From cb58c69ab4e21659e03215be3ad504ac47f80392 Mon Sep 17 00:00:00 2001 From: pimjager Date: Wed, 11 Nov 2015 14:48:19 +0100 Subject: [PATCH] Start with explenation of partitions --- a2/1cases.tex | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/a2/1cases.tex b/a2/1cases.tex index 6eaa380..d77edb7 100644 --- a/a2/1cases.tex +++ b/a2/1cases.tex @@ -113,13 +113,32 @@ these partitions are given. \item Bits flipped in \emph{payload} \begin{enumerate} \item Correct payload - \item Payload with even number of bits flipped + \item Payload with bit flips \item Payload with odd number of bits flipped \end{enumerate} \item Correct or Incorrect \emph{checksum} \item Packets received in or out of order, or missing packets \end{enumerate} +These partitions were chosen since they correspond to key parts of the TCP +specification. + +TCP segments are send over a TCP connection from a \emph{source} to a \emph{destination port}. Therefore segments which are received which have a +source or destination port set to an incorrect value should not be regarded +as segments belonging to the connection. + +TCP uses a \emph{checksum} to catch any error introduced in headers, when this +checksum does not match the actual computed checksum the packet should be +disregarded. + +The TCP checksum is also an inherently weak one, as it is simply the +bitwise negation of the addition in ones complement arithmetic +of all 16 bit words in the header and data of the segment (excluding the +header). Therefore any bit error where the ones complement value of one word +increases by one, and the value of another decreases by one, is undetected. +The SUT should exhibit the same behavior and accept packets where these type +of bit error occur. + \textbf{hier iets over waarom deze partities relevant zijn! Waarom odd en even number of bits flipped bijv interessant?} \bigskip -- 2.20.1