What Is a Gigabit Ethernet?

Local Ethernet began to develop from 10M. After several changes, it has developed to the current Gigabit Ethernet. Gigabit Ethernet is characterized by high efficiency, high speed, and high performance. It has been widely used in industries such as finance, commerce, education, government agencies, factories and mining enterprises.

Local Ethernet began to develop from 10M. After several changes, it has developed to the current Gigabit Ethernet. Gigabit Ethernet is characterized by high efficiency, high speed, and high performance. It has been widely used in industries such as finance, commerce, education, government agencies, factories and mining enterprises.

Gigabit Ethernet, or Gigabit Ethernet, is a term describing various Ethernet frame transmission technologies at the rate of gigabits per second, defined by the IEEE 802.3-2005 standard. The standard allows half-duplex gigabit connections through hubs, but the speed achieved with full-duplex connections on switches in the market is truly compliant.

Chinese name

Gigabit Ethernet

Foreign name

Giga Bit Ethernet

Foundation

Ethernet Standard

Features

Efficient, high speed, high performance

Application

In finance, business, education, government agencies

Introduction to Gigabit Ethernet

Gigabit Ethernet Development Status

Gigabit Ethernet is a technology built on the underlying Ethernet standard. Gigabit Ethernet and heavily used Ethernet are fully compatible with Fast Ethernet and utilize all the technical specifications specified in the original Ethernet standard, including CSMA / CD protocol, Ethernet frames, full duplex, flow control, and IEEE802 .3 Management objects as defined in the standard. As an integral part of Ethernet, Gigabit Ethernet also supports traffic management technologies, which guarantee the quality of service on Ethernet. These technologies include IEEE 802.1P Layer 2 priority, Layer 3 priority QoS coding bits, Service and Resource Reservation Protocol (RSVP).

Gigabit Ethernet

Gigabit Ethernet also utilizes IEEE 802.1Q VLAN support, Layer 4 filtering, and Gigabit Layer 3 switching. Gigabit Ethernet was originally designed as a switching technology, using fiber optics as the uplink for connection between buildings. Later, Gigabit Ethernet was widely used in server connections and backbone networks. Due to the introduction of the IEEE802.3ab standard (Gigabit Ethernet standard using category 5 and above unshielded twisted pair), Gigabit Ethernet can Applicable to any large, medium and small enterprises and institutions.

Gigabit Ethernet has developed into a mainstream network technology. Large enterprises with tens of thousands of people, and small and medium-sized enterprises with dozens of people will use Gigabit Ethernet technology as the preferred high-speed network technology when building enterprise LANs. Gigabit Ethernet technology is even replacing ATM technology, becoming the main force in the construction of metropolitan area networks.

Gigabit Ethernet Features

1. Gigabit Ethernet provides a seamless migration path that fully protects investments in existing network infrastructure. Gigabit Ethernet will retain IEEE802.3 and Ethernet frame formats and 802.3 managed object specifications, allowing enterprises to upgrade to Gigabit performance while retaining existing cables, operating systems, protocols, and desktop applications Process and network management strategies and tools;

2. Gigabit Ethernet provides an optimal path compared to the original backbone network solutions such as Fast Ethernet, FDDI, and ATM. At least for now, it is a reliable and economical way to improve the backbone connection between the switch and the switch and between the switch and the server. Network designers can build high-speed infrastructures that efficiently use high-speed, mission-critical applications and file backups. Network administrators will provide users with faster access to the Internet, intranet, metropolitan area network, and wide area network.

3 The IEEE802.3 working group established the 802.3z and 802.3ab Gigabit Ethernet working groups, whose task is to develop Gigabit Ethernet standards that meet different needs. The standard supports full-duplex and half-duplex 1000Mbps, and the corresponding operation uses the IEEE 802.3 Ethernet frame format and CSMA / CD media access control methods. Gigabit Ethernet is also backward compatible with 10BaseT and 100BaseT. In addition, the IEEE standard will support multimode fiber with a maximum distance of 550 meters, single-mode fiber with a maximum distance of 70 kilometers, and copper-axis cables with a maximum distance of 100 meters. Gigabit Ethernet fills the gap of the 802.3 Ethernet / Fast Ethernet standard.

Gigabit Ethernet

Gigabit Ethernet build

Gigabit Ethernet is composed of Gigabit switches, Gigabit network cards, and integrated wiring systems. The Gigabit switch forms the backbone of the network. The Gigabit network card is inserted into the server and connected to the switch through the wiring system. Many 100M switches can be connected under the Gigabit switch, and the 100M switch is connected to the workstation. To desktop. " In some professional graphics production and video-on-demand applications, "Gigabit to desktop" may also be used, and a Gigabit switch is used to connect to a workstation with a Gigabit network card inserted, which meets the demand for high bandwidth in special applications.

