What does the router have to use?

The so-called route is refers to through the interconnection network moves the information from the source area spot to the goal place activity.Generally speaking, in the route process, the information can pass through or many middle nodes at least.Usually, the people carry on the route and the exchange the contrast, this will mainly be because will look like the function which in the average consumer both will realize is completely same.Actually, between the route and the exchange main difference is the exchange occurs in OSI reference model second (data link layer), but the route occurs in third, namely network level.This difference had decided the route and the exchange need to use the different control information in the motion information’s process, therefore both realize the respective function way are different.
As early as already appeared between more than 40 years to the route technology discussion, but only then gradually enters the commercialization until the 80s route technology the application.The reason that the route technology widely has not been used before coming out is mainly because the 80s’s network architecture is simple, the route technology does not have the opportunity.Until the recent several years, the large-scale Internet only then gradually is popular, has provided the good foundation and the platform for the route technology’s development.
The router is Internet’s main node equipment.Router through route determination data repeater.The repeater strategy is called the routing (routing), this is also the router name origin (router, repeater).As the different network between the interconnection key position, the router system constituted based on the TCP/IP international interconnecting network Internet main body vein, may also say, the router constituted the Internet skeleton.Its processing speed is one of network service main bottlenecks, its reliable immediate influence network interconnection quality.Therefore, in the campus net, the local net, and even in the entire Internet research area, the router technology is at the core position throughout, its development process and the direction, become the entire Internet research a miniature.When the current our country network infrastructure and the information construction are on the rise, the discussion router’s in interconnecting network function, the status and the development direction, regarding the domestic networking research, the network construction, as well as is clear about in the network market regarding the router and network interconnection each specious concept, has the vital significance.

Router function
——————————————————————————–
A router function is the connection different network, another function is the readout transmission line.Chooses the unobstructed quick shortcut, can raise the communication speed greatly, reduces the network system correspondence load, saves the network system resources, enhances the network system unimpeded rate, thus lets the network system display a bigger benefit.
Looking from the filtration network current capacity’s angle, the router function and the switchboard and the bridge is similar.But with the work in the network physics level, divides the webpage from physics the switchboard to be different, the router use special software agreement carries on logically to the entire network divides.For example, supports the IP agreement the router to be possible to divide the network Cheng Duoge the child webpage, only then aims at the special IP address the network current capacity only then to be possible to pass the router.The data packet which receives regarding each, the router can the recomputation its verification value, and reads in the new physical address.Therefore, the use router repeater and the filtration data’s speed often needs only to examine that the data packet physical address the switchboard is slower.But, regarding these structure complex network, the use router may enhance the network the overall efficiency.Router other obvious superiority is may the automatic filtration network broadcast.Generally speaking, increases the router in the network entire the switchboard which the installation process must insert immediately namely uses complex many.
In general, the heterogeneous network interconnection and many subnet interconnections should use the router to complete.
The router prime task is for seeks for a best transmission route after the router each data frame, and transmits effectively this data to the goal stand.Thus it can be seen, the choice optimal path’s strategy is the routing algorithm is the router key is.In order to complete; This work, is preserving each kind of transmission route correlation data – – way table in the router (Routing Table), for routing; When uses.In the way table is preserving the subnet symbol information, on-line router integer and next router contents and so on name.The way table may be establishes well fixedly by the system manager, may also by the system dynamic revision, be possible by the router automatic control, may also control by the main engine.
1.static way table
Establishes the good fixed way table by the system manager to call that beforehand it the static state (static) the way table, is generally when system installation in advance establishes according to the network disposition situation, it will not change along with the future network architecture change.
2.dynamic way table
Dynamic (Dynamic) the way table is the router basis network system’s operational aspect, but automatic control way table.Router function which (Routing Protocol) provides according to the routing information protocol, automatic study and memory network operational aspect, when need automatic computation data transmission optimal path.

