destination address, when the same in LAN A host to B host data transmission, packet in on the Internet for architecture is broadcast mode, by every one terminal through validation data baotou address information to determine whether to receive. That is to say, in this way of working under the same time on the network can only transmit a set of data frame of communications, if a collision still have to try again. This way is sharing network bandwidth.

The principle

Switches have a high bandwidth on the back of the bus and switching. Switch all ports are articulated in this bar back on the bus, control circuit receives packets, after processing port will find its address in memory cross-references to determine purpose MAC (NIC hardware addresses) NIC (nics) articulated in which ports, through packet switching quickly will transmit to the destination port, the purpose MAC without an radio to all ports, receiving port response after exchange opportunity "learning" new address, and make it added to internal MAC address list.

Use switches also can put network "segmentation", through contrast MAC address list, switches only allowed necessary network flow through switches. Through the filter and forwarding, switches can effectively isolate the broadcast storm, reduce packet and wrong bag by mistake, avoid sharing the emergence of conflict.

Switches at the same time on multiple ports for data transfer between. Each port can be an independent network segment, links in the network equipment enjoys all alone, without the bandwidth of the competition with other equipment use. When the node to A node D sending data, node B can simultaneously to the node C send data, and this two transmission network is entitled to full bandwidth, have own virtual connections. If used here is 10Mbps Ethernet switches, then the switch when the total circulation equals 2 x 10Mbps = 20Mbps, while the use of a Shared on 10Mbps, a on the total circulation also won't exceed 10Mbps.

Anyhow, the switch is a recognition based on MAC address, can finish the encapsulation forward packets function of network equipment. Switches can "learning" MAC address, and its internal address table, stored in a data frame through the initial goals and receiver to construct temporary switching path, make a data frame directly from the source address to the destination address.

Technology development history

The origin

In 1993, LAN exchange equipment appear, 1994, domestic lifted in the exchange of network technology boom. Actually, switching technology is a simplifying, low prices and high performance and high-end mouth dense characteristics of exchanging products, reflected the bridging technology complicated exchange technology in the OSI reference model of the second operation. With a bridge, as per a bag of switch MAC address relative simply forwarding decision information. And this kind of forwarding decision not generally consider bag hidden in the deeper other information. With a bridge different is switch forwarding delay is small, operating close to a single LAN performance, far exceeding ordinary bridging between Internet forwarding performance.

Exchange technology allows sharing type and special LAN segment for bandwidth adjustment, in order to reduce LAN between the bottleneck problem of the information circulation appear. Now existing Ethernet, fast Ethernet and ATM technology, FDDI exchange products.

Similar tradition of a bridge, switches provide many network interconnection function. Switch can economical network into smaller conflict domain, for every workstation provide higher bandwidth. Agreement in the transparency of making switches software configuration simple cases directly mounted on multi-protocol network, Switches use existing cable, Repeaters, hubs and station nic, need not be top hardware upgrades, Switches for the workstation are transparent, so that the management overhead cheap, simplified network nodes are added, mobile and network changes operation.

Use special design of integrated circuit can make the switch to line rate in all ports parallel to forward information, offers than traditional a bridge much higher operating performance. Such as theory of individual Ethernet port containing 64 octal number of packets, can provide 14880bps transmission rate. This means that one has 12 port, support 6 word parallel data stream "line speed" Ethernet switches must provide the overall 89280bps throughput rate (6 X14880bps/tao tao traffic flow). Application-specific integrated circuit technology makes the switch in more ports with afore-mentioned performance under the condition of the operation, its port cost less than traditional a bridge.

Artificially exchange

The history of signal exchange shall be traced back to the early telephone appear. When the telephone was invented, only need a root long enough at the end of the wire, plus two telephone, can cause the distant from two personal phonetic conversation.

Telephone more, want to make each have telephone can communicate, but we can't every two telephone between pull on a line. So they set up the telephone office, every phone users connect a line to the telephone office of a major printed circuit board. When A hope and B conversation, he begged for central operator connected B phone. Operator with A wire, A inserted in A receiving circuit boards hole, and the other end plug to B hole, which is "in", equivalent to temporary give A and B pull A phone line, when both sides can talk to each other. When a call is completed, the operator will wire removed, it is a "take out stitches." The whole process is "artificial exchange", it is actually a "close the switch on the" and "disconnect switch" process. Therefore, the "exchange" translated as "switch" technically easier to understand.

Circuit of SPC exchanges

Artificially exchange inefficient, cannot satisfy the needs of large-scale deployment telephone. With semiconductor technology development and switch circuit technology maturity, people find can use electronic technology substitution artificially exchange. Telephone terminal user as long as to send a string of electrical signals of electronic equipment, electronic equipment can according to the predetermined programme, will request and the requested circuit connected, and exclusive this circuit, not Shared with third parties (of course, of design flaws's sake, may appear people sharing circuit, photonsof ".fortunately "). This kind of exchange method called "program-controlled exchange". This equipment is also "pabx".

