Router (router) is a computer term. To explain the concept of the router, the first to introduce what is routing. The so-called "Route" refers to transfer data from one place to another, behavior and action, and a router, it is the action of the machine to perform such acts, it is the English name for the router. Using one or more network layer devices measure the factors, which determine the best path through the network of the communication. Router based on network layer information from the previous network packet to be forwarded to another network. Occasionally called a gateway (although this definition has now passes through the gateway). Internet router is one of the essential network device is a router or the network segment connected to a plurality of network devices, it will be data between different networks or network segments for "translation", so that they Mutual able to "read" to understand each other's data, so as to constitute a larger network. There are two typical router function, namely, data channel and control functions. Data channel features include forwarding decision, backplane and output link scheduling forwarding, generally by specific hardware to complete; control functions typically implemented in software, including the exchange of information between adjacent routers, system configuration, system administration, etc. .
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Router Function
Simply speaking, the router has the following main features: First, network interconnection, the router supports a variety of LAN and WAN interfaces, mainly for LAN and WAN interconnection, to achieve mutually different communication networks; Second, the data processing services including packet filtering, packet forwarding, priority, multiplexing, encryption, compression, and firewall functions; Third, network management, router, including configuration management, performance management, fault management and traffic control. To complete a "route" work, in the router holds various data transmission path - routing table (routing table), when used for routing. Subnet routing table holds a sign information, the number of Internet routers and the next router name and so on. Routing tables can be fixed by the system administrator to _set_ good, you can also automatically adjusted by the router dynamically modified by the system, can also be controlled by the host. Involved in the router to the name of two related concepts address, that is: static routing tables and dynamic routing table. _Set_ well fixed in advance by the system administrator is called static routing table (static) routing table, usually when the system is installed on a pre-_set_ according to the configuration of the network, it will not change in the future with the network structure is changed. Dynamic (dynamic) routing table is a router based on the operation of the network system automatically adjusts the routing table. According routing protocol router (routing protocol) provides functionality, automatic learning and memory, network operation, automatically calculates the best path for data transmission when needed. To briefly explain the working principle of the router, and now we assume that there is such a simple network. As shown, a, b, c, d are connected together by four network routers. Now we look at the network environment shown in Figure router and how to play its routing, data forwarding action. It is assumed that a network user in a network a1 c c3 would like to send a user request signal, the signal transmission procedure is as follows: Step 1: User a1 address of the destination user c3 c3, together with the data in the form of data frames sent by the hub or switch in the form of broadcast to all nodes in the same network, when the router a5 port listens to this address, analysis that is not issued by the destination node network segment requires routing forwarding, the received data frame to put down. Step 2: After receiving the router port a5 a1 of the user data frame, removing header start c3 ip address of the destination user, and computing a best path to the user according to the routing table c3. Because from the analysis that the same id number and c3 network router c5 network id number, so sent directly from the router port to c5 a5 port via the router should be the best signal transmission. Step 3: c5-port router again to remove the ip address of the destination user c3, c3 identify ip address of the host id number, if there is a switch in the network can be sent to the switch, the switch to find the mac address table according to specific network node position; If you do not switch the device directly to the data frame transmission based on their ip address host id to the user c3, so that a complete data communication forwarding process is complete. As can be seen from the above, no matter how complex the network, in fact, the work of the router is so short, so the entire router works basically the same. Of course, in the actual network also shown to be far more on the many complex, practical steps like these will not be so simple, but the overall process is as follows.
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Increase in basic protocol router involved
English name for the router router, a network used to connect multiple networks or network equipment. These networks can be several networks using different protocols and architectures (such as the Internet and LAN), can be several different segments of the network (such as large Internet networks in different sectors), when data is transmitted from one sector of information to the network Also when a department network, the router can be done. Now, more and more home network using a router to share broadband Internet way. When a router to connect different networks or network segments, the data information between these networks "translation" and then "translated" into both sides can "read" to understand the data, this can be achieved between different networks or network segments interoperability. It also has to determine the network address and choose the path of functional capabilities and filtration and separation of network traffic. Currently, the router has become the backbone network between the various internal, between the backbone and the connection between the hub and the Internet backbone. nat: full name of the network address translation (network address translation), nat router via LAN feature can be converted into a legitimate ip address ip address and access the internet. For example, there is the internal LAN ip address 192.168.0.1 computer, of course, through the ip address can communicate other computers within the network; But if the computer you want to access the external internet, then you need to convert nat function 192.168.0.1 as a legitimate WAN ip address, such as 210.113.25.100. dhcp: full name of the dynamic host configuration protocol (Dynamic Host Configuration Protocol), via dhcp function, the router can dynamically assigned ip address for the host in the network, without requiring each user to _set_ a static ip address and tcp / ip configuration parameter distribution legitimate network to the LAN clients. ddns: full name of the dynamic domain name server (Dynamic Domain Name System), commonly referred to as "dynamic dns", because dynamic ip address broadband Internet access for ordinary use are isp (Internet service providers) offer. If you create a server in the LAN internet users need access, then the function of the router by ddns dynamic ip address resolves to a fixed domain, such www.cpcw.com, so that internet users can be fixed by that domain internal network server access. pppoe: full name of the point to point protocal over ethernet (Point to Point Protocol over Ethernet), through pppoe technology that allows broadband modem (adsl, modem) users get a personal identity verification broadband access, can create a virtual dial-up connection for each user, This allows high-speed connection to the internet. Routers have this feature, you can automatically pppoe dial-up connection, the user so that the router can automatically connect to the internet. icmp: full name of the internet control message protocol (internet control message protocol), the protocol is tcp / ip protocol _set_ a sub-protocol mainly used between hosts and routers to pass control information, including reporting errors, exchange limited control and status information.
