In December 1984, Cisco Systems Inc. (Cisco_Systems, Inc.) was established in the United States, founded by a faculty couple at Stanford University, Leonard Posak (Leonard_Bosack), director of the computer center of the Department of Computer Science, and Santi, director of the computer center of the business school. Lerner (Sandy_Lerner).

The couple designed networking devices called "multiprotocol routers" for use on the Stanford Campus Network (SUNet), which brings together incompatible computer LANs on campus to form a unified network. This connected device is considered to be a sign that the connected age has truly arrived.

You say, how can a person like Fu Xin, the reincarnation of a great scientist, not know?

Routers can be divided into the first generation of single-bus single-CPU routers, the second-generation single-bus master-slave CPU structure routers, and the third-generation single-bus symmetrical multi-CPU structure routers. Fourth-generation multi-bus multi-CPU routers, fifth-generation shared memory routers, sixth-generation crossswitch architecture routers, and routers based on chassis systems.

A router has four elements: an input port, an output port, a switch switch, a route processor, and other ports. The input port is the entrance to the physical link and the input packet.

Ports are usually provided by line cards, and a line card generally supports 4, 8, or 16 ports, and one input port has many functions. The first function is to encapsulate and decapsulate the data link layer.

The second function is to determine the destination port by looking up the destination address of the input packet in the forwarding table (known as a route lookup), which can be implemented using common hardware or by embedding a microprocessor on each line card.

Third. In order to improve QoS (Quality of Service), the port divides the received packets into several predefined service levels.

Fourth. Ports may need to run data link-level protocols such as SLIP (Serial Line Internetwork Protocol) and PPP (Point-to-Point Protocol) or network-level protocols such as PPTP (Point-to-Point Tunneling Protocol).

Once the route lookup is complete, the packet must be sent to its output port with a switch switch. If the router is an input plus a queue. There are several inputs that share the same switch switch. The final function of such an input port is to participate in an arbitration agreement on a common resource, such as a switch switch.

Exchange switches can be implemented using a number of different technologies.

The most commonly used switching technologies today are buses, crossswitches, and shared storage.

The simplest switches use a single bus to connect all input and output ports, and the disadvantage of a bus switch is that its switching capacity is limited by the capacity of the bus and the additional overhead that comes with quorum for a shared bus.

Cross switches provide multiple data paths through switches, and a cross switch with N×N crosspoints can be considered to have 2N buses.

If a cross is closed, data on the input bus is available on the output bus, otherwise it is not available. The closing and opening of the intersection is controlled by the scheduler, which therefore limits the speed of the swap switch.

In a shared memory router, incoming packets are stored in a shared memory and only the pointer to the packet is exchanged. This increases the switching capacity, however, the speed of switching is limited by the access speed of the memory. Although memory capacity is doubling every 18 months, the access time of the memory is reduced by only 5% per year, which is an inherent limitation of the shared memory exchange switch.

The output port stores packets before they are sent to the output link, and can implement complex scheduling algorithms to support requirements such as prioritization. Like the input port, the output port needs to be able to support encapsulation and decapsulation at the data link layer, as well as many higher-level protocols.

The route processor computes the forwarding table to implement the routing protocol and runs the software that configures and manages the router. Meantime. It also handles packages whose destination address is not in the online card forwarding table.

Other ports generally refer to the control port, because the router itself does not have input and terminal display devices, but it needs to be configured before it can be used normally, so the general router has a control port 'Console'. It is used to connect with a computer or terminal device and configure the router through specific software. All routers are installed with console ports that enable users or administrators to communicate with the router using endpoints. Complete the router configuration.

This port provides an EIA/TIA-232 asynchronous serial interface for configuring the router locally (the first configuration must be done through the console port).

The console port is directly connected to the serial port of the computer using a dedicated cable. Use a terminal emulator (such as 'HyperTerminal' under Windows) to configure the router locally. Most of the console ports of routers are RJ-45 ports.

Routers play a pivotal role in computer networks and are the bridge of computer networks. It allows you to connect to not only different networks. It also allows you to choose the path of data transmission and block unauthorized access.

As a node of the backbone network, the multi-protocol router runs a certain Ad_Hoc network routing protocol to realize the function of routing and addressing the backbone network.

Ad_Hoc is derived from the Latin word meaning "for_this" and by extension, "for_this_purpose_only", that is, "set up for a certain purpose, special", i.e. the Adhoc network is a network with a special purpose.

