ent or mitigate network clock slips. Encapsulation means heading or surrounding a payload of bits or bytes with other bits and bytes for some functional purpose such as error correction, routing, or switching. System and network clocking and synchronization can be a messy subject to deal with in theory, but in practice it's simple, especially in content transport networks. Basically, there are three clocks to be concerned about-the clock in the content origination facility, the network clock and the clock on the other side of the network receiving the content. Each is independent of the others. These clocks might be in phase and running on the same frequency within very tight tolerances, or they might be running at their design limit permissible extremes. If the network is transporting content in non-real time, or as a file or object, there's no need to worry about synchronization or timing relation- ships. The file gets moved according to ftp rules, a chunk of bytes at a time. On the other hand if the content is being transported in real time, the process involves moving the payload from the originating source into the network timed domain without error, transporting it without error, and then moving it from the network domain to the second program content domain without error. PRACTICAL IP AND TELECOM FOR BROADCAST ENGINEERING AND OPERATIONS Digital video broadcastingasynchronous serial interface is an increas- ingly popular interface selected by designers for use in digital televi- sion facilities. Broadcast engineers with a good understanding of SMPTE-259 like it because it's a lot like what they already know. Communications engineers like it because it's a lot like E3, DS3, and STM1. Facility means generally, something physical such as a building with equipment and amenities used to produce content or provide service. Examples include editing facility, production facility, studio facility, and transmission facility in the broadcast world. Telecom facilities are often called services. For example, it's quite 