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                    pdfauthor={J. Blustein},%
                    pdftitle={Internet Network Layer Model},%
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  \newcommand{\Version}{22 May 2002 (1a)}

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   \title{Internet Network Layer Model}
   \author{CS 3171}
   \date{}
\begin{document}
  \maketitle
 % \begin{center}
 %  {\Large Internet Network Layer Model}%\\CS~3171
 % \end{center}
  \thispagestyle{plain}

 \vbox{
  \pdfbookmark[0]{Layer's purpose}{Layer's purpose}%
  \begin{tabular}{l l | p{.75\textwidth}}
   \multicolumn{2}{c}{\textsl{Layer}} & 
   \multicolumn{1}{l}{\textsl{Function}}\\\hline
   5 & Application & Performs end-user communication-based tasks\\
     &             & Connects applications to applications
 % \\&             & Many protocols, examples are HTTP, SMTP, FTP, \& Telnet
     \\&&\\
   4 & Transport   & Provides logical communication between processes
                     on different hosts~\cite[p.~167]{Ku:CN}\\
     &             & Connects processes to processes
                     (e.g. video \& audio streams in an application)
 % \\&             & Protocol is one of TCP or UDP
     \\&&\\
   3 & Network     & Transfers `transport-layer segments from one host to
                     another'~\cite[p.~271]{Ku:CN}\\ 
     & Service     & Connects end-hosts to end-hosts
 % \\&             & Protocol is Internet Protocol (IP)
     \\&&\\
   2 & Data Link   & Transfers datagrams across individual physical
                     links~\cite[p.~379]{Ku:CN}\\
     &             & Connects physical links (point-to-point)
 % \\&             & Examples of protocols are Ethernet \& PPP
     \\&&\\
   1 & Physical    & Transfers sequences of bits without awareness of
                     meaning\\ 
     &             & Connects nodes using a physical medium
 % \\&             & Many protocols for cabling, connectors, signaling, etc.
     \\\hline\hline
  \end{tabular}
 }%\vbox

  \vspace{\fill}

 \vbox{
  \pdfbookmark[0]{Value Added by Layer}{Value Added by Layer}%
  \begin{tabular}{l l | p{.75\textwidth}}
   \multicolumn{2}{c}{\textsl{Layer}} & 
   \multicolumn{1}{l}{\textsl{Value (added to layer below) \& Protocols}}
   \\\hline
   5 & Application & Type of connection \\
     &             & Many protocols, for example HTTP, SMTP, FTP, \& Telnet
     \\&&\\
   4 & Transport   & Flow control, congestion control, \& error correction\\
     &             & Protocol is one of TCP or UDP
     \\&&\\
   3 & Network     & Routing\\
     & Service     & Protocol is Internet Protocol (IP)
     \\&&\\
   2 & Data Link   & Frame formatting \& hardware addressing\\
     &             & Many protocols, for example Ethernet \& PPP
     \\&&\\
   1 & Physical    & (none)\\
     &             & Many protocols for cabling, connectors, signaling, etc.
     \\\hline\hline
  \end{tabular}
 }%\vbox

  \vspace{\fill}
  \begin{flushright} Continues on other side \ldots\end{flushright}
  \newpage

  \pdfbookmark[0]{Layer's data unit and implementation}%
                 {Layer's data unit and implementation}%
  \begin{minipage}{\textwidth}
    \begin{tabular}{ll | p{.13\textwidth} @{} p{.62\textwidth}}
     \multicolumn{2}{c}{}               & \textsl{Protocol} & \\
     \multicolumn{2}{c}{\textsl{Layer}} & \textsl{Data Unit}&
                     \textsl{Typical Implementation and Components}\\
     \hline

     5 & Application & Message & 
                       (Application software in host, at network edge,
                        e.g. gateway\footnotemark)
     \\&&&\\

    4 & Transport
      & Segment\footnotemark\addtocounter{footnote}{-1}
      & (System software in host, at network edge)
    \\&&&\\

      3 & Network & Datagram\footnotemark & Router \\
      & Service &                       & (Hardware \& Software, in network core)
    \\&&&\\

      2 & Data Link
      & Frame
      & Switch or Bridge\footnotemark\\
      &&& (Hardware \& Software, in network core)
    \\&&&\\

      1 & Physical
      & 1-PDU
      & Network interface card, cable, wire, repeater, modem\\
      & & & (Hardware)
    \\
    \hline\hline
   \end{tabular}
   \footnotetext[1]{
      \term{Gateway}s convert application data with one protocol to a
     different but equivalent protocol.
      They can span the top three layers.
    }
    \footnotetext[2]{
      The `Internet literature (for example, the RFCs)' refer to 4-PDUs
     for TCP as \term{segment}s but often refer to the PDU for UDP as
     \term{datagram}s.~\cite[p.~171]{Ku:CN}
       It may help to think of a datagram as an independent
     informational message.  If a datagram is lost, something must
     take care of it.
       A segment, however is part of a larger unit and so cannot be
     lost.
    %  4-PDUs are sometimes referred to as \term{datagram}s when UDP is the
    %  protocol.  Your textbook~\cite[p.~171]{Ku:CN} refers to both TCP and
    %  UDP 4-PDUs as \term{segment}s.
    }
    \footnotetext[3]{
       A \term{bridge} (aka a \term{hub}) is responsible only for
      signal regeneration, but a \term{switch} segments traffic and
      reduces broadcast domain.
       When a switch is saturated with traffic it acts as a bridge and
      begins to \term{flood}.
    }
  \end{minipage}\\
  \vspace{\fill}

  \pdfbookmark[0]{References}{References}%
  % \bibliography{nets}
  \begin{thebibliography}{1}
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    \bibitem[Kurose and Ross(2001)]{Ku:CN}
       James~F. Kurose and Keith~W. Ross.
       \newblock 
        {\em Computer Networking: A Top-Down Approach Featuring the Internet}.
       \newblock
        Addison-Wesley Longman, Inc., 2001.
       \newblock
        ISBN 0-201-47711-4.
  \end{thebibliography}
\end{document}
