From: Richard Whitehouse Date: Thu, 19 May 2011 15:08:16 +0000 (+0100) Subject: Changes based on annotations by mas90 X-Git-Url: https://git.richardwhiuk.com/?a=commitdiff_plain;h=63315c8f7f58e014ae9d5523177b450aebcd779a;p=ii-diss.git Changes based on annotations by mas90 --- diff --git a/evaluation.tex b/evaluation.tex index 322c0cf..fb7cf5e 100644 --- a/evaluation.tex +++ b/evaluation.tex @@ -6,49 +6,57 @@ The following experiments were carried out on the simulator with a Gigabit Ether \subsection{Operational Validation} -The first section of trials was done on the following network. These were done to check the protocols were performing correctly. +The first section of trials was done on the network shown in Figure~\ref{fig-net1}. These were done to check the protocols were performing correctly. \begin{figure}[h] +\centering \includegraphics[width=8cm]{simulation-1} \caption{Operational Validation Network} +\label{fig-net1} \end{figure} -In this set of tests, the first sends a packet, and then a second later, the second host replies. +In this set of tests, the first host sends a packet, and then a second later, the second host replies. \subsubsection{Local Transmission} -The first test shows that the local packets, i.e. packets which only traverse their local switch. In this case between Host 0 and Host 1. In both the Ethernet and MOOSE case the packet traverse the switch and go to the host correctly. In the MOOSE case, the address is rewritten in both directions. This provides evidence that the switches are working correctly with the respect to the protocol descriptions. +The first test shows that the local packets, i.e.\ packets which only traverse their local switch, are transmitted correctly. In this case, packets are sent between Host 0 and Host 1. In both the Ethernet and MOOSE case the packet traverse the switch and go to the host correctly. In the MOOSE case, the address is rewritten in both directions. In order to facilitate this, the ARP packet is also rewritten, to ensure that the sending host gets the correct hardware address. In addition, observation of the state file produced by the simulation show that both protocols have correctly learned the sending hosts and associated them with the correct addresses. \subsubsection{Remote Transmission} -Further evidence is provided in the second test, where a remote packet, i.e. a datagram which travels to a different switch, is shown. In this case, between Host 0 and Host Here we have evidence that the addressing and routing between switches is performing correctly and that the switch addressing is working correctly in the case of MOOSE. +The second test provides further evidence that the switches are operating correctly. In this test, a datagram sent to a host attached to a different switch is performed, in this case, between Host 0 and Host 2. Here we have evidence that the addressing and routing between switches is being performed correctly and that the switch addressing is working correctly in the case of MOOSE. Again, the switch performs ARP and header rewriting on the packets. -\subsubsection{Routing protocol} +\subsubsection{Forwarding protocol} -Evidence of the effect of the different routing systems can be found in the third test, where Host 4 sends a packet to Host 6. In the case of Ethernet, this is forced to travel via Switch 2, Switch 0, Switch 1 and then Switch 3, before arriving at Host 6, and the reverse for 6 to 4. In the case of MOOSE however, it travels from Host 4, to Switch 2 then Switch 3 then Host 6, and the reverse for 6 to 4. For the unicast packet this results in a large increase in the number of Ethernet datagrams required. +Evidence of the effect of the different forwarding systems can be found in the third test, where Host 4 sends a packet to Host 6. In the case of Ethernet, this is forced to travel via Switch 2, Switch 0, Switch 1 and then Switch 3, before arriving at Host 6, and the reverse for 6 to 4. In the case of MOOSE however, it travels from Host 4, to Switch 2 then Switch 3 then Host 6, and the reverse for 6 to 4. For the unicast packet this results in a large increase in the number of Ethernet datagrams required. -\subsection{Efficency of Routing} +\subsection{Efficency of Packet Forwarding} -In this test, we are looking at the efficency of the routing protocol. +In this test, we are looking at the efficency of the packet forwarding system. -We can measure this by the number of Ethernet frames for a packet to go between two hosts. With a ineffficent routing protocol it will require more frames than in an efficent routing protocol. +We can measure this by counting the total number of Ethernet frames for a packet to go between two hosts. With a ineffficent