Router type
——————————————————————————–
In the Internet each kind of rank’s network everywhere may see the router.The turning on network causes the family and the Small business may connect some Internet to serve the provider; In the enterprise network’s router connects in a campus or the enterprise tens of thousands of computers; On the backbone network router terminal system usually cannot visit directly, they connect on the long distance backbone network ISP and the enterprise network.Regardless of Internet’s fast development to the backbone network, the enterprise network or the access network has brought the different challenge.The backbone network request router can carry on the high speed route repeater to the minority link.Not only the enterprise router requests the port number to be many, low in price, moreover the request disposes simply convenient, and provides QoS.
1.turning on router
In turning on router connection family or ISP Small business customer.Not only the turning on router already started to provide SLIP or the PPP connection, but also supports such as PPTP and IPSec and so on hypothesized private network protocol.These agreements must be able to move on each port.Such as technologies and so on ADSL will enhance various families very quickly the available bandwidth, this will increase further turning on router the burden.As a result of these tendencies, the turning on router will support many isomerism and the high speed port in the future, and can move many kinds of agreements in each port, meanwhile must avoid the telephone exchange network.
2.enterprise router
The enterprise or the campus level router connects many terminal systems, its essential target is realizes as far as possible many vertex interconnections by as far as possible cheap method, and further requests the support different grade of service.Many existing enterprise networks are the ether webpages which connects by Hub or the bridge.Although these equipment price small advantage, easy to install, does not need to dispose, but they do not support the grade of service.On the contrary, has the network which the router participation to be able the machine to divide into many collision territories, and, can therefore control a network the size.In addition, the router also supports certain grade of service, allows to divide into many first ranks at least.But the router each port construction cost wants expensive, and before can use must carry on the massive disposition work.Therefore, the enterprise router’s success or failure lies in whether to provide the massive ports, and each port’s construction cost is very low, whether easy to dispose, whether to support QoS.In addition requests the enterprise router to support the broadcast and the multicast effectively.The enterprise network also needs to process the historical carry-over each kind of LAN technology, supports many kinds of agreements, including IP, IPX and Vine.They must support the firewall, the package filtration as well as the massive management and the security policy as well as VLAN.
3.backbone level router
The backbone level router realizes the enterprise network interconnection.To its request is the speed and the reliability, but the price is in the secondary position.The hardware reliability may use the technology which in the telephone exchange network uses, like the hot backup, the double power source, the double data path and so on obtain.These technologies speaking of all backbone router almost are the standard.The backbone IP router’s main performance bottleneck is in transfers in the publication to search the time which some route consumes.When receives a package, inputs the port to transfer in the publication to search this package’s destination address by to determine its goal port, when the package is shorter or when the package must send out many goal ports, will increase the price which inevitably the route searches.Therefore, the goal port which often visits some puts to the buffer in can enhance the efficiency which the route searches.No matter is the input block or outputs the cushion router, has the bottleneck problem which the route searches.Except the performance bottleneck question, the router stability is also one often the question which neglects.
4.too bit router
Will use in the future core Internet in three kind of major techniques, the optical fiber and DWDM already were very mature, and will be ready-made.If not provides with the existing optical fiber technology and the DWDM technology the primitive band width correspondence’s router, the new network infrastructure will be unable fundamentally to be improved performance, therefore the development high performance’s backbone exchange/router (too a bit router) already became an urgent request.Too the bit router technology also is mainly at the development laboratory stage now.

Router structure
——————————————————————————–
Router architecture
Looked from the architecture that the router may divide into the first generation of single main line list CPU structure router, the second generation of single main line main from the CPU structure router, the third generation single main line symmetrical expression multi-CPU structure router; Fourth generation of main line multi-CPU structure router, fifth generation of sharing memory type structure router, sixth generation of overlapping switch architecture router and based on airplane group system’s router and so on many kinds.
Router constitution
The router has four essential factors:Inputs the port, the output port, to exchange the switch and the route processor.
Inputs the port is the physical link and an input package of entry.The port usually provides by the line card, the line card supports 4, 8 or 16 ports generally together, an input port has many functions.The first function is carries on the data link layer the seal reconciliation seal.The second function is in transfers in the publication to search the input package of destination address, thus the decision goal port (is called route search), the route search may use the common hardware to realize, or through inserts a microprocessor in each line card to complete.Third, to provide QoS (grade of service), the port must to the package which receives divide into several pre-definitions the service ranks.Fourth, the port possibly needs to move such as SLIP (serial line internet protocol) and PPP (point to point protocol) such data link level agreement or such as PPTP (point-to-point tunnel agreement) such network level agreement.Once the route search completes, must use to exchange the switch to deliver the package its output port.If the router is the input end adds the formation, then has several input end sharing identical exchange switch.The such input port’s last function participates in (for example exchanges switch) to the public resource the arbitral agreement.
