CINXE.COM

<!DOCTYPE html> <html class="client-nojs vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-sticky-header-enabled vector-toc-available" lang="en" dir="ltr"> <head> <meta charset="UTF-8"> <title>Consistent Overhead Byte Stuffing - Wikipedia</title> <script>(function(){var className="client-js vector-feature-language-in-header-enabled vector-feature-language-in-main-page-header-disabled vector-feature-page-tools-pinned-disabled vector-feature-toc-pinned-clientpref-1 vector-feature-main-menu-pinned-disabled vector-feature-limited-width-clientpref-1 vector-feature-limited-width-content-enabled vector-feature-custom-font-size-clientpref-1 vector-feature-appearance-pinned-clientpref-1 vector-feature-night-mode-enabled skin-theme-clientpref-day vector-sticky-header-enabled vector-toc-available";var cookie=document.cookie.match(/(?:^|; )enwikimwclientpreferences=([^;]+)/);if(cookie){cookie[1].split('%2C').forEach(function(pref){className=className.replace(new RegExp('(^| )'+pref.replace(/-clientpref-\w+$|[^\w-]+/g,'')+'-clientpref-\\w+( |$)'),'$1'+pref+'$2');});}document.documentElement.className=className;}());RLCONF={"wgBreakFrames":false,"wgSeparatorTransformTable":["",""],"wgDigitTransformTable":["",""],"wgDefaultDateFormat":"dmy", "wgMonthNames":["","January","February","March","April","May","June","July","August","September","October","November","December"],"wgRequestId":"f066c325-b331-46cf-9561-76fc63e1b5f7","wgCanonicalNamespace":"","wgCanonicalSpecialPageName":false,"wgNamespaceNumber":0,"wgPageName":"Consistent_Overhead_Byte_Stuffing","wgTitle":"Consistent Overhead Byte Stuffing","wgCurRevisionId":1244549534,"wgRevisionId":1244549534,"wgArticleId":29719643,"wgIsArticle":true,"wgIsRedirect":false,"wgAction":"view","wgUserName":null,"wgUserGroups":["*"],"wgCategories":["Articles with short description","Short description matches Wikidata","Encodings"],"wgPageViewLanguage":"en","wgPageContentLanguage":"en","wgPageContentModel":"wikitext","wgRelevantPageName":"Consistent_Overhead_Byte_Stuffing","wgRelevantArticleId":29719643,"wgIsProbablyEditable":true,"wgRelevantPageIsProbablyEditable":true,"wgRestrictionEdit":[],"wgRestrictionMove":[],"wgNoticeProject":"wikipedia","wgCiteReferencePreviewsActive":false, "wgFlaggedRevsParams":{"tags":{"status":{"levels":1}}},"wgMediaViewerOnClick":true,"wgMediaViewerEnabledByDefault":true,"wgPopupsFlags":0,"wgVisualEditor":{"pageLanguageCode":"en","pageLanguageDir":"ltr","pageVariantFallbacks":"en"},"wgMFDisplayWikibaseDescriptions":{"search":true,"watchlist":true,"tagline":false,"nearby":true},"wgWMESchemaEditAttemptStepOversample":false,"wgWMEPageLength":10000,"wgEditSubmitButtonLabelPublish":true,"wgULSPosition":"interlanguage","wgULSisCompactLinksEnabled":false,"wgVector2022LanguageInHeader":true,"wgULSisLanguageSelectorEmpty":false,"wgWikibaseItemId":"Q5163224","wgCheckUserClientHintsHeadersJsApi":["brands","architecture","bitness","fullVersionList","mobile","model","platform","platformVersion"],"GEHomepageSuggestedEditsEnableTopics":true,"wgGETopicsMatchModeEnabled":false,"wgGEStructuredTaskRejectionReasonTextInputEnabled":false,"wgGELevelingUpEnabledForUser":false};RLSTATE={"ext.globalCssJs.user.styles":"ready","site.styles":"ready", "user.styles":"ready","ext.globalCssJs.user":"ready","user":"ready","user.options":"loading","ext.cite.styles":"ready","ext.pygments":"ready","skins.vector.search.codex.styles":"ready","skins.vector.styles":"ready","skins.vector.icons":"ready","ext.wikimediamessages.styles":"ready","ext.visualEditor.desktopArticleTarget.noscript":"ready","ext.uls.interlanguage":"ready","wikibase.client.init":"ready","ext.wikimediaBadges":"ready"};RLPAGEMODULES=["ext.cite.ux-enhancements","ext.pygments.view","site","mediawiki.page.ready","mediawiki.toc","skins.vector.js","ext.centralNotice.geoIP","ext.centralNotice.startUp","ext.gadget.ReferenceTooltips","ext.gadget.switcher","ext.urlShortener.toolbar","ext.centralauth.centralautologin","mmv.bootstrap","ext.popups","ext.visualEditor.desktopArticleTarget.init","ext.visualEditor.targetLoader","ext.echo.centralauth","ext.eventLogging","ext.wikimediaEvents","ext.navigationTiming","ext.uls.interface","ext.cx.eventlogging.campaigns","ext.cx.uls.quick.actions" ,"wikibase.client.vector-2022","ext.checkUser.clientHints","ext.growthExperiments.SuggestedEditSession"];</script> <script>(RLQ=window.RLQ||[]).push(function(){mw.loader.impl(function(){return["user.options@12s5i",function($,jQuery,require,module){mw.user.tokens.set({"patrolToken":"+\\","watchToken":"+\\","csrfToken":"+\\"}); }];});});</script> <link