CSN305 Lab 8

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Dec 6, 2023

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CSN305 - Lab 8 – Failure Analysis Lab 8 – What if a controller fails? Student Full Name Abdulmanan Khalid _________/10 Marks Objective To understand what messages to expect and procedure to perform if a controller fails. Instructions  Use a different font and color to write your answers .  Do not erase anything from this document.  Resize the screenshots to make them easily readable. Be sure that your name and the date and time are visible when inserting your screenshot in this report file. Procedure: Read this article carefully and visit the links below to learn about the Open vSwitch commands. Connection Interruption: In the case that a switch loses contact with all controllers, because of echo request timeouts, TLS session timeouts, or other disconnections, the switch must immediately enter either “fail secure mode” or “fail standalone mode”, depending upon the switch implementation and configuration. In “ fail secure mode ”, the only change to switch behavior is that packets and messages destined to the controllers are dropped. Flow entries should continue to expire according to their timeouts in “fail secure mode”. In “ fail standalone mode ”, the switch processes all packets using the OFPP_NORMAL reserved port, in other words, the switch acts as a legacy Ethernet switch or router. The “fail standalone mode” is usually only available on Hybrid switches. Upon connecting to a controller again, the existing flow entries remain. The controller then has the option of deleting all flow entries, if desired. The first time a switch starts up, it will operate in either “fail secure mode” or “fail standalone mode” mode, until it successfully connects to a controller. Configuration of the default set of flow entries to be used at startup is outside the scope of the OpenFlow protocol. (openflow-spec-v1.3.2 - Ch. 6.3.2) Links from www.openvswitch.org : https://www.openvswitch.org/support/dist-docs/ovs-vsctl.8.html https://www.openvswitch.org/support/dist-docs/ovs-ofctl.8.html pg. 1

CSN305 - Lab 8 – Failure Analysis To do this lab, you need Wireshark, Mininet VM and ODL VM. Use commands and the same kind of setting as the previous lab. The following is a list of some new commands you can use for this lab. (you can find out what is the application of each one before starting the lab) ovs-vsctl show ovs-vsctl get-fail-mode s1 ovs-vsctl set-fail-mode s1 secure ovs-vsctl set-fail-mode s1 standalone ovs-ofctl dump-flows s1 ovs-ofctl dump-ports s1 Part1 1- Create a topology with a switch and two hosts (you can use the same topology as the previous lab). Insert the screenshot of the created topology here. (1 mark) 2- Check the topology in ODL interface and run PING ALL. pg. 2

CSN305 - Lab 8 – Failure Analysis Insert the screenshot of the output of this command here. (1 mark) 3- What are the flows in S1 tables? What is the “ fail” mode of S1? Explain: flow table of S1 contains flow entries that direct traffic from h1 to h2 and vice versa. These flow entries are usually installed by the controller when the hosts first start communicating. The “fail” mode of s1 is secure. (1 mark) 4- Do h1 ping h2 and disconnect the controller. What happens to the result of the PING command? Repeat the PING command to check. Insert the screenshot of the output of this command here. (1 mark) 5- While controller is disconnected, what are the flows in S1 tables? How different is your response from the answer to question 3? Explain: The flows in s1 tables are the same as they were before. The ping commands go through using the existing flow table entries. (1 mark) 6- Now return the controller back to normal operation. (you can restart Mininet and controller if there is any communication issue) Part2 1- Now that everything works normal, again do h1 ping h2. 2- Change the “fail” mode of S1 to be “standalone” pg. 3

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