Circuit Emulation Service

Circuit Emulation Service (CES) is a method of data transmission in which time-division multiplex (TDM) data is transmitted over an asynchronous network with packet switching such as ATM , Ethernet or any network based on Internet Protocol (IP). CES in the narrower sense is sometimes only understood to mean transmission via ATM (also known as CESoATM), while the abbreviation CESoP (Circuit emulation services over packet) is mostly used for transmission via IP.

The method is used for devices of traditional telephone technology, whose digitized speech can be transmitted over modern networks. A direct wire connection (“circuit”) or other transmission path of the TDM signal is “simulated” ( emulated ) for these devices , although the underlying data connection works completely differently, namely with data packets that are transmitted over a network .

TDM is a continuous data stream with precise timing information. CES converts this into packets, which are then transmitted, for example, via ATM or IP networks. After transmission, the data packets are temporarily stored, combined to form a TDM signal and forwarded to the target device at a fixed rate. The prerequisite for error-free transmission is that all data packets arrive in time to be combined to form the TDM signal. Therefore, QoS information is added before transmission over the network in order to achieve a sufficient priority of the transmitted data. Furthermore, the timing of the original TDM signal must be exactly restored so that there is no loss of data due to bit slips .

With ATM, the standardized AAL 1 is used for the CES . PCM with a bit rate of 2.048 Mbit / s is used almost exclusively as the time division multiplex method.

The importance of CESoP is increasing due to the rapid development of computer networks and the increasing number of IP networks.