rel="stylesheet" href="/w/load.php?lang=en&modules=ext.cite.styles%7Cext.pygments%2CwikimediaBadges%7Cext.uls.interlanguage%7Cext.visualEditor.desktopArticleTarget.noscript%7Cext.wikimediamessages.styles%7Cskins.vector.icons%2Cstyles%7Cskins.vector.search.codex.styles%7Cwikibase.client.init&only=styles&skin=vector-2022"> <script async="" src="/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector-2022"></script> <meta name="ResourceLoaderDynamicStyles" content=""> <link rel="stylesheet" href="/w/load.php?lang=en&modules=site.styles&only=styles&skin=vector-2022"> <meta name="generator" content="MediaWiki 1.44.0-wmf.17"> <meta name="referrer" content="origin"> <meta name="referrer" content="origin-when-cross-origin"> <meta name="robots" content="max-image-preview:standard"> <meta name="format-detection" content="telephone=no"> <meta name="viewport" content="width=1120"> <meta property="og:title" content="Consistent Overhead Byte Stuffing - Wikipedia"> <meta property="og:type" content="website"> <link rel="preconnect" href="//upload.wikimedia.org"> <link rel="alternate" media="only screen and (max-width: 640px)" href="//en.m.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuffing"> <link rel="alternate" type="application/x-wiki" title="Edit this page" href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit"> <link rel="apple-touch-icon" href="/static/apple-touch/wikipedia.png"> <link rel="icon" href="/static/favicon/wikipedia.ico"> <link rel="search" type="application/opensearchdescription+xml" href="/w/rest.php/v1/search" title="Wikipedia (en)"> <link rel="EditURI" type="application/rsd+xml" href="//en.wikipedia.org/w/api.php?action=rsd"> <link rel="canonical" href="https://en.wikipedia.org/wiki/Consistent_Overhead_Byte_Stuffing"> <link rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en"> <link rel="alternate" type="application/atom+xml" title="Wikipedia Atom feed" href="/w/index.php?title=Special:RecentChanges&feed=atom"> <link rel="dns-prefetch" href="//meta.wikimedia.org" /> <link rel="dns-prefetch" href="login.wikimedia.org"> </head> <body class="skin--responsive skin-vector skin-vector-search-vue mediawiki ltr sitedir-ltr mw-hide-empty-elt ns-0 ns-subject mw-editable page-Consistent_Overhead_Byte_Stuffing rootpage-Consistent_Overhead_Byte_Stuffing skin-vector-2022 action-view"><a class="mw-jump-link" href="#bodyContent">Jump to content</a> <div class="vector-header-container"> <header class="vector-header mw-header"> <div class="vector-header-start"> <nav class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-dropdown" class="vector-dropdown vector-main-menu-dropdown vector-button-flush-left vector-button-flush-right" title="Main menu" > <input type="checkbox" id="vector-main-menu-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-main-menu-dropdown" class="vector-dropdown-checkbox " aria-label="Main menu" > <label id="vector-main-menu-dropdown-label" for="vector-main-menu-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-menu mw-ui-icon-wikimedia-menu"></span> <span class="vector-dropdown-label-text">Main menu</span> </label> <div class="vector-dropdown-content"> <div id="vector-main-menu-unpinned-container" class="vector-unpinned-container"> <div id="vector-main-menu" class="vector-main-menu vector-pinnable-element"> <div class="vector-pinnable-header vector-main-menu-pinnable-header vector-pinnable-header-unpinned" data-feature-name="main-menu-pinned" data-pinnable-element-id="vector-main-menu" data-pinned-container-id="vector-main-menu-pinned-container" data-unpinned-container-id="vector-main-menu-unpinned-container" > <div class="vector-pinnable-header-label">Main menu</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-main-menu.