00000015.htm

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<?xml version="1.0" encoding="gb2312"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312"/><title>TFTP                                   turbolinux </title></head><body><center><h1>BBS 水木清华站∶精华区</h1></center><a name="top"></a>发信人:&nbsp;hellow&nbsp;(收复台湾是我心),&nbsp;信区:&nbsp;Embedded&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<br />标&nbsp;&nbsp;题:&nbsp;TFTP&nbsp;<br />发信站:&nbsp;BBS&nbsp;水木清华站&nbsp;(Sun&nbsp;Nov&nbsp;&nbsp;5&nbsp;09:30:15&nbsp;2000)&nbsp;<br />&nbsp;<br />&nbsp;<br />Network&nbsp;Working&nbsp;Group&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;K.&nbsp;Sollins&nbsp;<br />Request&nbsp;For&nbsp;Comments:&nbsp;1350&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;MIT&nbsp;<br />STD:&nbsp;33&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;July&nbsp;1992&nbsp;<br />Obsoletes:&nbsp;RFC&nbsp;783&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;THE&nbsp;TFTP&nbsp;PROTOCOL&nbsp;(REVISION&nbsp;2)&nbsp;<br />Status&nbsp;of&nbsp;this&nbsp;Memo&nbsp;<br />&nbsp;&nbsp;&nbsp;This&nbsp;RFC&nbsp;specifies&nbsp;an&nbsp;IAB&nbsp;standards&nbsp;track&nbsp;protocol&nbsp;for&nbsp;the&nbsp;Internet&nbsp;<br />&nbsp;&nbsp;&nbsp;community,&nbsp;and&nbsp;requests&nbsp;discussion&nbsp;and&nbsp;suggestions&nbsp;for&nbsp;improvements.&nbsp;<br />&nbsp;&nbsp;&nbsp;Please&nbsp;refer&nbsp;to&nbsp;the&nbsp;current&nbsp;edition&nbsp;of&nbsp;the&nbsp;&quot;IAB&nbsp;Official&nbsp;Protocol&nbsp;<br />&nbsp;&nbsp;&nbsp;Standards&quot;&nbsp;for&nbsp;the&nbsp;standardization&nbsp;state&nbsp;and&nbsp;status&nbsp;of&nbsp;this&nbsp;protocol.&nbsp;<br />&nbsp;&nbsp;&nbsp;Distribution&nbsp;of&nbsp;this&nbsp;memo&nbsp;is&nbsp;unlimited.&nbsp;<br />Summary&nbsp;<br />&nbsp;&nbsp;&nbsp;TFTP&nbsp;is&nbsp;a&nbsp;very&nbsp;simple&nbsp;protocol&nbsp;used&nbsp;to&nbsp;transfer&nbsp;files.&nbsp;&nbsp;It&nbsp;is&nbsp;from&nbsp;<br />&nbsp;&nbsp;&nbsp;this&nbsp;that&nbsp;its&nbsp;name&nbsp;comes,&nbsp;Trivial&nbsp;File&nbsp;Transfer&nbsp;Protocol&nbsp;or&nbsp;TFTP.&nbsp;<br />&nbsp;&nbsp;&nbsp;Each&nbsp;nonterminal&nbsp;packet&nbsp;is&nbsp;acknowledged&nbsp;separately.&nbsp;&nbsp;This&nbsp;document&nbsp;<br />&nbsp;&nbsp;&nbsp;describes&nbsp;the&nbsp;protocol&nbsp;and&nbsp;its&nbsp;types&nbsp;of&nbsp;packets.&nbsp;&nbsp;The&nbsp;document&nbsp;also&nbsp;<br />&nbsp;&nbsp;&nbsp;explains&nbsp;the&nbsp;reasons&nbsp;behind&nbsp;some&nbsp;of&nbsp;the&nbsp;design&nbsp;decisions.