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The difference between the switch
Overall, the main difference between routers and switches in the following areas: Different (1) working level The first switch is in the data link layer osi / rm open architecture, which is the second layer, and the router at the beginning of the design of the network layer osi model. Since the switch to work in osi second layer (data link layer), so it works is relatively simple, and the router work in osi third layer (network layer), you can get more information on the agreement, the router can make more intelligent forwarding decisions. Different objects (2) on the basis of the data forwarding Switch is to use a physical address or mac address to determine the destination address for forwarding data. The router is to determine the data forwarding address using different network id number (ie ip address). ip address is implemented in software, describes where the network equipment, sometimes also known as the third layer protocol address or the address of the network address. mac address is usually the hardware that comes from the card manufacturer to distribution, and has solidified to the card and going, in general, can not be changed. The ip address is usually assigned automatically by the network administrator or system. (3) the traditional switch can split the collision domain, can not be split broadcast domains; while the router can be split broadcast domains Segments connected by the switch still belong to the same broadcast domain, broadcast packets will be spread across all segments connected to the switch, and in some cases can lead to traffic congestion and security vulnerabilities. Connected to the router on the segment will be assigned to a different broadcast domain, broadcast data will not pass through the router. Although the third floor above the switch with vlan function can also be split broadcast domains, but can not communicate between each sub broadcast domain, the exchange between them still need a router. (4) The router provides firewall services Router forwards packets only a specific address, does not transmit packet transmission transfer data do not support the routing protocol packets and unknown target network, which can prevent broadcast storms. Switch is typically used to connect the lan-wan, the switch attributed to the bridge, is a data link layer device, and some switches can also be achieved third layer switching. Wan-wan router for connecting between the opposite sex can be solved forward packets between networks, the role of the network layer. They only accept input from a line, and then forwarded to another line. These two lines may belong to different networks and different protocols. In comparison, the router features than switch to powerful, but the speed is also relatively slow, expensive, and the third layer switch both switches packets at wire speed forwarding capability, but also good control router functions, it can be widely applied. Currently individuals are more broadband access is adsl, so I would adsl access to simple to explain. Most cats buy now adsl routing function (many manufacturers in the factory when the routing shield, mostly because telecommunications installation routing function is not enabled, enable dhcp. Opened adsl routing functions), if an individual or a small Internet By itself, a few adsl can, if the computer you just need to buy more of one or more hubs or switches. Considering the price of hubs and switches now very little difference, not a special reason, please buy a switch. Do not have to pursue expensive, because now the product homogeneity is very serious, I switch now the cheapest without any problems. Give you a reference offer, I suggest you buy an 8 to meet expansion requirements, the general price of around $ 100. Connected to the switch, then all the computers connected to the switch on the line. The rest have to do only the network cable is _insert_ed into each machine interface of the switch, the cat's network cable into uplink interface. Then _set_ the routing function, dhcp, etc., can be shared online. Readers should read the explanation of the above switches, hubs, routers have some understanding of current usage is primarily based switches, routers use a combination of main, specific combinations can be determined according to the specific circumstances and needs of the network.
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Router works
1, the router receives data from a site in which it is connected. 2, the data is passed up the router, and (if necessary) reassembled ip datagram. 3, the router checks the destination address ip header, if the destination address in the data issued by the network, the router will put the data is considered to have reached the destination, because the data is transmitted over the network where the destination computer. 4, if the data to be sent to another network, the router will check the routing table to determine the data to be forwarded to the destination. 5, the router determines which adapter is responsible for receiving the data, the data is transmitted through the corresponding software to transfer data to the network.
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Trends router
Chip speed to double every 18 months, while Internet traffic to double every six months. As an Internet hub, router is moving faster, easier and better service quality and management in three directions integrated development. Router functionality trends specific analysis before the router, we briefly explain the function of the router. Traditionally, network routers work at Layer 7 protocol called third layer, whose main task is to receive data packets from one network interface, based on the destination address contained therein, to which the decision to forward the next destination (possibly router may be the final destination point), and decide which network interface forwarded from. This is the most basic function of a router - packet forwarding. In order to maintain and use a router, the router also need to configure or control functions. According tcp / ip protocol, the router forwards the packet specific process is: Receiving a packet network interface; physical layer is responsible for this processing step, the data signal that is modulated by the encoded data to restore. Different physical network media determines the different network interfaces, such as corresponding to 10base-t Ethernet router 10base-t Ethernet interface, which corresponds to sdh, sdh router interface that corresponds to the ddn, v.35 router interfaces According to the network physical interface, the router calls the appropriate link layer (Layer 7 network protocol second layer) processing function module to explain this packet link layer protocol header. This step is relatively simple treatment, mainly for data integrity verification, such as crc check, frame length check. In recent years, ip over something trend is very clear, especially the rapid development of fiber-optic network technology and ip as the de facto standard established, so that dwdm (Dense Wavelength Division Multiplexing) optical fiber, ip (at the network layer - Layer 7 network The third protocol layer) is skipped and directly loaded link layer above the physical layer. After the completion of the link layer frame integrity verification of the data, the router begins the data frame processing ip layer. This process is the core router function. Data frame ip address ip header goal, to find the next hop router ip address, ip packet header ttl (time to live) field began subtraction, and calculate the new checksum (checksum) according to the routing table. If the received data frame network interface type and forwarding data frames of different types of network interfaces, the ip packets may also be because the specified maximum frame length and segmented or restructuring. According to those found in the routing table the next hop ip address, ip packets sent to the corresponding output link layer, is the package corresponding link layer header, the final output is sent via the network physical interface. The following details the development trend of the router. Faster Traditionally, the router is generally considered a bottleneck network speed. When LAN speed already reached hundreds of megabytes, the processing speed of the router only up to tens of megabits rate. With the explosive growth in recent years of the Internet, we study the router is also reflected in the emphasis on improving the router's processing speed. Between 1996 and 1997, the United States appeared in a number of highly innovative small companies, such as nexabit, juniper, avici, etc., to improve the processing speed of the router to an extreme degree, in the immediate future have launched a Gigabit router. Even cisco company can hold a candle in terms of speed in this regard. Since these are high-speed router invariably introduces the structure of the exchange, these routers are also known as Gigabit Switch Router (gsr-gigabit switch router) and a router bit exchange too (tsr). These routers optical interface speed quickly from oc-12 (622mbps) jump oc-48 (2.5gbps) then oc-192 (10gbps), this rate had to switch atm far behind. Since then, atm irreplaceable position in the core network completely wavered. Protracted ip - indisputable atm technology has finally come to an end ip overwhelming advantage. However, from the following analysis, we can see that the improved ip router speed is a direct benefit atm concepts and