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-main-menu.unpin">hide</button> </div> <div id="p-navigation" class="vector-menu mw-portlet mw-portlet-navigation" > <div class="vector-menu-heading"> Navigation </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-mainpage-description" class="mw-list-item"><a href="/wiki/Main_Page" title="Visit the main page [z]" accesskey="z"><span>Main page</span></a></li><li id="n-contents" class="mw-list-item"><a href="/wiki/Wikipedia:Contents" title="Guides to browsing Wikipedia"><span>Contents</span></a></li><li id="n-currentevents" class="mw-list-item"><a href="/wiki/Portal:Current_events" title="Articles related to current events"><span>Current events</span></a></li><li id="n-randompage" class="mw-list-item"><a href="/wiki/Special:Random" title="Visit a randomly selected article [x]" accesskey="x"><span>Random article</span></a></li><li id="n-aboutsite" class="mw-list-item"><a href="/wiki/Wikipedia:About" title="Learn about Wikipedia and how it works"><span>About Wikipedia</span></a></li><li id="n-contactpage" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us" title="How to contact Wikipedia"><span>Contact us</span></a></li> </ul> </div> </div> <div id="p-interaction" class="vector-menu mw-portlet mw-portlet-interaction" > <div class="vector-menu-heading"> Contribute </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="n-help" class="mw-list-item"><a href="/wiki/Help:Contents" title="Guidance on how to use and edit Wikipedia"><span>Help</span></a></li><li id="n-introduction" class="mw-list-item"><a href="/wiki/Help:Introduction" title="Learn how to edit Wikipedia"><span>Learn to edit</span></a></li><li id="n-portal" class="mw-list-item"><a href="/wiki/Wikipedia:Community_portal" title="The hub for editors"><span>Community portal</span></a></li><li id="n-recentchanges" class="mw-list-item"><a href="/wiki/Special:RecentChanges" title="A list of recent changes to Wikipedia [r]" accesskey="r"><span>Recent changes</span></a></li><li id="n-upload" class="mw-list-item"><a href="/wiki/Wikipedia:File_upload_wizard" title="Add images or other media for use on Wikipedia"><span>Upload file</span></a></li><li id="n-specialpages" class="mw-list-item"><a href="/wiki/Special:SpecialPages"><span>Special pages</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> <a href="/wiki/Main_Page" class="mw-logo"> <img class="mw-logo-icon" src="/static/images/icons/wikipedia.png" alt="" aria-hidden="true" height="50" width="50"> <span class="mw-logo-container skin-invert"> <img class="mw-logo-wordmark" alt="Wikipedia" src="/static/images/mobile/copyright/wikipedia-wordmark-en.svg" style="width: 7.5em; height: 1.125em;"> <img class="mw-logo-tagline" alt="The Free Encyclopedia" src="/static/images/mobile/copyright/wikipedia-tagline-en.svg" width="117" height="13" style="width: 7.3125em; height: 0.8125em;"> </span> </a> </div> <div class="vector-header-end"> <div id="p-search" role="search" class="vector-search-box-vue vector-search-box-collapses vector-search-box-show-thumbnail vector-search-box-auto-expand-width vector-search-box"> <a href="/wiki/Special:Search" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only search-toggle" title="Search Wikipedia [f]" accesskey="f"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </a> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail cdx-typeahead-search--auto-expand-width"> <form action="/w/index.php" id="searchform" class="cdx-search-input cdx-search-input--has-end-button"> <div id="simpleSearch" class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia" aria-label="Search Wikipedia" autocapitalize="sentences" title="Search Wikipedia [f]" accesskey="f" id="searchInput" > <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <nav class="vector-user-links vector-user-links-wide" aria-label="Personal tools"> <div class="vector-user-links-main"> <div id="p-vector-user-menu-preferences" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-userpage" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-dropdown" class="vector-dropdown " title="Change the appearance of the page's font size, width, and color" > <input