Three-layer switching technology exchange technology
is: two or three-forward switching technology + technology. It solves the division of the LAN segment, the segment in the subnet must rely on the router to manage the situation, to solve the traditional low-speed routers, complex network bottlenecks caused by the problem.
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Introduction to the third layer switching technology to deploy the basic principle of the third layer switching technology easy to understand the network topology of the second and third layers of the exchange layer the second layer the second layer switching advantage of the exchange of exchange of the third layer third layer switching advantages deployment of the third layer switch 20/80 rule 80/20 rule 20/80 rule to resolve the problem layer switching deployment of the third example of what is the principle of exchange of three-tier three-tier exchange Three types of switches, switching technology compared with other technologies to deploy a third layer switching is rapidly developing into a launch platform for next-generation applications can be used as the most suitable network technology. This article details how to deploy this technology, and the third level of the exchange to get the maximum efficiency. LAN switching is a third layer in many regions (including the core and focal point for the server) the key components, because the technology can solve many performance, security and control issues. However, in some areas of the network, the use of the technology effect is not very significant, especially in the desktop connectivity. This article will focus on the case of low network performance, especially in the new generation of high-level exchange of the fourth layer of the desktop technology has to offer today's high-performance and control. This paper will elaborate on the second (d) layer switch is how to provide lower cost, simpler, more manageable desktop solutions. Introduction of any new technology into the market, industry professionals have experience with this technology and the new term These new technical terms often leads to confusion, even contradictory,
air force 1 shoes, depending on suppliers to use to them. For example, the third layer switching, the fourth layer switching, multilayer switching, multi-layer packet classification and routing switches,
nike air force one, new terms such as switches and routers to make the traditional distinction between become blurred. In addition, many vendors in the original room for the second layer of wiring on the switch platform provides a third layer switching technology, which makes even more confusing. These changes make it difficult for network design to understand how to deploy cost-effective network solution. Therefore, we must Quweicunzhen, and focus on the basics, can really understand when, where and why the use of the third layer exchange. The third layer switching technology, the basic principle of exchange of the third layer is introduced in the network switches routers routing module and replace the traditional switching and routing to achieve a combination of network technology. It is based on the practical application of the circumstances, the flexibility in the network layer of the second layer or third segment the network. With three switching device is a third layer with a second layer of routing switches, but it is the combination of both, not simply the router hardware and software equipment, superimposed on the LAN switch. The third layer switch design is based on a careful analysis of IP routing, the IP routing each message must be extracted through the process, this process is very streamlined process. The majority of IP packet routing is a packet does not contain the option, so in most cases, IP option packet processing work is redundant. Different network packet length is different, in order to adapt to different network, IP packet fragmentation to achieve the function, but in all the Ethernet environment, the network frame length is fixed, so the packet is fragmented may be omitted work. The third layer switching technology is not up to the router using the address mask matching method, but use the exact address match approach, so that is conducive to the hardware for fast lookup. It uses the method of using the cache, the recent frequent use of the host route into the hardware lookup table, only in this cache will be unable to match the project to go forward through the software. In store and forward flow used during the exchange, the exchange in the flow, analyzing the first packet to determine whether that represents a stream or a group with the same source and destination addresses of packets. If the first reported stationery with the right features, then the follow-up to identify the stream of packets will have the same priority, the same class in subsequent packets are switched to the destination address on the second floor, and now the three Switch to high-speed switching, have adopted flow exchange. IP routing in the handling has been improved to achieve a simplified IP forwarding process, the use of dedicated hardware forwarding ASIC chip, so the vast majority of message processing can be implemented in hardware, only a very small number of reported Wencai need to use the software forwarding, the forwarding performance of the whole system can be increased a thousand fold, the same performance at the cost of equipment has also been significantly reduced. Each VLAN corresponds to a IP network segment. On the second floor, VLAN isolation between, this is the engine with the second floor of the exchange switch functionality is exactly the same. Between different IP network segment access to cross VLAN, to use the three inter-VLAN forwarding engine provides routing capabilities. Layer switches and routers use the network, each IP network segment needs to communicate with other IP network segment will need to use a router interface as the gateway. The third layer is equivalent to the traditional network forwarding engine of the router, when