technology, many new concepts and technologies in the field of ip raised a considerable part of the direct or indirect source in atm, two kinds of excellent technical gradually began to integration. In fact, many companies engaged in research and development of high-speed routers ip is past research technician atm technology research and development personnel. Specifically, the sharp increase in technological advances from the following four aspects ip router speeds. Member architecture. Router hardware architecture has gone through six changes (discussed in detail in the "Architecture of the router"), from the earliest single-bus, single cpu architecture development to a single bus, multiple bus and then to multi-multi-cpu cpu. Up to now, high-speed multi-draw atm ip router method, using Crossbar way to achieve wire-speed non-blocking interconnection between the various ports. High-speed crossbar switch technology has been very mature, high-speed parallel computer atm and has long been widely used, can be purchased directly on the market rate to as high-speed crossbar 50gbps. With the introduction of high-speed crossbar switch, and also introduced some relevant technical issues, especially for ip multicast, broadcast, and quality of service (qos), the use of sophisticated scheduling strategies and algorithms, these issues have been satisfactorily resolved . asic technology. Over the years, because of cost and performance considerations, asic used more widely, almost adhere asic. In the router to dramatically improve the speed, the first thought is also asic. Some do with asic packet forwarding, routing some with asic investigation and find ipv4 routing asic chip already on sale. Flourish in asic, the trend of the large number of applications, there is a trend worth noting that this is the emergence of the so-called programmable asic, this may be a result of changing the network itself caused. Because the inputs asic considerable design and production, in general, aisc only for completely standardized procedure, and the network structure and protocol changes again very fast, so that the respective devices in the network area, for a peculiar " Programmable asic ". Currently, there are two types of so-called "programmable asic", a kind of 3com company fire (flexible intelligent routing engine) chip represented Fengyun asic chip embedded in a one cpu, so it has a certain degree of flexibility; Another kind of vertex networks of hisc ASIC represented the chip is cpu, cpu architecture designed specifically for a specialized communication protocol processing adaptation protocol processing, by rewriting microcode enables ASIC has Fengyun processing capacity to accommodate different protocols from ipv4 to ipv6 similar changes. Three-tier exchange. This is a revolutionary breakthrough agreement process, and is now the source of gsr and tsr name. Since the unknown ipsilon company launched the "first route, then swap" ipswitch technology in 1994, major companies have launched their own proprietary three-switching technology. Such as cisco's tag switch, 3com's label switch and so on. The combination of these advantages of proprietary technology, ietf finally launched the superior performance of the multi-protocol label switching in 1998 (mpls). Compared with the "one route, and then exchange" was originally thought, mpls network structure from a higher level to consider the three-tier exchange technology, trying to solve the problem in one fell swoop tier exchange network traffic management. With the initial ipswitch technology is different, mpls ip protocol to the agreement on the package to make changes at the network edge, mpls ip router for each incoming packet label (label), the subsequent transfer, the core routing and switching equipment will only the forwarding path based on the label decided that this approach has been very similar atm in the world of virtual circuit concept. This aspect of the present study is still in progress, the main technical difficulty is how to determine the label distribution scheme on the edge of the network routers in the network autonomous system, and how to adjust the program based on dynamic adaptive network load and fault conditions. ip over sdh, ip over dwdm. Technical progress in this area is completely derived from the progress of optical fiber communication technology. With the core of ip gradually being recognized, ip over atm, then atm over sdh manner directly over sdh ip replaced by the way. sdh using time division multiplexing mode bearer multiplexed data. So in the core network requires extensive use of cross-connect multiplexer. dwdm (Dense Wavelength Division Multiplexing) makes a single fiber using different wavelengths transmitted multiplexed signal. While running on a single fiber is generally four wavelengths can be called dwdm. Since 1996, 16 wavelengths dwdm optical fiber communication products available, now 40 wavelengths dwdm technology has practical, 80 and even 96 wavelengths dwdm products will also be launched in the year 2000, China also has the ability to develop eight wavelengths The dwdm technology. As a result of WDM technology, data transmission when the fiber becomes quite simple, progressive optical communications technology allows the optical signal can be transmitted directly within the 800 km-long range without any optical or bare regenerative amplifier. ip packet directly modulated on a wavelength no longer after multiplexing, demultiplexing. Even in the core network, wavelength information used directly as the ip route information data stream. Better quality of service In front of the router to improve the speed is still just to adapt to the rapid increase in data traffic. The more fundamental trends router, more profound changes are: ip packet switched data to be quickly replaced based on the circuit the past century has been the development of the exchange of communication in the coming years to become mainstream communications business model. This means, ip router not only provides faster speeds to accommodate the rapid growth of traditional computer data traffic, and, ip router will gradually provide the original telecommunications network provided by the various businesses. But the traditional ip router does not know the type of business concerned ip packet, generally only by advanced, first-out principle forwarding packets, voice telephone data, real-time video data, Internet browsing data, etc. of various types of data services be treated indiscriminately. Thus, ip router in order to provide all services, including telecommunications, including radio, improve quality of service (qos) is the key. It is also the major network equipment vendors (including cisco, 3com, nortel, etc.) in the direction of the current efforts to promote. The new major manufacturers of high, medium and low-grade routers have varying degrees of support qos, such as cisco's most upscale 12000 series, from hardware and software protocols for qos terms of both strong support, and its new low end product 2600 Series also supports voice calls this new business applications. In fact, qos is not only a trend router to router as the core of the entire ip networks are moving in that direction. "Triple play" of such a concept is a product of this direction. However, the traditional core of the network ip router can not meet the "triple play" trend, countries led by the U.S. in advance to provide better and faster service quality research and development of network technology. Router which is one of the key research and development, the company became the main driving force to promote the technology. Qos support from both hardware and software. From the hardware side, a faster forward speed and wider bandwidth is the basic premise. From the software side agreement, the efforts of recent years, the performance of the following results: pv4 header type of service field. ipv4 header in a three priority areas in order to identify this ip packet. Accordingly priority, ip router can determine the priority of different ip forwarding packets. It can be said, from the date of ip protocol developed since, it has been _set_ aside to provide better qos assurance mechanism for the future. However, due to the booming early ip network does not focus qos. Thus, the general area and the person 3 is not used. However, as we can see the following analysis, only the definition of the type of service is absolutely not enough in ip packets through signaling must ensure that the required quality of service support in all aspects of the entire network. rsvp (Resource Reservation Protocol) and the corresponding series of agreements. This is a step of profound significance ip router to provide better quality of service moving forward. Ip router traditionally only responsible for packet forwarding, router address that is close by routing protocols. Rsvp is similar to the circuit-switched signaling protocol is the same system to notify each node (ip router) through it for a data stream, in consultation with the endpoint for this data stream to provide quality assurance. rsvp agreement appeared, widely recognized immediately, was appointed as basically solved the problem of resource reservation. But over time, the explosive growth of the network, rsvp are exposed more and more problems, mainly reflected in the following aspects: The most fundamental is, rsvp each data stream based on the service object for the negotiation, in the case of the explosive growth in network traffic, the number of data streams router forwarding the rapid