The Ad_Hoc structure is a peer-to-peer network structure built without the wireless intermediary device AP, as long as the wireless network card is installed, the computers can realize wireless interconnection with each other; The principle is that a computer host in the network establishes a point-to-point connection, which is equivalent to a virtual AP, and other computers can directly interconnect and share the network through this point-to-point connection.

Ad_Hoc network, also known as mobile ad hoc network and multi-hop network, has the characteristics of flexible and fast networking, and is not affected by wired network. It can be widely used in military and rescue and other occasions where it is impossible or inconvenient to lay network facilities in advance.

Ad_Hoc wireless network has its own particularity, when forming a wireless working network that is actually used. The application scale and scalability of the network, as well as the reliability and real-time requirements of the application, must be fully considered. Select the appropriate network topology.

At present Ad_Hoc wireless network is developing in the direction of large-scale, and gradually showing a trend of hierarchical, represented by two-level network.

In a two-tier network, the network is divided into two levels: backbone network and subnet. At the subnet level, each subnet can form an independent Ad_Hoc network with different routing protocols. The backbone network is composed of multi-protocol router nodes and common nodes, among which the ordinary nodes mainly complete the distribution of data and control information in the backbone network; In addition to the functions of ordinary nodes, multi-protocol routers are also responsible for the management, control, and data interaction of subnets, and are the core equipment of the backbone network.

In a hierarchical Ad_Hoc network. The multi-protocol router manages the subnet by interacting with the subnet gateway for data. Communication within a subnet is similar to a general Ad_Hoc network; The communication between subnets needs to be transited through the subnet gateway node and the backbone network node, which can be divided into two situations - the communication between homogeneous/heterogeneous subnets under the same router and the communication between homogeneous/heterogeneous subnets under different routers. In order to achieve effective communication between subnets, routers need to complete the conversion between multiple protocols.

The need for Internet access necessitates the presence of an access point AP (Access_Point) in a hierarchical AdHoc network. Considering the network environment, this function needs to be implemented by a multi-protocol router. Therefore, multi-protocol routers mainly implement the three functions of APs for backbone network routing addressing, protocol conversion, and Internet access.

In general, routers in an AdHoc network are vehicle-mounted or piggyback-on, so multi-protocol routers must have high integration and mobility.

The hardware structure of a multi-protocol router is divided into two parts: one is the core module (MCF5272), which is composed of a microcontroller module and a memory module (including SDRAM and Flash); The other part is the communication interface module, which is composed of an asynchronous serial control and transceiver module, an Ethernet control and transceiver module and a universal serial bus USB (UniversalSerialBus) interface module.

Core module section. The microprocessor module is primarily responsible for processing data.

The memory module is divided into two parts: one part is Flash (composed of two pieces of Flash, a total of 4MB), which is used as program memory to store the operating system kernel, various routing protocols and routing table constants; The other part is SDRAM. As a data store, it is used as a running space for the operating system and various routing programs.

In the communication interface module, the asynchronous serial control and transceiver module is used for wireless connection with multiple backbone network nodes at the same time. Connect multiple subnet gateway PRUs (i.e., packet radio control units). The Ethernet control and transceiver module can realize the Internet access function. The USB interface module is used to connect network devices to the control terminal, and to realize the storage control of USB devices (such as USB standard mobile hard disks, which are used to store important routing information) by routers.

"Minister Zhou. That's a good thing! Fu Xin took a cursory look at the information and smiled happily.

Zhou Zhengming nodded. commanded: "I won't tell you how this thing came about, you can guess for yourself!" But I can tell you, this is from Stanford University, it is not easy to get this information, you don't leak it, you can put it away after reading it, show it to others, you must give it to someone you can trust, you must remember! ”

"Minister Zhou, don't worry, I know the importance of this thing, the multi-protocol router was made by Cisco in December 1984, so this is advanced technology, I know its importance, I will definitely keep it!" Fu Xin said seriously, there is no need for Zhou Zhengming to say anything else, he also knows what happened to this thing, perhaps, this is still a bloodstained information, he must cherish it!

"By the way, Fu Xin, the third factory of Beijing components, just give their leaders a lesson, don't be too ruthless, after all, they have cooperation with the Commission of Science, Technology and Industry for National Defense, which has affected their production, and it will be difficult for us to explain it at that time!" Zhou Zhengming admonished again.

"Okay." Fu Xin nodded thoughtfully! He Fu Xin likes to kill everything, but at the same time, slap in the face or something, he agrees to like to play. (To be continued......)