Before constructing a network, whether to use gigabit or 100 megabytes should be based on actual conditions and applications and consider what functions the network should have. Different applications have different requirements, and there are almost no networks with a single service. However, among various businesses, productive business is definitely the highest priority. If voice is transmitted in the network, voice services also need to be prioritized. If the demand for business priorities is high, the network must have QoS guarantees. Such a network must be intelligent. It can identify what types of services pass through the switch ports, and then queue different services and allocate different bandwidths for different services, so as to ensure the operation of critical services. The data service itself is intelligent. It can be transmitted no matter how much bandwidth, but only for a short time, but the voice or video is not the same. If the bandwidth is small, you can't hear it immediately, or the image is jittery. This is all not allowed. So QoS is very important. For pure data networks, the demand for QoS is very low. When planning a network, you must first understand which functions are necessary and which can be ignored. For example, multicast is one of the more important performances. If images need to be transmitted on the network, and the network does not have the characteristics of multicast, then the bandwidth waste of the network will be very serious, or even impossible to achieve.

Gigabit Ethernet International Standard

In January 1997, the first draft of IEEE802.3z was adopted;

In June 1997, draft V3.1 was adopted, and the final technical details were formulated accordingly;

In June 1998, the IEEE802.3z standard was officially approved;

In June 1999, the IEEE802.3ab standard (1000Base-T) was officially approved, and twisted-pair cables can be used in Gigabit Ethernet.

The Gigabit Ethernet standard is mainly targeted at three types of transmission media: single-mode fiber; long-wave laser on multi-mode fiber (called 1000BaseLX); short-wave laser on multi-mode fiber (called 1000BaseSX); 1000BaseCX medium, which It can be transmitted on a balanced shielded 150 ohm copper cable. The 1000BaseT standard simulated by the IEEE802.3z committee allows the transmission distance of Gigabit Ethernet on Category 5, Ultra Category 5, and Category 6 UTP twisted pair wires to be 100 meters, so that most of the wiring in buildings adopts Category 5. UTP twisted pair cable protects users' previous investments in Ethernet and Fast Ethernet. For network managers, there is no need to receive new training. With the knowledge of Ethernet networks, they can completely manage and maintain Gigabit Ethernet.

Gigabit Switch

The standardization of Gigabit Ethernet includes three main modules: encoding / decoding, transceivers and network media. Different transceivers correspond to different types of network media. When 1000BASE-LX is based on the 1300nm single-mode optical cable standard, it uses 8B / 10B encoding and decoding methods, and the maximum transmission distance is 5000 meters. 1000BASE-SX is based on 780nm FibreChannel optics, uses 8B / 10B encoding and decoding methods, and uses 50-micron or 62.5-micron multimode optical cables with a maximum transmission distance of 300 meters to 500 meters. The SC-type optical fiber connector used to connect the optical fiber is the same model as the connector used for Fast Ethernet 100BASEFX. 1000BASE-CX is a copper-based standard that uses 8B / 10B encoding and decoding methods, with a maximum transmission distance of 25 meters. 1000BASE-T is based on unshielded twisted-pair transmission media, using 1000BASE-T copper physical layer Copper PHY encoding and decoding method, and the transmission distance is 100 meters. 1000BASE-T uses all four pairs of twisted pairs in transmission and works in full duplex mode. This design uses PAM-5 (5-level pulse amplification modulation) coding to transmit 250Mbps on each wire pair. Bidirectional transmission requires that all four wire pair transceiver ports must use mixed magnetic field lines, because the perfect mixed magnetic field line cannot be provided, so the transmitting and receiving circuits cannot be completely isolated. Any transmit and receive lines will echo the device. Therefore, to achieve the required error rate (BER), the echo must be cancelled. 1000BASE-T cannot filter the frequency band concentrated above 125MHz, but using the scrambling technology and trellis coding can filter the frequency band after 80MHz. In order to solve the limitation of Category 5 lines due to near-end crosstalk in such a high frequency range, a suitable scheme should be adopted to cancel the crosstalk.

The original Gigabit Ethernet used high-speed 780 nanometer fiber channel optical elements to transmit signals on the optical fiber, and used 8B / 10B encoding and decoding methods to achieve serialization and restoration of optical signals. The data operation rate of Fibre Channel technology is 1.063Gbps, which will be increased to 1.250Gbps in the future, making the data rate reach a complete 1000Mbps. For longer connection distances, a 1300 nm optical element will be used. In order to adapt to the development of silicon technology and digital signal processing technology, a medium-independent logic interface should be established between the MAC layer and the PHY layer, so that Gigabit Ethernet works in an unshielded twisted pair cable system. This logical interface will be applicable to the encoding method of unshielded twisted pair cable system and is independent of the encoding method of Fibre Channel. The following figure illustrates the composition of Gigabit Ethernet.

Gigabit Ethernet

There are not many conditions for upgrading 10M and 100M networks to Gigabit. The most important thing is the comprehensive wiring conditions. Gigabit Ethernet refers to the bandwidth of the network backbone. It is required that the trunk wiring system must meet the requirements of Gigabit Ethernet. If the original network covers multiple buildings separated by several hundred meters to several kilometers, the original backbone wiring generally uses multimode or single-mode fiber, which can meet the requirements of the gigabit backbone, and it is not necessary to re-lay the fiber. In the case where the distance between buildings is less than 550 meters, generally the relatively low-cost multimode fiber can meet the needs of Gigabit Ethernet.

