&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;destination=&nbsp;69.&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2.&nbsp;Host&nbsp;&nbsp;B&nbsp;&nbsp;sends&nbsp;&nbsp;a&nbsp;&quot;ACK&quot;&nbsp;(with&nbsp;block&nbsp;number=&nbsp;0)&nbsp;to&nbsp;host&nbsp;A&nbsp;with&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;source=&nbsp;B's&nbsp;TID,&nbsp;destination=&nbsp;A's&nbsp;TID.&nbsp;<br />&nbsp;&nbsp;&nbsp;At&nbsp;this&nbsp;point&nbsp;the&nbsp;connection&nbsp;has&nbsp;been&nbsp;established&nbsp;and&nbsp;the&nbsp;first&nbsp;data&nbsp;<br />&nbsp;&nbsp;&nbsp;packet&nbsp;can&nbsp;be&nbsp;sent&nbsp;by&nbsp;Host&nbsp;A&nbsp;with&nbsp;a&nbsp;sequence&nbsp;number&nbsp;of&nbsp;1.&nbsp;&nbsp;In&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;next&nbsp;step,&nbsp;and&nbsp;in&nbsp;all&nbsp;succeeding&nbsp;steps,&nbsp;the&nbsp;hosts&nbsp;should&nbsp;make&nbsp;sure&nbsp;<br />&nbsp;&nbsp;&nbsp;that&nbsp;the&nbsp;source&nbsp;TID&nbsp;matches&nbsp;the&nbsp;value&nbsp;that&nbsp;was&nbsp;agreed&nbsp;on&nbsp;in&nbsp;steps&nbsp;1&nbsp;<br />&nbsp;&nbsp;&nbsp;and&nbsp;2.&nbsp;&nbsp;If&nbsp;a&nbsp;source&nbsp;TID&nbsp;does&nbsp;not&nbsp;match,&nbsp;the&nbsp;packet&nbsp;should&nbsp;be&nbsp;<br />&nbsp;&nbsp;&nbsp;discarded&nbsp;as&nbsp;erroneously&nbsp;sent&nbsp;from&nbsp;somewhere&nbsp;else.&nbsp;&nbsp;An&nbsp;error&nbsp;packet&nbsp;<br />&nbsp;&nbsp;&nbsp;should&nbsp;be&nbsp;sent&nbsp;to&nbsp;the&nbsp;source&nbsp;of&nbsp;the&nbsp;incorrect&nbsp;packet,&nbsp;while&nbsp;not&nbsp;<br />&nbsp;&nbsp;&nbsp;disturbing&nbsp;the&nbsp;transfer.&nbsp;&nbsp;This&nbsp;can&nbsp;be&nbsp;done&nbsp;only&nbsp;if&nbsp;the&nbsp;TFTP&nbsp;in&nbsp;fact&nbsp;<br />&nbsp;&nbsp;&nbsp;receives&nbsp;a&nbsp;packet&nbsp;with&nbsp;an&nbsp;incorrect&nbsp;TID.&nbsp;&nbsp;If&nbsp;the&nbsp;supporting&nbsp;protocols&nbsp;<br />&nbsp;&nbsp;&nbsp;do&nbsp;not&nbsp;allow&nbsp;it,&nbsp;this&nbsp;particular&nbsp;error&nbsp;condition&nbsp;will&nbsp;not&nbsp;arise.&nbsp;<br />&nbsp;&nbsp;&nbsp;The&nbsp;following&nbsp;example&nbsp;demonstrates&nbsp;a&nbsp;correct&nbsp;operation&nbsp;of&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;protocol&nbsp;in&nbsp;which&nbsp;the&nbsp;above&nbsp;situation&nbsp;can&nbsp;occur.&nbsp;&nbsp;Host&nbsp;A&nbsp;sends&nbsp;a&nbsp;<br />&nbsp;&nbsp;&nbsp;request&nbsp;to&nbsp;host&nbsp;B.