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1、成都理工大学学生毕业设计（论文）外文译文学生姓名：杨飞学号:3200905010807专业名称：信息工程译文标题（中英文）：SMTP模型The SMTP Model译文出处:RFC 821-Simple Mail Transfer Protocol: The SMTP Model (chapter 2)指导教师审阅签名：外文译文正文:SMTP模型简单邮件传输协议（SMTP）的目标是可靠高效地传送邮件，它独立于传送子系统而且仅要求一条可以 保证传送数裾单元顺序的通道。附求A，B，C和D描述了不同传送服务卜SMTP的使川。在名词表中还定义 了本文捫中使用的术语。SMTP的一个要特点是它能够在传送中
2、接力传送邮件，传送服务提供了进程间通信环境（1PCE）,此 环境可以包括一个网络，儿个网络或一个网络的子网。理解到传送系统（或TPCE）不是-对一的是很重要 的。进程可能亢接和其它进程通过已知的TPCE通信。邮件是一个应用程序或进程间通信。邮件可以通过连 接在不同IPCE上的进程跨网络进行邮件传送。更特别的足，邮件可以通过不同网络上的主机接力式传送。SMTP设计基丁以下通信模型：针对用户的邮件请求，发送SMTP建立与接收SMTP之间建立一个双叫传 送通道。接收SMTP可以是最终接收者也可以是中间传送者。SMTP命令由发送SMTP发出，由接收SMTP接 收，而应荇则反力血传送。一旦传送通道建立，
3、SMTP发送者发送MAIL命令指明邮件发送者。如果SMTP接收者可以接收邮件则返 回0K应答。SMTP发送者再发出RCPT命令确认邮件是否接收到。如果SMTP接收者接收，则返回0K应答; 如果不能接收到，则发出祀绝接收应答（识不中止整个邮件操作），双方将如此重ii多次。当接收者收到 企部邮件后会接收到特别的序列，如果接收齐成功处理了邮件，则返回0K应答。SMTP提供传送邮件的机制，如果接收万与发送77连接在同一个传送服务下时，邮件可以直接巾发送力 主机传送到接收方主机：或者，当两者不在同一个传送服务不时，通过中继SMTP服务器传送。为了能够对 SMTP服务器提供中继能力，它必须拥有最终S的主机
4、地址和邮箱名称。MAIL命令参数是冋复路径，它指定邮件从何处來；而RCPT命令的参数是转发路径的，它指定邮件向 何处去。叫前路径是源路径，而回S路径是返回路径（它用于发生错误时返回邮件）。当同一个消息要发往不同的接收者时，SMTP遇到了 14不同接收者发送同一份数据的乂制品的问题，邮 件命令和应答有一个比较奇怪的语法，应答也有一个数字代码。在下囬，例子中可以看到哪些使用实际的 命令和应答。完整的命令和应答在第四节。命令与应答对大小写不敏感，也就是说，命令和应答可以是大写，小写或两齐的混合，但这一点对用 户邮件名称却不一定是对的，因为冇的主机对川广名人小写是敏感的。这样SMTP实现中就将川广邮箱
5、名称 保留成初始吋的样子，主机名称对大小写不敏感。命令与应答由ASCII字母表组成，当传送服务提供8位字节传送通道，毎7位字符正确传送，而最岛 位被填充为0。当指定一般的命令或应答格式后，参数会由一些类似于语言的字符串表示出来，如string 或reverse-pathZ,这甲.尖括号表示这是一种类似于语言的变S:。SMTP命令定义了邮件传输或由川广定义的系统功能。它的命令是由CRLF结束的字符串。而在带冇参 数的情况下，命令本身山SP和参数分开，如果未带参数可以直接和CRLF连接。邮箱的语法格式必须和 接收站点的格式一致。下面讨论SMTP命令和应答。发送邮件操作涉及到不同的数裾对象，它们由不
6、同的参数相互连接。回复路径就是MAIL命令的参数， 而转发路径则是RCPT命令的参数，邮件口期是DATA命令的参数。这些参数或再数裾对象必须跟在命令后。 这种模式也就要求存不同的缓冲区来存储这些对象，也就是说，荇一个回复路径缓冲区，一个转发路径缓 冲区，一个邮件内容缓冲区。特定的命令产生自己的缓冲区，或使一个或多个缓冲的内容被清除。（正文页而不够可加页，并在正文后附外文原文，统一川A4纸张打印或手工脊写）英语原文:The SMTP ModelThe objective of Simple Mail Transfer Protocol (SMTP) is to transfermail reli
7、ably and efficiently. SMTP is independent of the particular transmission subsystem and requires only a reliable ordered data stream channel. Appendices A，B，C，and D describe the use of SMTP with various transport services. A Glossary provides the definitions of terms as used in this document.An impor
8、tant feature of SMTP is its capability to relay mail across transport service environments. A transport service provides an interprocess communication environment (IPCE). An IPCE may cover one network，several networks，or a subset of a network. It is important to realize that transport systems (or IP
9、CEs) are not one-to-one with networks. A process can communicate directly with another process through any mutually known IPCE. Mail is an application or use of interprocess communication. Mail can be communicated between processes in different IPCEs by relaying through a process connected to two (o
10、r more) IPCEs. More specifically，mail can be relayed between hosts on different transport systems by a host on both transport systems.The SMTP design is based on the following model of communication: as the result of a user mail request，the sender-SMTP establishes a two-way transmission channel to a
11、 receiver-SMTP. The receiver-SMTP may be either the ultimate destination or an intermediate. SMTP commands are generated by the sender-SMTP and sent to the receiver-SMTP. SMTP replies are sent from the receiver-SMTP to the sender-SMTP in response to the commands.Once the transmission channel is esta
12、blished, the SMTP-sender sends a MAIL command indicating the sender of the mail. If the SMTP-receiver can accept mail it responds with an OK reply. The SMTP-sender then sends a RCPT command identifying a recipient of the mail. If the SMTP-receiver can accept mail for that recipient it responds with
13、an OK reply; if not，it responds with a reply rejecting that recipient (but not the whole mail transaction). The SMTP-sender andSMTP-receiver may negotiate several recipients. When the recipients have been negotiated the SMTP-sender sends the mail data, terminating with a special sequence. If the SMT
14、P-receiver successfully processes the mail data it responds with an OK reply. The dialog is purposely lock-step，one-at-a-time.The SMTP provides mechanisms for the transmission of mail; directly from the sending users host to the receiving users host when the two host are connected to the same transp
15、ort service，or via one or more relay SMTP-servers when the source and destination hosts are not connected to the same transport service.To be able to provide the relay capability the SMTP-server must be supplied with the name of the ultimate destination host as well as the destination mailbox name.T
16、he argument to the MAIL command is a reverse-path，which specifies who the mail is from. The argument to the RCPT command is a forward-path，which specifies who the mail is to. The forward-path is a source route, while the reverse-path is a return route (which may be used to return a message to the sender when an error occurs with a relayed message).When the same message is sent to multiple re
