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<html><head><meta http-equiv="Content-Language" content="en-us"><meta http-equiv="Content-Type" content="text/html; charset=windows-1252"><title>UDT Reference</title></head><body><table border="1" cellpadding="0" cellspacing="0" style="border-collapse: collapse" width="100%" id="AutoNumber1" bgcolor="#99CCFF" bordercolor="#99CCFF"> <tr> <td width="100%"><font face="Verdana" size="2"><i> UDT Frequent Asked Questions</i></font></td> </tr></table><h1><font size="4" face="Verdana">Frequent Asked Questions</font></h1><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#1">1. What is UDT?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#2">2. Who developed UDT?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#3">3. Why do I need UDT?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#4">4. My application uses UDT, can I run it over a traditional low bandwidth network, or even on the public Internet?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><a href="#3"><font face="Verdana" size="2">5</font></a><font face="Verdana" size="2"><a href="#5">. Why can't I reach the expected high throughput with Gigabit NIC?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><a href="#5"><font face="Verdana" size="2">6</font></a><font face="Verdana" size="2"><a href="#6">. Can you give me some hints in tuning the performance?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><a href="#7"><font face="Verdana" size="2">7</font></a><font face="Verdana" size="2"><a href="#7">. I use UDT for file transfer, but it seems significantly slower than memory-memory transfer. Why?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><a href="#8"><font face="Verdana" size="2">8</font></a><font face="Verdana" size="2"><a href="#8">. When I run the example applications, it prompts for missing library error. What happens?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><a href="#9"><font face="Verdana" size="2">9</font></a><font face="Verdana" size="2"><a href="#9">. Does UDT care about the byte order conversion between different platforms?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><a href="#10"><font face="Verdana" size="2">10</font></a><font face="Verdana" size="2"><a href="#10">. Why can't the UDT connection be set up? Why listen or connect call fails?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><a href="#11"><font face="Verdana" size="2">11</font></a><font face="Verdana" size="2"><a href="#11">. Is the UDT connection secure?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#12">12. Why does my application often have packet loss even though the throughput is much lower than the available bandwidth?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#13">13. Is UDT TCP friendly?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#14">14. What copyright and license issues shall I be aware of when using UDT? </a> </font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#15">15. Is UDT only suitable for bulk data?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#16">16. What's the relationship between UDT and SABUL?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#17">17. Where can I find help regarding to the use of UDT library?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#18">18. What background knowledge is necessary in order to use UDT?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#19">19.Why UDT consumes so much memory even if I just send a small file?</a></font></p><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2"><a href="#20">20.When I try to start the example application, an error of "No buffer spaceavailable" occurs, what happened?</a></font></p><p style="margin-top: 0; margin-bottom: 0"> </p><hr><h4><font face="Verdana" size="2"><a name="1"></a>1. What is UDT?</font></h4><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2">UDT Stands for UDP-based Data Transfer. It can refer to both the UDT protocol and its implementation (the UDT library). Basically, UDT is built on top of UDP by adding reliability control and congestion control.</font></p><h4><font face="Verdana" size="2"><a name="2"></a>2. Who developed UDT?</font></h4><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2">UDT is a research product of the National Center for Data Mining (NCDM) at the University of Illinois at Chicago. The project was supported in part by US National Science Foundation, US Department of Energy, and US Army.</font></p><h4><font face="Verdana" size="2"><a name="3"></a>3. Why and when do I need UDT?</font></h4><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2">The original (and major) purpose of UDT is to provide a high performance transfer interface to distributed data intensive applications over a wide area network, where TCP seldom works well for efficiency and fairness reasons. It can also be used in other situation where TCP is not suitable (e.g., multimedia streaming, firewall punching, partial reliability, etc.)<br><br>There is no explicit standard to determine when to use UDT or when not to. Generally speaking, if you are not satisfied with TCP's performance or functionality, UDT is probably what you need, especially in high speed networks where a small number of bulk sources share the abundant bandwidth.</font></p><h4><font face="Verdana" size="2"><a name="4"></a>4. My application uses UDT, can I run it over a traditional low bandwidth network, or even on the public Internet?</font></h4><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2">Yes, you can do it. But please be aware that your application may usea large amount of bandwidth and may be regarded as attack or improper use of network by ISPs and firewalls.In addition, UDT's impact on the Internet is not comprehensively tested yet.</font></p><h4><font face="Verdana" size="2"><a name="5"></a>5. Why can't I reach the announced high throughput with my Gigabit NIC?</font></h4><p style="margin-top: 0; margin-bottom: 0"><font face="Verdana" size="2">There are many factors that can affect the throughput, especially for Gigabit NICs.<br><br>First of all, you need to test it using some other benchmark tools like IPerf. They will give you the highest performance for the current configuration. If UDT has similar performance, then it is all right, and you need to tune your network settings.<br><br>⌨️ 快捷键说明
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