1. introduction
The traditional router has the isolation network, the isolation broadcast, the route repeater as well as firewall’s work in the network, and along with network unceasing development, router load also in explosive growth. And a substantial clause is stems from aspect and so on security and management convenience considerations, VLAN (virtual local area network) technology in network massive applications. The VLAN technology may logic isolate each different webpage, the port even main engine, but during each different VLAN correspondence must complete the repeater after the router. Because in the local area network the data current capacity is very big, VLAN the massive exchange of information must complete the repeater through the router, at this time grew the router along with the data current capacity to become the network bottleneck unceasingly. In order to solve confined network this bottleneck, many enterprise interior, school and when plot construction local area network has used three switchboards. Three exchange technologies will exchange the technology to introduce the network level, three switchboard’s applications from the initial hub’s backbone level, the gathering level have also seeped to the network edge turning on level.
2. third exchange technology
The third exchange technology is also called the IP exchange technology or the high speed route technology and so on, is opposite in the traditional exchange concept proposes. It is well known, the traditional exchange technology is carries on the operation in the OSI network standard model second aerodynamic data link level, but the third exchange technology has realized the data packet high speed repeater in network model third. Puts briefly, the third exchange technology is: Second exchange technology third repeater technology, this is one kind uses in the third agreement the information to strengthen the second exchange function the mechanism. Has the third exchange function equipment has the third routing function second switchboard, but it is the two’s organic synthesis, is not simply superimposes simply the router equipment’s hardware and the software on the local area network switchboard.
2.2 three exchange principles
Realizes from the hardware on looked, at present, the second switchboard’s interface module is through the high speed back board/main line exchange data. In the third switchboard, also peg grafts with the router related third route hardware module on the high speed back board/main line, this way causes the route module to be possible with to need during other modules route’s to exchange the data high speed, thus broke the traditional external connection router interface rate limit (10Mbit/s—100Mbit/s). In the software aspect, the third switchboard has carried on the tradition based on software’s router the limits:
(1). data wrapped gift repeater: If the IP/IPX wrapped gift’s repeater, these orderly processes realize high speed through the hardware;
(2). third route software: If routing information’s renewal, routing list maintenance, route computation, route’s functions and so on determination, with the optimization, the highly effective software realize.
The supposition has two to use the IP agreement the stand, carries on the correspondence through the third switchboard the process is: If transmits stand A when starts transmits, the known goal stands the B IP address, but still did not know that it MAC address which the sending station needs on the local area network, then needs to use the address to analyze (ARP) to determine B the MAC address. A compares own IP address and the B IP address, uses the subnet mask which in its software disposes to withdraw the network address to determine B whether with in identical subnet. If B and A in the identical subnet, A broadcast ARP to request, B returns to its MAC address, after A obtains the B MAC address, gets up this address buffer, and with this MAC address wrapped gift repeater data, the second exchange module searches the MAC address table to determine that ships to the goal port the data packet. If two stands not in identical subnet, then A must send out ARP to ” the default gateway ” (address analysis) the wrapped gift, but ” default gateway ” the IP address already established in the system software, this IP address in fact corresponds the third switchboard’s third exchange module. When A is right ” the default gateway ” when the IP address broadcasts a ARP request, if the third exchange module obtained the B MAC address in the former course of communications, approaches transmission station A to reply B the MAC address; Otherwise the third exchange module broadcasts ARP according to the routing information to the goal station to request that B obtains this ARP to request the backward third exchange module replies its MAC address, the third exchange module preserves this address and replies gives transmission station A. Later, when will carry on between again A and B the data packet repeater, will use the final goal stand the MAC address wrapped gift, the data repeater process completely to give second exchange processing, the information can high speed exchange [1].
2.3 third exchange characteristics
The prominent characteristic is as follows:
(1). The organic hardware union causes the data exchange acceleration;
(2). The optimized route software causes the route process efficiency enhancement;
(3). Besides essential route decision process, majority of data repeater process by second exchange processing;
(4). When many subnet interconnections is only with the third exchange module logical link, does not look like traditional external connection router such to increase the port, has protected user’s investment.
The third exchange’s goal is, so long as has the more direct second circuit between the source address and the destination address, is not unnecessary after the router repeater data packet. The third exchange uses the third route agreement determination transmission path, this way may only use one time, may also save, for the later use. Afterward the data packet bypasses the router through an empty electric circuit to transmit fast.
The third exchange technology’s appearance, after having solved in the local area network the webpage division, in the webpage the subnet must rely on the router to carry on the management the aspect, has solved the network bottleneck problem which the traditional router low speed, complex creates. Certainly, three exchange technologies are not the network switchboard and the router simple superimposition, but is the two’s organic synthesis, forms an integration, the complete solution.
3.1 model of third switchboard’s designs
Considered the market requirement, the switchboard cost and the proprietary intellectual property rights factor, we designed develop had the proprietary intellectual property rights VLSW 4150 series switchboards. The VLSW 4150 series switchboards are the high performance which, the multi-level solutions provides for the enterprise. VLSW 4150 are also suitable for ISP and the service provider, particularly regarding some large-scale operators, will be able to strengthen it in the IP market competitive power.