growth of high-speed forwarding, router designed a lot has impossible to sophisticated resource reservation protocol for each data stream. Secondly, because the line is busy or when a router failure and other reasons, the route changes, a relatively time-consuming need to re-rsvp process. For these two reasons, ietf has launched another new qos policy - diffserv (differentiated service). Diffserv current framework has been basically established, the United States internet2 also choose diffserv as qos policy. Compared with diffserv, rsvp is an integrated service, centralized control strategy, and diffserv is a decentralized control strategy, and its essence is the only path to control each hop (per hop) behavior. Terminal applications through sla (service level agreement) in consultation with the edge router to get their application data streams can be guaranteed service levels. According to this level of service, the edge router for each received data packet to the marked level mark, and the behavior of the core routers only mobilized forwarding packets according to the service level of the marker determined for each time. As customers only in consultation with the edge router and access service level assurance, in a large network of interrelated, since the non-uniform network traffic and other reasons, the actual quality of the same level of service edge routers of different levels of service offered is not the same, this also need to provide different mutual exchange of traffic information through sla to avoid or reduce the occurrence of the above situation between qos service level areas of the network. Multi-Protocol Label Switching (mpls) qos also be used to solve the problem. But the core network router coverage. To establish a reasonable core routing switching path between the need for regular exchange between the core router status information flow. Management more intelligent With the explosive growth of network traffic, network size swelling, as well as the network quality of service requirements are high, NMS router is becoming increasingly important, the network connection has become a daily work and life indispensable part. In the case of quality assurance to maximize the use of bandwidth, early detection and diagnosis of equipment failures, quickly and easily change the configuration as needed, these network management functions are increasingly becoming a direct impact on network users and network operators benefit important factor. In the seven layer model of network protocols, network management applications are high-level, currently an important trend is the manufacturers of network management to intelligent direction. The so-called intelligent and reflected in two aspects, one is intelligent information exchange between network devices (routers); Second, the interaction between the intelligent information network equipment and network managers. In the trend of intelligent network management, the "policy-based management" and "traffic engineering" of these two technologies is the most compelling concepts. Each router manufacturers in all newly launched products advertised their network management support system with or part with these two functions. "Policy-Based Management" concept will also affect the behavior patterns of information exchange between the router and the router and network managers. Allows network managers to define and easier constraint network behavior from the user's perspective, and these policies will directly affect the upper basic network behavior, the traditional routing algorithm development policy based routing algorithm, making information exchange between routers must bear Strategic content covered. "Traffic Engineering" is the core of the problem network operators are most concerned about, such as new protocols mpls label switching at the same time to solve, but also provides a method to solve the "traffic engineering" is a good one. That router three interactive traffic status of each client and other information, with the convergence algorithm to calculate the mark within the network over time explicit path constraint shortest path first algorithm is adopted to allow traffic across the network in each time try to keep the balance. You can say that the development of network technology is changing. When Shen Qin in our great joy to ip-based Internet to bring us in, the router technology, especially the core router technology is undergoing dramatic changes, the router then Wu Amon had non-borrowed Bill Gates words, we do not know the router from only 18 months.
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Router Function
Simply speaking, the router has the following main features: First, network interconnection, the router supports a variety of LAN and WAN interfaces, mainly for LAN and WAN interconnection, to achieve mutually different communication networks; Second, the data processing services including packet filtering, packet forwarding, priority, multiplexing, encryption, compression, and firewall functions; Third, network management, router, including configuration management, performance management, fault management and traffic control. Router (router) is responsible for routing a network device, it looks for the least amount of a communications network path from multiple paths in the interconnection network to the user communications. Router for connecting separate multiple logical networks. To provide users with the best communication path, routers use routing tables to _select_ data transmission path, the distance between the routing table contains a list of network addresses and the addresses of routers use routing tables to find the correct path a packet from the current location to the destination address. Routers use the minimum time algorithm or optimal path algorithm to adjust the path of information transfer, if a network path failure or blockage, the router can choose another path, in order to ensure the normal transmission of information. Routers can convert data formats become necessary equipment for network interconnection between different protocols. Routers use routing protocols to obtain network information-based "routing matrix" routing algorithm and criteria to _select_ the optimal path. According to osi reference model, the router is a network layer system. Routers and router into a single multi-protocol router protocol. To complete a "route" work, in the router holds various data transmission path - routing table (routing table), when used for routing. Subnet routing table holds a sign information, the number of Internet routers and the next router name and so on. Routing tables can be fixed by the system administrator to _set_ good, you can also automatically adjusted by the router dynamically modified by the system, can also be controlled by the host. Involved in the router to the name of two related concepts address, that is: static routing tables and dynamic routing table. _Set_ well fixed in advance by the system administrator is called static routing table (static) routing table, usually when the system is installed on a pre-_set_ according to the configuration of the network, it will not change in the future with the network structure is changed. Dynamic (dynamic) routing table is a router based on the operation of the network system automatically adjusts the routing table. According routing protocol router (routing protocol) provides functionality, automatic learning and memory, network operation, automatically calculates the best path for data transmission when needed. To briefly explain the working principle of the router, and now we assume that there is such a simple network. As shown, a, b, c, d are connected together by four network routers. Now we look at the network environment shown in Figure router and how to play its routing, data forwarding action. It is assumed that a network user in a network a1 c c3 would like to send a user request signal, the signal transmission procedure is as follows: Step 1: User a1 address of the destination user c3 c3, together with the data in the form of data frames sent by the hub or switch in the form of broadcast to all nodes in the same network, when the router a5 port listens to this address, analysis that is not issued by the destination node network segment requires routing forwarding, the received data frame to put down. Step 2: After receiving the router port a5 a1 of the user data frame, removing header start c3 ip address of the destination user, and computing a best path to the user according to the routing table c3. Because from the analysis that the same id number and c3 network router c5 network id number, so sent directly from the router port to c5 a5 port via the router should be the best signal transmission. Step 3: c5-port router again to remove the ip address of the destination user c3, c3 identify ip address of the host id number, if there is a switch in the network can be sent to the switch, the switch to find the mac address table according to specific network node position; If you do not switch the device directly to the data frame transmission based on their ip address host id to the user c3, so that a complete data communication forwarding process is complete. As can be seen from the above, no matter how complex the network, in fact, the work of the router is so short, so the entire router works basically the same. Of course, in the actual network also shown to be far more on the many complex, practical steps like these will not be so simple, but the overall process is as follows.