Because of program-controlled exchange technology long-term by developed countries monopoly, equipment expensive, our telephone is always is not high. As in huawei, zte communications enterprise in succession independently developed pabx, phone in our rapid popularity.

At present, the voice of SPC exchanges with the widespread use of communication protocol for ss7 (Signalling System No. 7)

Ethernet switches

Along with the computer and Internet technology (also known as the so-called "network") to the rapid development of Ethernet became so far short of the second highest popularity of computer network. Which Ethernet the core component is Ethernet switches.

Whether artificially exchange or program-controlled exchange, all is for the sake of transmission of speech signal, it is need exclusive line "circuit switching". Which Ethernet is a computer network, is needs to be transmitted data and therefore USES is the "packet. But no matter what kinds of exchange between two ways, switches for providing "exclusive access" characteristics will not change. Just Ethernet device is concerned, switches and hub of substaintial distinction is that when A send message to B, if through hub, then access all the network nodes hub will receive this message (i.e. to broadcast sent), just nics in hardware level will not send the machine filter out the information; And if through switches, unless A notice switches, otherwise the radio to B C will never receive information acquisition switch control privileges and (except in the case of surveillance).

At present, Ethernet switches manufacturers according to the market demand, launched three layer even 4 layer switches. However, its core function is still 2 Ethernet packet switching, just with a certain processing IP layer even more high-rise packet ability.

Optical switching

Optical switching is people are developing the next generation of exchange technology. Now all the switching technology is based on the signal, even if the current fiber switches is first will light signals into electrical signals, after a swap deal, after turn back light signals sent to another root of optical fiber. Because of photoelectric conversion rate is low, at the same time circuit processing speed exist in physics bottleneck, so people hope designed an without a photoelectric conversion "light switches", its internal not circuit but light path, the logical original not switch circuit but switch light path. This will greatly improve the switches processing rate.

