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The construction of local area network in high-speed electronic publishing system

the introduction of network technology into electronic publishing system is a development trend at present and in the future. However, how to follow the rapid development of network technology and establish a high-speed and efficient local area with fast operation speed, good interconnection, strong network hardware matching and low cost is the key to the introduction of network technology into electronic publishing system

based on the current situation that the fast Ethernet used in local area network (LAN) is 100m, it can be said that the transmission rate greater than 100m can be regarded as a high-speed local area network. Currently, the technologies that have been adopted are Gigabit Ethernet and ATM, and 10 Gigabit Ethernet is being tested. Because Gigabit Ethernet has strong advantages and meets the requirements of fast running speed, good interconnection, strong network hardware matching and low cost of ownership, it can be determined as the preferred group technology

first, several technologies used to build high-speed local area network

1. Wiring technology

network wiring should adopt the wiring method of combining optical fiber and unshielded twisted pair. At present, most of the computer network wiring installed is unshielded twisted pair, and the standards followed are generally the "super class 5" standards published by EIA/TIA and ISO. With the strong support of the state, these performance standards can meet the requirements of asynchronous transmission mode with Gigabit Taihe rate higher than 1.2gbps. In local area construction, the data transmission rate is not the decisive factor of using optical fiber. The cost comparison also shows that unshielded twisted pair continues to be the main reason for media selection in the horizontal channel connecting workstations. The cost of optical fiber is much higher than that of unshielded twisted pair. The cost of passive components in optical fiber wiring is more than three times that of unshielded twisted pair. If you add the cost of active equipment, such as hubs and network interface cards, the cost will further increase. However, the distance limit is the inevitable choice of optical fiber for floor connection and interconnection in the park. In addition, with the continuous popularization of network technology and the explosive growth of bandwidth demand, network cabling must consider the smooth upgrade in the future. Therefore, in structured cabling, because the backbone installation conditions are generally very difficult, network planners must consider using the highest capacity cable. In the construction of the park, it is generally required that optical fiber reach the community and the building. On the other hand, the cost of optical fiber cabling is declining significantly. This makes multimode fiber and single-mode fiber have high cost performance. Now, composite cables are being installed in many buildings, that is, multimode fiber and single-mode fiber are used at the same time. This represents a new development trend, which is very noteworthy. In short, the network wiring in the electronic publishing system can use the wiring between office buildings and optical fiber, and the computers in an office building can use unshielded twisted pair connection

2. link layer technology

Gigabit Ethernet can provide 1Gbps of communication bandwidth, and has the simplicity of Ethernet. It uses the same CSMA/CD protocol, the same frame format and the same frame length, and also supports full duplex, etc. Like Taihe Fast Ethernet, the physical layer of Gigabit Ethernet only defines the physical layer and media access control layer. The physical layer is the key component of Gigabit Ethernet. Three transmission media are defined in ieee802.3z: multimode fiber, single-mode fiber and coaxial cable, and ieee802.3ab defines unshielded twisted pair media. In addition to the above transmission media, there is also a multi manufacturer defined standard 1000ba, which is also an optical fiber standard through strict process discipline se-lh. The transmission distance can reach 100 kilometers at most. Another feature of Gigabit Ethernet physical layer is 8B/10B encoding, which is the same as fiberchannel technology. The same benefit is that network equipment manufacturers can use the existing 8B/10B encoding/decoding chips, which will undoubtedly shorten the development cycle of products and reduce costs

3. multi layer switching technology

switching technology can be divided into layer 2 switching and multi-layer switching. Multi layer switching technology includes layer 3 switching and layer 4 switching

layer 2 switching is called OSI layer 2 or MAC layer switching, which is the switch in our usual sense. The technology has been very mature. It works in the data link layer, and the switching is based on MAC address

layer 3 switching, or network layer switching, is the third layer of OSI protocol. It provides higher-level services, such as routing functions. In the past, routers were usually used to realize interconnection through software, but the router is expensive and the forwarding speed is slow, which has increasingly become the bottleneck of the network. Now, with the help of line speed switching technology, the routing function is integrated into the switch, which is called routing switch or layer 3 switch. It can realize line speed switching at all network levels, and its performance is greatly improved, while retaining the network topology and services on layer 3. These structures and services have great advantages in network segmentation, security, manageability and radio suppression. The goal of layer 3 switch is to replace the existing router, which provides information flow communication between subsystems, and improves the communication speed from hundreds of packets per second to millions of packets per second. Layer 3 switching aims to forward multiple protocols at high speed, or provide firewalls to protect network resources, or reserve bandwidth, and local backbone switches will be layer 3 switches

the fourth layer switch can make an intelligent decision on where to forward the session transmission flow according to the shape and foundation drawing. Because of this, the user's request can be forwarded to" best "according to different rules On the server. Therefore, layer 4 switching technology is an ideal mechanism for data transmission and load balancing among multiple servers

now, multi-layer switching technology has been described as an integrated and complete solution that can support various local architectures. It intelligently combines switching technology and routing technology. Multi layer switching technology combines the optimal characteristics of local switching technology and routing technology. It has higher performance price ratio and stronger flexibility than the traditional local backbone based on router. It is the basis of high-speed local implementation

2. Problems to be considered

the group mode of high-speed local area is now very simple, and there is no better choice: basically, it takes Gigabit Ethernet as the backbone, and uses high-performance layer 2 and layer 3 switches as the core; In terms of network cabling, multi-mode or single-mode optical fiber is recommended for the connection between the backbone and the switch, and horizontal cabling