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diff --git a/assignment7.tex b/assignment7.tex index bf9ea1e..5be9ff5 100644 --- a/assignment7.tex +++ b/assignment7.tex @@ -91,20 +91,55 @@ \section{Address Resolution Protocol} \begin{enumerate} - \item - A --- 192.168.1.100; B --- 192.168.1.200;\\ - C --- 192.168.2.100; D --- 192.168.2.200;\\ - E --- 192.168.3.100; F --- 192.168.3.200. \item We call the left router R and the right router S. Let $R_i$ be the interface of router $R$ for subnet $i$. Then: + A --- 192.168.1.100; B --- 192.168.1.200;\\ + C --- 192.168.2.100; D --- 192.168.2.200;\\ + E --- 192.168.3.100; F --- 192.168.3.200;\\ + R$_1$ --- 192.168.1.1; R$_2$ --- 192.168.2.1;\\ + S$_2$ --- 192.168.2.2; S$_3$ --- 192.168.3.2;\\ + + \item A --- 00.00.00.00.00.A0; B --- 00.00.00.00.00.B0;\\ C --- 00.00.00.00.00.C0; D --- 00.00.00.00.00.D0;\\ E --- 00.00.00.00.00.E0; F --- 00.00.00.00.00.F0;\\ R$_1$ --- 88.88.88.00.00.00; R$_2$ --- 88.88.88.00.88.00;\\ S$_2$ --- 88.88.88.88.00.00; S$_3$ --- 88.88.88.88.88.00. - \item %todo - \item %todo + + \item Host E looks up the MAC address of the first hop router (S$_3$), and + sends the datagram there. Router S receives the datagram, figures out that + the next hop is router R, looks up the MAC address of R$_2$ and sends the + datagram there. Router R then forwards the datagram in a frame to host B on + interface R$_1$. Concretely, the following frames are sent: + + \begin{table}[h] + \centering + \begin{tabular}{l | l | l | l} + Src. IP & Src. MAC & Dest. IP & Dest. MAC \\\hline + 192.168.3.100 & 00.00.00.00.00.E0 & 192.168.3.2 & 88.88.88.88.88.00\\ + 192.168.2.2 & 88.88.88.88.88.00 & 192.168.2.1 & 88.88.88.00.88.00\\ + 192.168.1.1 & 88.88.88.00.88.00 & 192.168.1.200 & 00.00.00.00.00.B0\\ + \end{tabular} + \end{table} + + \item The same happens, but before E can send the frame to S$_3$, it has to + get to know its address. It sends an ARP request to the broadcast address + with the request for 192.168.3.2's (that is, S$_3$'s) MAC address. The + router replies with an ARP packet. After this, E has all the addresses it + needs (and all other nodes as well), so the same as above happens. + + \begin{table}[h] + \centering + \begin{tabular}{l | l | l | l | l} + Src. IP & Src. MAC & Dest. IP & Dest. MAC & Protocol\\\hline + 192.168.3.100 & 00.00.00.00.00.E0 & 192.168.3.2 & FF.FF.FF.FF.FF.FF & ARP\\ + 192.168.3.2 & 88.88.88.88.88.00 & 192.168.3.100 & 00.00.00.00.00.E0 & ARP\\ + 192.168.3.100 & 00.00.00.00.00.E0 & 192.168.3.2 & 88.88.88.88.88.00 & IP\\ + 192.168.2.2 & 88.88.88.88.88.00 & 192.168.2.1 & 88.88.88.00.88.00 & IP\\ + 192.168.1.1 & 88.88.88.00.88.00 & 192.168.1.200 & 00.00.00.00.00.B0 & IP\\ + \end{tabular} + \end{table} \end{enumerate} \section{Self-learning} |