If the original network covers only one building, and the distance between the farthest network node and the network center does not exceed 100 meters, you can use the original Category 5 or Super Category 5 wiring system. If the original wiring system does not meet the Category 5 standard, or a bus-type wiring system is used instead of a star-type wiring system, the Category 5 wire must be re-routed.

To upgrade to Gigabit Ethernet, you must first upgrade the network backbone switch to Gigabit to increase the data traffic that the network backbone can withstand, thereby achieving the purpose of accelerating the speed of the network. The previous 100M switches were used as branch switches, and the previous hubs could be used where wiring points were insufficient. There are many products of Gigabit switches, which can be selected according to the actual conditions of the network requirements and budget.

Gigabit Ethernet

The server on the network needs to handle a large amount of data. If the network backbone is upgraded to Gigabit, but the server network card is still at the level of 100M, the server network card will become the bottleneck of the network. You must use the Gigabit network card to eliminate this bottleneck and solve the problem. The method is to add a gigabit network card to the original server. Note that you should preferentially choose a 64-bit PCI Gigabit network card, which has a higher performance than ordinary PCI Gigabit network cards. Gigabit network card can be selected according to the actual situation such as network requirements and budget.

The backbone of the network is upgraded, and the branches of the network should be upgraded as well. If the original user computer has 10M / 100M adaptive network card installed, you do not need to upgrade the network card, just connect the network card to the 100M switch; if the original 10Mbps network card is used, you need to replace the network card with 10M / 100M adaptive network card, so as to improve the speed of workstations accessing the server.

Gigabit Ethernet Forecast

It is expected that by 2005, the data transmission volume will increase by three times each year, and will exceed the voice transmission volume in that year, becoming the main transmission mode of the global communication network. In the face of increasing data flow and multimedia services, the market size of high-end, high-capacity, high-speed, and multi-functional network products will continue to expand. It is foreseeable that the market share of Gigabit Ethernet switches will increase. With the development of the Internet and the emergence of endless applications on the network, 10 Gigabit Ethernet will be the mainstream in the future, and Gigabit Ethernet will still be the mainstream in the market.

Gigabit Ethernet technology advantages

In order to maintain the maximum collision area with a diameter of 200 meters in the local area network, the minimum CSMA / CD carrier time, the Ethernet time slice has been extended from 512 bits to 512 bytes (4096 bits), and the minimum frame length has become 512 bytes. The length is still 1518 bytes. The carrier extension feature solves the inherent timing problems of CSMA / CD without modifying the minimum packet size. Although these changes may affect the performance of small packets, this effect has been offset by a feature called packet burst transfer in the CSM / CD algorithm. The biggest advantage of Gigabit Ethernet is its compatibility with existing Ethernet.

Like 100M-bit Ethernet, Gigabit Ethernet uses the same frame format and frame size as 10M-bit Ethernet, and the same CSMA / CD protocol. This means that the majority of Ethernet users can upgrade the existing Ethernet smoothly without interruption, and without adding additional protocol stacks or middleware. At the same time, Gigabit Ethernet also inherits other advantages of Ethernet, such as higher reliability and easy management.

Gigabit Ethernet has the advantage of large bandwidth compared to 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, the priority control mechanism and protocol standards based on the Ethernet frame layer and the IP layer and various QoS support technologies have gradually matured, providing a basis for implementing applications that require better quality of service. With the advancement of optical fiber manufacturing and transmission technology, the transmission distance of Gigabit Ethernet can reach 100 kilometers, which makes it gradually become a technology choice for building metropolitan area networks and even wide area networks.

The advantage of using Gigabit Ethernet for the backbone is that 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 and priority standard 802.1p developed for 10/100/1000 Mbps have been promoted. Gigabit network has become the mainstream technology that forms the backbone of the network.

The first Gigabit Ethernet standard, 802.3, which was developed in June 1998, targets full-duplex links using fiber optic cables and short-range copper cables. The standard 802.3ab for half-duplex and remote copper cables was introduced in 1999.

The high-speed multi-layer packet forwarding capability of Gigabit Ethernet is a strong example of the best performance-price ratio that Gigabit Ethernet technology can provide. Not only that, Gigabit Ethernet technology is also very beneficial for reducing the long-term cost of ownership of the network.

Gigabit Ethernet switching technology

Since the end of 1996, some companies have successively launched switch products that integrate Layer 2 switching and Layer 3 routing. This technology is called "multilayer switching". It adds routing layer services for Layer 2 switching technology, supports selective broadcast and multicast suppression, supports VLAN and packet forwarding and firewall functions between VLANs, and fully supports TCP / IP and IPX routing.