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What router
Router: connect to the Internet each LAN, WAN equipment, it will automatically _select_ and configure the routing to the best path, according to the order before the signal transmission device according to the situation of the channel. What is interconnected to the network? A router. Routers English name Router, the router is the hub of the Internet, "traffic cop." Currently the router has been widely used in various industries, various grades of products have become the backbone to achieve a variety of internal connections, the main force of the backbone interconnection and interoperability with the Internet backbone business. The so-called routing means connected to each other via a network to move the information from the source location to the destination location of activities. In general, the process of routing information at least through one or more intermediate nodes. Often, people will compare routing and switching, mainly because it seems both ordinary users realized exactly the same function. In fact, the main difference is the routing and switching exchange occurs between the second layer (data link layer) OSI reference model, which occurs in the third layer routing, the network layer. This difference determines the routing and exchange of information in the process of moving to use different control information, the method to realize the respective functions of the two are different. As early as 40 years ago would have been a discussion between routing technology, but until the 1980s it gradually routing technologies into commercial applications. The reason why there is no routing technology is widely used in the beginning mainly because of the advent of the 1980s before the network structure is very simple routing technology useless. Until recent decades, large-scale network gradually become popular for the development of routing technology to provide a good foundation and platform. Routers are the main node device Internet. Router to forward data via routing decision. Forwarding strategy called routing (routing), which is the origin of the name of the router (router, forwarder). As a hub of interconnection between different networks, the router system constitutes the main context based on TCP / IP Internet Internet can also be said that the routers are the backbone of the Internet. Its processing speed is one of the major bottlenecks in network traffic, its reliability directly affects the quality of interconnection. Thus, in the park, regional networks, and the whole field of Internet research, router technology has always been at the core of its development process and direction to become a microcosm of the entire Internet research. In our current network infrastructure and information infrastructure in the ascendant occasion to explore the role of the router interconnection network, the status and direction of development for the domestic network technology research, networking, and a clear market for network routers and network interconnection various specious notion has important significance.
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Principle router
Router (Router) is used to connect multiple logically separate networks, so-called representatives of the logical network is a separate network or subnet. When transferring data from one subnet to another subnet, can be accomplished through a router. Therefore, the router has to determine the network address and choose the path of the function, it can interconnect in a multi-network environment, the establishment of a flexible connection, available completely different data packets and media access method to connect the various subnets, routers only accept station or other source router, the Internet is a network layer device. It does not care about the hardware used for each subnet, but required to run consistent with the network layer protocol software. The local router and remote router of the router, the local router is used to connect to the network transmission medium, such as optical fiber, coaxial cable, twisted pair; remote router is used to connect the remote transmission media, and request the corresponding device, such as telephone lines to With modem, a wireless receiver for the wireless transmitter. It works as follows: (1) workstation A workstation address 12.0.0.5 B's information along with the data in the form of data frames sent to the router 1. (2) After a router receives a packet from a workstation A, starting with the header to remove the address 12.0.0.5, and calculate the best path to the starting station B, according to the path table: R1-> R2-> R5-> B; and The data frames sent to the router 2. (3) Repeat the router 1 router 2, and will be forwarded to the router data frame 5. (4) Remove the same destination address of the router 5, found in the 12.0.0.5 network is connected to the router, so the data frame directly to the workstation B. (5) workstation A workstation B receives the data frame, and a communication process came to an end. In fact, the router in addition to the routing of the main function, but also has a network flow control function. Some routers support only a single protocol, but most routers can support multiple transport protocols, namely multi-protocol router. Since each protocol has its own rules, to complete the algorithm in a variety of protocols router, is bound to reduce the performance of the router. Therefore, we believe that the relatively low support for multi-protocol router performance. When users buy a router, you need according to their actual situation, they need to choose a router network protocols. In recent years there has been exchange router products come from nature that it is not a new technology, but in order to improve communications capabilities, the combination of the principles of the switch to the router, so that data transmission capacity faster and better.
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The role of the router
A role of the router is different communication network and the other role is to _select_ the information transmission lines. Choose smooth and fast shortcut, can greatly increase the communication speed, reduce network traffic load and save network resources, improve network system flow rate, so that the network system to play a greater benefit. From the perspective view of the filter network traffic, and the role of routers and bridges are very similar to switches. But with the work in the network physical layer, from the physical network segment on a different partition switches, routers use specialized software protocol logically divide the entire network. For example, a router that supports IP protocol network can be divided into multiple sub-segments, only point to specific IP addresses of network traffic can pass router. For each received packet, the router will re-calculate the checksum value, and writes the new physical address. Therefore, the use of a router forwarding and filtering data speeds are often slower than packet switches only see physical address. But for those complex networks using routers can improve the overall efficiency of the network. Another obvious advantage is that the router can automatically filter webcasts. Generally speaking, adding the entire installation process in the network router switch plug and play much more complicated than that. In general, heterogeneous network interconnection with multiple subnets interconnected routers should be adopted to complete. The main job of the router is to go through each data frame router to find a best path, and transfer this data to the destination site. Thus, the strategy is to choose the best path routing algorithm is the key to the router. To accomplish this, the router maintains a variety of related data transmission path - the path table (Routing Table), used for routing. Path table holds a sign subnet information, the number of Internet routers and the next router name and so on. Path table can be fixed by the system administrator to _set_ good, you can also automatically adjusted by the router dynamically modified by the system, can also be controlled by the host. 1. Static route table Pre-_set_ by the system administrator a good fixed path table called static (static) routing table, usually when the system is installed on the configuration of the network according to pre-_set_, it does not change with changes in the structure of the future network. 2. Dynamic Path Table Dynamic (Dynamic) path router table is based on the operation of the network system automatically adjusts the routing table. Routers based on routing protocol (Routing Protocol) provides functionality, automatic learning and memory network operation, automatically calculates the best path for data transmission when needed.
