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Recently, I have made a preliminary investigation on DDOS attacks, and have some superficial understanding of the causes of DDOS attacks and their detection and defense mechanisms. This paper focuses on some thoughts on DDOS attacks in metropolitan area network environment under traditional network architecture.Polylactic acid (PLA) is a new bio-based and renewable biodegradable material, which is made of starch raw materials proposed by renewable plant resources (such as corn). Starch raw materials are saccharified to obtain glucose, then glucose and certain strains are fermented to produce high purity lactic acid, and polylactic acid with certain molecular weight is synthesized by chemical synthesis method. It has good biodegradability, can be completely degraded by microorganisms in nature under specific conditions after use, and finally generates carbon dioxide and water without polluting the environment, which is very beneficial to environmental protection and is recognized as an environment-friendly material. This thing is actually a long piece, and then "curled up" in it and wrapped in a cylinder shape. What's the use? You will see it in a short time.The attack uses the method of sending a large number of domain name resolution requests to the attacked server, Usually the domain name requested to be resolved is randomly generated or does not exist on the network. When the attacked DNS server receives the domain name resolution request, it will first look for whether there is a corresponding cache on the server. If it cannot be found and the domain name cannot be directly resolved by the server, the DNS server will recursively query the domain name information from its upper DNS server. The process of domain name resolution brings a great load to the server. If the number of domain name resolution requests exceeds a certain number per second, the DNS server will time out to resolve domain names."What happened later?" I knew the story was far from over, so I couldn't wait to ask him./introduction　　声由于锋芒太露而引起犯罪头子蒋文浩的不满，派人强奸其旧女友阮静雯，声大为愤怒，誓要缉凶，并与浩的集团作战到底。晖因癫痫病被调离警局，无意中加入了浩的犯罪集团并成为其左右手，被迫与声为敌，另一方面，杰在一次意外中翻然醒悟，恢复良知，决助声对付恶势力，潜伏于浩集团做卧底。结果，杰在找到罪证时被晖打至残废，声为主持正义不得不与生死之交以枪相向……　　面对昔日的恋人、妻子所承受的精神折磨，邵钧内心多次被动摇。但少年时的家破人去楼空的记忆蒙蔽了他原本善良的心。为了能够掌权安氏企业，邵钧费尽心机，倾尽才华。在与竞争对手宋氏集团的较量中，邵钧面对的不仅仅是商场上的竞争，更有情敌之间的较量。