Gigabit Ethernet

After nearly four years of development, these functions have been continuously improved and enhanced, making multilayer switches 8 to 16 times more expensive than traditional routers. The new generation of multi-layer switches with Gigabit Ethernet switching technology as the core can provide a more attractive performance-to-price ratio. It is the most ideal switch that can provide multi-layer switching in departmental networks and data center networks. At the same time, its direct transmission distance has now reached 130 kilometers, which can completely realize a large enterprise local area network with Gigabit Ethernet as the backbone, and the backbone transmission rate is 2Gbps (full duplex mode).

The main factors driving the development of technology The biggest factor driving the development of high-speed multi-layer switching technology is the large-scale deployment of the Internet and intranet using cheap 10 / 100M adaptive network cards. The network has moved farther and farther away from the hierarchical structure of the traditional c / s computing model. The traditional 80/20 traffic rule of the c / s model has passed. In terms of network design, the traditional network deployment model of routers plus Hubs or Layer 2 switches will also become history.

In addition, the intranet supports more complex and bandwidth-sensitive multimedia data streams, such as data, files, pictures, animation, sound, and video. An intranet end user requires at least 50% to 100% more bandwidth than a non-intranet user. At the same time, broadband access has become a development trend.

Another issue worth noting is that providing users with a Fast Ethernet connection can provide more bandwidth margin to handle sudden traffic, which is unmatched by 10BASE-T technology. Burst traffic is one of the characteristics of IP network applications. Cheap and high bandwidth makes Fast Ethernet widely used in both client and server.

In order to strike a balance between non-blocking and the ability to handle burst traffic, the new generation of switch platforms must provide backbone connections that are 8 to 16 times faster than user-requested connections, and the Gigabit Ethernet backbone is just to satisfy users Service request for a fast Ethernet connection at the end. This is important to fully handle burst traffic.

At the same time, in the campus network or metropolitan area network, no matter how many network layers are crossed, it is required to provide end-to-end continuous high performance for random intranet traffic. To achieve this, it is the only solution to have high-performance Layer 2 and Layer 3 forwarding capabilities in one switch.

Non-blocking ability and selective forwarding function are the main requirements of users. And a variety of very effective network management tools enable network administrators to effectively and efficiently inject business strategies into the forwarding engine, and its performance can be monitored in real time by network management software. This will fundamentally help users determine and deliver the required network services based on the company's short- and long-term business development needs. The new generation Gigabit Ethernet switch supports these features and services, and also supports common routing protocols such as IP / RIP or IP / OSPF. This also greatly reduces the complexity of network equipment.

Gigabit Ethernet Goals

The high performance of the network system requires that the core switch meet the requirements of the massive data exchange at the network center, and the communication link bandwidth of the connection center can meet the application's performance requirements for the network. Whether it is an enterprise network, a metropolitan area network, or a wide area network, the information applications on it are developing at an unprecedented speed. New multimedia applications and new data applications have put forward higher requirements on bandwidth. Taking the intranet network model generally adopted by enterprises, its WWW server, FTP server, Lotus Notes groupware application server, Novell Server and other server groups support the entire enterprise information service environment. Client application software for users in all departments of the enterprise accesses the central server through the network, requests applications, and queries the database. The load flow of the network is mainly the data exchange from the edge device to the core. With the development of enterprise business, the expansion of the network scale, and the increase in the amount of information exchange, the enterprise network usually has a communication bottleneck at the core. To improve the network data exchange performance of the enterprise campus LAN, it is often the first to expand the exchange performance of the core switch and increase the data communication bandwidth from the edge device to the core to reduce the bottleneck of the entire network and improve the performance and efficiency of the application software. Therefore, when designing the LAN of an enterprise campus, the data exchange processing capability of the core device and the bandwidth of the edge device to the core that meet the network scale requirements should be considered first.

Gigabit Ethernet reliability and availability

The equipment in the network system design has high reliability and high system availability; all key components of the core switch are required to achieve redundant work, which can be replaced online (plugged), and the recovery time of the failure is completed within a second interval. Multi-level fault-tolerant design is based on the high reliability of a single device to further improve system availability.

As far as enterprise applications are concerned, it uses advanced computer and network information technology to realize automatic control of the production process and paperless office automation, which has improved the production and management efficiency and level of the enterprise. The infrastructure supporting enterprise applications is the enterprise's campus network. Its working conditions will directly affect the enterprise's office application environment, business environments such as transactions, production, development, and design, financial management, parts management and other environments, information retrieval, and database query. , Internet browsing and other necessary service facility functions to support the normal operation of the enterprise. The reliability requirement of the network is the first condition to ensure the normal operation of the enterprise application environment. While the network requires reliability, it also requires the network to have high availability. The selection of network equipment, especially the core chassis-type equipment, should be able to configure redundant components. There is no single point of failure for key components. That is to say, components such as the power supply, fans, switching engines, and management modules of the switch can be redundantly backed up. Damage to any of these components will not affect the normal operation of the device and will not affect network connectivity. Provide the reliability of network equipment. Another requirement for fault tolerance is that when the equipment is damaged, no downtime is required, and no restart is required after replacing the components. That is to say, the replacement of components can be performed online, which can reduce downtime. To the smallest. It is very important to improve the high reliability and high availability of the network on the principle of designing the campus network of the enterprise. It not only requires the redundancy of the components of the equipment, but also the redundancy of the network links. It can be combined with the physical layer, link layer, and The third layer of technology is implemented to ensure that the network can provide information access services at any time and any place.

