Network status
1. China public PSDN in September 1993, 1996 at the end of the opening has covered the whole country at or above the county level cities and a distribution of area, with the world of villages and towns in 23 countries and regions 44 data networks interconnected.
Network status
Packet switching is post and telecommunications departments construction and development of the earliest based data communications network collaterals. Switching to CITTX25 Suggestions for group based, can satisfy different rate, not the end with the computer, the computer and the computer room and communication between the local area network. Packet switching is a foundation of the data communication network, the network platform can structure various value-added services, such as E-mail, electronic data exchange, fax store-and-forward, etc.
ChinaPAC by national backbone and the provinces (city, area) of the province nets. Before covering all eyes between backbone, capital city of the province, covering a business requirements to network of cities and towns have developed. Through the Internet and telephone network, ChinaPAC can cover the telephone netcom reach all parts of the. ChinaPAC exchange center and a level 1, level 2 change center in exchange center between the incomplete mesh structure, level 1 exchange center to the respective level 2 exchange Lenovo G450 battery center between the star shape structure; ChinaPAC in Beijing and Shanghai, guangzhou has a international inward to Hong Kong and Macao regions, to complete the entrance with international data networking.
The network characteristics and functions
Packet switching is the advantages in a physical electrical lines and open multiple virtual circuits, for DuoGe users use at the same time; Network has dynamic road out of function and complex complete error correction function. X.25 agreement is in physical link transmission quality was poor affection condition developed, in order to guarantee the reliability of the data transmission, it in every period of links to enforce a mistake inspection and error retransmission; This kind of complex error verification mechanisms although make the transmission efficiency of it is limited, but really for the safety of the user data transmission provides a good protection.
ChinaPAC provide business as follows:
Basic business functions
Basic business function is pointing to any numeral terminal equipment provides basic business functions. It can satisfy user communication basic requirements. There are two kinds of basic business, exchange type a virtual circuit; Permanent virtual circuits.
Choose a business function
Users choose a business function is to meet the special needs of customers, provide special business functions, such as the FengZu, a call FengZu call, one-way into the logical channel, one way out of the logical channel, etc.
The other business functions
Chinanet also provide other fee ITU-T suggested business functions, such as virtual private network TCP/IP packet multiple address broadcast, call redirection, etc. The net users Chinanet way provides two access. Line way
Apply to communications portfolio is large, heavy use of the high demand, applications, but need to use special line, the relatively high cost. Special line for 9.6-64 net rate kbpa. dialup
Apply to business is not big, intermittent period is longer, can tolerate failure should use the call. Because of its use the existing phone lines, the need for additional investment, and data can be Shared with voice lines, thus greatly saving investment, users are ideal for scattered the access method. Can be divided into X. 28 HP f500 battery asynchronous dial-up access or X. 32 synchronous dial-up into the net, net dial-up speed rate for 1200-9600 BPS.
Fees policy
ChinaPAC current have two kinds of charging methods, one is the timing measurement fee, 2 it is the bag fee on system.
And DDN frame relay compare, business group is cheaper, charges it is the user structure its internal wan the most economic a choice. In the need to build at the same time a multipoint connection, through the group of a virtual circuit switching function, can replace expensive more DDN line.
China public digital data networks
Digital communication network is using digital channels provide permanent, half permanent connection, to transmit data signal digital transmission network mainly. It can provide each kind of flexible data interface for transmit data service signal. Because of its simple, rate is higher, agreement in our country have developed rapidly.
By digital channels, DDN DDN node, network management system and the subscriber loop, it provides of point-to-point and point to more digital special line business, can also provide frame relay and compressed voice/G3 fax service. The main features are: DDN
Transmission quality high, because at present by using optical fiber transmission channels of DDN, 1 have to transmission quality is much improved;
The transmission rate is high, the rate between 2400 BPS-2 Mbps between; Agreement simple. Because the time multiplex and DDN main cross connection | technology
Art, the transparent to the user information transmission, and the technical requirements of users less flexible, application;
On the net, and with motions DDN advanced network technology, the line scheduling, fault
Monitor can realize the centralized management, the line of fault when still can automatic routing circuitous, users of the circuit to high utilization rate.
DDN mainly provide point-to-point digital special line business. Widely used in the silver line, securities, weather, cultural education, etc, and is suitable for the mutual lans and wans, different network interconnection al etc. For example, a company’s headquarters is in a different place and division, the communication between two points and very frequently, not only wanted to keep telephone links, and computer network communication. If renting a DDN line ends, and set the distribution for reuse, both the telephone system and computer system, can link up in two to convenient communication between. Such already save between two of the long distance telephone charges, and can realize the interworking computer system.
DDN also provide more business, mainly refers to the business, two-way radio more business (multipoint polling; and the conference TV business. Radio more business features are: data information flow in from point to transmit can be more, make more and get the same information. Multicast business apply to information issued < stock, news, weather forecast, etc); . Two-way more business mainly refers to a stood a moment can and a two-way communication from the station master station regularly visit from a standing, and from standing exchange information. Two-way communication business applies to more concentrated surveillance, credit card verification, and data services, reservations system, etc. The meeting is to use the TV business multipoint bridging DDN functions more images and the exchange of information such as voice. The meeting television system each site can serve as main communication with other sites, but a moment there can only be one host. More Dell 9400 battery business characteristic is, a point the only a interface can finish and more communications, saving client equipment and network resources, and reduce the information technology. In addition, use the online DDN frame relay resource module and words sound compression module, still can realize open frame relay business and compressed voice/G3 fax service industry.
China public frame relay nets China public frame relay broadband business backbone is China’s first will be provided to the public service of the data communication network, the broadband of our country will put into production of the informationization of the national economy have a positive impact on our country’s information, will become an important part of highway.
ChinaFRN provides more than 64 K in high speed data communication services. Business types can be an unexpected, also can be the real time.
ChinaFRN can also be for other data communication network provide high-speed relay transmission, make each network performance can strengthen, and improve the efficiency.
China public frame relay broadband business the backbone of the main characteristic is a team, ATM technology platform with, meanwhile, we also provide frame relay and believe yuan relay, etc. China public frame relay broadband business the backbone of the main technical features include:
Equipment advanced, integral sex is good single network, take the network connection backbone hub.
Network full range of business, provide frame relay PVC, ATMPVC and basic business SVC.
Port complete kinds, wide range of speed. To frame relay business, network provide the interface types including V35, X. 21, E1, channelized E1, ISDNPRI, E3, etc. For ATM business, provides the network interface type have E1, E3, STM-1, etc.
The user access is flexible. Support frame relay or eight agreement can directly access terminal equipment; LAN routers, LAN switches can be through direct access; Other agreement terminal can be through the FRAD equipment to access. In addition, because network port itself FRAD function, support built-in HDLC, SDLC and PPP agreement also direct access to the terminal.
Support frame relay ATM communication function.
China science and technology network
China science and technology network experienced four no word of the development stage, namely NCFC engineering,
CASnet, CERnet, CSTnet.
