If data switching is required for computer equipment, most institutions also employ some sort of LAN arrangement for electronic messaging and other such data services. Although the integration of voice and data using only one network via PDXs seems a natural step to take, it requires careful planning, and the management or corporate structure often assigns communications needs and data needs to different groups within in a company, so maintaining the separation between these services. With a LAN such as Ethernet, there is inherently a CL mode of operation while PDXs are circuit switches. It is likely that if PDXs are incorporated in to such a LAN environment they will be used to interconnect LAN segments. Data requirements are ofted of a bursty nature and this is often because the exchange of data, unlike most phone calls, can often have very different data rates depending on direction.
PSEs switch data by considering the header data provided as part of each packet.
The destination, on accepting the call, assigns another VCI to the call request and forwards it. VCIs only have local significance. When the call request reaches the destination, a VC is said to exist between the two end-points. The VC maybe set up through a route that has many PSEs, although this is transparent to the end-points. Such a packet switched network is the X.25 network.