you need to communicate with the other VLAN in the three-tier exchange engine also assigns a routing interface to do VLAN gateway. The three routes on the switch interface is in the three-forwarding engine and forwarding engine on the second floor, is transmitted by configuring the chip to achieve, and the router interface different, it is not visible. The following example to illustrate the communication process. Suppose two sites using the IP protocol A, B communicate through a third layer switch, sending station A is sent at the beginning, his own IP address and IP address of station B comparison to determine whether the B station in the same subnet with its own inside, if the destination station B sends station A and in the same subnet, then forwarded to the second floor, not on the same subnet if the two sites, such as the sending station A to station B with the purpose of communication, the sending station A to the three Layer three switching module switches to issue ARP (Address Resolution) packets. When the sending station A on the IP address of three switching modules broadcast an ARP request, if the three-tier switching modules in the communication process in the past already know the MAC address of station B, then A replies to the sending station B's MAC address, or three-layer routing information exchange module according to the station broadcast an ARP request for B, B stops to get this ARP request back to the three-tier switching module MAC address of its three-tier switching module to save this address and respond to the sender station A, while B Station The MAC address to the MAC layer switching engine in the address table. From that point on, A to B to send all packets to the second floor of the exchange will be treated to high-speed exchange of information. As can be seen only in the routing process only requires three processing, most of the data transmitted through the second floor of the exchange, three fast switches, proximity switches, the speed of the second floor. The third layer switching technology used in the simple topology of the backbone switch to connect to the server equipment, switches, hubs, workstations, and so on. The core switch is a third layer switches, by which to divide the logic functions of two different subnets, to achieve communication between different VLAN. It can be seen from Figure 1, in the same virtual subnet within three switches VIAN only have the function of the exchange floor in order to ensure the transmission speed requirements, and between different subnets VIAN, three switches, but also for three The role of the exchange, ARP can correctly parse the data stream to ensure the correct transmission, while it also supports multicast, frame and packet filtering, traffic calculation and other functions to ensure the security and user needs. In order to fully understand the network layers to understand the third layer switching, in which it is necessary to use most of the current network architecture of the strong hierarchical model for analysis. As shown, network infrastructure equipment (such as bridges, routers and switches) has traditionally been classified by OSI layered model. The OSI model is still the reference hierarchical model of data networks, because it simplifies the two computers to communicate with the tasks to be performed, each has a specific function. OSI model defines the way these layers interact, and in turn defines the role of the various network components to determine how these components integrated with the hierarchical network. Network components, switches (layer) switches on each port provides a unique network segment, resulting in the separation of collision domains. Router (third layer) routers detachable broadcast domain, and can connect to different networks. Router is the address of the target network layer (third layer) rather than the workstation data link layer MAC address to direct Internet traffic. Routers are usually based on software, so performance is relatively slow compared with the second layer switches. The third layer switch (third layer) The third layer switch in the use of traditional routers can be deployed anywhere on the LAN. The third layer switch to provide senior's ASIC technology is much higher than the performance of traditional routers,
nike air force 1, making them ideal for bandwidth-intensive applications. In addition, the third layer of a typical router switches combined bridge separated from each other (second layer) and routing (Layer) capabilities. The combination of these technologies provides a greatly improved ability to more natural expansion of the network architecture. Exchange of the second and third tiers in order to keep the advantages of the third layer switching and how to more effectively use the third layer switching, we must first understand the current network design can be used for the exchange of two ways: exchange of the second layer, third layer switching (routing). Exchange is received from an interface, and then sent through another process of the interface. Exchange of the second layer and third layer is the difference between the output interface to determine the correct frame type of information. ¨ In the second layer exchange, the exchange of frames based on MAC address information. ¨ In the third layer switching, the frame on network layer information exchange, such as the IP address. The second layer switching exchange is in front of the second layer of the OSI model described the data link layer. It checks the frame, and the target MAC address forwarding frames. If you know the destination address, and the second layer of switches, Ethernet frames will be forwarded to the appropriate interface. If the second layer switches do not know where to send the frame, it broadcasts the frame to all ports forwarded to the proper destination address. The second layer switches use this technology to build and maintain a tracking frame destination address of the exchange table. For larger networks, this broadcast forwarding operation will have a serious problem, because all of the