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Type of router
Internet various levels of network routers can be seen everywhere. Access network allows families and small businesses can connect to an Internet service provider; enterprise network router to connect a computer on campus or enterprise thousands; backbone routers terminal systems are usually not directly accessible, they ISP to connect long-distance backbone and enterprise networks. Whether the rapid development of the Internet backbone network, enterprise network or access network have brought a different challenge. Backbone routers requires a small number of high-speed link is routed. Enterprise-class multi-port router requires not only the number, inexpensive, and requires configuration is simple and convenient, and provide QoS. 1. Access Router Access Router ISP connection within the family or small business customers. Access Router has started not only to provide SLIP or PPP connection, also supports virtual private network protocols such as PPTP and IPSec, etc. These agreements must be able to run on each port. ADSL technology, such as the family to quickly raise the available bandwidth, which will further increase the burden on the access router. Because of these trends, the access router will support the future of many heterogeneous and high-speed ports, and the ability to run multiple protocols on each port, but also to avoid the switched telephone network. 2. Enterprise-class router Enterprise or campus-level router to connect many end systems, and its main goal is to try to achieve as much as possible cheap method endpoint interconnection, and further support the different requirements of quality of service. Many existing enterprise networks are connected by a bridge Hub or Ethernet segment. Although these devices are cheap, easy to install, no configuration, but they do not support the service level. Instead, there is a network capable of participating router into multiple collision domains machine, and thus can control the size of a network. In addition, the router also supports a certain level of service, at least allow into multiple priority levels. But the cost per port router to be more expensive, and before you can use to configure a lot of work. Therefore, the success of the enterprise router is whether a large port and a low cost per port, is easy to configure, support QoS. Also required to effectively support enterprise-class routers broadcast and multicast. Enterprise networks had to deal with a variety of legacy LAN technology to support multiple protocols, including IP, IPX and Vine. They also support firewall, packet filtering, and a lot of management and security policies and VLAN. 3. Backbone routers Internet backbone routers to achieve enterprise-level networks. Its speed and reliability requirements, at the expense of a back seat. Hardware reliability can be switched telephone network using the technology used, such as hot backup, dual power, dual data paths, etc. to get. These techniques in terms of almost all backbone routers are standard. The main performance bottleneck backbone IP router is to find a route the consumption of time in the forwarding table. When a packet is received, the input port to find the destination address of the packet in the forwarding table to determine the destination port, the shorter the package when the package to be sent or when many purposes when the port is bound to increase cost routing lookup. Therefore, the purpose of regular access to some ports into the cache can improve the efficiency of routing lookup. Regardless of the input buffer or output buffer router, there are bottlenecks route lookup. In addition to performance bottlenecks, stability router is also an often overlooked problem. 4. Terabit router In the coming three main technologies used in the core of the Internet, fiber and DWDM are already very mature and is readily available. Raw bandwidth corresponding router, the new network infrastructure if not provided with existing DWDM optical fiber technology and technology will not be radically improved performance, so the development of high-performance backbone switches / routers (terabit router) has become an urgent requirement. Terabit router technology is still mainly in the experimental stage of development. 5 Multi. WAN Router Back in 2000, Beijing welcomes all to engineers working on a multi-link (Multi-Homing) solution is found, the entire multi-WAN port Ethernet protocol devices there is a huge market demand in China. With welcomes all to the success of product development, the country's first dual WAN router was born in the year 2002, China's first dual-WAN broadband router is named NuR8021. Dual WAN router has two WAN ports physically as external network access, so you can go through the computer network load balancing features dual WAN router while using two external network access lines, a substantial increase in network bandwidth. There are currently dual WAN router "bandwidth aggregation" and "dual network" application advantages, which is the traditional single-WAN routers can not.
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Common router Glossary
Broadband Router In recent years, the emerging broadband router is a networking product, it came into being along with the spread of broadband. Broadband router in a compact box is integrated router, firewall, bandwidth control and management functions, with fast-forwarding capabilities, flexible network management and extensive network status and other characteristics. Most broadband routers Chinese optimized design for broadband applications, network traffic can meet different environment, with a good grid adaptability to meet and network compatibility. Most broadband router using a highly integrated design, integrated 10/100Mbps Broadband Ethernet WAN interface and built-in multi-port 10/100Mbps auto switch, easy multiple machines connected to the internal network and the Internet, can be widely used in homes, schools, offices, cafes , residential access, government, business and other occasions. Modular Router Modular router mainly refers to the router interface types and some extensions are based on the actual needs of the router can be configured to the user, these routers at the factory generally only provide the most basic routing functions, the user can according to the type of network you want to connect _Select_ the appropriate module, different modules can provide different connectivity and management capabilities. For example, most modular routers can allow the user to _select_ the network interface type, some modular router can provide VPN and other functional modules, some modular router provides firewall capabilities, and so on. Most current routers are modular routers. Non-modular router Non-modular routers are low-end routers, such non-modular router is usually home. This class is mainly used to connect the home router or ISP's small business customers. It not only provides SLIP or PPP connection, also supports virtual private network protocols such as PPTP and IPSec, etc. These agreements must be able to run on each port. Technologies such as ADSL broadband will soon increase the availability of each family, which will further increase the burden of access routers. Because of these trends, the future of such routers will support many heterogeneous and high-speed ports, and the ability to run multiple protocols on each port, but also to avoid the switched telephone network Virtual Router Virtual router virtual realistic Recently, some of the new IP backbone network equipment technology breakthrough for the future realization of the Internet has paved the way for new services. Virtual Router is such a new technology, it makes possible a number of new Internet services. With these new services, users will be able to network performance, Internet addresses and routing and network security control. Israel RND Networks, Inc. is a provider from LAN to WAN solutions for manufacturers, the company first proposed the concept of a virtual route. Core Routers Core router, also known as "the backbone routers," is located in the center of the network router. Edge of the network is called a router access router. Core routers and edge routers are relative concepts. They all belong to the router, but with different size and capacity. The core router is a layer another layer of edge routers. Wireless Router Wireless router is the router with wireless coverage feature, which is mainly used for Internet access and wireless coverage. Popular wireless routers on the market are generally support line xdsl / cable, dynamic xdsl, pptp four access methods, it also has some other network management functions, such as dhcp service, nat firewall, mac address filtering and more. One-armed router The concept of one-armed router appeared before three switches, network communications between each VLAN can be associated with ISL to achieve, in that case, the router will become a "one-armed router", the data transmission between the VLAN to enter the first router processing, and output, so that most of the network packets with the same VLAN will not need a router directly exchanged between devices in high-speed transmission. The disadvantage of this approach is that it is still the route is a centralized routing policy, and therefore the backbone generally provided with a plurality of redundant "one-armed" router, to share data processing tasks, which can reduce the router cause bottleneck problems, but also can increase the redundant links, but if the data transmission between the network VLAN than the larger, then the router will be formed at the bottleneck. One-armed router is now being replaced by basic Layer 3 switches
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Architecture router
From an architectural point of view, the router can be divided into first-generation single-bus single-CPU architecture router, the second-generation CPU architecture from a single bus master router, the third generation of a single symmetric multi-CPU bus architecture router; fourth-generation multi-CPU Multibus structure router, the fifth-generation routers shared memory structure, the sixth generation crossbar switch architecture, routers and router-based cluster systems and other types.
