<!DOCTYPE html><html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /></head><body><div data-html-editor-font-wrapper="true" style="font-family: arial, sans-serif; font-size: 13px;" dir="rtl"><div><div><div style="font-family: arial, sans-serif;font-size: 13px"><p style="direction: ltr">Dear ndnSIM Community,</p><p style="direction: ltr">My name is Mohammad Reza Shakoutnia, and I am a PhD candidate in Computer Science at the University of Tehran, Iran. I hope this message finds you well. I am writing to report a bug I encountered while installing ndnSIM on Ubuntu 22.04, and to share a solution that might benefit others facing the same issue.</p><p style="direction: ltr"><strong>Issue Description:</strong> During the installation process, after running the <code>./waf</code> command, I received an error indicating that the <code>std::optional</code> template was not recognized. This error prevented the successful compilation and installation of ndnSIM.</p><p style="direction: ltr"><strong>Solution Implemented:</strong> To resolve this issue, I added the following line at the beginning of the <code>scheduler.hpp</code> file located in the <code>ns3/ndnSIM/ndn-cxx/util</code> directory:</p><pre style="direction: ltr"><span style="color: rgb(221, 17, 68);font-size: 12px">#include <optional></span></pre><p style="direction: ltr">This inclusion resolved the compilation error related to <code>std::optional</code>.</p><p style="direction: ltr"><strong>Steps to Replicate:</strong></p><ol dir="ltr"><li>Set up a fresh installation of Ubuntu 22.04.</li><li>Follow the standard installation procedure for ndnSIM.</li><li>Run the <code>./waf</code> command and observe the mentioned error.</li></ol><p style="direction: ltr"><strong>Suggested Actions:</strong> It may be beneficial for the maintainers to include this header file in future releases to ensure compatibility with Ubuntu 22.04 environments, preventing similar issues for other users.</p><p style="direction: ltr">I appreciate your attention to this matter and am happy to provide any further details if needed. Thank you for your ongoing support and development of ndnSIM.</p><p style="direction: ltr">Best regards,<br><strong style="background-color: transparent;font-family: arial, sans-serif">ــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــــ<br>Mohammad Reza Shakournia</strong></p><signature><div style="direction: ltr"><span style="background-color: transparent;font-family: arial, sans-serif">PhD Candidate in Computer Science,</span></div><div style="direction: ltr"><span style="background-color: transparent;font-family: arial, sans-serif">Member of Router Laboratory,</span></div><div style="direction: ltr"><span style="background-color: transparent;font-family: arial, sans-serif">Electrical and Computer Engineering Department,</span></div><div style="direction: ltr"><span style="background-color: transparent;font-family: arial, sans-serif">University of Tehran.</span></div></signature></div></div></div></div></body></html>