processing of these broadcasts will cause a significant reduction in performance. The solution to the problem in this white paper will be discussed later. Advantage of the second level of the exchange is relatively simple because the second layer switching, network administrators can create management is simple and can be extended to hundreds of nodes in the network, and will not encounter too many problems of the second layer broadcast. The second layer switches for the network provides the following advantages: l High bandwidth: the second layer switches by dedicated bandwidth assigned to each port for each user to provide excellent performance. Each switch port represents a different network segment, so each user can access a specific amount of bandwidth. In addition, each specific business segment along with an individual can receive broadcast business. l VLAN: switch to the second layer of the various ports into logical workgroups (virtual LAN or VLAN). Each VLAN group is logically separated with the rest of the switch, the second layer to help control the broadcasting business in a specific VLAN group. This provides two main advantages: 1. VLAN network designers can use to build the second floor to avoid the serious problem of large broadcast domain the second layer network. 2. The network around the moves, adds and changes easier, because no matter the physical location where the user is always in their own VLAN. The third layer switch or router on the VLAN communication is indispensable. l type of business priorities: the second layer of certain classes of business on the switch (CoS) prioritization allows the network administrator of the agreement, IP address and type of standard Ethernet LAN services to the distribution of different types of priority levels. This enables network administrators to under the agreement, application or user control of the business flow, thereby ensuring a more efficient network operation. l User Security: The second layer switches provide robust security based on the user's machine quality, this machine quality network-based login (802.1x) technology to prevent any unauthorized users accessing the network. The third layer third layer switching in the network switching layer. It examines packet information and forwards the network layer destination address packet. Addressing the second layer and the fixed systems, the third layer address by the network administrator to install the network layer to determine. IP, IPX, and AppleTalk protocols such as use of the third layer addressing. Addressing system using the third layer, network administrators can create an address group (subnet). These subnets allows the network administrator for a unit (subnet) subnet in the form of easy to manage members, to support the establishment of a hierarchical addressing system can be extended. The third layer addressing system is also more dynamic than the second layer of the system. If the user moves to another location, the terminal will receive a new address of the third layer, the second layer MAC address remains the same. This is similar to someone moving from one city to another city: postal address will change, but the personal name and identity remain unchanged. Thus, the third layer routing logical addressing structure of the network can connect to the physical infrastructure, thus providing a second layer of the network than the more flexible and scalable hierarchical structure. The advantages of the third layer switching provides the following advantages Third Exchange: l improve network efficiency: The third layer switch by allowing the network administrator on the second VLAN routing operations to ensure control of the second layer broadcast within a VLAN, reduce traffic load. l Sustainable development: the OSI layer model of the layered characteristics of the third layer switches to create a more easy to extend and maintain a larger network. l broader topology options: router-based network to support any topology, and can more easily than the second layer switching network similar to a larger scale and complexity. l Working Group and server security: The third layer device network address according to the third layer to create access policy, which allows network administrators to control and block some of the VLAN to VLAN traffic, blocking some IP addresses, and even prevent some of the sub- Net to access specific information. l more excellent performance: by using advanced ASIC technology, the third layer switch can provide far higher than traditional software-based router performance. For example, 40 million packets per second of 300,000 packets per second. Gigabit network switches for the third layer the bandwidth-intensive infrastructure that provides the necessary routing performance. Thus, the third layer of switches can be deployed in the network has a higher strategic significance in many locations. The deployment of the third layer switch to know the second and third tiers of the relative merits of the switch, you can know that every switch in the network where the greatest effect. 80/20 rule early nineties, establishing the rule of thumb, it believed that 80% of all traffic should be on the local subnet, only 20% of traffic should be passed to the router. Over the years, the law has been accurate, but the router can be fairly easily handle a variety of traffic levels. As more of the broadcasting service is controlled in a specific local network segment, in the second layer using the VLAN on the switch have some effect. 