&nbsp;Somewhere&nbsp;in&nbsp;the&nbsp;network,&nbsp;the&nbsp;request&nbsp;packet&nbsp;is&nbsp;<br />&nbsp;&nbsp;&nbsp;duplicated,&nbsp;and&nbsp;as&nbsp;a&nbsp;result&nbsp;two&nbsp;acknowledgments&nbsp;are&nbsp;returned&nbsp;to&nbsp;host&nbsp;<br />&nbsp;&nbsp;&nbsp;A,&nbsp;with&nbsp;different&nbsp;TID's&nbsp;chosen&nbsp;on&nbsp;host&nbsp;B&nbsp;in&nbsp;response&nbsp;to&nbsp;the&nbsp;two&nbsp;<br />&nbsp;&nbsp;&nbsp;requests.&nbsp;&nbsp;When&nbsp;the&nbsp;first&nbsp;response&nbsp;arrives,&nbsp;host&nbsp;A&nbsp;continues&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;connection.&nbsp;&nbsp;When&nbsp;the&nbsp;second&nbsp;response&nbsp;to&nbsp;the&nbsp;request&nbsp;arrives,&nbsp;it&nbsp;<br />&nbsp;&nbsp;&nbsp;should&nbsp;be&nbsp;rejected,&nbsp;but&nbsp;there&nbsp;is&nbsp;no&nbsp;reason&nbsp;to&nbsp;terminate&nbsp;the&nbsp;first&nbsp;<br />&nbsp;&nbsp;&nbsp;connection.&nbsp;&nbsp;Therefore,&nbsp;if&nbsp;different&nbsp;TID's&nbsp;are&nbsp;chosen&nbsp;for&nbsp;the&nbsp;two&nbsp;<br />&nbsp;&nbsp;&nbsp;connections&nbsp;on&nbsp;host&nbsp;B&nbsp;and&nbsp;host&nbsp;A&nbsp;checks&nbsp;the&nbsp;source&nbsp;TID's&nbsp;of&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;messages&nbsp;it&nbsp;receives,&nbsp;the&nbsp;first&nbsp;connection&nbsp;can&nbsp;be&nbsp;maintained&nbsp;while&nbsp;<br />&nbsp;&nbsp;&nbsp;the&nbsp;second&nbsp;is&nbsp;rejected&nbsp;by&nbsp;returning&nbsp;an&nbsp;error&nbsp;packet.&nbsp;<br />5.&nbsp;TFTP&nbsp;Packets&nbsp;<br />&nbsp;&nbsp;&nbsp;TFTP&nbsp;supports&nbsp;five&nbsp;types&nbsp;of&nbsp;packets,&nbsp;all&nbsp;of&nbsp;which&nbsp;have&nbsp;been&nbsp;mentioned&nbsp;<br />&nbsp;&nbsp;&nbsp;above:&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;opcode&nbsp;&nbsp;operation&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Read&nbsp;request&nbsp;(RRQ)&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Write&nbsp;request&nbsp;(WRQ)&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Data&nbsp;(DATA)&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Acknowledgment&nbsp;(ACK)&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Error&nbsp;(ERROR)&nbsp;<br />&nbsp;&nbsp;&nbsp;The&nbsp;TFTP&nbsp;header&nbsp;of&nbsp;a&nbsp;packet&nbsp;contains&nbsp;the&nbsp;&nbsp;opcode&nbsp;&nbsp;associated&nbsp;&nbsp;with&nbsp;<br />&nbsp;&nbsp;&nbsp;that&nbsp;packet.