&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a.&nbsp;Parties&nbsp;may&nbsp;only&nbsp;request&nbsp;a&nbsp;change&nbsp;in&nbsp;option&nbsp;status;&nbsp;i.e.,&nbsp;a&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;party&nbsp;may&nbsp;not&nbsp;send&nbsp;out&nbsp;a&nbsp;&quot;request&quot;&nbsp;merely&nbsp;to&nbsp;announce&nbsp;what&nbsp;mode&nbsp;it&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;is&nbsp;in.&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;b.&nbsp;If&nbsp;a&nbsp;party&nbsp;receives&nbsp;what&nbsp;appears&nbsp;to&nbsp;be&nbsp;a&nbsp;request&nbsp;to&nbsp;enter&nbsp;some&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;mode&nbsp;it&nbsp;is&nbsp;already&nbsp;in,&nbsp;the&nbsp;request&nbsp;should&nbsp;not&nbsp;be&nbsp;acknowledged.&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;This&nbsp;non-response&nbsp;is&nbsp;essential&nbsp;to&nbsp;prevent&nbsp;endless&nbsp;loops&nbsp;in&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;negotiation.&nbsp;&nbsp;It&nbsp;is&nbsp;required&nbsp;that&nbsp;a&nbsp;response&nbsp;be&nbsp;sent&nbsp;to&nbsp;requests&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;for&nbsp;a&nbsp;change&nbsp;of&nbsp;mode&nbsp;--&nbsp;even&nbsp;if&nbsp;the&nbsp;mode&nbsp;is&nbsp;not&nbsp;changed.&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;c.&nbsp;Whenever&nbsp;one&nbsp;party&nbsp;sends&nbsp;an&nbsp;option&nbsp;command&nbsp;to&nbsp;a&nbsp;second&nbsp;party,&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;whether&nbsp;as&nbsp;a&nbsp;request&nbsp;or&nbsp;an&nbsp;acknowledgment,&nbsp;and&nbsp;use&nbsp;of&nbsp;the&nbsp;option&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;will&nbsp;have&nbsp;any&nbsp;effect&nbsp;on&nbsp;the&nbsp;processing&nbsp;of&nbsp;the&nbsp;data&nbsp;being&nbsp;sent&nbsp;from&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;the&nbsp;first&nbsp;party&nbsp;to&nbsp;the&nbsp;second,&nbsp;then&nbsp;the&nbsp;command&nbsp;must&nbsp;be&nbsp;inserted&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;in&nbsp;the&nbsp;data&nbsp;stream&nbsp;at&nbsp;the&nbsp;point&nbsp;where&nbsp;it&nbsp;is&nbsp;desired&nbsp;that&nbsp;it&nbsp;take&nbsp;<br />Postel&nbsp;&amp;&nbsp;Reynolds&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;2]&nbsp;<br />&nbsp;<br />RFC&nbsp;854&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;May&nbsp;1983&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;effect.