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Ethernet broadband access is introduced

...... Ethernet is a LAN technology developed in the 1980 s, since it has advantages of easy use, low price and high rate, has become the mainstream in the local area network (LAN) soon.As gigabit Ethernet (GbE) mature and Wan Zhao Ethernet (10 GbE), and low cost in the optical fiber directly architecture of GbE and 10 GbE technology mature, Ethernet into metropolitan area network and wan area.If the access network also USES Ethernet will form from the local area network, access network, metropolitan area network to all is the structure of the Ethernet wan.Used the unified agree with IP Ethernet frame structure, the seamless connection between network, do not need any format conversion, the middle will be able to improve the operation efficiency, convenient management, reduce the cost.

Based on Ethernet technology of broadband access network by the bureauequipmentAnd the clientequipment, generally located in the office end or commercial buildings in the district, the client devices are located in residential buildings;Office end devices provide an interface with IP backbone network, connects with the user terminal computer user equipment to provide 10100 base-t interface.Client devices, unlike Ethernet switches, Ethernet switch isolation unicast data frames, not isolated broadcast address data frames, and the function of the client device is simply the Ethernet frame multiplexing and reuse;Office end equipment is different from the router, the router maintenance is port - network address mapping table, and maintenance of office end is port - host address mapping table.Only for the link layer function, working under the multiplex way, each user in the physical layer and link layer between isolated, thus ensuring the safety of the user data;Office end device support for user authentication, authorization, and billing, and user IP address dynamically allocated, also has the function of convergence for network management information.

Ethernet is the most widely used LAN technology.Due to its simplicity, low cost, strong scalability, and can be well combined with the characteristics of IP network, the application of Ethernet technology is from the enterprise internal network, moving to the public telecommunication networks.Ethernet access refers to the Ethernet technology and the combination of integrated wiring, as public telecommunication network access network, directly to the customers with a variety of business based on IP transmission channel.

Ethernet technology is the essence of a layer of medium access control technology, can be sent in five classes online, can also be combined with other access to the media, to form a variety of broadband access technology.Ethernet combined with telephone copper of VDSL, forming EoVDSL technology;To combine with the passive optical network, produce the EPON technology;In the wireless environment, the development of WLAN technology.

The main technical problems in Ethernet

But due to the access network is a public network environment, so its requirements and local area network (LAN), a private network environment to be very different, it only use for local Ethernet frame structure and interface, network structure and working principle of completely different, because the Ethernet in essence is a kind of LAN technology, using this technology to provide public telecommunication network access, construction operations, management of broadband access network, the need to properly solve a series of technical problems, including the authentication billing and user management, users and network security, network management, service quality control, etc.

Authentication billing: Ethernet as a LAN technology, no mechanisms such as authentication, billing, but want to use this technique as user access way of operation, management, must consider user authentication billing authorization (AAA).

AAA generally includes user terminals, AAA Client, AAA Server and billingsoftwareThe four part.AAA of communication between the Client and AAA Server using the RADIUS protocol.The AAA Server and billingsoftwareThe communication between the internal agreement.Can be according to the need of the management way on the billing, considering long on time, frequency, flow, application, bandwidth and so on a variety of ways.Between the user terminal and AAA Client communication mode is often referred to as "authentication", the current main technology has the following three

1) standard, equipment mature PPPoE ways;Load data and certification shall be via PPPoE encapsulation, to the user control ability is strong, but the network performance and equipment processing efficiency is low, easy to form the traffic bottleneck;Equipment price is high.

No special packaging (2) the DHCP + WEB way, certification by carrying forward, data can be directly after the network performance and equipment processing efficiency is higher, but with a relatively low ability for the user to control;No matter whether through the authentication, all take up IP address;In addition, certification. High level will affect the efficiency, also can bring a certain security of some of the network resources.

(3) recently, the IEEE 802.1 x technology develops very fast, this way of carrying data channel and certification, network performance and equipment processing efficiency is higher;After certification by assigning IP addresses;Certification efficiency is higher;The kernel, and, more importantly, it is based on Ethernet implementation is simpler, and Ethernet device can very good fusion, equipment cost is low.In conclusion, three ways have their own characteristics, the reasonable selection should be based on specific application situation.

Users and network security, and network security for the whole telecommunication network, especially the data communication network is a major issue, in Ethernet networks, mainly reflected in the user communication information confidentiality, the safety of the user account and password, the user IP address security and important network equipment, such as the DHCP server security, etc.