type="checkbox" id="vector-appearance-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-appearance-dropdown" class="vector-dropdown-checkbox " aria-label="Appearance" > <label id="vector-appearance-dropdown-label" for="vector-appearance-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-appearance mw-ui-icon-wikimedia-appearance"></span> <span class="vector-dropdown-label-text">Appearance</span> </label> <div class="vector-dropdown-content"> <div id="vector-appearance-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div id="p-vector-user-menu-notifications" class="vector-menu mw-portlet emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> <div id="p-vector-user-menu-overflow" class="vector-menu mw-portlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="https://donate.wikimedia.org/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en" class=""><span>Donate</span></a> </li> <li id="pt-createaccount-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:CreateAccount&returnto=Consistent+Overhead+Byte+Stuffing" title="You are encouraged to create an account and log in; however, it is not mandatory" class=""><span>Create account</span></a> </li> <li id="pt-login-2" class="user-links-collapsible-item mw-list-item user-links-collapsible-item"><a data-mw="interface" href="/w/index.php?title=Special:UserLogin&returnto=Consistent+Overhead+Byte+Stuffing" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o" class=""><span>Log in</span></a> </li> </ul> </div> </div> </div> <div id="vector-user-links-dropdown" class="vector-dropdown vector-user-menu vector-button-flush-right vector-user-menu-logged-out" title="Log in and more options" > <input type="checkbox" id="vector-user-links-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-user-links-dropdown" class="vector-dropdown-checkbox " aria-label="Personal tools" > <label id="vector-user-links-dropdown-label" for="vector-user-links-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-ellipsis mw-ui-icon-wikimedia-ellipsis"></span> <span class="vector-dropdown-label-text">Personal tools</span> </label> <div class="vector-dropdown-content"> <div id="p-personal" class="vector-menu mw-portlet mw-portlet-personal user-links-collapsible-item" title="User menu" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-sitesupport" class="user-links-collapsible-item mw-list-item"><a href="https://donate.wikimedia.org/?wmf_source=donate&wmf_medium=sidebar&wmf_campaign=en.wikipedia.org&uselang=en"><span>Donate</span></a></li><li id="pt-createaccount" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:CreateAccount&returnto=Consistent+Overhead+Byte+Stuffing" title="You are encouraged to create an account and log in; however, it is not mandatory"><span class="vector-icon mw-ui-icon-userAdd mw-ui-icon-wikimedia-userAdd"></span> <span>Create account</span></a></li><li id="pt-login" class="user-links-collapsible-item mw-list-item"><a href="/w/index.php?title=Special:UserLogin&returnto=Consistent+Overhead+Byte+Stuffing" title="You're encouraged to log in; however, it's not mandatory. [o]" accesskey="o"><span class="vector-icon mw-ui-icon-logIn mw-ui-icon-wikimedia-logIn"></span> <span>Log in</span></a></li> </ul> </div> </div> <div id="p-user-menu-anon-editor" class="vector-menu mw-portlet mw-portlet-user-menu-anon-editor" > <div class="vector-menu-heading"> Pages for logged out editors <a href="/wiki/Help:Introduction" aria-label="Learn more about editing"><span>learn more</span></a> </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="pt-anoncontribs" class="mw-list-item"><a href="/wiki/Special:MyContributions" title="A list of edits made from this IP address [y]" accesskey="y"><span>Contributions</span></a></li><li id="pt-anontalk" class="mw-list-item"><a href="/wiki/Special:MyTalk" title="Discussion about edits from this IP address [n]" accesskey="n"><span>Talk</span></a></li> </ul> </div> </div> </div> </div> </nav> </div> </header> </div> <div class="mw-page-container"> <div class="mw-page-container-inner"> <div class="vector-sitenotice-container"> <div id="siteNotice"></div> </div> <div class="vector-column-start"> <div class="vector-main-menu-container"> <div id="mw-navigation"> <nav