&nbsp;&nbsp;(It&nbsp;should&nbsp;be&nbsp;noted&nbsp;that&nbsp;some&nbsp;time&nbsp;will&nbsp;elapse&nbsp;between&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;the&nbsp;transmission&nbsp;of&nbsp;a&nbsp;request&nbsp;and&nbsp;the&nbsp;receipt&nbsp;of&nbsp;an&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;acknowledgment,&nbsp;which&nbsp;may&nbsp;be&nbsp;negative.&nbsp;&nbsp;Thus,&nbsp;a&nbsp;host&nbsp;may&nbsp;wish&nbsp;to&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;buffer&nbsp;data,&nbsp;after&nbsp;requesting&nbsp;an&nbsp;option,&nbsp;until&nbsp;it&nbsp;learns&nbsp;whether&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;the&nbsp;request&nbsp;is&nbsp;accepted&nbsp;or&nbsp;rejected,&nbsp;in&nbsp;order&nbsp;to&nbsp;hide&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&quot;uncertainty&nbsp;period&quot;&nbsp;from&nbsp;the&nbsp;user.)&nbsp;<br />&nbsp;&nbsp;&nbsp;Option&nbsp;requests&nbsp;are&nbsp;likely&nbsp;to&nbsp;flurry&nbsp;back&nbsp;and&nbsp;forth&nbsp;when&nbsp;a&nbsp;TELNET&nbsp;<br />&nbsp;&nbsp;&nbsp;connection&nbsp;is&nbsp;first&nbsp;established,&nbsp;as&nbsp;each&nbsp;party&nbsp;attempts&nbsp;to&nbsp;get&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;best&nbsp;possible&nbsp;service&nbsp;from&nbsp;the&nbsp;other&nbsp;party.&nbsp;&nbsp;Beyond&nbsp;that,&nbsp;however,&nbsp;<br />&nbsp;&nbsp;&nbsp;options&nbsp;can&nbsp;be&nbsp;used&nbsp;to&nbsp;dynamically&nbsp;modify&nbsp;the&nbsp;characteristics&nbsp;of&nbsp;the&nbsp;<br />&nbsp;&nbsp;&nbsp;connection&nbsp;to&nbsp;suit&nbsp;changing&nbsp;local&nbsp;conditions.&nbsp;&nbsp;For&nbsp;example,&nbsp;the&nbsp;NVT,&nbsp;<br />&nbsp;&nbsp;&nbsp;as&nbsp;will&nbsp;be&nbsp;explained&nbsp;later,&nbsp;uses&nbsp;a&nbsp;transmission&nbsp;discipline&nbsp;well&nbsp;<br />&nbsp;&nbsp;&nbsp;suited&nbsp;to&nbsp;the&nbsp;many&nbsp;&quot;line&nbsp;at&nbsp;a&nbsp;time&quot;&nbsp;applications&nbsp;such&nbsp;as&nbsp;BASIC,&nbsp;but&nbsp;<br />&nbsp;&nbsp;&nbsp;poorly&nbsp;suited&nbsp;to&nbsp;the&nbsp;many&nbsp;&quot;character&nbsp;at&nbsp;a&nbsp;time&quot;&nbsp;applications&nbsp;such&nbsp;as&nbsp;<br />&nbsp;&nbsp;&nbsp;NLS.&nbsp;&nbsp;A&nbsp;server&nbsp;might&nbsp;elect&nbsp;to&nbsp;devote&nbsp;the&nbsp;extra&nbsp;processor&nbsp;overhead&nbsp;<br />&nbsp;&nbsp;&nbsp;required&nbsp;for&nbsp;a&nbsp;&quot;character&nbsp;at&nbsp;a&nbsp;time&quot;&nbsp;discipline&nbsp;when&nbsp;it&nbsp;was&nbsp;suitable&nbsp;<br />&nbsp;&nbsp;&nbsp;for&nbsp;the&nbsp;local&nbsp;process&nbsp;and&nbsp;would&nbsp;negotiate&nbsp;an&nbsp;appropriate&nbsp;option.