\documentclass{article}
\input{6828-preamble}

\begin{document}
\psetnum{21}
\date{2004/11/24}

\begin{pset}
  \begin{problem}
    The output packet rate initially increases proportionally to the
    increase in the input packet rate because the router is forwarding
    the input packets.
  \end{problem}

  \begin{problem}
    The output packet rate begins to fall as the input rate increases
    because so much time is spent processing device interrupts caused
    by the input that there is not enough time for higher-level
    processing of the received packets.
  \end{problem}

  \begin{problem}
    The peak is the maximum rate of input packets the system can
    handle before it must drop packets. This is determined by the
    amount of processing time required per packet, and the total
    processing power available.
  \end{problem}

  \begin{problem}
    The rate at which the output rate falls is determined by the
    amount of interrupt-level processing time required per packet,
    relative to the total amount of processor time available.
  \end{problem}
\end{pset}
\end{document}