A form of network transmission in which packets from different lower-speed sources are encapsulated together to form a very large frame, up to several hundred bytes in length, which is then transported as a unit on a single higher-speed bearer. The frame will usually have a fixed length, and more or less fixed internal structure. The fixed size and relatively simple internal structure of the frames means that the switching activity can be implemented with a considerable degree of hardware assistance, while the larger frame size reduces the ratio of overheads to useful payload. In particular it is possible to allow packets to enter or leave the frame relay system using an assembly of standardized products.