一级理论和二级理论的区别

Second handshake: when the server receives syn packet, it must confirm the SYN (ack=j+1) of the customer, and at the same time it also sends a SYN packet (syn=k), that is, SYN + ACK packet. At this time, the server enters the SYN_RECV state;狮门宣布《疾速追杀》第四部定档2021年5月21日北美上映，2年后的今天。系列主演基努·里维斯是否回归尚未宣布，不过狮门应该会力保他回归，大家一起期待第四部的剧情发展。Since http is based on tcp, You need to complete a three-way handshake to establish a tcp connection before you can start http communication, Therefore, when http flood attacks are carried out, it is not possible to use forged source ip addresses to launch attacks. An attacker will typically use an http proxy server, Not only can the source be hidden from being traced, It also improves attack efficiency-after the attacker connects to the proxy server and sends the request, You can directly disconnect from the proxy server and start connecting to the next proxy server, At this time, the http connection between the proxy server and the target web server is still maintained, and the web server needs to continue to accept and process data. An efficient http flood attack should continuously send http requests for different resources and pages, and request resources that cannot be cached as much as possible (such as keyword search. User-related information, etc.)《雪人》根据挪威作家Jo Nesbo在2007年出版的同名畅销小说改编，这部书是他以奥斯陆侦探哈里（Harry Hole）为主角创作的第七本小说。故事主要讲述哈里在调查一位年轻妈妈失踪案件的时候，发现受害人院子里出现了一个神秘的雪人，而且它脖子上还围着这家孩子送给妈妈做圣诞礼物的粉红围巾。由此，哈里挖出了一系列有着相同情况的陈年旧案，一个总爱在落下第一场雪时作案的连环杀人犯浮出了水面…… 
　　《雪人》将由环球公司和Working Title公司联合摄制，如果影片反响良好的话，Jo Nesbo的另外六部侦探哈里小说也将有机会登上大银幕。濑文在和当麻办案的过程中，渐渐趋近了一个鲜为人知且充满阴谋和秘密的未知世界……ABC续订《初来乍到》第六季。