Metropolitan Area Network In a city is established within the scope of the computer network, the abbreviation MAN. Belong to broadband LAN. Because use has active exchange of components of the LAN technology, network transmission delay is lesser, its transmission medium mainly USES the optical fiber, transmission rate in l00 MBPS above. A MAN is used as a backbone important USES, through which will be located at different sites within the city with - the mainframe, database, and LAN and link up with each other etc, this and WAN role similarities, both in realizing methods and performance was very different.
paraphrase
Metropolitan Area a MAN (MAN), abbreviation based on a large LAN, usually use and LAN similar techniques. The MAN separate lists will be one of the main reasons is already have a standard: Distributed Queue Dual Bus DQDB (Distributed Queue Dual Bus), namely IEEE802.6. DQDB is by dual bus structure, all computers links on top.
So-called broadband intracity networks, is within the city limits to IP and ATM telecom technology as the foundation, the fiber as transmission medium, collect data, voice, video services in a high bandwidth, multi-function, multi-business access multimedia communication network.
It can satisfy the government agencies, finance, insurance, medium schools, companies, and other units to high rate, high quality data communication service increasingly strong demand, especially developed rapidly in broadband Internet user groups of high-speed Internet access requirements.
Network characteristics
The transmission rate high - broadband intracity networks with large capacity Packet Over SDH technology, for wire-speed routing and exchange provides transmission safeguard. Gigabit Ethernet technology in broadband intracity networks wide application, make the backbone routers port can high-speed effectively expands to the distribution layer switches. Optical fiber and cable to user desktops, make a data transfer rate reached 100M, 1000M.
Users less input, access simple - broadband intracity networks client-side equipment cheaper and popularization, can use routers, on even ordinary network adapter. Users need to will be proper optical fiber, cable connection, and simple configuration user nic or router related parameters can access broadband intracity networks. Individual user just on their own computers, install a ethercard, broadband interface insert nic construction.this is networking. Before installation process and the phone is same, just string replaced the telephone, computer instead of the phone.
Advanced technology, security - technology provides customers with the high security service and guarantee. Broadband intracity networks in the network provides a second VLAN isolation, make safety get ensuring. Due to the safety of the VLAN, only if the user in LAN computer can visit each other, the user in LAN computer will not through informal way to access the user's computer. If you want to visit, they must be off-line through normal routing and safety system. A hacker thus to use bottom hole destruction is impossible. Virtual dial-up of ordinary users through broadband access server online, after verification of the account and password can surf the Internet, the user can very conveniently self-controlling Internet time and place.
With LAN and wan difference
(1) LAN or wan is usually to a unit or system services, and for the whole city construction.this is rather than for a particular department service.
(2) construction LAN or wan including resources subnet and communication subnet two aspects, and the construction of construction.this mainly concentrated in communication subnet, which also contains two aspects: one is the urban backbone, it with national backbone connected: two is the city access network, it all local networking users and urban backbone connected.
Main purposes and application scope
High-speed Internet access - using broadband IP nets wide frequency band, fast characteristic, users can quickly access Internet and enjoy all related Internet services (including WWW, E-mail, newsgroups, BBS, Internet navigation, information search, remote file transfer, etc.), port velocity reached more than 10M.
Interactive games -- "interactive games nets" can let you enjoy the Internet gaming and LAN game of combining new gaming experience. Through the broadband network, even another.for 100 kilometers cross-city net friend, also can be neglected flow to meet play three-dimensional network game.
VOD VOD video -- let you sit at home using WEB browser VOD oneself follow one's inclinationsly favorite program, including movie high-quality goods, popular television series, and video news, sports programs, opera dance, the MTV, karaoke etc. Network television (NETTV) - breaking through the traditional TV mode, over time and space constraints on the web, realize unlimited channel TV viewing. Through the WEB browser direct from online television programs, to overcome the existing TV channel by district and climate factors, but also is beneficial to the malady constraints on a new interactive TV drama "" network jujubes, making and play.
Telemedicine, adopts advanced digital processing technology and broadband communication technology, medical staff for hundreds of kilometers far or thousands of kilometers away for diagnosis and treatment of patients, remote medical treatment is along with the rise of broadband multimedia communication and developed a new kind of medical treatment method.
Teleconferencing - different meeting without travel, also need not go out, in high-speed information on the network video conference system, "the end of the world if neighbor.the" feeling got the most perfect annotation.
Long-range education -- fundamentally overcome based on TV technology of one-way AnBoShi, based on WEB page of text inquires the type and based on expensive to enter family meeting TV three ways, the defects of using network-broadband latest products and technology will figure, words, sound and other multimedia information, in an interactive way into ordinary families, schools and enterprises and institutions, and students can through broadband network to stay at home and watch the teaching programs and with the teacher real-time interactive, But on Internet search information to Email via Email, etc homework assignments, and questions; etc. Absent searchable database to VOD broadcast course way the teacher video etc.
Remote monitoring (WEBCAM) - the system of remote jujubes, or anything else, supervise the authorized users through the WEB freedom of rotation and focus the lens etc operation, realize real-time monitoring management functions. Monitoring system USES digital monitor mode. Digital monitor is a good way to computer networks together, give full play to the advantages of construction.this bandwidth broadband. This is the future monitoring system development trends.
