Layer-3 Exchange Technology Analysis and Application Development

There are many things worth learning about the exchange technology. Here we mainly introduce the Analysis and Application of the Third-layer exchange technology. The third-layer switch is also called a routing switch. The third-layer switch can be seen as a model, it involves the second and third layers of the ISO Reference Model. As a switch, it has the same attributes as the second layer, and combines the advantages of the second layer switch and the third layer router into a flexible solution, it can provide line rate performance at all levels, so it has certain routing performance.

This integration structure also introduces policy management attributes, which not only associate Layer 2 with Layer 3, it also provides prioritized communication traffic processing, security, and a variety of other flexible functions, such as dynamic deployment of trunking, VPN and Intranet.
　
The interface layer includes all important LAN interfaces: 10/100 Mbit/s Ethernet, gibit Ethernet, FDDI, and ATM. The switching layer integrates multiple LAN interfaces and is supplemented by policy management. It also provides trunking, VLAN, and tag mechanisms. The routing layer provides the main LAN routing protocols: IP, IPX, and AppleT, and provides traditional routing or pass-through layer-3 forwarding technology through policy management. Policy management and administrative management enable the network administrator to adjust the network according to the specific needs of the enterprise or department. Compared with Layer 3, the level of adoption of Layer 2 determines the so-called network control classification, as shown in 3. A pure second-level solution, that is, the "Everywhere transformation" shown in the figure, which provides at least control over subnet division and broadcast restrictions. Layer-3 switches provide dynamic and integrated support for all levels in the classification. Traditional general-purpose routers and external switches can also achieve this goal, but compared with this solution, layer-3 switches only require less configuration, less wiring, and cheaper prices, and provides higher network performance.
　
Evolution of layer-3 Exchange Technology
 
With the continuous upgrade of hardware and software, the development of layer-3 switching technology has also undergone a "three generations" change. The first generation switch is a mixture of discrete electronic components and primitive software frameworks. The software function runs on a processing machine with fixed memory. With the improvement of management support and protocol functions, software functions are also increasing. When your daily business is more dependent on the network and the traffic on the network increases, the network device becomes a bottleneck. Although processors and memory become faster and more effective, the increase in communication traffic is more rapid. The first step to solve the problem is to simplify the network layer: replace vrouters with vswitches to reduce the overhead of data packets and significantly increase the transaction processing speed. Introduces a dedicated Integrated Circuit ASIC dedicated for optimizing Layer 2 processing. This improves the performance by 10 times and reduces the overall cost of the system. Figure 4 shows the first generation of architecture.
　
The third-generation exchange technology is not only based on the progress of the second generation, but also based on ASIC + RISC technology, which is an optional policy for layer-3 routing, multicast, and users) in terms of line rate performance, the total data throughput can exceed several million packets per second. Because a policy-based service mechanism is used to support QOS, the FIRE can be used to introduce distributed data packets to process DDP.) data packets can be quickly and independently transmitted to the system, at the same time, dynamic classification of PACE technology and RSVP are used to flexibly combine the performance of Layer 2 and Layer 3. In the layer-3 switch, you can use a built-in processor to support ASIC. For example, you do not need to upgrade hardware or sacrifice system performance. Layer-3 switches of the third generation support multimedia network communication, which can effectively reduce latency and ensure security. As switches, hubs, and NICs adopt a unified system environment, the vswitch supports image transmission over Ethernet.

Multi-layer exchange development prospects
 
With the development of layer-3 switching technology, layer-4 switching has emerged. It expands layer-3 and layer-2 switching and supports more fine-grained network adjustment, and the priority of communication streams. The layer-4 switch is a policy-based route. It is located on the layer-4 of the ISO Reference Model and uses the layer-4 information. According to the layer-4 Information, for example, the port number of the data packet in TCP/UDP is exchanged. It allows you to prioritize communication data based on applications and use a certain amount of bandwidth for important applications based on the traffic of a specific application.

In a sense, layer-4 Switching provides a service level COS in the network. This can reduce WWW or FTP traffic for an Intranet and set higher priority for E-MAIL or Telent traffic. Third, layer-4 switching is a process based on accelerated routing. Currently, stream or label-based routing technologies have also been released, for example, the Fast IP address and NHRP switch launched by 3Com and the MPLS Multi-Protocol Label Switch launched by Alcatel. Multi-layer switching helps bridge the LAN and WAN. With the development of information globalization, the boundaries between the LAN and WAN become increasingly blurred, layer-3 Exchange Technology lays a solid foundation for future scalable solutions.