X-Git-Url: https://git.martlubbers.net/?a=blobdiff_plain;f=a2%2F1cases.tex;h=9ffc07dce2d4223a2317f1b6a61f011304c2f4e6;hb=e0f0fe4cb2710b507fdcf6193ae61a9c32e2d539;hp=da3a34bddf405bd1a21a7d0aae2c3286656bfcf4;hpb=da69faad6643af30b9a9ed839e437ee03b0b8b47;p=tt2015.git

diff --git a/a2/1cases.tex b/a2/1cases.tex
index da3a34b..9ffc07d 100644
--- a/a2/1cases.tex
+++ b/a2/1cases.tex
@@ -89,13 +89,14 @@ a feasible test suite the tests are divided into equivalence partitions. Below
 these partitions are given.
 
 \begin{enumerate}
-	\item \emph{Number of packets} in request~\footnote{A request is considered
-		establishing a connection (handshake) and a number of payload packets}
+	\item \emph{Number of segments} in request~\footnote{A request is
+		considered establishing a connection (handshake) and a number of
+		payload segments}
 		\begin{enumerate}
-			\item 0 payload packets
-			\item 1 payload packet
-			\item n=small payload packets
-			\item n=big payload packets
+			\item 0 payload segments
+			\item 1 payload segments
+			\item n=small payload segments
+			\item n=big payload segments
 		\end{enumerate}
 	\item \emph{source port}
 		\begin{enumerate}
@@ -107,11 +108,11 @@ these partitions are given.
 			\item Correct
 			\item Incorrect
 		\end{enumerate}
-	\item Bits flipped in \emph{payload}
+	\item Bit errors in \emph{payload}
 		\begin{enumerate}
 			\item Correct payload
-			\item Payload with even number of bits flipped
-			\item Payload with odd number of bits flipped
+			\item Payload with bit flips that do not show in checksum
+			\item Payload with bit flips that do show in checksum
 		\end{enumerate}
 	\item \emph{checksum}
 		\begin{enumerate}
@@ -126,8 +127,32 @@ these partitions are given.
 		\end{enumerate}
 \end{enumerate}
 
-\textbf{hier iets over waarom deze partities relevant zijn! Waarom odd en 
-even number of bits flipped bijv interessant?}
+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 that have a 
+source or destination port set to an incorrect value should not be regarded
+as segments belonging to the connection by the SUT. 
+
+TCP uses a \emph{checksum} to catch any error introduced in headers, when this
+checksum does not match the actual computed checksum the SUT should
+disregard the received segment.
+
+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
+checksum itself). Therefore any \emph{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 errors occur.
+
+TCP guarantees that segments are delivered in order,even when they are received
+\emph{out of order} and that missing segments are resend. The SUT should
+exhibit the same behavior. If segments are received out of order it should
+deliver them in order. Missing segments should be re-requested (by ACK-ing
+the correct sequence number).  
+
 \bigskip
 
 Partitions 2 to 6 are tested using pairwise testing to keep the number of test