Gigabit Ethernet scalability

Network design scalability requirements, including the ability to expand switch hardware and the ability of the network to implement new applications. Core switch flexibility requirements: core switches should have flexible port expansion capabilities, module expansion capabilities to meet the expansion of the network scale; at the same time, improve performance and meet higher performance requirements. Ability to support new applications: The product has the technical preparations to support new applications, and can implement new applications conveniently and quickly.

Gigabit Ethernet scale and users

When designing a network solution, first of all, it is necessary to meet the needs of existing network users, while taking into account future business development and scale expansion.

Gigabit Ethernet access system

The network should be designed with flexible expansion capabilities for user ports. The core device is the hub of the entire network. The expansion of the number of user ports requires the addition of equipment at the edge working group of the wiring closet. At the same time as the addition of edge devices, the number of ports connected to the core backbone device is increased accordingly. To increase the number of ports flexibly. The chassis design of the core equipment should have a powerful backplane bandwidth and sufficient load slot capacity. For switches, the core switching engine should be able to switch port data packets without blocking under the maximum configuration. The expansion of the module does not affect the switching performance. The distributed switch structure is the best solution to realize this principle. The distributed switch structure realizes the parallel data exchange processing of the switch and optimizes the network performance. The distributed structure combining local switching and global switching reduces the core switching engine. pressure. Therefore, in designing large-scale campus networks, distributed switches are commonly used to implement flexible module and port expansion capabilities.

Gigabit Ethernet security

Network security is very important for network design. Reasonable network security control can effectively protect the information resources in the application environment, effectively control network access, and flexibly implement network security control strategies. In the enterprise campus network, only system administrators have the authority to operate and control key application servers and core network equipment. Application clients only have access to shared resources, and the network should be able to prevent any illegal operations. Packet filtering control functions based on protocols, Mac addresses, and IP addresses should be available on campus network devices. In the design of large-scale campus networks, dividing virtual subnets can effectively isolate a large number of broadcasts on the subnets, on the other hand, isolate communications between network subnets, control resource access rights, and improve network security. Sex. In designing the campus network, the network security control capability must be emphasized so that the network can be connected arbitrarily and the network access can be controlled from the second and third layers.

Gigabit Ethernet manageability

Network manageability requirements: Any device in the network can be controlled through the network management platform. The network device status and fault alarms can be monitored through the network management platform. The network management platform simplifies management and improves the efficiency of network management. .

In network design, it is essential to choose advanced network management software. Network management software is applied to network device configuration, network topology structure display, network device status display, network device failure 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 on network management personnel. The goal of network management is to achieve zero management and a policy-based management method. Network management is controlled globally by the management policy server by formulating a unified policy. The web-based network management interface is the development trend of network management software. Flexible operation methods simplify the work of management personnel. In the design of equipment for the campus network, the network equipment is required to support the standard network management protocol SNMP and the RMON / RMONII protocol. The core equipment is required to support the RAP (Remote Analysis Port) protocol to implement sufficient network management functions. The principle of designing the campus network should require the manageability of the equipment, and advanced network management software can support network maintenance, monitoring, and configuration functions.

Standardization of Gigabit Ethernet protocol

Network equipment adopts open technology and supports standard protocols: adopting standard protocols to protect users' investments and improve equipment interoperability. The equipment used in network design requires mainstream technology and developed standard protocols, has good interoperability, and can support different series of products from the same manufacturer, and seamless interconnection and communication between products from different manufacturers. On the principle of designing the campus network, and using the advanced technologies dedicated to products from different manufacturers, we must emphasize the standardization of equipment technology and protocols, reduce the problem of equipment interconnection, network maintenance costs, and effectively protect user investment.

Should consider whether the selected equipment is upgradeable, after the emergence of new standards, the system should be able to upgrade to the new standards. Therefore, we pay attention to the position of product manufacturers in the corresponding product and technology fields and their ability to participate in standardization.

In today's world, the development of communication technology and computer technology is changing rapidly. Network design should not only adapt to the trend of new technology development, ensure the advanced nature of the system, but also take into account the technical maturity to reduce the risks caused by immature factors in new technologies and new products.

Gigabit Ethernet Solution

The biggest advantage of Gigabit Ethernet is its compatibility with existing Ethernet. Like 100M-bit Ethernet, Gigabit Ethernet uses the same frame format and frame size as 10M-bit Ethernet, and the same CSMA / CD protocol. In the backbone network of the campus network, it gradually occupied the main position.