Family securities trading system - can be at home on the geometrial securities large rooms form of online fry, not only can real-time access deep, Shanghai stock market, obtain the comprehensive and timely financial information, but also through the various analysis tool, and can instantly analyzing real-time online trading order, reference experts to review.
Broadband business can also for the vast number of users with Internet information navigation, information query, sending and receiving e-mails, online game, multimedia online education, audio and video vod and many other services.
Man technologies and characteristic
1, optical fiber technology and features of direct link direct link technology refers to Ethernet switches and routers and switches IP intracity networks, ATM network equipment directly through fiber connected. Strictly speaking, this is not a metro transmission scheme, but because the present in IP in man has adopted many fiber connected directly scheme, so we here fiber connected directly as a kind of transmission technology to introduce.
IP intracity networks equipment in the light of interface point-to-point way connected directly, business access devices also through the optical fiber and backbone equipment directly connected. Optical fiber connected directly technology abandoned transmission equipment, scheme is simple, low cost, but there are obvious disadvantages: first, with no transport layer, optical fiber quality, performance monitoring and protection and can not be achieved.
Secondly, optical fiber lower utilization rate, waste is serious, every two business access points need a pair of optical fiber, a business contacts with other business contacts if having business communication, fiber quantity is factorial growth. Finally, business port pressure. Each join a new nodes, switch or router etc IP intracity networks need to add an access device port. Therefore, this kind of means only applies to the node number not many or nodes distance closer to local area network and so on.
2, multi-task transmitting platform technology (MSTP) and characteristics
Because sdh-based SONET has accounted for transmission network very large share, inevitable meeting in data communication, as a representative of the IP in man play an important role. Based on technical sophistication, reliability and overall cost etc., with comprehensive consideration on the basis of SONET/SDH more business solution will remain in the foreseeable future play an important role, this point in metropolitan application field seems particularly outstanding.
Sdh-based SONET loop in the network performance monitoring and fault recovery and reliability has an exceptional advantage, very suitable for time sensitive type voice traffic demand, at the same time satisfy the telecommunication level high-performance requirements. However, sdh-based SONET another in complex centralized supply and limited extensibility is the characteristic of system structure, handle hard to sudden and unbalanced feature of IP business.
SONET/SDH technology itself is in the unceasing development, sdh-based SONET technology the peculiar advantage of will in the near future to continue to maintain, it will continue in high and low end field and in support asynchronous transfer mode (ATM), IP and Ethernet transparent transmission etc, its full potential.
After the transformation of SONET/SDH function modules, first by various business interface module will a variety of service adaptation mapping to different VC, and then through high order crossover matrix deployment, realize the branch to branch, and branch to line, line to line of whole cross-connections. Actually, after the transformation of SDH/SONET equipment already broke the previous ADM model, branch and line has no rate respectively, but only on the flow of defined according to the business. The new generation sdh-based SONET platform can also add close wave device, points wave device, wavelength converter, etc. To support DWDM applications.
After the transformation of SONET/SDH again called multi-task transmitting platform (MSTP), fig.03 shows. In this platform, TDM business, ATM business, IP business can access, and can efficiently transmission; Further, three kinds of business still can cross and exchange. Therefore multi-task transmitting platform (MSTP) advantage is very clear and it can compatible now widely used TDM business, again can meet the increasing data service (IP and ATM) requirements, but also adopted at present most mature SDH network and protection technology.
MSTP technology is an eclectic solution, which has solved the operator needs both transmission TDM business, and the need to deal with data business, it is also the contradiction in a large number of SDH operators equipment installation operation conditions, for their own network evolution, to provide users with emerging business the better choice. But if in handling a large or pure IP business, MSTP also exist cannot dynamic, fair distribution of bandwidth wait for blemish.
Bearing business requirements and characteristics
Metro network is divided into three levels: the core layer, convergence layer and the access layer.
The core business mainly provide high-bandwidth bearing and transmission, complete and existing network (such as ATM, FR, DDN, IP network) interworking, its features for broadband transmission and high-speed operation.
Convergence layer's main function is to provide business access nodes users business data gathering and distributing processing, simultaneously must achieve business of service level classification.
The access layer by multiple access technology, bandwidth and business distribution, realize the user access, access nodes equipment to achieve more business division and transmission.
With the development of technology and demand increases unceasingly, business there are developing and changing, from the traditional voice traffic to image and video business, from basic audio-visual service to various value-added services, from 64 KB/s basic services to 2.5 Gb/s / 10 Gb/s rent line business, various business emerge in endlessly. Different business has different bandwidth demand, different service needs. From the service quality of service (QoS) Angle of speaking, business can be divided into the following several types: high service quality voice business and video business, Big customer special line, Data communications network (DCN) data business, Various data value-added services, Internet business.
Each type of business requirements of service level different, safety protection level is different also. As the Internet business and various value-added business developments, intracity networks required bandwidth is also more and more wide, current intracity networks has become the business development of "bottleneck". In addition, various types of business of construction.this comprehensive access and processing, but also put forward higher request. Overall, grouping is changed and broadband of business development trend.
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