Congestion Control
Although a link may be congested with frames, which may result in frame loss, most
data-link-layer protocols do not directly use a congestion control to alleviate congestion,
although some wide-area networks do. In general, congestion control is considered an
issue in the network layer or the transport layer because of its end-to-end nature. We will
discuss congestion control in the network layer and the transport layer in later chapters.