As a characteristic of campus network applications, most applications are not sensitive to delay and bandwidth. It can automatically identify changes in delay through the TCP / IP "slow start" mechanism, dynamically adapt to the bandwidth provided by TCP, and some applications require real-time service transmission. Support, QoS service guarantee. The proportion of this part of application is very small. With the acceleration of the modernization of teaching methods, the gradual popularization of multimedia courseware production tools and the gradual enrichment of multimedia courseware, the proportion is expected to gradually increase. The main bottleneck in transmitting real-time services over IP networks is that routers use software to implement route identification, calculation, and packet forwarding. Due to the slow speed of route identification and data forwarding, large delays and delay jitter, 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, calculation, and forwarding. The structure of this wire-speed routing switch is similar to that of the L2 switch. It has both the L3 router packet forwarding function and the L2 switching function. Some manufacturers also add some L4 application layer functions.

To provide QoS on a packet-switched IP network, services must be classified and classified services (CoS) implemented. Equipment manufacturers generally use congestion management to ensure network performance and provide the required bandwidth for some specialized services. One approach is to use RED (random early loss) detection and intelligently identify the instantaneous spike in traffic to distinguish it from true network congestion to avoid network congestion. By identifying the service category (802.1P) from the IPv4 service classification identifier (TOS) in the IP packet header, the priority of the data flow is determined, and a certain queue priority algorithm is used to ensure the QoS capability. You can also use access control lists (ACLs) to define policies to prioritize data flows. With the advancement of technology, it is foreseeable that the QoS capability on high-speed IP networks will reach a similar level as FR / ATM networks.

After analyzing and comparing the performance, price, and service of various L2 / L3 / L4 wire-speed routing switches in the market, a total of 11 Cajun P550R routing switches from Lucent Corporation were selected as the backbone switches of the campus network. Its main technical and performance indicators are:

Backplane capacity 45.76 Gbps

Switching throughput 22.88 Gbps

Layer 2 switching capacity 33,000,000 pps

Layer 3 switching capacity 18,000,000 pps

Multiple L2 / L3 interface modules

Redundant fans, power supplies

OpenTrunk / VLAN interoperability

CoS / QoS / RSVP support

In network design, the backbone switches are interconnected with each other through Gigabit Ethernet. All switches are configured with L3 switching engines to implement a distributed routing strategy, thereby reducing the pressure on the central switch's L3 routing analysis, packet forwarding, and controlling the scope of the broadcast domain. The network design and equipment configuration carefully consider the physical and logical redundancy of equipment and lines and routing, the firewall settings and security policies of the network-centric server farm.

Gigabit Ethernet technology

1000Base-T Gigabit Ethernet 1000Base-T technology

With the release of the country's "Gigabit Ethernet Switch Equipment Technical Specifications", the application of Gigabit Ethernet technology has developed rapidly.

1000Base-T (Gigabit Ethernet implemented on Category 5 twisted pair) is one of the best choices for network managers due to the following reasons. First, it mainly meets the rapidly increasing demand for bandwidth in existing networks. Second, in these networks, emerging applications continue to appear, and network edge switches are also increasing. Gigabit Ethernet can protect the company's existing investments in Ethernet and Fast Ethernet facilities. Third, it can provide a simple, effective, and inexpensive way to improve performance while continuing to use a large number of existing Horizontal cable transmission medium.

1000Base-T technology principle

Gigabit Ethernet Transmission Medium Specification

Gigabit Ethernet can take advantage of existing cable facilities, which gives it a good price-performance ratio. It can be adopted on the floor, in the building, and in the campus network because it can support multiple connected media and a wide range of connection distances. In particular, Gigabit Ethernet can operate on the following four media: fiber optics, with a maximum connection distance of at least 5 kilometers; mode fiber, with a maximum connection distance of at least 550 meters; balanced and shielded copper cables, with a maximum connection distance of at least 25 meters; Category 5 cables with a maximum connection distance of at least 100 meters.

The IEEE802.3z Gigabit Ethernet standard was approved in June 1998. It defines three transceivers for three transmission media: 1000Base-LX, 1000Base-SX, and 1000Base-CX. Among them, 1000Base-LX is used for installing single-mode fiber, 1000Base-SX is used for installing multimode fiber, 1000Base-CX is used for balanced and shielded copper cables, and it can be used for interconnection of computer rooms. The 1000Base-LX transceiver can also be used for multimode fiber, with a transmission distance of at least 550 meters.

Gigabit Ethernet Layered

Another special working group, IEEE802.3ab, has defined the physical layer that runs Gigabit Ethernet on the basis of Category 5 lines. The IEEE Standardization Committee approved the 1000Base-T standard in June 1999. 1000Base-T can continue to use the existing cable facilities, which stipulates a transmission distance of up to 100 meters on Category 5 lines.

1000Base-T's other important specifications make it a low-cost, not easily destroyed technology with good performance. First, it supports Ethernet MAC, and it is backward compatible with 10 / 100Mbps Ethernet technology. Second, many 1000Base-T products will support 100/1000 auto-negotiation function. Therefore, 1000Base-T can pass directly in the fast Ethernet network. The upgrade is realized. Third, 1000Base-T is a high-performance technology. For every 10 billion bits transmitted, the number of erroneous data bits will not exceed one. Rate is quite).