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Router configuration
Router has four elements: an input port, an output port, the exchange switches, routing processor and other ports. Input port is the physical link and enter the package. Usually provided by the line card port, a general line card supports 8 or 16 ports, one input port having many functions. The first feature is the packing and unpacking the data link layer. The second function is to find the input packet destination address in the forwarding table to determine the destination port (called routing lookup), the route lookup can be implemented using a general hardware, or by embedding a microprocessor on each line card to complete . Third, in order to provide QoS (Quality of Service), the port you want to receive the packet into several predefined service levels. Fourth, the port may need to run as SLIP (Serial Line Internet Protocol) and PPP (Point to Point Protocol) such data link level protocol or network-level protocols such as PPTP (Point to Point Tunneling Protocol). Once the route lookup is completed, the packet switch must be switched to the output port. If the router is the plus input terminal of the queue, there are several inputs share the same switching switch. Such a function of the input ports is to participate in the final of public resources (such as the exchange switch) arbitration agreement. Exchange switch can use a variety of different technologies. By far the most used technique is the bus exchange switch, crossbar and shared memory. The easiest switch to use a bus to connect all input and output ports shortcomings, the bus switch is its exchange capacity is limited to a shared bus arbitration overhead brought by the capacity of the bus as well. Crossbar providing multiple data paths through the switch, having N × N crosspoint switch can be considered to have a cross-2N bus. If an intersection is closed, the data input bus is available on the output bus, which is not available. Closing and opening by the scheduler to control the cross points, so the scheduler limits the switching speed of the switch. In the shared memory in the router, incoming packets are stored in the shared memory, packets are exchanged only pointers, which increases the switching capacity, however, limited by the switching speed of memory access speed. Although the memory capacity to double every 18 months, but the memory access time is only reduced by 5% per year, which is inherent in shared memory to exchange a limit switch. Output port before the packet is sent to the output link to the package store, you can achieve sophisticated scheduling algorithms to support the priority requirements. Like with the input port, an output port also to be able to support the packing and unpacking the data link layer, and many more advanced protocols. Route processor calculates the forwarding to achieve routing protocol, and run the router configuration and management software. It also does not deal with those online destination address in the packet forwarding card. Other ports generally refers to the control port, because the router itself does not end with the input and display devices, but it requires the necessary configuration to normal use, it is generally routers come with a control port "Console", used in conjunction with a computer or terminal equipment connected to the router through a specific software configuration. All routers are installed console port that allows users or administrators to use the terminal to communicate with the router, the router configuration is completed. The port provides a EIA/TIA-232 asynchronous serial interface for configuration (initial configuration must be through the console port) of the router locally. Console port to configure a dedicated cable to connect directly to the computer serial port using a terminal emulation program (such as "super terminal" Windows under) in the local router configuration. Console port router mostly RJ-45 port. Below contains a Console port configuration. Wi-Fi router Wi-Fi router is used to connect a wired and wireless network communications equipment, which can be via Wi-Fi technology to send and receive wireless signals to communicate with personal digital assistants and laptops and other equipment. Wi-Fi router can be _set_ up without cable, easy to build a computer network. However, when the outdoor data transmission over a wireless network, it's speed may be affected by the weather. Other wireless network also includes infrared, Bluetooth and satellite microwave.
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路由器的配置与调试
# Exit
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Router Function
(1) is sent to the remote network segment intercepted packets between networks, starting forward role. (2) _select_ the most reasonable route to guide traffic. To achieve this function, the router according to some routing protocol, routing table, routing table contains the path to the situation of each node contains the entire network, as well as between nodes and transmission costs associated with them. If the node has more than one specific path, based on predetermined criteria to _select_ the optimal (most economical) paths. Due to various network segments and their mutual connection may change, and therefore need to update the routing information of the case, this information is regularly updated by the routing protocol or by using a predetermined updating condition to complete the change. Each router in the network to dynamically update the routing table maintained by it in accordance with this rule, in order to maintain valid routes. (3) routers forward packets in the process, in order to facilitate transfer packets between networks, according to predetermined rules to break down large data packets to the appropriate size of the data packets to the destination and then packaged into packets decomposition original form. Router (4) multi-protocol communication protocol can be connected using a different network segments, different communication protocol as a communication network connected to the platform section. (5) the router's main task is to guide the traffic to the destination network, and then reach a particular node station address. After a function is accomplished by the decomposition of the network address. For example, to specify the allocation of a network address part of a group of nodes in the network, subnet, and the region, and the rest is used to specify a particular station in the subnetwork. Hierarchical addressing allows the router to have a lot of information network addressable storage node stations. Within the scope of the WAN router forwards packets according to their performance can be divided into two types, namely the intermediate node routers and edge routers. Despite the continuous improvement of various routing protocols, these two types of routers that use the name may be very different, but the role is played by the same. When an intermediate node routers in the network transmission, providing store and forward packets. Meanwhile the situation in accordance with the routing information maintained by the current routing table, and choose the best path to send packets. Companies from a plurality of interconnected routers LAN or corporate network consisting of WAN side and connected to the outside world, that is, the enterprise network edge router. It collects information from the external WAN to the corporate network addressing, forwarded to the network segment related to the corporate network; other centralized corporate network packets sent to each LAN segment external WAN, the relevant packets to determine the best transmission path.
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The difference between low-end and high-end routers
"Low-end routers and high-end routers are similar usage, why prices differ so far ah?" Actually, this is very well put, many friends are not familiar with the product technology will basically similar questions - "Why do the same function, this router is so expensive, and the other a so cheap "," Why Cisco routers so expensive? while the TP-LINK's so cheap? "," The main parameters of these two routers are the same, why the performance is so difference Far? " For these problems, we must talk about the basic principles of the router. Router works The simplest imaginable into one-way bus network, each computer can send packets to the bus to communicate with each other. But with the growth in the number of computers in the network, which is not feasible, it will generate a lot of questions: A broadband resource depletion. 2, each computer waste a lot of time to deal with independent broadcast data. 3, the network becomes unmanageable, any error could lead to paralysis of the entire network. 4, each computer can listen to communicate with other computers. The network segment can solve these problems, but you must provide a mechanism for different segments of the computer can communicate with each other, such that motivated the router device: Routers work at the network layer IP protocol for the forwarding of data between subnets. Routers typically have multiple network interfaces, including local and wide area network interface network interface. Each network interface to connect different networks, network routers recorded information for each network port is connected. At the same time there is a router also save routing table, which recorded destined to be sent to a different network address port number. Internet users use a variety of information services, the communication of information is ultimately boils down to information transmitted in IP packets as a unit, IP packets in addition to including the data information to be transmitted, but also contains information to be sent to the destination IP address, Source IP address of the information transmitted, and some related control information. When a router receives an IP packet, it looks for the packet routing table based on the destination IP address entries, based on the results of this search IP packets sent to the corresponding port. After the next station IP router receives this packet forwarding continues until sent to the destination. Can exchange routing information between routers routing protocol to update the routing table. Factors that affect the performance of the router After the above introduction, perhaps we still not very understanding of the work of the router, in fact, it does