&nbsp;<br />Acknowlegements&nbsp;<br />&nbsp;&nbsp;&nbsp;The&nbsp;protocol&nbsp;was&nbsp;originally&nbsp;designed&nbsp;by&nbsp;Noel&nbsp;Chiappa,&nbsp;and&nbsp;was&nbsp;<br />&nbsp;&nbsp;&nbsp;redesigned&nbsp;by&nbsp;him,&nbsp;Bob&nbsp;Baldwin&nbsp;and&nbsp;Dave&nbsp;Clark,&nbsp;with&nbsp;comments&nbsp;from&nbsp;<br />&nbsp;&nbsp;&nbsp;Steve&nbsp;Szymanski.&nbsp;&nbsp;The&nbsp;current&nbsp;revision&nbsp;of&nbsp;the&nbsp;document&nbsp;includes&nbsp;<br />&nbsp;&nbsp;&nbsp;modifications&nbsp;stemming&nbsp;from&nbsp;discussions&nbsp;with&nbsp;and&nbsp;suggestions&nbsp;from&nbsp;<br />&nbsp;&nbsp;&nbsp;Larry&nbsp;Allen,&nbsp;Noel&nbsp;Chiappa,&nbsp;Dave&nbsp;Clark,&nbsp;Geoff&nbsp;Cooper,&nbsp;Mike&nbsp;Greenwald,&nbsp;<br />&nbsp;&nbsp;&nbsp;Liza&nbsp;Martin,&nbsp;David&nbsp;Reed,&nbsp;Craig&nbsp;Milo&nbsp;Rogers&nbsp;(of&nbsp;USC-ISI),&nbsp;Kathy&nbsp;<br />&nbsp;&nbsp;&nbsp;Yellick,&nbsp;and&nbsp;the&nbsp;author.&nbsp;&nbsp;The&nbsp;acknowledgement&nbsp;and&nbsp;retransmission&nbsp;<br />&nbsp;&nbsp;&nbsp;scheme&nbsp;was&nbsp;inspired&nbsp;by&nbsp;TCP,&nbsp;and&nbsp;the&nbsp;error&nbsp;mechanism&nbsp;was&nbsp;suggested&nbsp;by&nbsp;<br />&nbsp;&nbsp;&nbsp;PARC's&nbsp;EFTP&nbsp;abort&nbsp;message.&nbsp;<br />&nbsp;&nbsp;&nbsp;The&nbsp;May,&nbsp;1992&nbsp;revision&nbsp;to&nbsp;fix&nbsp;the&nbsp;&quot;Sorcerer's&nbsp;Apprentice&quot;&nbsp;protocol&nbsp;<br />&nbsp;&nbsp;&nbsp;bug&nbsp;[4]&nbsp;and&nbsp;other&nbsp;minor&nbsp;document&nbsp;problems&nbsp;was&nbsp;done&nbsp;by&nbsp;Noel&nbsp;Chiappa.&nbsp;<br />&nbsp;&nbsp;&nbsp;This&nbsp;research&nbsp;was&nbsp;supported&nbsp;by&nbsp;the&nbsp;Advanced&nbsp;Research&nbsp;Projects&nbsp;Agency&nbsp;<br />&nbsp;&nbsp;&nbsp;of&nbsp;the&nbsp;Department&nbsp;of&nbsp;Defense&nbsp;and&nbsp;was&nbsp;monitored&nbsp;by&nbsp;the&nbsp;Office&nbsp;of&nbsp;Naval&nbsp;<br />&nbsp;&nbsp;&nbsp;Research&nbsp;under&nbsp;contract&nbsp;number&nbsp;N00014-75-C-0661.&nbsp;<br />1.&nbsp;Purpose&nbsp;<br />&nbsp;&nbsp;&nbsp;TFTP&nbsp;is&nbsp;a&nbsp;simple&nbsp;protocol&nbsp;to&nbsp;transfer&nbsp;files,&nbsp;and&nbsp;therefore&nbsp;was&nbsp;named&nbsp;<br />&nbsp;&nbsp;&nbsp;the&nbsp;Trivial&nbsp;File&nbsp;Transfer&nbsp;Protocol&nbsp;or&nbsp;TFTP.&nbsp;&nbsp;It&nbsp;has&nbsp;been&nbsp;implemented&nbsp;<br />&nbsp;&nbsp;&nbsp;on&nbsp;top&nbsp;of&nbsp;the&nbsp;Internet&nbsp;User&nbsp;Datagram&nbsp;protocol&nbsp;(UDP&nbsp;or&nbsp;Datagram)&nbsp;[2]&nbsp;<br />Sollins&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;[Page&nbsp;1]&nbsp;<br />&nbsp;<br />RFC&nbsp;1350&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;TFTP&nbsp;Revision&nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;July&nbsp;1992&nbsp;<br />&nbsp;&nbsp;&nbsp;so&nbsp;it&nbsp;may&nbsp;be&nbsp;used&nbsp;to&nbsp;move&nbsp;files&nbsp;between&nbsp;machines&nbsp;on&nbsp;different&nbsp;<br />&nbsp;&nbsp;&nbsp;networks&nbsp;implementing&nbsp;UDP.