leaf site

n. [obs.] Before pervasive TCP/IP, this term was used of a machine that
merely originated and read Usenet news or mail, and did not relay any
third-party traffic. It was often uttered in a critical tone; when the ratio
of leaf sites to backbone, rib, and other relay sites got too high, the
network tended to develop bottlenecks. Compare backbone site. Now that
traffic patterns depend more on the distribution of routers than of host
machines this term has largely fallen out of use.