&nbsp;<br />&nbsp;&nbsp;&nbsp;However,&nbsp;rather&nbsp;than&nbsp;then&nbsp;being&nbsp;permanently&nbsp;burdened&nbsp;with&nbsp;the&nbsp;extra&nbsp;<br />&nbsp;&nbsp;&nbsp;processing&nbsp;overhead,&nbsp;it&nbsp;could&nbsp;switch&nbsp;(i.e.,&nbsp;negotiate)&nbsp;back&nbsp;to&nbsp;NVT&nbsp;<br />&nbsp;&nbsp;&nbsp;when&nbsp;the&nbsp;detailed&nbsp;control&nbsp;was&nbsp;no&nbsp;longer&nbsp;necessary.&nbsp;<br />&nbsp;&nbsp;&nbsp;It&nbsp;is&nbsp;possible&nbsp;for&nbsp;requests&nbsp;initiated&nbsp;by&nbsp;processes&nbsp;to&nbsp;stimulate&nbsp;a&nbsp;<br />&nbsp;&nbsp;&nbsp;nonterminating&nbsp;request&nbsp;loop&nbsp;if&nbsp;the&nbsp;process&nbsp;responds&nbsp;to&nbsp;a&nbsp;rejection&nbsp;by&nbsp;<br />&nbsp;&nbsp;&nbsp;merely&nbsp;re-requesting&nbsp;the&nbsp;option.&nbsp;&nbsp;To&nbsp;prevent&nbsp;such&nbsp;loops&nbsp;from&nbsp;<br />&nbsp;&nbsp;&nbsp;occurring,&nbsp;rejected&nbsp;requests&nbsp;should&nbsp;not&nbsp;be&nbsp;repeated&nbsp;until&nbsp;something&nbsp;<br />&nbsp;&nbsp;&nbsp;changes.&nbsp;&nbsp;Operationally,&nbsp;this&nbsp;can&nbsp;mean&nbsp;the&nbsp;process&nbsp;is&nbsp;running&nbsp;a&nbsp;<br />&nbsp;&nbsp;&nbsp;different&nbsp;program,&nbsp;or&nbsp;the&nbsp;user&nbsp;has&nbsp;given&nbsp;another&nbsp;command,&nbsp;or&nbsp;whatever&nbsp;<br />&nbsp;&nbsp;&nbsp;makes&nbsp;sense&nbsp;in&nbsp;the&nbsp;context&nbsp;of&nbsp;the&nbsp;given&nbsp;process&nbsp;and&nbsp;the&nbsp;given&nbsp;option.&nbsp;<br />&nbsp;&nbsp;&nbsp;A&nbsp;good&nbsp;rule&nbsp;of&nbsp;thumb&nbsp;is&nbsp;that&nbsp;a&nbsp;re-request&nbsp;should&nbsp;only&nbsp;occur&nbsp;as&nbsp;a&nbsp;<br />&nbsp;&nbsp;&nbsp;result&nbsp;of&nbsp;subsequent&nbsp;information&nbsp;from&nbsp;the&nbsp;other&nbsp;end&nbsp;of&nbsp;the&nbsp;connection&nbsp;<br />&nbsp;&nbsp;&nbsp;or&nbsp;when&nbsp;demanded&nbsp;by&nbsp;local&nbsp;human&nbsp;intervention.&nbsp;<br />&nbsp;&nbsp;&nbsp;Option&nbsp;designers&nbsp;should&nbsp;not&nbsp;feel&nbsp;constrained&nbsp;by&nbsp;the&nbsp;somewhat&nbsp;limited&nbsp;<br />&nbsp;&nbsp;&nbsp;syntax&nbsp;available&nbsp;for&nbsp;option&nbsp;negotiation.