What are the typical and group programs for wireless networks?

In the LAN in order to maintain a maximum collision area of 200 meters in diameter, the minimum CSMA/CD carrier time, Ethernet time slice has been extended from the current 512 bits to 512 bytes (4096 bits), the minimum information packet size is still 64 bytes. The carrier expansion feature solves the timing problems inherent in CSMA/CD without modifying the minimum packet size. While these changes may affect the performance of small packets of information, however, this effect has been offset by a feature of the CSM/CD algorithm called packet burst transmission. The greatest advantage of Gigabit Ethernet is its compatibility with existing Ethernet networks. Like 100Mbps Ethernet, Gigabit Ethernet uses the same frame format and frame size as 10Mbps Ethernet, as well as the same CSMA/CD protocol. This means that a wide range of Ethernet users can perform smooth, non-disruptive upgrades to their existing Ethernet networks without adding additional protocol stacks or middleware. At the same time, Gigabit Ethernet inherits other advantages of Ethernet, such as higher reliability and ease of management. Gigabit Ethernet has the advantage of large bandwidth compared with other technologies and still has room for development, the relevant standards organizations are developing technical specifications and standards for 10G Ethernet networks. At the same time based on the Ethernet frame layer and the IP layer of the priority control mechanism and protocol standards and a variety of QoS support technology is also maturing, for the implementation of applications requiring better quality of service provides the basis. Along with the progress of optical fiber manufacturing and transmission technology, the transmission distance of Gigabit Ethernet can reach up to 100 kilometers, which makes it gradually become a technology choice for building metro and even wide-area networks. The benefits of using Gigabit Ethernet for the backbone are: Gigabit Ethernet will provide 10 times the performance of Fast Ethernet and is compatible with existing 10/100 Ethernet standards. At the same time, the virtual network standard 802.1Q, developed for 10/100/1000 Mbps, and the prioritization standard 802.1p have been rolled out, making Gigabit the dominant technology forming the backbone of the network. 802.3, the first Gigabit Ethernet standard, which was completed in June 1998, is aimed at full-duplex links using fiber optic cables and short-range copper cables. The standard 802.3ab for half-duplex and remote copper cables will be available in 1999. Gigabit Ethernet will provide a seamless migration path that fully protects investments in existing network infrastructure. Gigabit Ethernet will retain 802.3 and the Ethernet frame format, as well as the 802.3 managed object specification, which will allow organizations to upgrade to Gigabit performance while retaining existing cables, operating systems, protocols, desktop applications and network management strategies and tools. Gigabit Ethernet provides another reliable, cost-effective way to improve switch-to-switch backbone connectivity and switch-to-server connectivity over legacy Fast Ethernet, FDDI, ATM and other backbone solutions. Network designers will be able to build high-speed infrastructures that effectively utilize high-speed, mission-critical applications and file backups. Network administrators will provide users with faster access to the Internet, Intranet, Metro and WAN. Gigabit product providers, with a complete line of Gigabit Ethernet products, can provide a complete solution to fit user needs. From network backbone switches at the core to gigabit access for client servers at the edge, there are high-performance products designed to meet user needs. The deployment of Gigabit Ethernet switches is a very compelling technology. Currently, many vendors of switches to Layer 2 switching and Layer 3 switching into one, whether switching or routing, can provide at least 10 million pps forwarding rate, and even some products can reach 20 million pps. these high-performance characteristics of the Intranet has become very important, because the traditional LAN traffic 80/20 law of nature (i.e., 80% of the Traffic in the local workgroup network and 20% of the traffic flow to the backbone network) has become obsolete. Gigabit Ethernet's high-speed, multi-layer packet forwarding capability is a strong example of how Gigabit Ethernet technology offers the best price/performance ratio. Not only that, Gigabit Ethernet technology is also very beneficial to reduce the long-term cost of ownership of the network. 2. Gigabit switching technology Since the end of 1996, some companies have introduced switches that integrate Layer 2 switching and Layer 3 routing, a technology called ? Multilayer switching (multilayer switching). It adds routing layer services to Layer 2 switching technology, supports selective broadcast and multicast suppression, supports VLAN and inter-VLAN packet forwarding and firewall functions, and fully supports TCP/IP and IPX routing. After nearly 4 years of development, these features have been continuously improved and strengthened, making multilayer switches 8 to 16 times higher than traditional routers in terms of performance-to-price ratio. The new generation of multilayer switches, with Gigabit Ethernet switching technology at its core, offers even more attractive price/performance ratios, making it the ideal multilayer switch to replace traditional routers in departmental and data center networks. At the same time, its direct transmission distance has now reached 130 kilometers, fully capable of realizing large enterprise LANs with Gigabit Ethernet as the backbone, with a backbone transmission rate of 2Gbps (full-duplex mode). The main factors driving the development of the technology to promote the development of high-speed multi-layer switching technology is the biggest factor is the use of inexpensive 10/100M