&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;5]&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;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;bytes&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;string&nbsp;&nbsp;&nbsp;&nbsp;1&nbsp;byte&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;string&nbsp;&nbsp;&nbsp;1&nbsp;byte&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;------------------------------------------------&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;Opcode&nbsp;|&nbsp;&nbsp;Filename&nbsp;&nbsp;|&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;|&nbsp;&nbsp;&nbsp;&nbsp;Mode&nbsp;&nbsp;&nbsp;&nbsp;|&nbsp;&nbsp;&nbsp;0&nbsp;&nbsp;|&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;------------------------------------------------&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Figure&nbsp;5-1:&nbsp;RRQ/WRQ&nbsp;packet&nbsp;<br />&nbsp;&nbsp;&nbsp;RRQ&nbsp;and&nbsp;WRQ&nbsp;packets&nbsp;(opcodes&nbsp;1&nbsp;and&nbsp;2&nbsp;respectively)&nbsp;have&nbsp;the&nbsp;format&nbsp;<br />&nbsp;&nbsp;&nbsp;shown&nbsp;in&nbsp;Figure&nbsp;5-1.&nbsp;&nbsp;The&nbsp;file&nbsp;name&nbsp;is&nbsp;a&nbsp;sequence&nbsp;of&nbsp;bytes&nbsp;in&nbsp;<br />&nbsp;&nbsp;&nbsp;netascii&nbsp;terminated&nbsp;by&nbsp;a&nbsp;zero&nbsp;byte.&nbsp;&nbsp;The&nbsp;mode&nbsp;field&nbsp;contains&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;string&nbsp;&quot;netascii&quot;,&nbsp;&quot;octet&quot;,&nbsp;or&nbsp;&quot;mail&quot;&nbsp;(or&nbsp;any&nbsp;combination&nbsp;of&nbsp;upper&nbsp;<br />&nbsp;&nbsp;&nbsp;and&nbsp;lower&nbsp;case,&nbsp;such&nbsp;as&nbsp;&quot;NETASCII&quot;,&nbsp;NetAscii&quot;,&nbsp;etc.)&nbsp;in&nbsp;netascii&nbsp;<br />&nbsp;&nbsp;&nbsp;indicating&nbsp;the&nbsp;three&nbsp;modes&nbsp;defined&nbsp;in&nbsp;the&nbsp;protocol.&nbsp;&nbsp;A&nbsp;host&nbsp;which&nbsp;<br />&nbsp;&nbsp;&nbsp;receives&nbsp;netascii&nbsp;mode&nbsp;data&nbsp;must&nbsp;translate&nbsp;the&nbsp;data&nbsp;to&nbsp;its&nbsp;own&nbsp;<br />&nbsp;&nbsp;&nbsp;format.&nbsp;&nbsp;Octet&nbsp;mode&nbsp;is&nbsp;used&nbsp;to&nbsp;transfer&nbsp;a&nbsp;file&nbsp;that&nbsp;is&nbsp;in&nbsp;the&nbsp;8-bit&nbsp;<br />&nbsp;&nbsp;&nbsp;format&nbsp;of&nbsp;the&nbsp;machine&nbsp;from&nbsp;which&nbsp;the&nbsp;file&nbsp;is&nbsp;being&nbsp;transferred.&nbsp;&nbsp;It&nbsp;<br />&nbsp;&nbsp;&nbsp;is&nbsp;assumed&nbsp;that&nbsp;each&nbsp;type&nbsp;of&nbsp;machine&nbsp;has&nbsp;a&nbsp;single&nbsp;8-bit&nbsp;format&nbsp;that&nbsp;<br />&nbsp;&nbsp;&nbsp;is&nbsp;more&nbsp;common,&nbsp;and&nbsp;that&nbsp;that&nbsp;format&nbsp;is&nbsp;chosen.