Gigabit Ethernet Cable Specification

1000Base-T stipulates that data can be transmitted on five types of balanced twisted pairs. ANSI / EIA / TIA-568-A (1995) specifies the performance of the four-to-five category twisted pair used by it. Other link performance parameters (backhaul loss and ELFEXT) are specified in TIA / EIA-TSB-95. The standards for the five types of wires are specified in ISO / IEC 11801: 1995 ("Information technology: universal cables for user front-end equipment"). The second edition of ISO / IEC 11801: 1995 specifies some other cable performance parameters to support Gigabit Ethernet.

Gigabit Ethernet physical structure

1000Base-T is specifically designed for transmitting data on Category 5 twisted pairs. The transmission rate of 1Gbps can be regarded as equivalent on four twisted pairs, and the transmission rate of each pair is 250Mbps (250Mbps × 4 = 1Gbps).

1000Base-T and 100Base-T use the same transmission clock frequency (125MHz), but use a more powerful signal transmission and encoding / decoding scheme, which can transmit twice as much data on the link than 100Base-T . The following is a comparison of these two technical specifications:

1000Base-T: 125MHz × 2 bits = 250Mbps

1000Base-TX: 125MHz × 2 bits-symbol = 125M bits-symbol / s

Please note: 125M bit-symbols / s is equivalent to 100Mbps, because 1000Base-T uses a 4B / 5B encoding-before putting the signal on the cable for transmission, every 4-bit data is converted into 5 bit-symbols ; The effective bit transmission rate is: 125 × 4/5 = 100Mbps.

1000Base-T Gigabit Ethernet 1000Base-T encoding

In order to cost-effectively use 4 to 5 UTP, IEEE802.3ab does not use 8B / 10B coding, but defines a logical interface at the MAC sublayer and PHY layer, allowing the introduction of a more cost-effective coding scheme. Due to the limitation of the available bandwidth, it is obvious that each pair of category 5 UTPs should not exceed 125Mbaud (the category 5 UTP is 60.6MHz, and its ACR is 30.6dB). It is also considered that it can cover 28 = 256 and minimize the number of digits in the multivariate system, so we take quinary coding, which is 8B / 4Quinary. In this way, (1000/4) × (4/8) = 125Mbaud can meet the limitation of available bandwidth.

If four-level (quartemary) coding is used, the above requirements can also be met, and it can also cover 28 = 256, but the redundant one level in the five-level (quinary) coding can be used for the other four levels of error correction codes.

The recent 1000Base-T white paper of the Gigabit Ethernet Alliance recommends the use of PAM-5 codes. Each symbol (take one of +2, +1, 0, -1, -2) corresponds to two bits of binary information (four levels represent two Bits, one level is used for forward error correction code). The forward error correction code uses a 4-dimensional 8-state Trellis forward error correction code. Realizing these mainly depends on integrated circuit technology and digital signal processing (DSP) technology.

1000Base-T can support the existing fast Ethernet and V.90 / 56K modem technologies that have been practically tested, thus obtaining a good performance-price ratio. Advanced DSPs that implement signal transmission and encoding / decoding in 802.3 Fast Ethernet and V.90 or 56K modems can also be used to implement 1000Base-T.

Advantages

Gigabit Ethernet is a new type of high-speed local area network. It can provide 1 Gb / s communication bandwidth. It uses the same CSMA / CD protocol, frame format and frame length as the traditional 10/100 M Ethernet. The smooth and continuous network upgrade based on Ethernet can protect users' previous investment to the greatest extent.

Gigabit Ethernet conclusions

As more and more desktops and workgroups upgrade to Fast Ethernet, the centralized business of the network backbone will grow significantly. To handle this traffic, all new backbone switches should support Gigabit Ethernet uplinks. Gigabit Ethernet switches in the backbone network can be used to connect high transaction rate servers and network segment switches in a centralized Fast Ethernet workgroup. If the fiber optic network connection method of Gigabit Ethernet solves the high-speed connection between buildings, then the 1000Base-T Gigabit Ethernet technology is used to solve the high-speed connection between floors and even offices.

Gigabit Ethernet other types

Gigabit Ethernet Standard Ethernet

Initially, Ethernet only had a throughput of 10 Mbps, and it used a carrier sense multiple access (CSMA / CD, Carrier Sense Multiple Access / Collision Detection) access control method with collision detection. It is standard Ethernet.IEEE 802.3Mbps100mBaseBroad

·10Base5 0.450500m10Base5AUI

·10Base2 0.250185m10Base2BNCT

·10BaseT 100m10BaseT35RJ-45RJ-45

· 1Base5 500m1Mbps

· 10Broad-36 uses coaxial cable (RG-59 / U CATV), the maximum span of the network is 3600m, and the maximum network segment length is 1800m.

10Base-F uses optical fiber transmission medium, and the transmission rate is 10Mbps.