adaptive network card Internet and Intranet deployment of large numbers. Current networks have moved farther and farther away from the traditional hierarchical structure of the c/s computing model, and the 80/20 traffic rule of the traditional c/s model has become a thing of the past. In terms of network design, the traditional router plus Hub or Layer 2 switch network deployment model will also become history. In addition, Intranet supports more complex and bandwidth-sensitive multimedia data streams, such as data, files, pictures, animations, sound and video. An Intranet end-user bandwidth requirements than non-Intranet users at least 50% to 100% more. At the same time, broadband access has become a development trend. Another noteworthy issue is that providing users with Fast Ethernet connections provides more bandwidth headroom to handle bursty traffic than 10BASE-T technology can match. Bursting traffic is one of the characteristics of IP network applications. Cheapness and high bandwidth make Fast Ethernet widely used both on the user side and the server side. In order to strike a balance between non-blocking and the ability to handle bursty traffic, the new generation of switch platforms must provide higher than the user request connection 8 to 16 times the rate of the backbone connection, and Gigabit Ethernet backbone just to meet the user side of the Fast Ethernet connection service request. This is important to adequately handle bursty traffic. At the same time, in a campus or metro network, random Intranet traffic, regardless of how many network layers it spans, requires consistently high performance from end to end. To achieve this, high-performance Layer 2 and Layer 3 forwarding in a single switch is the only solution. Non-blocking capability and selective forwarding are the main requirements. A variety of highly effective network management tools enable network administrators to effectively and efficiently inject business policies into the forwarding engine, the performance of which can be monitored in real time by the network management software. This will fundamentally help users to identify and deliver the required network services according to the company's short-term and long-term business development needs. The new generation of Gigabit Ethernet switches support these features and services as well as common routing protocols such as IP/RIP or IP/OSPF. This also greatly reduces the complexity of network equipment. 3. Network design goals and principles of network systems, high-performance requirements of the core switch to meet the requirements of the network center of massive data exchange, uplink center of the communication link bandwidth to meet the application of the performance requirements of the network. Whether it is an enterprise network or metropolitan area network, wide area network, its information applications are developing at an unprecedented rate, new multimedia applications and new data applications on the bandwidth put forward higher requirements. Enterprises generally use Intranet network mode, its WWW server, FTP server, Lotus Notes groupware application server, Novell Server and other server groups to support the entire enterprise information service environment. Client application software of users in each department of the enterprise accesses the center server through the network to request applications and query the database. The load flow of the network is mainly from the edge of the equipment to the core of the data exchange, with the development of enterprise business, the expansion of the network scale, as well as the application of information exchange increased, making the enterprise network usually first in the core of the communication bottleneck phenomenon. To improve the network data exchange performance of enterprise campus LAN, it is often the first step to expand the switching performance of the core switch and increase the data communication bandwidth from the edge equipment to the core, in order to alleviate the bottleneck of the whole network, and to improve the performance and efficiency of the application software. Therefore, in the principle of designing enterprise campus LAN, the first thing that should be considered to meet the requirements of the network size of the core equipment data exchange processing capacity, as well as the edge equipment to the core of the link bandwidth.3.1 Reliability and AvailabilityNetwork system design of the equipment for high reliability and high availability of the system; the requirements of the core switch all key components can realize redundant work, can be replaced on-line (plug and play), the failure of the recovery time is accomplished within a second interval. Multi-level fault-tolerant design further improves system availability based on the high reliability of individual devices. As far as enterprise applications are concerned, it realizes automated control of production process and paperless office automation through advanced computer, network and other information technologies, which improves the production and management efficiency and level of the enterprise. Support for enterprise application infrastructure is the enterprise campus network, its working condition will directly affect the enterprise office application environment, trading, production, development, design and other business environments, financial management, parts management and other environments, information retrieval, database query, Internet browsing, and other support for the normal operation of the enterprise's necessary service facilities function. The reliability of the network is required to ensure the normal operation of the enterprise application environment is the first condition, the network requires reliability at the same time, the network is required to have high availability. Selection of network equipment, especially the core chassis-type equipment, should be able to configure redundant components, key components do not have a single point