In computer networks, the bit rate of the physical layer is always expressed in bits per second. One Mbps is one million bits per second and one Gbps is one billion bits per second. This is in contrast with memory specifications that are usually expressed in bytes (8 bits), KiloBytes ( 1024 bytes) or MegaBytes (1048576 bytes). Thus transferring one MByte through a 1 Mbps link lasts 8.39 seconds.