20/80 rule, however, over the past few years, the establishment of a large number of servers to help improve security and management, coupled with the increasing use of internal networks and client / server services, led to great changes in the LAN traffic. Now, 80% of all traffic is passed to the routing network, and only about 20% of the business is controlled on the local subnet. This new route network structure presented a huge demand, because each time a user access to the server in a different subnet, its communications business has to go through the third layer device (usually second only to forward 300,000 packets router) to solve the problem of 20/80 rule is clear, with a second layer of single core router network can not expand, and its on today's network flow is poor. Therefore, we must learn how to create a third layer of the right switches, hierarchical design. Need to consider the following three network components: the network core, focal point for the wiring closet, desktop, network access points l Core: The core network components should be considered in the design of performance and flexibility. The third layer switch gives his own in this role, because they are addressed by layering provides a natural flexibility, and they also provide far superior to the performance of traditional routers. l collection point wiring closets: The core layer can help to provide a boundary, and desktop access devices provide an important service. These services include VLAN routing, security, access and address sectoral focus. For larger network installation, the reason need a third layer switch because it switches to the desktop to provide the right service and provides the necessary route to the performance of the core switch. Third Exchange deployment sample solution 1: branch in this case, a need to connect branch offices and the headquarters of the local server. The third layer switches are deployed in the network backbone, responsible for implementing the local server, local area network to a broadband router business and the third layer switching. In short, three-tier exchange of technology is: two or three-forward switching technology + technology. It solves the division of the LAN segment, the segment in the subnet must rely on the router to manage the situation, to solve the traditional low-speed routers, complex network bottlenecks caused by the problem. What is the exchange of three-tier three-tier exchange (also known as multi-layer switching technology, or IP switching technology) is compared with the traditional concept of the proposed exchange. As we all know, the traditional exchange of technology is the standard model in the OSI network layer data link layer of the second operation, while the three-tier model in the network switching technology in the third layer of the high-speed packet forwarding. In short, three-tier exchange of technology is: two or three-forward switching technology + technology. Layer switching technologies, to solve the division of the LAN segment, the segment must rely on the router in the subnet to manage the situation, the solution to the traditional low-speed routers, complex network bottlenecks caused by the problem. Principles of a three-tier three-tier exchange switching equipment, is the third layer with a second layer of routing switches, but it is the combination of the two is not simply a router device in the hardware and software stack LAN switch. The principle is: if the two sites using the IP protocol A, B communicate through a third layer switch, sending site A is sent at the beginning, his own IP address and IP address of station B comparison to determine whether their B station in the same subnet. If the destination station B sends station A and in the same subnet, then forwarded to the second floor. If the two sites not on the same subnet as the sending station A to station B with the purpose of communication, the sending station A to the three-layer switch is actually switching module. A sending station when the . Otherwise the three-tier switching module according to the routing information to the station broadcast an ARP request for B, B stops to get this ARP request back to the three-tier switching module MAC address of its three-tier switching module to save this address and respond to the sender station A, while B Station MAC address to MAC address layer switching engine in the table. From that point on, when the A to B to send all packets to the second floor of the exchange will be treated to high-speed exchange of information. Since just before the routing process needs three handle the vast majority of data transmitted through the second floor of the exchange, so three fast switches, proximity switches, the speed of the second floor, while lower prices than many of the same router. Three-switch three types of switches can handle the data according to different hardware and software-divided into two pure class. (1) pure hardware technologies are relatively complex three-tier technology, high cost, but speed and performance, with load capacity. The principle is the use of ASIC chips, using the hardware approach to routing table lookup and refreshed. Figure 1. Figure 1 Principle of pure hardware three switches when the data come from the port interface chip after receiving the first chip in the second floor of the exchange aims to find the corresponding MAC address, if found, forward to the second floor, otherwise the data sent to the three-engine . In the three-engine, ASIC chip, the routing table to find the appropriate information, the purpose of IP addresses and data comparison, and then send the ARP packets to the destination host, to get the host's MAC address, MAC address will be sent to the second floor of the chip, chip from the second floor of the packet forwarding. (2) software-based three-layer switch technology is relatively simple, but slow and not suitable as a backbone. The principle is the use of CPU with a software way to find the routing table. Figure 2. Figure 2 software layer theory when the switch port interface chip receives the data come from the future, the first chip in the second floor of the exchange aims to find the corresponding MAC address, if found, forward to the second floor or the data sent to CPU. CPU to find the appropriate routing table information for the purpose of IP addresses and data comparison, and then send the ARP packets to the destination host by the host's MAC address, MAC address will be sent to the second floor of the chip, the chip from the second floor of the packet forwarding . CPU processing speed is slow because of low prices, so the