forwarding system it will require more frames than in an efficent forwarding system. + +I will use this to compare Ethernet's system, which combines a spanning tree with bridges which learn the addresses of packets which have been forwarded, to the MOOSE system, which uses a Link State routing protocol, as well as learning the address of hosts. We need to look at two different types of addressing as well. Packets in Ethernet can either be broadcast, or unicast, so both mechanisms will be studied. \subsubsection{Unicast} -Here we have a ring network topology with 25 switches in the ring. Switch 12 and 13 each have a host attached, 0 and 1 respectively. Host 0 sends a packet to host 1, and then host 1 sends a packet back to host 0. +Here we have a ring network topology, shown in Figure~\ref{fig-ring1} with 25 switches in the ring. Switch 12 and 13 each have a host attached, 0 and 1 respectively. Host 0 sends a packet to host 1, and then host 1 sends a packet back to host 0. \begin{figure} +\centering \includegraphics[width=6cm]{simulation-4} \caption{Unicast Routing Network} +\label{fig-ring1} \end{figure} -The network has been designed to exploit the worst case of the Ethernet protocol. Namely the spanning tree is constructed such that the the nodes are at the bottom of different branches of the tree. As such, the direct link between switches 12 and 13 is disabled, and the packets must traverse the entire ring. +The network has been designed to demonstrate the defficencies of the Ethernet protocol. This has been done by constructing the spanning tree such that the the hosts are at the bottom of different branches of the tree, as shown in Figure~\ref{fig-ring2}. As such, the direct link between switches 12 and 13 is disabled, and the packets must traverse the entire ring. While this is unlikely, it is a possible scenario, as if all hosts on a ring are communicating with each other, occasionally the worst case will be hit. \begin{figure} +\centering \includegraphics[width=2cm]{simulation-4-tree} \caption{Unicast Routing Spanning Tree} +\label{fig-ring2} \end{figure} Due to this, the Ethernet protocol performs very badly here, requiring 26 frames in each direction for the UDP packet and the ARP Response packet - giving a total of 52 unicast UDP packets, and 52 unicast ARP packets, combining to make a total of 104 unicast frames. @@ -59,14 +67,16 @@ MOOSE on the other hand, uses a routing protocol, which allows it to perform muc Broadcast is the mechanism by which each host on the network is delivered a copy of the packet. It is primarily used for ARP, the Address Resolution Protocol, which resolves IP addresses to Ethernet MAC addresses. -Here we have a mesh network topology with 25 switches in the mesh. Switch 12 and 13, like in the unicast example, have a host attached, 0 and 1 respectively. Host 0 sends a packet to host 1, and then host 1 sends a packet back to host 0. Before the transmission of a packet, the network must resolve the address of the host, causing a broadcast packet to be emitted. +Here we have a mesh network topology with 25 switches in the mesh, shown in Figure~\ref{fig-mesh}. Switch 12 and 13, like in the unicast example, have a host attached, 0 and 1 respectively. Host 0 sends a packet to host 1, and then host 1 sends a packet back to host 0. Before the transmission of a packet, the network must resolve the address of the host, by using an ARP Request, causing a broadcast packet to be emitted. \begin{figure} -\includegraphics[height=10cm]{simulation-5} +\centering +\includegraphics[width=10cm]{simulation-5} \caption{Broadcast Network} +\label{fig-mesh} \end{figure} -Using broadcast in a mesh network is problematic for MOOSE, as it utilises Reverse Path Forwarding to prevent broadcast storms, whereas Ethernet uses the Rapid Spanning Tree Protocol. s such, each broadcast packet is sent to the next switch, before it is culled in MOOSE, while in Ethernet, it doesn't need to send it any further as it knows the entire topology. +Using broadcast in a mesh network is problematic for MOOSE, as it utilises Reverse Path Forwarding to prevent broadcast storms, whereas Ethernet uses the Rapid Spanning Tree Protocol. As such, each broadcast packet is sent to the next switch, before it is culled in MOOSE, while in Ethernet, it doesn't need to send it any further as it knows the entire topology. Due to this, the MOOSE protocol performs especially badly here, requiring 1156 broadcast frames to perform the simulation, 578 from each transmission. One frame is from the host to the switch, then 24 frames to each of the connected switches, followed by each of those switches sending another 24 frames, plus an additional frame from one switch to the host.