Cellular Modem Router is a network device that connects multiple networks or network segments.It can "translate" data information between different networks or network segments so that they can "read" each other's data.Thus forming a larger network. Cellular Modem Router has two typical functions, namely data channel function and control function.Data channel functions include forwarding decisions, backplane forwarding, and output link scheduling, which are generally performed by specific hardware.The control functions are typically implemented in software,Including information exchange with adjacent Cellular Modem Router, system configuration, system management, etc.
Cellular Modem Router plays an important role in the computer network and is the bridge of the computer network.It can not only connect different networks, but also choose the path of data transmission, and can block illegal access.As the core equipment of IP network, Cellular Modem Router technology has become the key technology of the current information industry.The equipment itself plays a more and more important role in data communication.
Performance and service play a key role in the evolution of Cellular Modem Router technology.On the one hand, the growth of bandwidth and network scale promotes the performance and capacity of Cellular Modem Router. On the other hand,The development of service drives Cellular Modem Router to be more intelligent and have stronger service provision capability.Of these two key factors, performance plays a dominant role in the early development of Cellular Modem Router.With the rapid development of IP networks and services,Business factors or the value of business performance in the network will play an increasingly important role.
Over the years, the development of Cellular Modem Router has experienced ups and downs.In the middle of 1990s, the traditional Cellular Modem Router became the bottleneck of the development of Internet.Instead, the ATM switch becomes the core of the IP backbone, and the Cellular Modem Router becomes a supporting role.In the late 1990s, the scale of the Internet was further expanded, the traffic doubled every six months, and the ATM network became a bottleneck.Cellular Modem Router is making a comeback, and after the GBPS routing switch was introduced in 1997,People began to replace ATM switches with GBPS routing switches to build a backbone network with Cellular Modem Router as the core.Today is the fifth era of Cellular Modem Router.Let's take a look at the application development of Cellular Modem Router technology and its typical representative products.
The original IP network was not large, and the devices that needed to be connected to the gateway and the load that needed to be processed were also very small.At this time, the gateway (Cellular Modem Router) can basically be implemented by inserting multiple network interface cards into one computer.The interface card is connected with the central processing unit (CPU) through an internal bus, and the CPU is responsible for all transaction processing,Including route collection, forwarding processing, device management, and so on.After receiving the message, the network interface transmits it to the CPU through the internal bus, and the CPU completes all the processing and transmits it out from another network interface.
Because each message is sent to the CPU for processing through the bus, with the increase of network users, the network traffic is increasing.The bottleneck effect of the number of interfaces, bus bandwidth and CPU is becoming more and more prominent.So it is natural to think: how to increase the number of network interfaces, how to reduce the burden of CPU, bus?To solve this problem, the 2g cellular modem router performs some intelligent processing on the network interface card.Because network users typically visit only a few places,Therefore, we can consider keeping a small number of commonly used routing information on the service interface card by using Cache technology.In this way, most of the packets can be forwarded directly through the routing table of the service board Cache to reduce the demand on the bus and CPU.
The Web technology that appeared in the 1990s has made the IP network develop rapidly, and the user's access has been greatly broadened.The place of access is no longer as fixed as in the past, so it is often impossible to find a route from the Cache.The bottleneck effect of bus and CPU appears again.In addition, the problems caused by the increase of users and the insufficient number of Cellular Modem Router interfaces have been exposed again.In order to solve these problems, the third generation Cellular Modem Router came into being.The 3G cellular modem router adopts a fully distributed structure,The main control board is responsible for the management of the whole equipment and the collection and calculation of the route, and issues the forwarding table formed by calculation to each service board;Each service board can independently perform route forwarding according to the stored route forwarding table.In addition, the bus technology has also been greatly developed, and the data forwarding between the bus and the service board is completely independent of the main control board.The parallel high-speed processing is realized, and the processing performance of the Cellular Modem Router is doubled.
With The commercialization of IP network and the appearance of Web technology in the middle and late 1990s, Internet technology has been developed unprecedentedly.The number of Internet users is increasing rapidly. Network traffic, especially core network traffic, is growing exponentially.The traditional IPCellular Modem Router based on software has been unable to meet the needs of network development.Taking the common 2.5g POS port of the backbone node as an example, it is calculated according to the IP minimum message of 40 bytes.The 2.5G POS port has about 6.5Mpps of traffic at line speed.But also include complex operations such as QoS guarantee, route search, delamination/addition of that frame head of the second layer,It is impossible to achieve in the traditional way.Therefore, some manufacturers have proposed ASIC implementations, which implement all the details of the forwarding process in hardware.In addition, Crossbar or shared memory is used to solve the problem of internal exchange.As a result, the Cellular Modem Router has gigabit performance,The early gigabit switched Cellular Modem Router.
Hardware forwarding mode is used in 4G cellular modem router to solve the bottleneck problem of insufficient bandwidth capacity and performance.However, it also leaves a hidden danger: ASIC-based hardware forwarding achieves high performance at the expense of business flexibility.This is related to the implementation of ASIC technology. When designing ASIC chips, a lot of optimization has been done to the forwarding process.The IP forwarding is realized in a simple and fixed way, so that the IP forwarding is solidified and hardware-based.If you have to do some complex additional processing in IP forwarding, ASIC can't do anything.Moreover, the design cycle of ASIC is very long, and it usually takes two to three years to design a stable ASIC chip.In the field of IP Internet, business development is very rapid, and a new business will emerge every six months on average.These services may have an impact on the forwarding process and require appropriate adjustments to the forwarding process to obtain high-quality support.VPN technology has gradually become popular, and operators need to develop VPN services in backbone networks and metropolitan area networks.At this time, it was found that the 4G cellular modem router originally used in the backbone network could not provide high-performance VPN services.It is necessary to upgrade or build a special VPN bearer network.In the current operating environment where bandwidth is no longer the main contradiction and business applications are king,The inherent problems of ASIC, such as poor flexibility and insufficient service support, have become the main contradiction in the development of Cellular Modem Router.New needs bring about new contradictions, which will lead to new development.The rise of network processor technology has led to the emergence of 5G cellular modem router.
From the first generation to today's 5g cellular modem router technology is different.The development of technology is rapid with the application of network technology.