Gigabit Ethernet Fast Ethernet

With the development of the network, the traditional standard Ethernet technology has been unable to meet the increasing demand for network data traffic speed. Prior to October 1993, for LAN applications requiring more than 10 Mbps of data traffic, only Fiber Distributed Data Interface (FDDI) was available, but it was a very expensive LAN based on 100Mpbs fiber optic cables. In October 1993, Grand Junction launched the world's first Fast Ethernet hub Fastch 10/100 and network interface card FastNIC100. Fast Ethernet technology was officially applied. Subsequently, Intel, SynOptics, 3COM, BayNetworks and other companies have also launched their own Fast Ethernet devices. At the same time, the IEEE802 engineering group has also studied various standards of 100Mbps Ethernet, such as 100BASE-TX, 100BASE-T4, MII, repeater, full duplex and other standards. In March 1995, IEEE announced the IEEE802.3u 100BASE-T Fast Ethernet standard (Fast Ethernet), and thus began the era of Fast Ethernet.

Compared with the original FDDI operating at 100 Mbps bandwidth, Fast Ethernet has many advantages. The most important aspect is that Fast Ethernet technology can effectively protect users' investment in the implementation of wiring foundation. It supports dual-type 3, 4, and 5. The connection of twisted wires and optical fibers can effectively use the existing facilities. The shortcomings of Fast Ethernet are actually the shortcomings of Ethernet technology. That is, Fast Ethernet is still based on CSMA / CD technology. When the network load is heavy, the efficiency will be reduced. Of course, this can be compensated by switching technology. The 100Mbps Fast Ethernet standard is further divided into three subclasses: 100BASE-TX, 100BASE-FX, and 100BASE-T4.

· 100BASE-TX: It is a fast Ethernet technology using Category 5 data-level unshielded twisted pair or shielded twisted pair. It uses two twisted pairs, one for sending and one for receiving data. The 4B / 5B coding method is used in transmission, and the signal frequency is 125MHz. Meets EIA586 Category 5 cabling standards and IBM's SPT Category 1 cabling standards. Use the same RJ-45 connector as 10BASE-T. Its maximum segment length is 100 meters. It supports full-duplex data transmission.

· 100BASE-FX: is a fast Ethernet technology using fiber optic cables, which can use single-mode and multi-mode fiber (62.5 and 125um). The maximum distance for multimode fiber connections is 550 meters. The maximum distance for a single-mode fiber connection is 3000 meters. The 4B / 5B coding method is used in transmission, and the signal frequency is 125MHz. It uses MIC / FDDI connectors, ST connectors, or SC connectors. Its maximum network segment length is 150m, 412m, 2000m or longer to 10 kilometers, which is related to the type of optical fiber used and the working mode. It supports full-duplex data transmission. 100BASE-FX is especially suitable for the environment with electrical interference, large distance connection, or high security environment.

· 100BASE-T4: It is a fast Ethernet technology that can use category 3, 4, and 5 unshielded twisted pair or shielded twisted pair. 100Base-T4 uses four twisted pairs, three of which are used to transmit data at the frequency of 33MHz, and each pair works in half-duplex mode. The fourth pair is used for CSMA / CD conflict detection. The 8B / 6T coding method is used in the transmission, and the signal frequency is 25MHz, which conforms to the EIA586 structured wiring standard. It uses the same RJ-45 connector as 10BASE-T, and the maximum network segment length is 100 meters.

Gigabit Ethernet

The 10 Gigabit Ethernet specification is included in the IEEE 802.3ae supplementary standard IEEE 802.3ae, which extends the IEEE 802.3 protocol and MAC specifications to support 10 Gb / s transmission rates. In addition, through the WAN interface sublayer (WIS: WAN interface sublayer), 10 Gigabit Ethernet can also be adjusted to a lower transmission rate, such as 9.548440 Gb / s (OC-192), which allows 10 Gigabit Ethernet devices are compatible with the Synchronous Optical Network (SONET) STS-192c transmission format.

· 10GBASE-SR and 10GBASE-SW mainly support short-wave (850 nm) multimode fiber (MMF), and the fiber distance is 2m to 300m.

10GBASE-SR mainly supports "dark fiber" (dark fiber). Dark fiber refers to the fiber that has no light transmission and is not connected to any equipment.

10GBASE-SW is mainly used to connect SONET devices, and it is used for remote data communication.

· 10GBASE-LR and 10GBASE-LW mainly support long-wave (1310nm) single-mode fiber (SMF), and the fiber distance is 2m to 10km (about 32808 feet).

When 10GBASE-LW is mainly used to connect SONET devices,

10GBASE-LR is used to support "dark fiber".

· 10GBASE-ER and 10GBASE-EW mainly support ultra-long wave (1550nm) single-mode fiber (SMF), and the fiber distance is 2m to 40km (about 131233 feet).

10GBASE-EW is mainly used to connect SONET devices.

10GBASE-ER is used to support "dark fiber".

· 10GBASE-LX4 uses wavelength division multiplexing technology to send signals on a single optical fiber cable at four times the optical wavelength. The system operates in multimode or single-mode dark fiber mode at 1310nm. The system is designed for multimode fiber mode from 2m to 300m or single mode fiber mode from 2m to 10km.

Ethernet connection

Future network development trends