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Fix Design/P4/BMV2

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Nico Schottelius 3 years ago
parent
commit
002887533a
  1. 55
      doc/Design.tex
  2. BIN
      doc/Thesis.pdf

55
doc/Design.tex

@ -259,25 +259,7 @@ session table inside the python controller. While the Jool and Tayga
both support cleaning up old session entries,
our P4 based solution does not support this feature at the moment.
% ----------------------------------------------------------------------
\section{\label{Design:BMV2}BMV2}
Development of the thesis took place on a software emulated switch
that is implemented using Open vSwitch~\cite{openvswitch}
and the behavioral model~\cite{_implem_your_switc_target_with_bmv2}.
The development followed
closely the general design shown in section
\ref{design:nat64}. Within the software emulation checksums can be
computed with two different methods:
\begin{itemize}
\item Recalculating the checksum by inspecting headers and payload
\item Calculating the difference between the translated headers
\end{itemize}
The BMV2 model is rather sophisticated and provides many standard
features including checksumming over payload. This allows the BMV2
model to operate as a full featured host, including advanced features
like responding to ICMP6 Neighbor discovery requests~\cite{rfc4861}
that include payload checksums.
A typical code to create the checksum can be found in figure
\ref{fig:checksum}.
\section{\label{design:bmv2}P4/BMV2}
\begin{figure}[h]
\begin{verbatim}
/* checksumming for icmp6_na_ns_option */
@ -306,12 +288,39 @@ update_checksum_with_payload(meta.chk_icmp6_na_ns == 1,
);
\end{verbatim}
\centering
\caption{IPv4 Pseudo Header}
\label{fig:checksum}
\caption{P4/BMV2 checksumming}
\label{fig:bmv2checksum}
\end{figure}
The software emulated switch that is implemented using
Open vSwitch~\cite{openvswitch} and the
behavioral model~\cite{_implem_your_switc_target_with_bmv2}
offers the fastest and easiest way of P4 development. All NAT64
features are tested first on P4/BMV2 and in a second step ported to
P4/NetFPGA and modified, where necessary.
The development follows closely the general design shown in section
\ref{design:nat64}.
As outlined in section \ref{background:checksums}, checksums inside
higher level protocols need to be adjusted after translation.
Within the software emulation checksums can be
computed with two different methods:
\begin{itemize}
\item Recalculating the checksum by inspecting headers and payload
\item Calculating the difference between the translated headers
\end{itemize}
The BMV2 model is sophisticated and provides direct support
for calculating the checksum over the payload. This allows the BMV2
model to operate as a full featured host, including advanced features
like responding to ICMP6 Neighbor discovery requests~\cite{rfc4861}
that include payload checksums. Sample code that calculates the
required checksum for answering NDP queries is shown in figure
\ref{fig:bmv2checksum}. The code shows how the field
\texttt{hdr.icmp6.checksum} is updated with the \texttt{csum16} method
depending on the IPv6 and ICMP6 headers as well as the payload. The
second option of using the differences is described in section
\ref{design:netpfga}.
% ok
% ----------------------------------------------------------------------
\section{\label{Design:NetPFGA}NetFPGA - FIXME: relate things}
\section{\label{design:netpfga}NetFPGA - FIXME: relate things}
While the P4-NetFPGA project ~\cite{netfpga:_p4_netpf_public_github}
allows compiling P4 to the NetPFGA, the design slightly varies.
In particular, the NetFPGA P4 compiler does not support reading

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