Technical Selection of High-speed LAN

High speed is a relative concept. speed is faster than speed. Therefore, a high-speed LAN can be considered based on the fact that fast Ethernet is 100 M in the LAN. Technologies used in this area are mainly Gigabit Ethernet and ATM, and 10 Gigabit Ethernet is being tested. Due to its low cost, good interconnectivity, and many manufacturers, GE Ethernet has become the mainstream technology of high-speed LAN.

Construction of High-speed LAN technology

Wiring Technology

Most of the network cabling currently installed is unshielded twisted pair wires. The standards followed are generally the "cat5e" standards published by EIA/TIA and ISO (of course, the earliest cabling is not met ). These performance standards can meet the requirements of Gigabit Ethernet and asynchronous transmission modes with a speed higher than Gbps. The predefined cat6 cabling frequency limit is 200 MHz, so it is hard to say how high the future encoding system will achieve at a maximum speed of MHz. Therefore, in LAN construction, the data rate is not the deciding factor for optical fiber steering.

The cost comparison also shows the main reason why unshielded twisted pair wires continue to be used as the media in the horizontal channel connected to the workstation. Obviously, the cost of Fiber-to-desktop is much higher than that of unshielded twisted pair wires. In general, the cost of passive components in the former is more than three times that of the latter. If the cost of the source device, such as the hub and network interface card (NIC), the cost difference will be further increased.

However, the distance limit is an inevitable choice for the use of optical fiber for interconnection within the floor connection region. In addition, the explosive growth of bandwidth demand requires that network cabling be considered for future smooth upgrades. Therefore, in structured cabling, network planners must consider using cables of the highest capacity due to the difficulty of trunk installation conditions. During campus network construction, optical fiber is usually required to the residential area and optical fiber to the building.

On the other hand, the cost of optical fiber cabling is obviously decreasing. This makes multimode and single-mode optical fibers highly cost-effective. Composite cables are being installed in many buildings, that is, multi-mode optical fiber and single-mode optical fiber. This represents a new development trend and is worthy of reference.

Link Layer Technology

Gigabit Ethernet can provide 1 Gbps communication bandwidth and is easy to use over Ethernet. It adopts the same CSMA/CD protocol, the same frame format and the same frame length, also supports full duplex and EtherChannel. For the majority of network users, this means that the existing investment can continue to Gigabit Ethernet with reasonable initial overhead. In this way, Gigabit Ethernet can be smoothly transitioned on the basis of the current Ethernet, balancing various factors such as the existing endpoint workstation, management tools, and training basis, resulting in a very low overall overhead, it is the preferred technology in LAN construction.

The physical layer of Gigabit Ethernet is the same as that of Fast Ethernet. Only the physical layer and media access control layer are defined. In terms of implementation, the physical layer is a key component of Gigabit Ethernet. In 802.3z, three transmission media are defined: multimode optical fiber, single-mode optical fiber, and coaxial cable. 802.3ab defines unshielded twisted pair wires. In addition to the above transmission media, there is also a multi-vendor-defined standard 1000Base-LH, which is also a kind of optical fiber standard with a maximum transmission distance of 100 kilometers. Another feature of the Gigabit Ethernet physical layer is the 8B/10B encoding method, which is the same as the Fiber Channel technology, network device manufacturers can use the existing 8B/10B encoding/decoding chip, which will undoubtedly shorten the product development cycle and reduce costs.

Multi-layer exchange technology

Currently, the exchange technology can be divided into Layer 2 switching and multi-layer switching, but strictly speaking, switching means the connection between the source and the destination address, any technology above Layer 2 cannot be an exchange technology. To a large extent, Server Load balancer has replaced the fourth layer of exchange, just as the application cognitive word has largely replaced the Seventh Layer of exchange.

Layer 2 switching is the switch between the OSI Layer 2 or MAC layer. This is a common switch that is technically mature. It works on the second layer of the OSI 7 layer model, that is, the data link layer. The exchange is based on the MAC address.

Layer-3 switches, or network-layer switches, are on the layer-3 of the OSI protocol. They provide higher-level services, such as routing functions. Previously, routers often use software to interconnect networks. However, vrouters are expensive and slow to forward, which is increasingly becoming a network bottleneck. Layer-3 switching integrates the routing function into a vswitch by means of wire speed switching technology. This type of switch is called a route switch or a layer-3 switch. Layer-3 switching can achieve line rate switching at all network layers, greatly improving the performance. At the same time, it retains the network topology and services on the third layer. These structures and services have great advantages in network segmentation, security, manageability, and broadcast suppression. The purpose of the layer-3 switch is to replace the existing router. It provides information flow communication between subnets, so that the communication speed increases from several hundred packets per second to several million packets per second. Layer-3 switching is designed to forward multiple protocols at high speed, provide firewalls to protect network resources, or reserve bandwidth. All LAN backbone switches are L3 switches.

Layer-4 switching technology uses information in layer-3 and layer-4 headers to identify Application Data Stream sessions. With this information, the layer-4 switch can make intelligent decisions on where to forward session transmission streams. Because of this, user requests can be forwarded to the "best" server according to different rules. Therefore, layer-4 switching is an ideal mechanism for data transmission and load balancing among multiple servers.

Currently, many products support multi-layer switching, such as Cisco Catalyst 5509/6509, Extreme Diamond Series, Foundry BigIron series and Alteon ACE-180e.

Now, the multi-layer switch technology has been described as an integrated and complete solution that supports various LAN architectures. It intelligently integrates the exchange technology and routing technology. The multi-layer switching technology combines the LAN switching technology and the optimal routing technology, with higher performance and price ratio than the traditional router-based LAN trunk, and more powerful flexibility, it is the basis for high-speed LAN implementation.

Issues to consider

The high-speed LAN network mode is now very simple, and there is no better choice: basically, Gigabit Ethernet is the main backbone, using high-performance second-and third-layer switches as the core; network wiring, multi-mode or single-mode optical fiber cables are recommended for connecting the trunk and switch, and cat5e unshielded twisted pair wires can be used for horizontal cabling. As described above, this structure is easy to expand and upgrade. Vswitch products include Cisco 6509/6509 OSR, Foundry BigIron 8000/4000, Extreme Black Diamond 6816/6808, Alcatel PowerRail 5200/2200, Lucent Cajun P880, Riverstone RS32000/RS8600, Huawei MD5500, Dragon RS6006G/rs6004 g, and the ar.

However, if a network is successfully built, you must consider the following questions:

Business availability

Whether the business can be carried out and whether the functions are restricted is the main criteria for various technical judgments. Currently, the high-speed information network is built for comprehensive services including voice, video, and data. Therefore, whether to support various VLANs and IP multicast is supported, this is an issue that must be considered during product selection.

Mature technology

Computer Network Technology, including Gigabit LAN and high-speed routers, is actually subject to incomplete control domains. Many insurmountable obstacles exist in key data services or continuous media communication. Whose products are well solved or not good, there must be examples to prove that you cannot listen to the product documentation or the manufacturers' boast. Immature network technologies should not be used easily. This is the basic principle for establishing a high-speed LAN for key services.

Network Connectivity

Network connectivity is the most important manifestation of network value. Network connectivity is not only manifested in the geographical coverage area, but also in the interconnection with other networks. The interconnectivity of High-speed LAN is mainly reflected in the intercommunication with the original network and with a higher-level network.

Network Reliability

Network Reliability must be supported through the network protocol, device backup, and route backup, especially whether the control and management system of the network protocol has high reliability.