论文部分内容阅读
邮政储蓄网络系统是跨区域的网络系统,分布在不同的地区,因此既涉及本地网络建设,即局域网络,又涉及到利用公共的通信媒体将不同地区的局域网络连接起来,传输业务数据的工程,即广域网络工程。广域网的建设是构筑在公用电信信道之上的。目前我国通信部门提供的主要数据信道如下:数字数据网(CHINADDN)通信质量高、传输延迟短,能实现实时传输。其缺点是实现成本较高,对于数据传输量较小的用户而言,使用费用较高;分组交换数据网(CHINAPAC)特点是带宽较低,最高访问速率为64Kbps,传输时延较长。但具有带宽的统计复用能力和突发性业务量处理能力,其入网费用较低,对传输数据量较小的用户适用;帧中继网的特点是高效、可靠、灵活,与DDN和X.25相比具有较强的性能价格比优势。随着异步传输模式(ATM)的迅速发展,帧中继与ATM相辅相成,成为用户接入ATM的最佳机制。提供帧中继业务的还有中国国家金融数据通信网(CNFN);ISDN网络具有很多优点,但在我国尚不普及,有的
Postal savings network system is a cross-regional network system, distributed in different regions, it involves both local network construction, that is, local area network, but also to the use of public communications media to connect different regions of the local area network, the transmission of business data engineering , That is, wide area network project. WAN construction is built on the public telecommunications channel above. At present, China’s communications sector to provide the main data channels are as follows: Digital Data Network (CHINADDN) high-quality communications, short transmission delay, enabling real-time transmission. The disadvantage is that the implementation cost is higher, and the usage cost is higher for users with smaller data transmission rates. The packet switching data network (CHINAPAC) features low bandwidth, a maximum access speed of 64 Kbps and a long transmission delay. However, with the bandwidth of statistical multiplexing capabilities and sudden traffic capacity, the lower the cost of its network, the smaller amount of data transmission users apply; Frame Relay network is characterized by efficient, reliable and flexible, and DDN and X .25 compared with a strong cost performance advantage. With the rapid development of Asynchronous Transfer Mode (ATM), Frame Relay and ATM complement each other and become the best mechanism for users to access ATM. There are also China National Financial Data Communication Network (CNFN) that provide frame relay services; ISDN network has many advantages, but it is not yet popular in our country, and some