Packet or cell switched data traffic is variable and bursty. For these services, the traffic carrying capacity of a typical port (1.5Mbps) is used to convert traffic units. For data services that are sold with a fixed capacity, such as ISDN, the maximum payload capacity of service is used (e.g. 128kbps). Circuit-switched traffic, such as voice, uses a continuous traffic capacity. MOUs are converted directly into Mbps using the fact that voice traffic generally uses 64kb/s. The chart below shows the methodology used to convert disparate traffic units into a common traffic unit of Mbps for our standard information service. For custom TRAFFICast requests, we work closely with our clients to develop assumptions that uniquely represent their particular requirements.