of failure, that is, like the switch's power supply, fan, switching engine, management module, these components can be redundant backup, which one of any part of the damage will not affect the normal operation of the equipment, will not affect the network connectivity. Provide network equipment reliability, fault tolerance, another requirement is the equipment damaged parts replacement, no downtime, replacement of parts do not need to restart, that is, the replacement of components can be carried out online operation, which can minimize the downtime. In the principle of designing enterprise campus network to improve the network's high reliability, high availability principle is crucial, not only requires equipment component redundancy, while requiring the network link redundancy, can be combined with the physical layer, link layer and the third layer of technology to ensure that the network can be at any time, any place to provide information access services. [page_break] 3.2 scalability network design scalability requirements, including the expansion of switch hardware and the ability of the network to implement new applications. Flexible expansion of the core switch requirements: the core switch should have flexible port expansion capabilities, module expansion capabilities to meet the expansion of the network scale; while improving performance to meet the requirements of higher performance. The ability to support new applications: the product has the technology to support new applications to prepare, can be structured to facilitate the implementation of new applications quickly.3.3 Scale and users in the design of the network program, first of all, to meet the needs of users of the existing scale of the network, while taking into account the future development of the business, the expansion of the scale, should be designed to have a network of user ports with a flexible expansion capabilities. Core equipment is the hub of the entire network, the expansion of the number of user ports, the need to increase the edge of the working group between the distribution of equipment, increase the edge of the equipment at the same time, the number of ports required to connect to the core backbone of the equipment increased accordingly, so the core equipment should be able to increase the number of ports through the addition of modules to increase flexibility. The chassis design of the core equipment should have strong backplane bandwidth and enough load slot capacity. For switches, the core switching engine should be able to meet the maximum configuration, non-blocking port packet switching, module expansion does not affect the switching performance. Distributed switching architecture is the best solution to achieve this principle. Distributed switching architecture realizes parallel data exchange processing of switches and optimizes the performance of the network, and the distributed architecture combining local switching and global switching reduces the pressure on the core switching engine. Therefore, in the design of large-scale campus network in principle commonly used distributed switch to achieve flexible modules, port expansion capabilities.3.4 Security network security is very important for network design, reasonable network security control, can make the application environment of information resources to be effectively protected can be effective control of access to the network, flexible implementation of the network's security control strategy. In the enterprise campus network, key application servers, core network equipment, only the system administrator has the power to operate and control. Application clients only have the authority to access *** enjoy resources, the network should be able to prevent any illegal operation. On the campus network equipment should be able to carry out protocol-based, Mac address-based, IP address-based packet filtering control function. In the design of large-scale campus networks, the division of virtual subnets, on the one hand, can effectively isolate a large number of broadcasts within the subnet, and on the other hand, isolate the communication between the network subnets, control the access rights to the resources, and improve the security of the network. In the principle of designing the campus network must emphasize the network security control ability, so that the network can be connected arbitrarily, but also from the second and third layers to control the access to the network.3.5 ManageabilityThe manageability of the network requires that: any device in the network can be controlled through the network management platform, the status of the network's equipment, fault alarms and so on can be monitored through the network management platform to simplify the network management platform and improve the efficiency of network management. Simplify the management work and improve the efficiency of network management through the network management platform. In network design, the choice of advanced network management software is essential. Network management software is applied to network device configuration, network topology representation, network device status display, network device fault event alarm, network traffic statistical analysis and billing. The application of network management software can improve the efficiency of network management and reduce the burden of network administrators. The goal of network management is to achieve zero management, policy-based management approach, network management is through the development of a unified policy, by the management policy server for global control. Web-based network management interface, is the development trend of network management software, flexible operation simplifies the work of managers. In designing the equipment selection of the campus network, the network equipment is required to support the standard network management protocol SNMP, as well as support for RMON/RMONII protocols, and the core equipment is required