3.1 system designs
The VLSW 4150 switchboards have 24 RJ45 the 10/100BASE-TX auto-adapted port, provides optical fiber 10/100BaseTx ether mouth which, 100BaseFx fast ether port or milliardfold ethernet mouth 2 may elect (SX, LX, ZX), and other provides a serial port and a 100M ethernet mouth carries on the disposition to the switchboard.
The VLSW 4150 switchboard’s architectures may support to the 11Gbps speed, the multi-layered exchange speed achieve 6.6Mpps high; May support 8,192 MAC addresses; For better directed net current capacity and network security, but also supports take 1M as the length of stride speed limitation; Supports Tagged VLAN and the MAC-based frame filtration as well as RIP, OSPF and the BGP route agreement.
The VLSW 4150 switchboards provide the storehouse technology to be possible to manage many switchboards by a logical IP address, and may take a good photo likely other data packet in a mouth, provides debugs the switchboard based on the Web network management system as well as the CLI way. VLSW 4150 support the SNMP agreement, RMON and the Telnet function is advantageous for the management.
3.2 hardware architectures
The VLSW 41,503 switchboard’s hardware architectures divide into two parts, the processor module and the exchange module, between them is connected through the PCI connection, simultaneously coordinates the corresponding peripheral circuit to form the complete three switchboard system, see Figure 1.
Figure 1 hardware architecture
(1) processor module
As shown in Figure 2, the processor department uses section of MOTOROLA PowerQUICC II CPU, constitutes three switchboard’s processor parts with some external storage unit as well as some peripheral circuit. The processor module is mainly moves the embedded operating system, the disposition system and the routing list maintenance, but is not the data retransmits circuit’s constituent. After CPLD preserves some CPU initialization some dispositions guarantee on the electricity, the CPU normal start, the Flash chip uses in all softwares which and the related disposition saves three switchboards to need, SDRAM, in the system initiation writes down in FLASH afterward the procedure, guarantee system normal operation. The processor module provides a fast ethernet connection and an asynchronous mouth at the same time, uses in carries on the disposition and the debugging to the switchboard; On the other hand is connected through the PCI connection and the exchange module, carries on the control through the PCI connection to the exchange module, and carries on data transmission [2]. 
Figure 2 processor module hardware composition
(2) exchange module
As shown in Figure 3, the exchange module used BROADCOM Corporation’s BCM5645 to take the ASIC chip, carried on the correspondence through the PCI connection and the processor module to complete the data transmission, through memory connection which 5645 provided, might give the exchange module to provide 64M exterior SDRAM, thus enhanced switchboard’s volume of goods handled and the exchange rate. 5645 connect 24 100,000,000,000,000 ethernet and 2 milliardfold ethernet [3] separately through the MII connection and the GMII connection.
Figure 3 exchange module hardware composition
3.3 software architectures
The VLSW 41,503 switchboard’s software systems have used the modulation, the distributional design method, based on real-time multi-duty operating system. Software system’s structure assumes the hierarchical structure, an establishment in another foundation, each uses the service which the close neighbor its next institute provides, and provides a higher first-level service for its above one, its merit is: May to the upper formation software masking first floor operation, enhance the upper formation software’s probability, enhances software’s maintainability.
As shown in Figure 4, the software divides into three stratification planes roughly:
(1) actuation level
The driver has carried on the upper formation software and the hardware system the connection, renews, the management and the disposition order the upper formation software’s route transforms the form which can distinguish for the hardware system, thus achieves renews its internal data structure like routing list, address table and so on, control and management hardware exchange system’s goal; Simultaneously the device driver the route which receives the first floor hardware renews each kind of information transmission which the text, the control supervisor frame and receives for upper formation software processing;
(2) agreement stack
Has realized agreements and so on TCP/IP, 802.1D and 802.1Q, provides the good connection for the upper formation application procedure;
(3) application layer
Mainly included the route module and the network management module, the route module has realized agreements and so on RIP and OSPF, namely realized the third route’s major function; The network management module has realized network management modules and so on SNMP and RMON, enables three switchboards to have the partial network management function, guarantees three switchboard well normal works. 
Figure 4 software architecture
4. third switchboard’s application
The third switchboard’s main application is replaces the traditional router to take the network the core, therefore, everything does not have the macrozonality connection demand, simultaneously needs the router the place, may use the third switchboard to replace. In the enterprise network and the campus net, will use generally the third switchboard in the network core level, will connect the different subnet or VLAN with a third switchboard’s on milliardfold port either 100,000,000,000,000 ports. The third switchboard solved local area network VLAN to rely on the router to carry on the management the aspect, has solved the network bottleneck problem which the traditional router speed low, complex created. Divides VLAN using three switchboards in the local area network, may satisfy the subscriber’s premises many kinds of nimble logical combinations, has prevented the broadcast storm production, may according to need to establish the different access authority to different VLAN, increases the network by the overall security, raises network administrator’s working efficiency enormously, moreover the third switchboard may dispose the information resource reasonably, reduces the network configuration cost, causes between the switchboard to connect becomes nimble.