id="mw-panel" class="vector-main-menu-landmark" aria-label="Site"> <div id="vector-main-menu-pinned-container" class="vector-pinned-container"> </div> </nav> </div> </div> <div class="vector-sticky-pinned-container"> <nav id="mw-panel-toc" aria-label="Contents" data-event-name="ui.sidebar-toc" class="mw-table-of-contents-container vector-toc-landmark"> <div id="vector-toc-pinned-container" class="vector-pinned-container"> <div id="vector-toc" class="vector-toc vector-pinnable-element"> <div class="vector-pinnable-header vector-toc-pinnable-header vector-pinnable-header-pinned" data-feature-name="toc-pinned" data-pinnable-element-id="vector-toc" > <h2 class="vector-pinnable-header-label">Contents</h2> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-toc.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-toc.unpin">hide</button> </div> <ul class="vector-toc-contents" id="mw-panel-toc-list"> <li id="toc-mw-content-text" class="vector-toc-list-item vector-toc-level-1"> <a href="#" class="vector-toc-link"> <div class="vector-toc-text">(Top)</div> </a> </li> <li id="toc-Packet_framing_and_stuffing" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Packet_framing_and_stuffing"> <div class="vector-toc-text"> <span class="vector-toc-numb">1</span> <span>Packet framing and stuffing</span> </div> </a> <ul id="toc-Packet_framing_and_stuffing-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Encoding_examples" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Encoding_examples"> <div class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Encoding examples</span> </div> </a> <ul id="toc-Encoding_examples-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Implementation" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Implementation"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Implementation</span> </div> </a> <ul id="toc-Implementation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Consistent Overhead Byte Stuffing</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 2 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-2" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">2 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Consistent_overhead_byte_stuffing" title="Consistent overhead byte stuffing – Polish" lang="pl" hreflang="pl" data-title="Consistent overhead byte stuffing" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%92%D1%81%D1%82%D0%B0%D0%B2%D0%BA%D0%B0_%D0%B1%D0%B0%D0%B9%D1%82%D0%BE%D0%B2_%D1%81_%D1%84%D0%B8%D0%BA%D1%81%D0%B8%D1%80%D0%BE%D0%B2%D0%B0%D0%BD%D0%BD%D0%BE%D0%B9_%D0%B8%D0%B7%D0%B1%D1%8B%D1%82%D0%BE%D1%87%D0%BD%D0%BE%D1%81%D1%82%D1%8C%D1%8E" title="Вставка байтов с фиксированной избыточностью – Russian" lang="ru" hreflang="ru" data-title="Вставка байтов с фиксированной избыточностью" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li> </ul> <div class="after-portlet after-portlet-lang"><span class="wb-langlinks-edit wb-langlinks-link"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q5163224#sitelinks-wikipedia" title="Edit interlanguage links" class="wbc-editpage">Edit links</a></span></div> </div> </div> </div> </header> <div class="vector-page-toolbar"> <div class="vector-page-toolbar-container"> <div id="left-navigation"> <nav aria-label="Namespaces"> <div id="p-associated-pages" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-associated-pages" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-nstab-main" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Consistent_Overhead_Byte_Stuffing" title="View the content page [c]" accesskey="c"><span>Article</span></a></li><li id="ca-talk" class="vector-tab-noicon mw-list-item"><a href="/wiki/Talk:Consistent_Overhead_Byte_Stuffing" rel="discussion" title="Discuss improvements to the content page [t]" accesskey="t"><span>Talk</span></a></li> </ul> </div> </div> <div id="vector-variants-dropdown" class="vector-dropdown emptyPortlet" > <input type="checkbox" id="vector-variants-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-variants-dropdown" class="vector-dropdown-checkbox " aria-label="Change language variant" > <label id="vector-variants-dropdown-label" for="vector-variants-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">English</span> </label> <div