&nbsp;&nbsp;For&nbsp;example,&nbsp;on&nbsp;a&nbsp;<br />&nbsp;&nbsp;&nbsp;DEC-20,&nbsp;a&nbsp;36&nbsp;bit&nbsp;machine,&nbsp;this&nbsp;is&nbsp;four&nbsp;8-bit&nbsp;bytes&nbsp;to&nbsp;a&nbsp;word&nbsp;with&nbsp;<br />&nbsp;&nbsp;&nbsp;four&nbsp;bits&nbsp;of&nbsp;breakage.&nbsp;&nbsp;If&nbsp;a&nbsp;host&nbsp;receives&nbsp;a&nbsp;octet&nbsp;file&nbsp;and&nbsp;then&nbsp;<br />&nbsp;&nbsp;&nbsp;returns&nbsp;it,&nbsp;the&nbsp;returned&nbsp;file&nbsp;must&nbsp;be&nbsp;identical&nbsp;to&nbsp;the&nbsp;original.&nbsp;<br />&nbsp;&nbsp;&nbsp;Mail&nbsp;mode&nbsp;uses&nbsp;the&nbsp;name&nbsp;of&nbsp;a&nbsp;mail&nbsp;recipient&nbsp;in&nbsp;place&nbsp;of&nbsp;a&nbsp;file&nbsp;and&nbsp;<br />&nbsp;&nbsp;&nbsp;must&nbsp;begin&nbsp;with&nbsp;a&nbsp;WRQ.&nbsp;&nbsp;Otherwise&nbsp;it&nbsp;is&nbsp;identical&nbsp;to&nbsp;netascii&nbsp;mode.&nbsp;<br />&nbsp;&nbsp;&nbsp;The&nbsp;mail&nbsp;recipient&nbsp;string&nbsp;should&nbsp;be&nbsp;of&nbsp;the&nbsp;form&nbsp;&quot;username&quot;&nbsp;or&nbsp;<br />&nbsp;&nbsp;&nbsp;&quot;<a href="mailto:username@hostname".">username@hostname".</a>&nbsp;&nbsp;If&nbsp;the&nbsp;second&nbsp;form&nbsp;is&nbsp;used,&nbsp;it&nbsp;allows&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;option&nbsp;of&nbsp;mail&nbsp;forwarding&nbsp;by&nbsp;a&nbsp;relay&nbsp;computer.&nbsp;<br />&nbsp;&nbsp;&nbsp;The&nbsp;discussion&nbsp;above&nbsp;assumes&nbsp;that&nbsp;both&nbsp;the&nbsp;sender&nbsp;and&nbsp;recipient&nbsp;are&nbsp;<br />&nbsp;&nbsp;&nbsp;operating&nbsp;in&nbsp;the&nbsp;same&nbsp;mode,&nbsp;but&nbsp;there&nbsp;is&nbsp;no&nbsp;reason&nbsp;that&nbsp;this&nbsp;has&nbsp;to&nbsp;<br />&nbsp;&nbsp;&nbsp;be&nbsp;the&nbsp;case.&nbsp;&nbsp;For&nbsp;example,&nbsp;one&nbsp;might&nbsp;build&nbsp;a&nbsp;storage&nbsp;server.&nbsp;&nbsp;There&nbsp;<br />&nbsp;&nbsp;&nbsp;is&nbsp;no&nbsp;reason&nbsp;that&nbsp;such&nbsp;a&nbsp;machine&nbsp;needs&nbsp;to&nbsp;translate&nbsp;netascii&nbsp;into&nbsp;its&nbsp;<br />&nbsp;&nbsp;&nbsp;own&nbsp;form&nbsp;of&nbsp;text.&nbsp;&nbsp;Rather,&nbsp;the&nbsp;sender&nbsp;might&nbsp;send&nbsp;files&nbsp;in&nbsp;netascii,&nbsp;<br />&nbsp;&nbsp;&nbsp;but&nbsp;the&nbsp;storage&nbsp;server&nbsp;might&nbsp;simply&nbsp;store&nbsp;them&nbsp;without&nbsp;translation&nbsp;in&nbsp;<br />&nbsp;&nbsp;&nbsp;8-bit&nbsp;format.&nbsp;&nbsp;Another&nbsp;such&nbsp;situation&nbsp;is&nbsp;a&nbsp;problem&nbsp;that&nbsp;currently&nbsp;<br />&nbsp;&nbsp;&nbsp;exists&nbsp;on&nbsp;DEC-20&nbsp;systems.