Exchanges the switch to be possible to use many kinds of different technologies to realize.Until now uses most exchange switch technology is the main line, the overlapping switch and the sharing memory.The simple the switch uses a main line to connect all inputs and the output port, bus switch’s shortcoming is its exchange capacity as well as to share the overhead which limited to main line’s capacity the bus arbitration brings.The overlapping switch provides many data paths through the switch, has N×N the intersection overlapping switch to be possible to consider that has the 2N strip main line.If one overlapping is closed, on input bus’s data on storage-out bus available, otherwise not available.Intersection closing and opens by the dispatcher controls, therefore, the dispatcher limited has exchanged switch’s speed.In shares in the memory router, comes in the diaper storage in the sharing memory, is only package’s indicator which exchanges, this enhanced the exchange capacity, but, switch’s speed is restricted in memory’s access speed.Although memory capacity every 18 months can double, but memory’s access time only reduces 5% every year, this is shares the memory to exchange a switch’s inherent limitation.
The output port in the diaper transmits before the output link to a package of storage, may realize the complex dispatch algorithm to support requests and so on priority.Is the same with the input port, the output port must be able similarly the support data link level seal reconciliation seal, as well as many high-level protocols.
The route processor computation transfers the publication to realize the route agreement, and moves to the router carries on the disposition and the management software.At the same time, it also processes these destination address not online card to transfer in the publication the package Reference:http://baike..com/view/1360.htm Router function
A router function is the connection different network, another function is the readout transmission line.Chooses the unobstructed quick shortcut, can raise the communication speed greatly, reduces the network system correspondence load, saves the network system resources, enhances the network system unimpeded rate, thus lets the network system display a bigger benefit.Looking from the filtration network current capacity’s angle, the router function and the switchboard and the bridge is similar.But with the work in the network physics level, divides the webpage from physics the switchboard to be different, the router use special software agreement carries on logically to the entire network divides.For example, supports the IP agreement the router to be possible to divide the network Cheng Duoge the child webpage, only then aims at the special IP address the network current capacity only then to be possible to pass the router.The data packet which receives regarding each, the router can the recomputation its verification value, and reads in the new physical address.Therefore, the use router repeater and the filtration data’s speed often needs only to examine that the data packet physical address the switchboard is slower.But, regarding these structure complex network, the use router may enhance the network the overall efficiency.Router other obvious superiority is may the automatic filtration network broadcast.Generally speaking, increases the router in the network entire the switchboard which the installation process must insert immediately namely uses complex many.In general, the heterogeneous network interconnection and many subnet interconnections should use the router to complete.The router prime task is for seeks for a best transmission route after the router each data frame, and transmits effectively this data to the goal stand.Thus it can be seen, the choice optimal path’s strategy is the routing algorithm is the router key is.In order to complete; This work, is preserving each kind of transmission route correlation data – – way table in the router (RoutingpTable), for routing; When uses.In the way table is preserving the subnet symbol information, on-line router integer and next router contents and so on name.The way table may be establishes well fixedly by the system manager, may also by the system dynamic revision, be possible by the router automatic control, may also control by the main engine.1.static way table p establishes the good fixed way table by the system manager to call that beforehand it the static state (static) the way table, is generally when system installation in advance establishes according to the network disposition situation, it will not change along with the future network architecture change.2.dynamic way table p dynamic (Dynamic) the way table is the router basis network system’s operational aspect, but automatic control way table.Router function which (RoutingpProtocol) provides according to the routing information protocol, automatic study and memory network operational aspect, when need automatic computation data transmission optimal path.The simple said that is realizes many computer surfers with a mesh wire
Does not have the route only then the cat only to be able on a machine
Added the route to be possible many computers to access the net with the identical root mesh wire The group local area network, facilitates links CS