<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hi Chengcheng,<div class=""><br class=""></div><div class=""><div><blockquote type="cite" class=""><div class="">On Nov 3, 2014, at 5:41 PM, Chengcheng Li <<a href="mailto:lengcangche@bupt.edu.cn" class="">lengcangche@bupt.edu.cn</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="line-height: 23.3240013122559px;" class="">Hi, everyone</span><br class=""><span style="line-height: 23.3240013122559px;" class=""></span><span style="line-height: 23.3240013122559px;" class="">I'm so confused about the concept 'limit' in the ndnsim code.</span><div style="line-height: 23.3240013122559px;" class="">1. On this page '<a href="http://ndnsim.net/fw.html'" class="">http://ndnsim.net/fw.html'</a>, a equation is presented according to which limit is set. What are the meanings of Delay and Bandwidth? Is it about a single link or all the links?</div></div></blockquote><div><br class=""></div><div>This is something similar to TCP’s delay-bandwidth product (<a href="http://en.wikipedia.org/wiki/Bandwidth-delay_product" class="">http://en.wikipedia.org/wiki/Bandwidth-delay_product</a>). To “fill the pipe” with Interest-Data, you need to allow a certain number of outstanding Interests and this certain number would depend on path’s delay.</div><br class=""><blockquote type="cite" class=""><div class=""><div style="line-height: 23.3240013122559px;" class="">2. And I notice that the dimension(量纲) of limit in this equation is number of interest, not number per second. I think this doesn't comply with <a class="external reference" href="http://ndnsim.net/doxygen/classns3_1_1ndn_1_1_limits_1_1_rate.html" title="" target="_blank" style="color: rgb(145, 165, 1); text-decoration: none; font-weight: bold; border-bottom-width: 1px; border-bottom-style: dashed; border-bottom-color: rgb(145, 165, 1); font-family: 'Lucida Grande', Verdana, Geneva, Arial, sans-serif; font-size: 15px; line-height: 19.0666675567627px; text-align: justify;">ns3::ndn::Limits::Rate</a> situation.</div></div></blockquote><div><br class=""></div><div>It still applies, but just in a different way. Limits::Rate implements a token bucket shaping algorithm (<a href="http://en.wikipedia.org/wiki/Token_bucket" class="">http://en.wikipedia.org/wiki/Token_bucket</a>) and `limit` defines the size of the bucket = number of allowed burst (bucket is “refilled” with a certain rate). Limits::Window implements a simple windowing mechanism, where `limit` is just a number of outstanding interests.</div><br class=""><blockquote type="cite" class=""><div class=""><div style="line-height: 23.3240013122559px;" class="">3. Following that, a code is presented: '<span class="n" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">ndnHelper</span><span class="p" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">.</span><span class="n" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">EnableLimits</span><span style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;" class=""> </span><span class="p" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">(</span><span class="nb" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap; color: rgb(0, 112, 32);">true</span><span class="p" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">,</span><span style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;" class=""> </span><span class="n" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">Seconds</span><span style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;" class=""> </span><span class="p" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">(</span><span class="mf" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap; color: rgb(32, 128, 80);">0.2</span><span class="p" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">),</span><span style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;" class=""> </span><span class="mi" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap; color: rgb(32, 128, 80);">40</span><span class="p" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">,</span><span style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;" class=""> </span><span class="mi" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap; color: rgb(32, 128, 80);">1100</span><span class="p" style="font-size: 15px; line-height: 17.6000003814697px; white-space: pre-wrap;">);</span><span style="line-height: 1.7;" class="">', does this mean that all the links' delay in topology are 0.2?</span></div></div></blockquote><div><br class=""></div><div>It doesn’t mean, but implies that in your simulation scenario paths over which Interest/Data are exchanges will be ~200ms. This method makes a big assumption that this will be constant, which may not be applicable for some scenarios.</div><div><br class=""></div><div>—</div><div>Alex</div><div><br class=""></div></div><br class=""></div></body></html>