&nbsp;&nbsp;The&nbsp;intent&nbsp;of&nbsp;the&nbsp;simple&nbsp;<br />&nbsp;&nbsp;&nbsp;syntax&nbsp;is&nbsp;to&nbsp;make&nbsp;it&nbsp;easy&nbsp;to&nbsp;have&nbsp;options&nbsp;--&nbsp;since&nbsp;it&nbsp;is&nbsp;<br />&nbsp;&nbsp;&nbsp;correspondingly&nbsp;easy&nbsp;to&nbsp;profess&nbsp;ignorance&nbsp;about&nbsp;them.&nbsp;&nbsp;If&nbsp;some&nbsp;<br />&nbsp;&nbsp;&nbsp;particular&nbsp;option&nbsp;requires&nbsp;a&nbsp;richer&nbsp;negotiation&nbsp;structure&nbsp;than&nbsp;<br />&nbsp;&nbsp;&nbsp;possible&nbsp;within&nbsp;&quot;DO,&nbsp;DON'T,&nbsp;WILL,&nbsp;WON'T&quot;,&nbsp;the&nbsp;proper&nbsp;tack&nbsp;is&nbsp;to&nbsp;use&nbsp;<br />&nbsp;&nbsp;&nbsp;&quot;DO,&nbsp;DON'T,&nbsp;WILL,&nbsp;WON'T&quot;&nbsp;to&nbsp;establish&nbsp;that&nbsp;both&nbsp;parties&nbsp;understand&nbsp;<br />&nbsp;&nbsp;&nbsp;the&nbsp;option,&nbsp;and&nbsp;once&nbsp;this&nbsp;is&nbsp;accomplished&nbsp;a&nbsp;more&nbsp;exotic&nbsp;syntax&nbsp;can&nbsp;be&nbsp;<br />&nbsp;&nbsp;&nbsp;used&nbsp;freely.&nbsp;&nbsp;For&nbsp;example,&nbsp;a&nbsp;party&nbsp;might&nbsp;send&nbsp;a&nbsp;request&nbsp;to&nbsp;alter&nbsp;<br />&nbsp;&nbsp;&nbsp;(establish)&nbsp;line&nbsp;length.&nbsp;&nbsp;If&nbsp;it&nbsp;is&nbsp;accepted,&nbsp;then&nbsp;a&nbsp;different&nbsp;syntax&nbsp;<br />&nbsp;&nbsp;&nbsp;can&nbsp;be&nbsp;used&nbsp;for&nbsp;actually&nbsp;negotiating&nbsp;the&nbsp;line&nbsp;length&nbsp;--&nbsp;such&nbsp;a&nbsp;<br />&nbsp;&nbsp;&nbsp;&quot;sub-negotiation&quot;&nbsp;might&nbsp;include&nbsp;fields&nbsp;for&nbsp;minimum&nbsp;allowable,&nbsp;maximum&nbsp;<br />&nbsp;&nbsp;&nbsp;allowable&nbsp;and&nbsp;desired&nbsp;line&nbsp;lengths.&nbsp;&nbsp;The&nbsp;important&nbsp;concept&nbsp;is&nbsp;that&nbsp;<br />Postel&nbsp;&amp;&nbsp;Reynolds&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;3]&nbsp;<br />&nbsp;<br />RFC&nbsp;854&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;May&nbsp;1983&nbsp;<br />&nbsp;&nbsp;&nbsp;such&nbsp;expanded&nbsp;negotiations&nbsp;should&nbsp;never&nbsp;begin&nbsp;until&nbsp;some&nbsp;prior&nbsp;<br />&nbsp;&nbsp;&nbsp;(standard)&nbsp;negotiation&nbsp;has&nbsp;established&nbsp;that&nbsp;both&nbsp;parties&nbsp;are&nbsp;capable&nbsp;<br />&nbsp;&nbsp;&nbsp;of&nbsp;parsing&nbsp;the&nbsp;expanded&nbsp;syntax.