to support the RAP (Remote Analysis Port) protocol, which implements the full network management functions. In the principle of designing the campus network, the manageability of the equipment should be required, while the advanced network management software can support network maintenance, monitoring, configuration and other functions.3.6 Standardized protocols Network equipment adopts open technology and supports standard protocols: the use of standardized protocols to protect the user's investment and improve the interoperability of equipment. The equipment used for network design is required to adopt mainstream technology, developed standard protocols, with good interoperability, able to support different series of products of the same manufacturer, and seamless interconnection and communication between products of different manufacturers. In principle, in the design of the campus network, the play of different manufacturers of products dedicated to advanced technology at the same time, it is necessary to emphasize the examination of the technology of the equipment, the protocol standardization, to reduce the problem of interconnection of equipment, the cost of network maintenance, so that the user's investment is effectively protected. Should consider whether the choice of equipment is scalable, after the emergence of new standards, the system should be able to upgrade to new standards. Thus focusing on the product manufacturer's status and ability to participate in standardization in the corresponding product and technology fields. In today's world, the development of communication technology and computer technology is changing rapidly. The network design should not only adapt to the trend of new technology development to ensure the advancement of the system, but also take into account the maturity of the technology to reduce the risk of immature factors due to new technologies and products.4. Campus Network Solutions The biggest advantage of Gigabit Ethernet lies in its compatibility with the existing Ethernet. Like 100Mbps Ethernet, Gigabit Ethernet uses the same frame format and frame size as 10Mbps Ethernet, as well as the same CSMA/CD protocol. This means that a wide range of Ethernet users can perform smooth, non-disruptive upgrades to their existing Ethernet networks without adding additional protocol stacks or middleware. At the same time, Gigabit Ethernet inherits other advantages of Ethernet, such as higher reliability and ease of management. In the campus network backbone, it is now gradually occupying a major position. As a characteristic of campus network applications, most of the applications are less sensitive to latency and bandwidth, which can be automatically recognized by TCP/IP?slow start? mechanism automatically recognizes changes in delay and dynamically adapts to the bandwidth provided by TCP. Some applications require real-time service transmission support and QoS service guarantee. This part of the application currently accounts for a small proportion, with the acceleration of the modernization of teaching methods, the gradual popularization of multimedia courseware production tools, multimedia courseware gradually rich, the proportion is expected to gradually increase.IP network transmission of real-time business is the main bottleneck in the router using software to achieve the routing identification, computation and packet forwarding, due to the slow speed of routing identification, data forwarding, delay and delay jitter, large. Quality of Service (QoS) cannot be guaranteed. Since the second half of 1997, some companies have introduced new wire-speed routing switches that use hardware-specific circuits (ASICs) for route identification, computation and forwarding. The structure of this wire-speed routing switch is similar to that of L2 switch, with both L3 router packet forwarding function and L2 switching function, and some vendors also add some L4 application layer functions into it. To provide QoS on a packet-switched IP network, services must be categorized and classified as a service (CoS). Equipment manufacturers generally use congestion management to ensure network performance and provide the bandwidth required for some specialized services. One approach is to avoid network congestion by using RED (Random Early Loss) to detect and intelligently identify transient spikes in traffic, distinguishing them from true network congestion. The class of service (802.1P) is identified by identifying the IPv4 class-of-service (TOS) from the IP packet header, prioritizing that data flow, and based on some queue prioritization algorithm in order to ensure QoS capability. Policies can also be defined using Access Control Lists (ACLs) to prioritize data flows. As technology advances, it is foreseeable that QoS capabilities on high-speed IP networks will reach similar levels on FR/ATM networks. On the basis of analyzing and comparing the performance, price, and service of a variety of L2/L3/L4 wire-speed routing switches in the market, 11 Cajun P550R routing switches*** from Lucent are selected as the backbone switches of the campus network. Its main technical and performance indicators are: backplane capacity 45.76 Gbps switching throughput capacity 22.88 Gbps Layer 2 switching capacity 33,000,000 pps Layer 3 switching capacity 18,000,000 pps a variety of L2/L3 interface modules redundant fan, power supply OpenTrunk/VLAN interoperability CoS/QoS/RSVP support In the network design, the backbone switches are interconnected with each other via Gigabit Ethernet. All switches are configured with an L3 switching engine that implements a distributed routing policy to reduce the pressure on the center switch for L3 route resolution, packet forwarding, and to control the extent of the broadcast domain. The network design and device configuration carefully considers physical and logical redundancy of devices and lines and routes, firewall settings and security policies for the server farm at the network center.