&nbsp;&nbsp;(This&nbsp;should&nbsp;not&nbsp;exclude&nbsp;the&nbsp;possibility&nbsp;<br />&nbsp;&nbsp;&nbsp;of&nbsp;implementing&nbsp;TFTP&nbsp;on&nbsp;top&nbsp;of&nbsp;other&nbsp;datagram&nbsp;protocols.)&nbsp;&nbsp;It&nbsp;is&nbsp;<br />&nbsp;&nbsp;&nbsp;designed&nbsp;to&nbsp;be&nbsp;small&nbsp;and&nbsp;easy&nbsp;to&nbsp;implement.&nbsp;&nbsp;Therefore,&nbsp;it&nbsp;lacks&nbsp;most&nbsp;<br />&nbsp;&nbsp;&nbsp;of&nbsp;the&nbsp;features&nbsp;of&nbsp;a&nbsp;regular&nbsp;FTP.&nbsp;&nbsp;The&nbsp;only&nbsp;thing&nbsp;it&nbsp;can&nbsp;do&nbsp;is&nbsp;read&nbsp;<br />&nbsp;&nbsp;&nbsp;and&nbsp;write&nbsp;files&nbsp;(or&nbsp;mail)&nbsp;from/to&nbsp;a&nbsp;remote&nbsp;server.&nbsp;&nbsp;It&nbsp;cannot&nbsp;list&nbsp;<br />&nbsp;&nbsp;&nbsp;directories,&nbsp;and&nbsp;currently&nbsp;has&nbsp;no&nbsp;provisions&nbsp;for&nbsp;user&nbsp;authentication.&nbsp;<br />&nbsp;&nbsp;&nbsp;In&nbsp;common&nbsp;with&nbsp;other&nbsp;Internet&nbsp;protocols,&nbsp;it&nbsp;passes&nbsp;8&nbsp;bit&nbsp;bytes&nbsp;of&nbsp;<br />&nbsp;&nbsp;&nbsp;data.&nbsp;<br />&nbsp;&nbsp;&nbsp;Three&nbsp;modes&nbsp;of&nbsp;transfer&nbsp;are&nbsp;currently&nbsp;supported:&nbsp;netascii&nbsp;(This&nbsp;is&nbsp;<br />&nbsp;&nbsp;&nbsp;ascii&nbsp;as&nbsp;defined&nbsp;in&nbsp;&quot;USA&nbsp;Standard&nbsp;Code&nbsp;for&nbsp;Information&nbsp;Interchange&quot;&nbsp;<br />&nbsp;&nbsp;&nbsp;[1]&nbsp;with&nbsp;the&nbsp;modifications&nbsp;specified&nbsp;in&nbsp;&quot;Telnet&nbsp;Protocol&nbsp;<br />&nbsp;&nbsp;&nbsp;Specification&quot;&nbsp;[3].)&nbsp;&nbsp;Note&nbsp;that&nbsp;it&nbsp;is&nbsp;8&nbsp;bit&nbsp;ascii.&nbsp;&nbsp;The&nbsp;term&nbsp;<br />&nbsp;&nbsp;&nbsp;&quot;netascii&quot;&nbsp;will&nbsp;be&nbsp;used&nbsp;throughout&nbsp;this&nbsp;document&nbsp;to&nbsp;mean&nbsp;this&nbsp;<br />&nbsp;&nbsp;&nbsp;particular&nbsp;version&nbsp;of&nbsp;ascii.);&nbsp;octet&nbsp;(This&nbsp;replaces&nbsp;the&nbsp;&quot;binary&quot;&nbsp;mode&nbsp;<br />&nbsp;&nbsp;&nbsp;of&nbsp;previous&nbsp;versions&nbsp;of&nbsp;this&nbsp;document.)&nbsp;raw&nbsp;8&nbsp;bit&nbsp;bytes;&nbsp;mail,&nbsp;<br />&nbsp;&nbsp;&nbsp;netascii&nbsp;characters&nbsp;sent&nbsp;to&nbsp;a&nbsp;user&nbsp;rather&nbsp;than&nbsp;a&nbsp;file.&nbsp;&nbsp;(The&nbsp;mail&nbsp;<br />&nbsp;&nbsp;&nbsp;mode&nbsp;is&nbsp;obsolete&nbsp;and&nbsp;should&nbsp;not&nbsp;be&nbsp;implemented&nbsp;or&nbsp;used.)