P0961CA | Foxboro DNS解析的功能是向上一級(jí)的DNS服務(wù)器（運(yùn)營(yíng)商服務(wù)中心動(dòng)態(tài)分配的DNS服務(wù)器）發(fā)出請(qǐng)求，令其幫助查找該域名的映射信息。在DNS協(xié)議里，查詢信息的方法有兩種：遞歸查詢和迭代查詢。大多數(shù)情況下，為了使用上的方便，默認(rèn)的都是遞歸查詢。這樣對(duì)于運(yùn)營(yíng)商的DNS服務(wù)器而言，其解析域名的過(guò)程跟 WDTU終端查詢域名的方法相同：先查詢服務(wù)器自身的緩存，若查到則過(guò)程完成，否則再向服務(wù)器的上一級(jí)DNS服務(wù)器查詢域名信息。而花生殼公司的服務(wù)器地址會(huì)直接或間接地存放在運(yùn)營(yíng)商的服務(wù)器鏈表中（這一部分由運(yùn)營(yíng)商和花生殼公司合作實(shí)現(xiàn)），從而可以從花生殼公司的服務(wù)器數(shù)據(jù)系統(tǒng)中得到該域名的映射IP。運(yùn)營(yíng)商的DNS服務(wù)器得到花生殼返回的數(shù)據(jù)包以后，過(guò)程完成。最后再?gòu)倪\(yùn)營(yíng)商動(dòng)態(tài)分配的DNS服務(wù)器返回的DNS應(yīng)答數(shù)據(jù)包中提取IP地址信息。DNS系統(tǒng)整體的工作原理如圖3所示。
由于工業(yè)對(duì)于借助無(wú)線網(wǎng)絡(luò)實(shí)現(xiàn)遠(yuǎn)距離數(shù)據(jù)傳輸?shù)囊蠛蛻?yīng)用越來(lái)越多，而傳統(tǒng)的數(shù)據(jù)傳輸必須有固定的公網(wǎng)IP，這使得成本要求較高，限制了產(chǎn)品的使用范圍。本設(shè)計(jì)的創(chuàng)新點(diǎn)在于，使WDTU無(wú)線終端實(shí)現(xiàn)了DNS功能，這樣任意一臺(tái)主機(jī)都可作為“具有公網(wǎng)IP”的傳統(tǒng)數(shù)據(jù)中心主機(jī)使用，使產(chǎn)品的應(yīng)用成本降低，對(duì)于提高產(chǎn)品的整體功能，促進(jìn)產(chǎn)品的推廣具有重要的現(xiàn)實(shí)意義。
P0961CA | Foxboro
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