Ethernet technology used inside the enterprise, the need for each other between different user information, reflect on the device, the traditional layer 2 Ethernet switches, unicast frame and broadcast frame can be exchanged between different ports.When Ethernet technology is used to provide access to the public telecommunication networks, due to the distrust of the relations between different users, must implement the second isolation between the user and the three layers is controlled.This requires Ethernet switch port isolation, the current main methods are divided based on 802.1 q VLAN, adopting the port of chips, or by other private technology (such as using only in effective VLAN on the switch or other Settings to achieve the purpose of port isolation, but not change 802.1 q VLAN tag).

The user account and password security rely on encryption transmission of relevant information.User IP address anti-theft purposes can be achieved through the binding mechanism, such as IP address and MAC address, the user port binding.For the safety of the DHCP server, should prevent users from changing MAC address to apply for IP address and running out of resources.

Service quality control: in terms of quality of service (QoS), Ethernet technology only flow control, CoS (p 802.1), and other relatively simple mechanism.To improve the quality of service, on the one hand, should guarantee the enough bandwidth on the network, on the other hand, can refer to some methods of Diffserv, such as plastic (shaping), control (policing), classification, queue scheduling (such as using WFQ algorithm), congestion control (such as using WRED algorithm), etc.How to through the Ethernet technology to ensure quality of service is a more complex problems, further research is needed, the basic requirement of this area is able to restrict user access to the highest bandwidth.

Network management: due to the traditional Ethernet is mainly used in the enterprise internal, so the network management function of Ethernet switches generally weaker.In order to meet the needs of the telecom network operation, maintenance, management, shall propose a comprehensive network management functions of equipment requirements.At present, Ethernet access network elements in the network equipment should support SNMPv2 based management.

The main principle of development of Ethernet technology

Represented by TCP/IP, Ethernet, computer network technology and the traditional telecom network represented by PSTN, ATM technology has the characteristics of different, should also be different to the requirement of the network performance.

For manufacturers and operators, to technology and technology, and should be in the market, benefit as the center.Only to meet user demand, market needs, low cost, high benefit of technology have vitality.Therefore, the development of Ethernet technology should be based on the advantage of Ethernet original of equipment was improved, the increased costs, but more in lower performance under the condition of extension, trying to find technology, market and benefit, function, performance and cost balance.

New progress in Ethernet technology application

Ethernet technology as the data link layer of a simple and efficient technology, with its as the core, combined with other physical layer technology, Ethernet technology access system.EoVDSL method combines the characteristics of Ethernet technology and VDSL technology, and ADSL (5 kinds of online) and Ethernet technology, compared with a certain number of potential advantages.The application of WLAN technology promotion, EPON technology research and development is to achieve positive progress.With the operations, management related key technical problems to solve gradually, Ethernet technology access system will get more extensive application in the field of broadband access.

At the same time, the application of Ethernet technology is extended to the metropolitan area network field.IEEE802.17 in keeping the original Ethernet RPR technology advantages, on the basis of introducing or enhance the self-healing protection, priority and fairness algorithm, the function such as OAM, is an important innovation of Ethernet technology.

Anyhow, Ethernet technology due to its simplicity, low cost, the advantages of easy to extend, on the user's desktop system and enterprise internal network has been very popular, with the development of technology innovation, and its application field is gradually to access network, metropolitan area network, or even wan/backbone network expansion, forming based on IP/Ethernet end-to-end seamless connection.

Access to compare

At first, the computer is through the communication and data communication network to realize data sharing;At this time of the computer network, and basically to telecommunication network as the carrier of information.For example, the Internet is through the telecom network x. 25, DDN network, data transmission of IP packets, such as frame relay network.Nowadays, IP technology as the core of information network will become the subject of network information transmission, data transmission will become the main business of network, some traditional telecom business will also be opened on the information network, but its volume accounts for only a small part of the information service.As broadband integrated information service platform for the bearing, telecommunication network, computer network, cable television network access, the user in an affordable cost, can provide different service content and so on, the applicable scope is also different, therefore, several kinds of access network in technology also exist significant difference.

Telecommunication network

Traditional telecom network has more than one hundred years of history, it has a large and good user groups, transmission technology has been used by it from the public telephone network to ADSL Modem, DDN, ISDN conversion.Even so, the telecommunication network is widely used in the user's access is still the Modem, the Modem maximum transmission rate only 56 KB/s, it is not a way of broadband access, far cannot meet the needs of network users.To platform in the traditional telecom network for transmission of broadband service, improve the data traffic, telecommunications company successively in the network application of the techniques such as DDN, ISDN, however the transmission rate of these techniques are far short of the needs of users, therefore, the recent ADSL technology is widely used in the telecommunications network platform, in order to improve the data traffic, foreshadowing for broadband telecommunications sector further multi-function business good physical network foundation.ADSL technology can provide various application service based on ATM.And the demand of broadband IP access rapidly, ADSL access to become a new kind of broadband Internet access methods.Because of ADSL still maintain the original system and structure, the front-end DSLAM equipment is provided by the ATM interface, so it needs to connect to the Internet through a router, eventually realize the Internet access.