&nbsp;<br />&nbsp;&nbsp;&nbsp;In&nbsp;summary,&nbsp;WILL&nbsp;XXX&nbsp;is&nbsp;sent,&nbsp;by&nbsp;either&nbsp;party,&nbsp;to&nbsp;indicate&nbsp;that&nbsp;<br />&nbsp;&nbsp;&nbsp;party's&nbsp;desire&nbsp;(offer)&nbsp;to&nbsp;begin&nbsp;performing&nbsp;option&nbsp;XXX,&nbsp;DO&nbsp;XXX&nbsp;and&nbsp;<br />&nbsp;&nbsp;&nbsp;DON'T&nbsp;XXX&nbsp;being&nbsp;its&nbsp;positive&nbsp;and&nbsp;negative&nbsp;acknowledgments;&nbsp;similarly,&nbsp;<br />&nbsp;&nbsp;&nbsp;DO&nbsp;XXX&nbsp;is&nbsp;sent&nbsp;to&nbsp;indicate&nbsp;a&nbsp;desire&nbsp;(request)&nbsp;that&nbsp;the&nbsp;other&nbsp;party&nbsp;<br />&nbsp;&nbsp;&nbsp;(i.e.,&nbsp;the&nbsp;recipient&nbsp;of&nbsp;the&nbsp;DO)&nbsp;begin&nbsp;performing&nbsp;option&nbsp;XXX,&nbsp;WILL&nbsp;XXX&nbsp;<br />&nbsp;&nbsp;&nbsp;and&nbsp;WON'T&nbsp;XXX&nbsp;being&nbsp;the&nbsp;positive&nbsp;and&nbsp;negative&nbsp;acknowledgments.&nbsp;&nbsp;Since&nbsp;<br />&nbsp;&nbsp;&nbsp;the&nbsp;NVT&nbsp;is&nbsp;what&nbsp;is&nbsp;left&nbsp;when&nbsp;no&nbsp;options&nbsp;are&nbsp;enabled,&nbsp;the&nbsp;DON'T&nbsp;and&nbsp;<br />&nbsp;&nbsp;&nbsp;WON'T&nbsp;responses&nbsp;are&nbsp;guaranteed&nbsp;to&nbsp;leave&nbsp;the&nbsp;connection&nbsp;in&nbsp;a&nbsp;state&nbsp;<br />&nbsp;&nbsp;&nbsp;which&nbsp;both&nbsp;ends&nbsp;can&nbsp;handle.&nbsp;&nbsp;Thus,&nbsp;all&nbsp;hosts&nbsp;may&nbsp;implement&nbsp;their&nbsp;<br />&nbsp;&nbsp;&nbsp;TELNET&nbsp;processes&nbsp;to&nbsp;be&nbsp;totally&nbsp;unaware&nbsp;of&nbsp;options&nbsp;that&nbsp;are&nbsp;not&nbsp;<br />&nbsp;&nbsp;&nbsp;supported,&nbsp;simply&nbsp;returning&nbsp;a&nbsp;rejection&nbsp;to&nbsp;(i.e.,&nbsp;refusing)&nbsp;any&nbsp;<br />&nbsp;&nbsp;&nbsp;option&nbsp;request&nbsp;that&nbsp;cannot&nbsp;be&nbsp;understood.&nbsp;<br />&nbsp;&nbsp;&nbsp;As&nbsp;much&nbsp;as&nbsp;possible,&nbsp;the&nbsp;TELNET&nbsp;protocol&nbsp;has&nbsp;been&nbsp;made&nbsp;server-user&nbsp;<br />&nbsp;&nbsp;&nbsp;symmetrical&nbsp;so&nbsp;that&nbsp;it&nbsp;easily&nbsp;and&nbsp;naturally&nbsp;covers&nbsp;the&nbsp;user-user&nbsp;<br />&nbsp;&nbsp;&nbsp;(linking)&nbsp;and&nbsp;server-server&nbsp;(cooperating&nbsp;processes)&nbsp;cases.&nbsp;&nbsp;It&nbsp;is&nbsp;<br />&nbsp;&nbsp;&nbsp;hoped,&nbsp;but&nbsp;not&nbsp;absolutely&nbsp;required,&nbsp;that&nbsp;options&nbsp;will&nbsp;further&nbsp;this&nbsp;<br />&nbsp;&nbsp;&nbsp;intent.&nbsp;&nbsp;In&nbsp;any&nbsp;case,&nbsp;it&nbsp;is&nbsp;explicitly&nbsp;acknowledged&nbsp;that&nbsp;symmetry&nbsp;is&nbsp;<br />&nbsp;&nbsp;&nbsp;an&nbsp;operating&nbsp;principle&nbsp;rather&nbsp;than&nbsp;an&nbsp;ironclad&nbsp;rule.&nbsp;<br />&nbsp;&nbsp;&nbsp;A&nbsp;companion&nbsp;document,&nbsp;&quot;TELNET&nbsp;Option&nbsp;Specifications,&quot;&nbsp;should&nbsp;be&nbsp;<br />