&nbsp;&nbsp;Neither&nbsp;netascii&nbsp;nor&nbsp;octet&nbsp;accesses&nbsp;all&nbsp;<br />&nbsp;&nbsp;&nbsp;the&nbsp;bits&nbsp;in&nbsp;a&nbsp;word.&nbsp;&nbsp;One&nbsp;might&nbsp;create&nbsp;a&nbsp;special&nbsp;mode&nbsp;for&nbsp;such&nbsp;a&nbsp;<br />&nbsp;&nbsp;&nbsp;machine&nbsp;which&nbsp;read&nbsp;all&nbsp;the&nbsp;bits&nbsp;in&nbsp;a&nbsp;word,&nbsp;but&nbsp;in&nbsp;which&nbsp;the&nbsp;receiver&nbsp;<br />&nbsp;&nbsp;&nbsp;stored&nbsp;the&nbsp;information&nbsp;in&nbsp;8-bit&nbsp;format.&nbsp;&nbsp;When&nbsp;such&nbsp;a&nbsp;file&nbsp;is&nbsp;<br />&nbsp;&nbsp;&nbsp;retrieved&nbsp;from&nbsp;the&nbsp;storage&nbsp;site,&nbsp;it&nbsp;must&nbsp;be&nbsp;restored&nbsp;to&nbsp;its&nbsp;original&nbsp;<br />&nbsp;&nbsp;&nbsp;form&nbsp;to&nbsp;be&nbsp;useful,&nbsp;so&nbsp;the&nbsp;reverse&nbsp;mode&nbsp;must&nbsp;also&nbsp;be&nbsp;implemented.&nbsp;&nbsp;The&nbsp;<br />&nbsp;&nbsp;&nbsp;user&nbsp;site&nbsp;will&nbsp;have&nbsp;to&nbsp;remember&nbsp;some&nbsp;information&nbsp;to&nbsp;achieve&nbsp;this.&nbsp;&nbsp;In&nbsp;<br />&nbsp;&nbsp;&nbsp;both&nbsp;of&nbsp;these&nbsp;examples,&nbsp;the&nbsp;request&nbsp;packets&nbsp;would&nbsp;specify&nbsp;octet&nbsp;mode&nbsp;<br />&nbsp;&nbsp;&nbsp;to&nbsp;the&nbsp;foreign&nbsp;host,&nbsp;but&nbsp;the&nbsp;local&nbsp;host&nbsp;would&nbsp;be&nbsp;in&nbsp;some&nbsp;other&nbsp;mode.&nbsp;<br />&nbsp;&nbsp;&nbsp;No&nbsp;such&nbsp;machine&nbsp;or&nbsp;application&nbsp;specific&nbsp;modes&nbsp;have&nbsp;been&nbsp;specified&nbsp;in&nbsp;<br />&nbsp;&nbsp;&nbsp;TFTP,&nbsp;but&nbsp;one&nbsp;would&nbsp;be&nbsp;compatible&nbsp;with&nbsp;this&nbsp;specification.&nbsp;<br />&nbsp;&nbsp;&nbsp;It&nbsp;is&nbsp;also&nbsp;possible&nbsp;to&nbsp;define&nbsp;other&nbsp;modes&nbsp;for&nbsp;cooperating&nbsp;pairs&nbsp;of&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;6]&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;hosts,&nbsp;although&nbsp;this&nbsp;must&nbsp;be&nbsp;done&nbsp;with&nbsp;care.&nbsp;&nbsp;There&nbsp;is&nbsp;no&nbsp;requirement&nbsp;<br />&nbsp;&nbsp;&nbsp;that&nbsp;any&nbsp;other&nbsp;hosts&nbsp;implement&nbsp;these.&nbsp;&nbsp;There&nbsp;is&nbsp;no&nbsp;central&nbsp;authority&nbsp;<br />&nbsp;&nbsp;&nbsp;that&nbsp;will&nbsp;define&nbsp;these&nbsp;modes&nbsp;or&nbsp;assign&nbsp;them&nbsp;names.&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;bytes&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2&nbsp;bytes&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;n&nbsp;bytes&nbsp;<br />