slow processing speed of three switches. Market Selection in recent years become a hot spot of broadband IP network construction, located in below to access for small and medium-scale layer or aggregation layer of the third layer switch products, for example, three switches are some specific techniques. The mainstream in the market access third layer switch, there are Cisco's Catalyst 2948G-L3, Extreme's Summit24 and AlliedTelesyn the Rapier24 so that several three-layer switch products with different features, covering the three characteristics most applications the switch . Of course, in the choice of the third layer switch, the user can according to their needs, determine and select the product or products of other manufacturers such as Nortel Networks Passport / Acceler series, the former Cabletron's SSR series (one in four in Cabletron after SSR three switches have been incorporated into most of Riverstone Company), Avaya's Cajun M series, 3Com's Superstack3 4005 series. In addition, the domestic network vendors Digital Network, TCL Network, Shanghai SVA to be sure, here Network Alliance, Capitel so on, have launched a three-switch products. The following three products which are introduced to enable you to more comprehensive understanding of the three switches, and for the right to choose their own models. Cisco Catalyst 2948G-L3 switches with industry-standard IOS provide a complete solution, in the version 12.0 (10) or more full support for IOS access control lists ACL, with the core Catalyst 6000, a comprehensive end to end to complete the construction of broadband metropolitan area network (Catalyst 6000 MSFC module to complete its use of multilayer switching services, and had stopped using the RSM Route Switch Module,
air force 1 high, IOS more than version 6.1 fully supports ACL). Extreme layer switching products solutions company, providing unique capabilities of the Ethernet bandwidth allocation, cutting unit is 500kbps or 200kbps, service providers can charge based on bandwidth usage, enabling a fixed delay of audio and video transmission. AlliedTelesyn company Rapier24 three switches feature provides PPPoE, enrich and improve the user authentication and accounting methods may be suitable for multiple access networks, applications, flexible, easy to implement business options, while protecting existing investment in current users, and the other with NAT (network address translation) and DHCP-Server and other functions, as many service providers promising. In short, the three made the switch from the concept to today's popular applications, though only after a few years time, but its function has been extended by a wealth of practical application. With the ASIC chip technology, hardware development and practical application of the promotion, three switching technologies and products will be further developed. Layer switching technology compared with other technologies can be seen, the second floor is mainly used in small local area network switches, the number of machines in the second, thirty sets the following, such a network environment,
nike air force one high, the broadcast packets has little effect on the second floor switch quickly switching, multiple access ports and low prices for small network users with a very complete solution. In such a small network routing functions did not need to introduce in order to increase the difficulty and cost of management, there is no need to use a router, of course, no need to use three switches. Three switches designed for IP, interface type simple, with a strong layer packet processing capabilities, so for large local area network,
air force one shoes, in order to reduce the broadcast storm damage, must be large local area network by function or geography and other factors into a program he a small local area network, which is a one of a small network segment, so this will inevitably lead to different segments there are a lot of visits, the switch can not simply use the second floor of the exchange of visits and simple to achieve interconnection using a router, then the number of ports limited and slow route, which limits the size of the network and the access speed, so this kind of environment, from the second floor of switching and routing technology from the three-switch combination on the most suitable. Many types of router ports, support for multi-layer protocols, routing capability, it is suitable for the interconnection between a large network, even though a lot of three-layer switch has a heterogeneous network interconnection switch ports, but in general large network of interconnect port small, connected devices is not the main function of rapid exchange between the ports, but to choose the best path for load sharing, link backup and the most important routing information with other networks exchange, all of which are routes to complete the function. In this case, the natural can not use the floor switch, but whether to use the three switches, then, as the case down. The main factors affect network traffic, response time requirements and the investment budget. Three of the most important purpose of the switch is to accelerate the exchange of data within a large local area network, but also blend into the routing services for this purpose, so it's routing capabilities of the professional-grade router is not the same intensity. In the case of a large network traffic, the switch only if the three do the exchange within the network, it did the interconnection routing, will be significantly increasing its burden of response speed. In a large network traffic, but requires high speed of response by the three switches to do under the exchange within the network, the router responsible for routing the work of interconnection, which can give full play to the advantages of different devices, is a good cooperation. Of course, if by the investment budget constraints, the three switches also offering interconnection interconnection, is also a good choice. Atlas Atlas entry for more extended reading: 1
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