Switch is a used for signal transmitted network equipment. It can be for the two random access switches provide exclusive network nodes signal pathways. The most common switches is Ethernet switches. Other common speech and telephone switches, optical switch etc.Switching is according to the need of both ends to transfer information communication, use manual or automatic equipment complete method to the information transmitted to comply with the requirements of the corresponding technical routing collectively. The generalized switches (switch) it is a kind of complete information exchange communication system function of equipment. In computer networks [1] systems, exchange concept of improved sharing work mode. We've been introduced to the HUB on A Shared equipment is, on itself cannot identify the destination address, when the same in LAN A host to B host data transmission, packet in on the Internet for architecture is broadcast mode, by every one terminal through validation data baotou address information to determine whether to receive. That is to say, in this way of working under the same time on the network can only transmit a set of data frame of communications, if a collision still have to try again. This way is sharing network bandwidth.The principleSwitches have a high bandwidth on the back of the bus and switching. Switch all ports are articulated in this bar back on the bus, control circuit receives packets, after processing port will find its address in memory cross-references to determine purpose MAC (NIC hardware addresses) NIC (nics) articulated in which ports, through packet switching quickly will transmit to the destination port, the purpose MAC without an radio to all ports, receiving port response after exchange opportunity "learning" new address, and make it added to internal MAC address list.Use switches also can put network "segmentation", through contrast MAC address list, switches only allowed necessary network flow through switches. Through the filter and forwarding, switches can effectively isolate the broadcast storm, reduce packet and wrong bag by mistake, avoid sharing the emergence of conflict.Switches at the same time on multiple ports for data transfer between. Each port can be an independent network segment, links in the network equipment enjoys all alone, without the bandwidth of the competition with other equipment use. When the node to A node D sending data, node B can simultaneously to the node C send data, and this two transmission network is entitled to full bandwidth, have own virtual connections. If used here is 10Mbps Ethernet switches, then the switch when the total circulation equals 2 x 10Mbps = 20Mbps, while the use of a Shared on 10Mbps, a on the total circulation also won't exceed 10Mbps.Anyhow, the switch is a recognition based on MAC address, can finish the encapsulation forward packets function of network equipment. Switches can "learning" MAC address, and its internal address table, stored in a data frame through the initial goals and receiver to construct temporary switching path, make a data frame directly from the source address to the destination address.Technology development historyThe originIn 1993, LAN exchange equipment appear, 1994, domestic lifted in the exchange of network technology boom. Actually, switching technology is a simplifying, low prices and high performance and high-end mouth dense characteristics of exchanging products, reflected the bridging technology complicated exchange technology in the OSI reference model of the second operation. With a bridge, as per a bag of switch MAC address relative simply forwarding decision information. And this kind of forwarding decision not generally consider bag hidden in the deeper other information. With a bridge different is switch forwarding delay is small, operating close to a single LAN performance, far exceeding ordinary bridging between Internet forwarding performance.Exchange technology allows sharing type and special LAN segment for bandwidth adjustment, in order to reduce LAN between the bottleneck problem of the information circulation appear. Now existing Ethernet, fast Ethernet and ATM technology, FDDI exchange products.Similar tradition of a bridge, switches provide many network interconnection function. Switch can economical network into smaller conflict domain, for every workstation provide higher bandwidth. Agreement in the transparency of making switches software configuration simple cases directly mounted on multi-protocol network, Switches use existing cable, Repeaters, hubs and station nic, need not be top hardware upgrades, Switches for the workstation are transparent, so that the management overhead cheap, simplified network nodes are added, mobile and network changes operation.Use special design of integrated circuit can make the switch to line rate in all ports parallel to forward information, offers than traditional a bridge much higher operating performance. Such as theory of individual Ethernet port containing 64 octal number of packets, can provide 14880bps transmission rate. This means that one has 12 port, support 6 word parallel data stream "line speed" Ethernet switches must provide the overall 89280bps throughput rate (6 X14880bps/tao tao traffic flow). Application-specific integrated circuit technology makes the switch in more ports with afore-mentioned performance under the condition of the operation, its port cost less than traditional a bridge.Artificially exchangeThe history of signal exchange shall be traced back to the early telephone appear. When the telephone was invented, only need a root long enough at the end of the wire, plus two telephone, can cause the distant from two personal phonetic conversation.Telephone more, want to make each have telephone can communicate, but we can't every two telephone between pull on a line. So they set up the telephone office, every phone users connect a line to the telephone office of a major printed circuit board. When A hope and B conversation, he begged for central operator connected B phone. Operator with A wire, A inserted in A receiving circuit boards hole, and the other end plug to B hole, which is "in", equivalent to temporary give A and B pull A phone line, when both sides can talk to each other. When a call is completed, the operator will wire removed, it is a "take out stitches." The whole process is "artificial exchange", it is actually a "close the switch on the" and "disconnect switch" process. Therefore, the "exchange" translated as "switch" technically easier to understand.Circuit of SPC exchangesArtificially exchange inefficient, cannot satisfy the needs of large-scale deployment telephone. With semiconductor technology development and switch circuit technology maturity, people find can use electronic technology substitution artificially exchange. Telephone terminal user as long as to send a string of electrical signals of electronic equipment, electronic equipment can according to the predetermined programme, will request and the requested circuit connected, and exclusive this circuit, not Shared with third parties (of course, of design flaws's sake, may appear people sharing circuit, photonsof ".fortunately "). This kind of exchange method called "program-controlled exchange". This equipment is also "pabx".Because of program-controlled exchange technology long-term by developed countries monopoly, equipment expensive, our telephone is always is not high. As in huawei, zte communications enterprise in succession independently developed pabx, phone in our rapid popularity.At present, the voice of SPC exchanges with the widespread use of communication protocol for ss7 (Signalling System No. 7)Ethernet switchesAlong with the computer and Internet technology (also known as the so-called "network") to the rapid development of Ethernet became so far short of the second highest popularity of computer network. Which Ethernet the core component is Ethernet switches.Whether artificially exchange or program-controlled exchange, all is for the sake of transmission of speech signal, it is need exclusive line "circuit switching". Which Ethernet is a computer network, is needs to be transmitted data and therefore USES is the "packet. But no matter what kinds of exchange between two ways, switches for providing "exclusive access" characteristics will not change. Just Ethernet device is concerned, switches and hub of substaintial distinction is that when A send message to B, if through hub, then access all the network nodes hub will receive this message (i.e. to broadcast sent), just nics in hardware level will not send the machine filter out the information; And if through switches, unless A notice switches, otherwise the radio to B C will never receive information acquisition switch control privileges and (except in the case of surveillance).At present, Ethernet switches manufacturers according to the market demand, launched three layer even 4 layer switches. However, its core function is still 2 Ethernet packet switching, just with a certain processing IP layer even more high-rise packet ability.Optical switchingOptical switching is people are developing the next generation of exchange technology. Now all the switching technology is based on the signal, even if the current fiber switches is first will light signals into electrical signals, after a swap deal, after turn back light signals sent to another root of optical fiber. Because of photoelectric conversion rate is low, at the same time circuit processing speed exist in physics bottleneck, so people hope designed an without a photoelectric conversion "light switches", its internal not circuit but light path, the logical original not switch circuit but switch light path. This will greatly improve the switches processing rate.