【正文】 Raicu and Zeadally, 2020) was measured ?rst. The average transmission latency is the time taken for a packet to be transmitted across a work connection from sender to receiver. Tests were performed using the ping Fig. 2. Packet Reception. 5 Time (ms) program run on a reliable ICMP Inter layer. The ping utility sends ICMP echo request packets to the mand argument speci?ed node and checks for a replayed message, to determine whether a particular node is alive. Latency was measured by sending packets of size 64,128,256,512 and 768 bytes from a client to a server. Upon receipt of a packet the server replays the packet back to the client. The whole process is repeated。所以程序需要從服務器獲得 IPv4地址，這個程序也許利用 DHCPv6或者 RPCv6，再或者利用 特別設計的目標，同樣地服務器需要維護全局的 IPv4地址。同時， NAT型機制也有同樣的缺陷作為網(wǎng)關型機制直到點對點通信而言。它們共同的缺點是打破因特網(wǎng)點對點的原則，而此原則對電子商務以及商業(yè)通信非常的重要。吞吐量一般隨著數(shù)據(jù)包大小的增加而增大。隨著數(shù)據(jù)包字節(jié)的改變，總值呈現(xiàn)出 由 7%到 30%的變化。接收函數(shù)移除 IPv6 頭信息并且模擬另一個接收程序，此時一個 IPv4 數(shù)據(jù)包被接收，虛擬界面的一些參數(shù)被調整以便 IPv4 數(shù)據(jù)包的接收可通過虛擬設備來模擬。隧道參數(shù)可存儲于界面的私有數(shù)據(jù)結構中。 2. 若目的地為 IPv6 主機，則為遠程主機創(chuàng)建一個隧道。注冊的回收函數(shù)返回下面五個值中的一個 :NF_ACCEPT(接受數(shù)據(jù)包并繼續(xù)數(shù)據(jù)鏈 )， NF_DROP (丟棄數(shù)據(jù)包 ), NF_QUEUE(將數(shù)據(jù)包排隊到用戶空間中 )或者 NF_STOLEN (從網(wǎng)絡中竊得的數(shù)據(jù)包 )。在圖的頂端有兩個鉤子，NF_IP_LOCAL_IN 和 NF_IP_LOCAL_OUT。網(wǎng)濾器鉤可用來探測是否需要在節(jié)點上安裝這樣一個隧道。這允許 IPv6 節(jié)點與純 IPv4 節(jié)點通訊，或者純 IPv4 應用程序在 IPv6 節(jié)點上不用修改而運行。 fax: +912332300831. Email addresses: (. Raste), (. Kulkarn i). 10848045/$ see front matter r 2020 Published by Elsevier Ltd. doi: 2 1. 引言 在純 IPv6 網(wǎng)絡（ Dunn， 2020）中，最初的 IPv6 配置（ Davies,2020）需要緊密成對使用 IPv4 地址來支持 IPv4 與 IPV6 之間的網(wǎng)絡互連。 received in revised form 28 June 2020。當大部分網(wǎng)絡轉換成只涉及最小 IPv4 路由的 IPv6 網(wǎng)絡時，此方案將會很有用處。因此在這種情況下建議用戶只配置 IPv6 網(wǎng) 絡。在需要發(fā)送第一個 IPv4 包時，客戶端會獲得一個 TEP 的 IPv6 地址 (Affifi and Tountain,1999)，此信息將用來配置 4到 6 的界面。它允許用戶定義的內 3 圖 1. 網(wǎng)濾器鉤 . 核模塊將回收函數(shù)注冊到這些鉤子上。假設一個本地進程為一個遠程進程創(chuàng)建一個數(shù)據(jù)包，作為一個數(shù)據(jù)包如何橫越這些鉤子的例子：首先，數(shù)據(jù)包橫越 NF_IP_LOCAL_OUT鉤子。因此，創(chuàng)建一個隧道暗指在內核中創(chuàng)建一個虛擬界面，并將封裝信息保留在專用數(shù)據(jù)結構中。為此，它會生成一個對 DNS 服務器的 DNS 查詢。 一個 IPv6 域中的用戶空間守護程序被配置用于傳達在 IPv4 目的地建立隧道的需求，或者是邊界路由器的目的地 在 IPv4 域中。 延遲的測量是從客戶端向服務器發(fā)送 64， 128， 258， 512 及 768 字節(jié)的數(shù)據(jù)包，服務器一旦收到數(shù)據(jù)包即立刻回送給客戶端。圖 4 是對 64 字節(jié)到 768 字節(jié)的數(shù)據(jù)包大小的吞吐量的分析。但是它不可以減少對全局路由 IPv4 地址的需求，以及提高 IPv4 與 IPv6 混合路由設施的網(wǎng)絡復雜性。 SIIT (Nordmark,2020)提供了一個從 IPv4到 IPv6靈活與無狀態(tài)的轉化，但是它是不完 備的，因為它沒有指定在 IPv6網(wǎng)絡里如何從 IPv4包到 IPv6包轉化。 標準模型假設 IPv6節(jié)點含有有效的 IPv4與 IPv6地址，在將來當節(jié)點升級為 IPv6領域，這時 IPv4地址只需要臨時 IPv4節(jié)點通信。 Ipv6 1. Introduction The initial deployment of IPv6 (Davies, 2020) will require a tightly coupled use of IPv4 addresses to support the interoperation of IPv6 and IPv4 within an IPv6only Network (Dunn, 2020). Nodes will still need to municate with IPv4 nodes that do not have a dual IP layer supporting both IPv4 and IPv6. The mechanism proposed is based on the use Corresponding author. Tel.:+ 912332301327。 P/L, where T is the throughput, P is the packet size in kbits and L is the latency that corresponds to a packet of that size. The following ?gure plots the throughput for packet size ranging from 64 to 768 bytes. The packet size was kept less than 1440 bytes to avoid potential fragmentation problem in the IPv6 protocol stack. The maximum throughput is reached for largest packet size. The throughput generally increases with the increase in packet size. The overhead varies from 7% to 30% depending upon the packet size. The overhead decreases with increase in the packet size (Fig. 4). 7. Comparison with other mechanisms In this section, some related works proposed under IETF Next Generation Transition Working group (Ngtrans) (Waddington and Chang, 2020). 4 3 IPv4 Tunneled Latency 2 1 0 64 128 256 Packet Size 512 768 Fig. 3. Latency analysis. 6 Throughput (kbps) 2500 Throughput 2020 IPv4 Tunneled 1500 1000 500 0 64 128 256 512 768 Packet Size (bytes) Fig. 4. Throughput analysis. Dual stack (Bound and Tountain, 1999) mechanism is one of two basic transition mechanisms, which mandates the plete support for both IPv4 and IPv6 in hosts and routers. But it does not reduce the demand for globally routable IPv4 addresses and increases the work plexity due to the need for a mixture of IPv4 and IPv6 routing infrastructure. Application Level Gateway (ALG), SOCKS64 (Kitamura et al., 2020) and TCP Relay (Kitamura et al., 2020) are proxybased mechanisms which can provide munication between IPv4 nodes and IPv6 nodes. They all split one IP connection into two closed connections on application or TCP layer, one is in the IPv4 work and the other is in the IPv6 work. Their mon demerit is that they break the endtoend principle of the Inter, which is important aspect for emerce and business munications. ALG is an applicationdependent mechanism, which means for the different applications it should provide different application gateway