ATM incorporates the advantages of circuit exchange and packet switching. It can not only flexibly allocate bandwidth, but also eliminates complicated flow control and dramatically reduces transmission time delay. It can be used for the interconnection of local area network and improving real-time multimedia service with QoS guarantee. Setting about from the demand of user and basing on the advanced backbone optical network and MAN access network spread across the country, China Unicom launched large-capacity ATM Dedicated Line Service.

Service Characteristics

ATM is connection-oriented communication mode. The so-called connection orientation refers to that before communication a connection is established between transmitting and receiving terminals and message or information is transmitted on this connection continuously. Therefore, when there are many messages or information in one communication, the routing from transmitting end to receiving end is fixed.

ATM is a packet switching mode with fixed packet length while the packet length in traditional packet switching is not fixed. ATM is cell switching. ATM provides statistics multiplexing capability and provides overbalance bandwidth service. In practical use, user may transmit data at the rate higher than agreed rate but does not bear additional expenses.

ATM network supports various services. Unicom ATM network has provided user with SVC (dynamically establishing virtual circuit according to demand; when data is transmitted, circuit will be automatically terminated; more economical), non-balance circuit, etc. (meeting the demand for two-way transmission asymmetrical bandwidth), well satisfying the demand of user. Unicom ATM network is highly unified with wide coverage.