&nbsp;&nbsp;Additional&nbsp;<br />&nbsp;&nbsp;&nbsp;modes&nbsp;can&nbsp;be&nbsp;defined&nbsp;by&nbsp;pairs&nbsp;of&nbsp;cooperating&nbsp;hosts.&nbsp;<br />&nbsp;&nbsp;&nbsp;Reference&nbsp;[4]&nbsp;(section&nbsp;4.2)&nbsp;should&nbsp;be&nbsp;consulted&nbsp;for&nbsp;further&nbsp;valuable&nbsp;<br />&nbsp;&nbsp;&nbsp;directives&nbsp;and&nbsp;suggestions&nbsp;on&nbsp;TFTP.&nbsp;<br />2.&nbsp;Overview&nbsp;of&nbsp;the&nbsp;Protocol&nbsp;<br />&nbsp;&nbsp;&nbsp;Any&nbsp;transfer&nbsp;begins&nbsp;with&nbsp;a&nbsp;request&nbsp;to&nbsp;read&nbsp;or&nbsp;write&nbsp;a&nbsp;file,&nbsp;which&nbsp;<br />&nbsp;&nbsp;&nbsp;also&nbsp;serves&nbsp;to&nbsp;request&nbsp;a&nbsp;connection.&nbsp;&nbsp;If&nbsp;the&nbsp;server&nbsp;grants&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;request,&nbsp;the&nbsp;connection&nbsp;is&nbsp;opened&nbsp;and&nbsp;the&nbsp;file&nbsp;is&nbsp;sent&nbsp;in&nbsp;fixed&nbsp;<br />&nbsp;&nbsp;&nbsp;length&nbsp;blocks&nbsp;of&nbsp;512&nbsp;bytes.&nbsp;&nbsp;Each&nbsp;data&nbsp;packet&nbsp;contains&nbsp;one&nbsp;block&nbsp;of&nbsp;<br />&nbsp;&nbsp;&nbsp;data,&nbsp;and&nbsp;must&nbsp;be&nbsp;acknowledged&nbsp;by&nbsp;an&nbsp;acknowledgment&nbsp;packet&nbsp;before&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;next&nbsp;packet&nbsp;can&nbsp;be&nbsp;sent.&nbsp;&nbsp;A&nbsp;data&nbsp;packet&nbsp;of&nbsp;less&nbsp;than&nbsp;512&nbsp;bytes&nbsp;<br />&nbsp;&nbsp;&nbsp;signals&nbsp;termination&nbsp;of&nbsp;a&nbsp;transfer.&nbsp;&nbsp;If&nbsp;a&nbsp;packet&nbsp;gets&nbsp;lost&nbsp;in&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;network,&nbsp;the&nbsp;intended&nbsp;recipient&nbsp;will&nbsp;timeout&nbsp;and&nbsp;may&nbsp;retransmit&nbsp;his&nbsp;<br />&nbsp;&nbsp;&nbsp;last&nbsp;packet&nbsp;(which&nbsp;may&nbsp;be&nbsp;data&nbsp;or&nbsp;an&nbsp;acknowledgment),&nbsp;thus&nbsp;causing&nbsp;<br />&nbsp;&nbsp;&nbsp;the&nbsp;sender&nbsp;of&nbsp;the&nbsp;lost&nbsp;packet&nbsp;to&nbsp;retransmit&nbsp;that&nbsp;lost&nbsp;packet.&nbsp;&nbsp;The&nbsp;<br />&nbsp;&nbsp;&nbsp;sender&nbsp;has&nbsp;to&nbsp;keep&nbsp;just&nbsp;one&nbsp;packet&nbsp;on&nbsp;hand&nbsp;for&nbsp;retransmission,&nbsp;since&nbsp;<br />&nbsp;&nbsp;&nbsp;the&nbsp;lock&nbsp;step&nbsp;acknowledgment&nbsp;guarantees&nbsp;that&nbsp;all&nbsp;older&nbsp;packets&nbsp;have&nbsp;<br />&nbsp;&nbsp;&nbsp;been&nbsp;received.&nbsp;&nbsp;Notice&nbsp;that&nbsp;both&nbsp;machines&nbsp;involved&nbsp;in&nbsp;a&nbsp;transfer&nbsp;are&nbsp;<br />
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