not matter, this is not our purpose, we mainly with you to explain the working principle of the router determines that it must use the chip to complete the necessary judgment and forwarding data packets, and this work is done by a processor, a variety of pending or packet there is a good deal of memory inside, so the operating frequency of the processor and memory capacity largely determines a paragraph router performance. However, the performance of the router can not fully see the processor frequency and memory capacity, processor performance using a router was really poor, but in turn, the processor performance is not necessarily a good router is good; processor clocked at just one processor performance its bus width (16 or 32), Cache size and structure, the internal bus structure, a single-CPU or multi-CPU distributed processing, operation mode indicators will affect processor performance. RISC CPU communications professionals are almost all routers, so "using communications professionals RISC CPU" is equivalent to saying nothing, the key depends on this CPU in the end with what the kernel, how the internal structure. Memory is the same memory size is not everything, if the load is not, then 4M and 8M of RAM memory effect when using perhaps would not have much difference, so depending on memory size to absolute judgment router performance is not science (Of course, memory capacity still good). Decided router grade index Although the above has been said, the processor and memory performance is largely decided by the router, but the router determines a grade of indicators is that they do not, which is why the main parameters of the product often do not see these two parameters marked , then what is generally used to measure the quality of a router it? way of saying that the load capacity, is also popular with a number of machines called. However, the amount of data that is not a standardized quantity with a machine, it is to be based on actual usage to measure, such as Internet cafes all buried in the Internet chat, games, and almost all of the data through the WAN port, so the heavy load ; But if it is a corporate network, most people are busy engaged in the design, write reports, make plans, at the same time only a small number of people using the network, and most of all internal data flow in the enterprise network, so the router load is light, it can simultaneously load more clients. If it is said that the maximum load 253, it does not make sense, because the DHCP IP addresses can be assigned the maximum is 254, minus the router it myself one is 253, which can not be called indicators, basically bluffing. So, we look at the actual load capacity of a router, rather than theoretical load capacity. Since there are many uncertainties and deceptive load capacity, so the other indicators are also popular concern, and that is throughput. Throughput refers to the amount of data that can be processed per second router, this parameter is the LAN-to-WAN throughput, the measurement results should be opened under NAT, firewall turned off, the Chariot, respectively, and with two test methods Smartbits respectively. With Smartbits way when comparing test data packet 64Byte, compete with established contractors; Chariot test is best carried out in a multi-connection, the connection can generally choose 100 pairs basically you can see the difference between products. The reason the price impact of the router After the above discussion, we are finally able to return to the question to be answered: why the price difference between different routers so big? The main reason: 1. Different performance, strong performance router built-powerful processor and large memory capacity, so the cost is relatively high. 2 different applications, the strong performance of the router can be used to network more load, and low-end routers too much. 3 different functions, although the same basic functionality, but some routers also built other more useful features, like a professional firewall functionality, VPN these, so the higher technical requirements, the price will naturally follow to improve.
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Difference between routers and switches
Evolved from the traditional switch bridge, the second layer that is part of OSI data link layer device. It is based on MAC addressing, routing table by station, station table by the establishment and maintenance of automatic switches. Routers that belong to the third layer OSI network layer device that can be addressed by IP address, routing protocols generated by the routing table. The greatest advantage of the switch is fast, because the switch only needs to identify the MAC address of the frame, _select_ the forwarding port directly produce simple algorithm based on MAC address, to facilitate ASIC implementation, and therefore high forwarding speed. However, the working mechanism of the switch also brought some problems. A loop: establishment algorithm based on learning and stations switch address tables, there is a loop between the switches are not allowed. Once the existence of the loop, you must start the spanning tree algorithm, blocking off the port circuit generates. The router's routing protocol does not have this problem, how can pathway between routers to balance the load and improve reliability. 2 Load concentration: there is a path between the switch only such information _set_ on a communication link can not be dynamically allocated, to balance the load. The router's routing protocol algorithm can avoid this, OSPF routing protocol algorithm not only can produce multiple routes, but also to choose the best route to their different for different network applications. 3 Broadcast Control: Switch can reduce collision domains, but can not reduce the broadcast domain. Entire switched network is a large broadcast domain, broadcast packets scattered throughout the switched network. The router can isolate broadcast domains, broadcast packets through the router can not continue to broadcast. 4 subnetting: switch can only identify the MAC address. MAC address is a physical address, and the use of a flat address structure, and therefore can not be divided into subnets based on MAC addresses. And identify the IP address of the router, IP address assigned by the network administrator, is a logical address and the IP address has a hierarchical structure, is divided into network number and host number, can be very easily used for subnetting, the main function of the router is used connect different networks. 5 confidentiality issues: Although the switch can also be based on the source MAC address of the frame, the destination MAC address and the contents of other frames in the implementation of the filter frame, but the router packets based on source IP address, destination IP address, TCP port address and other content on newspaper Man implement filtering, more intuitive and convenient. 6 medium dependent: switch the device can also be used as a bridge to complete the conversion of different link layer and physical layer, but the conversion process is more complex, not suitable for ASIC implementation is bound to reduce the forwarding speed switch. So now the main switch to complete the same or similar physical media and link protocol internetworking, and will not be used between physical media and link layer protocol falls far short of the network interconnect. The router is different, it is mainly used for the interconnection between different networks, so they can connect to the network in different physical media, the link layer protocol and network layer protocols. Although the function of a router took advantage, but expensive, low packet forwarding rate.
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The difference between wireless router and wireless AP
Functional distinction between the wireless AP and wireless router Wireless Router: wireless router is a combination of simple broadband router AP; which by means of router functions, enabling wireless home network Internet connection sharing, and residential broadband ADSL wireless shared access, in addition, a wireless router It can be through wireless and wired connection terminals are assigned to a subnet, a variety of devices to exchange data within this subnetwork is very convenient. It can be said that the wireless router is AP, routing, and aggregation switches to support wired and wireless composed on the same subnet, directly connected to MODEM. The wireless AP is equivalent to a wireless switch, connected to the wired switch or router, the wireless network card connected to it share IP from the router there. To apply the distinction between the wireless AP and wireless router Independent AP AP those needed for large area coverage of the large companies use more than, all connected via Ethernet and the AP is connected to a separate wireless LAN firewall. Wireless router used most often in a SOHO environment, in this environment, an AP is sufficient. In this case, the integration of broadband access router and wireless AP router provides a single solution to the machine, it is compared to the two separate solutions to be easy to manage the machine and cheaper. Wireless routers typically include a network address translation (NAT) protocol to support wireless LAN users to share network connections - which is a function of good use SOHO environment. They may also have a basic firewall or packet filter to prevent port scanning software and other attacks against broadband connection. Finally, most wireless routers include a four-port Ethernet switch, you can connect several wired PC. This is for the management of the router or to a printer connected to the LAN is very convenient. Network topology analysis to wireless AP and wireless router AP is not directly connected with ADSL MODEM, so must be used to add a switch or hub; When using the above topologies, AP, and the use of the wireless router is the same. However, most wireless routers due to the ability to have broadband dial-up, it can be directly connected with broadband ADSL MODEM share: To analyze the cost of wireless AP and wireless router 802.11B wireless AP and wireless router almost the same price, generally more expensive wireless routers around 100 yuan; 802.11G will depend on the specific case, the difference in price depending on the brand and have additional features ranging from a few hundred dollars gap, but also cheaper products spread over 100 yuan.