A series of measurements of a computer link using the Switched Multimegabit Data Service (SMDS), as provided in the United Kingdom SuperJANET network, are described in this paper. The computer link is subject to the effects of using several access networks at the peripheries of SuperJANET, making the measurements valid only in the context of the link from one computer to another, rather than describing any attributes of SuperJANET in general. However, the measurement mechanism is refined several times in an attempt to filter out non-SuperJANET phenomema.