ADSL access advantages are: the city can take advantage of the existing telephone network and telephone exchange machine room, don't need to large-scale transformation of network, thus greatly reduces the construction and maintenance costs, and telephone service is not subject to any influence, so using ADSL can have been connected to the Internet and does not affect the use of the telephone.

ADSL access the disadvantage is that: it on line quality demand is higher, when the line quality is not high, promote the use of difficult.ADSL actual speed is between the user and telephone bureau telephone line length and the quality of telephone lines;And ADSL system outside the building in building are shielded twisted-pair cable, so the weather interference resistance ability is poor;Its bandwidth scalable potential are slim.ADSL, therefore, cannot satisfy the demand of the increasing rate of access in the future, can only become a kind of transitional product, used in single user request is not high old community broadband access transformation.

The computer network

Ethernet is the most widely used computer local area network transmission way, universal and practical protocol has been a shift from the IEEE802.3 10 base-t fast Ethernet 100 base-t, it USES the baseband transmission, through twisted-pair and transmission equipment (routers, switches, etc.), achieve 10 m / 100 m / 1 gb/s network transmission, application is very extensive, mature technology.From the original 10 MB/s on the coaxial cable of the sharing, development to the present 100 MB/s on the twisted-pair cable and optical fiber even 1 gb/s transmission technology, exchange of technology, etc.Ethernet technology mature, simple structure, stability, good scalability, convenient for network upgrades.At the same time can be relatively easy to achieve real-time monitoring, intelligent property management, to provide intelligent, informatization office, household environment, meet the needs of different levels of people to the information.At present, 80 to 90% of global enterprises and users are using Ethernet access, the dominant access has become the enterprises and users.Using Ethernet as enterprises and user access method is the main reason of the existing network foundation knowledge and long-term experience, and now all popular operating systems and applications are also compatible with Ethernet.Due to pricing, quality, addressing, cost management, security, access and a variety of factors such as privacy, Ethernet as the common network access still needs further improvement.The inherent mechanism of Ethernet technology is not able to provide end-to-end packet delay, packet presented.according to and bandwidth control capacity, difficult to support real-time business service quality;At the same time, Ethernet can provide fault location and multi-user Shared node and the network the necessary billing statistical capacity;And, as a result of family homes are scattered, Ethernet access cost is higher, the family of broadband access general rarely adopt the way of construction of Ethernet.In urban area, if the Ethernet access solution, may need to be done to data network, structured cabling for the city of ordinary users is not acceptable.Therefore, the traditional Ethernet must be converted to successfully applied to public access.

Cable networks

In our country, because of the coaxial cable of the penetration is very high, so make full use of the resources to carry out the Internet access service is the development direction of cable operation, using the cable modem technology in HFC transmission IP data service will be developed rapidly, a strong contender for the Internet access.HFC transmission of IP data on main equipment have a cable modem terminal system CMTS and cable modems CM.Among them, the CMTS generally located in the location of the cable network front-end, with public node machine such as ATM switch or router interface, CM is located in the user's home, to provide an interface with the user's computer.Communication between the CMTS and CM are different from ordinary Modem, Ethernet.Ordinary Modem communication between point to point, one-to-one, Ethernet card is Shared bus, half duplex communication between, between the CMTS and CM communication is to point to multipoint, full-duplex, any communication between the CM must be through the CMTS to complete.On HFC, IP data transmission of point to multipoint systems exist the problem of multiple access, the solution is to use more time division multiple access (TDMA).


At present, the way of information transmission between CMTS and CM for: downward is broadcast mode, the upside is TDMA mode.In the downward direction, CMTS sent to specific CM data frame contains information on logo CM, so only conform to the identity of the CM will continue to process the data frame, other CM will be lost the data frame, in the upward direction, the channel is divided into fragments of continuous time, inform all CM CMTS in the downlink channel which fragments of uplink channel time can send data frames by which CM, then the CM in the available time period in accordance with the provisions of CMTS sending data frames.At present, to transmit data in HFC equipment standards are mostly adopted by the MCNS DOCSIS / 1.0/1.1, part adopts the DVB/DAVIC ETS300 800, make between different manufacturers of CMTS and CM will not be able to each other.From the development trend of manufacturer specialized standards will gradually die, DOCSIS standard can provide interoperability for different cable modems, will become the dominant standard.
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