The intent is to treat the device as a unit without regard to the internal structure. Speed mismatch between input and output data rates. This does not refer to frame rate per se, it refers to the actual data rate of the data path. Networks that make use of serial links between local high speed networks will usually have link speed mismatch at each end of the serial links. The performance of network devices can be significantly affected by having to fragment frames.
Network devices perform many functions in addition to forwarding frames.
These tasks range from internal hardware testing to the processing of routing information and responding to network management requests. It is useful to know what the effect of these sorts of tasks is on the device performance. It would be good to know of this sort of behavior. Any quantitative understanding of this behavior is by the determination of its effect on other measurements. Devices in an overloaded state will lose frames.