class="vector-dropdown-content"> <div id="p-variants" class="vector-menu mw-portlet mw-portlet-variants emptyPortlet" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> </ul> </div> </div> </div> </div> </nav> </div> <div id="right-navigation" class="vector-collapsible"> <nav aria-label="Views"> <div id="p-views" class="vector-menu vector-menu-tabs mw-portlet mw-portlet-views" > <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-view" class="selected vector-tab-noicon mw-list-item"><a href="/wiki/Consistent_Overhead_Byte_Stuffing"><span>Read</span></a></li><li id="ca-edit" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-history" class="vector-tab-noicon mw-list-item"><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=history" title="Past revisions of this page [h]" accesskey="h"><span>View history</span></a></li> </ul> </div> </div> </nav> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-dropdown" class="vector-dropdown vector-page-tools-dropdown" > <input type="checkbox" id="vector-page-tools-dropdown-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-tools-dropdown" class="vector-dropdown-checkbox " aria-label="Tools" > <label id="vector-page-tools-dropdown-label" for="vector-page-tools-dropdown-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet" aria-hidden="true" ><span class="vector-dropdown-label-text">Tools</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-tools-unpinned-container" class="vector-unpinned-container"> <div id="vector-page-tools" class="vector-page-tools vector-pinnable-element"> <div class="vector-pinnable-header vector-page-tools-pinnable-header vector-pinnable-header-unpinned" data-feature-name="page-tools-pinned" data-pinnable-element-id="vector-page-tools" data-pinned-container-id="vector-page-tools-pinned-container" data-unpinned-container-id="vector-page-tools-unpinned-container" > <div class="vector-pinnable-header-label">Tools</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-page-tools.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-page-tools.unpin">hide</button> </div> <div id="p-cactions" class="vector-menu mw-portlet mw-portlet-cactions emptyPortlet vector-has-collapsible-items" title="More options" > <div class="vector-menu-heading"> Actions </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="ca-more-view" class="selected vector-more-collapsible-item mw-list-item"><a href="/wiki/Consistent_Overhead_Byte_Stuffing"><span>Read</span></a></li><li id="ca-more-edit" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit" title="Edit this page [e]" accesskey="e"><span>Edit</span></a></li><li id="ca-more-history" class="vector-more-collapsible-item mw-list-item"><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=history"><span>View history</span></a></li> </ul> </div> </div> <div id="p-tb" class="vector-menu mw-portlet mw-portlet-tb" > <div class="vector-menu-heading"> General </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-whatlinkshere" class="mw-list-item"><a href="/wiki/Special:WhatLinksHere/Consistent_Overhead_Byte_Stuffing" title="List of all English Wikipedia pages containing links to this page [j]" accesskey="j"><span>What links here</span></a></li><li id="t-recentchangeslinked" class="mw-list-item"><a href="/wiki/Special:RecentChangesLinked/Consistent_Overhead_Byte_Stuffing" rel="nofollow" title="Recent changes in pages linked from this page [k]" accesskey="k"><span>Related changes</span></a></li><li id="t-upload" class="mw-list-item"><a href="//en.wikipedia.org/wiki/Wikipedia:File_Upload_Wizard" title="Upload files [u]" accesskey="u"><span>Upload file</span></a></li><li id="t-permalink" class="mw-list-item"><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&oldid=1244549534" title="Permanent link to this revision of this page"><span>Permanent link</span></a></li><li id="t-info" class="mw-list-item"><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=info" title="More information about this page"><span>Page information</span></a></li><li id="t-cite" class="mw-list-item"><a href="/w/index.php?title=Special:CiteThisPage&page=Consistent_Overhead_Byte_Stuffing&id=1244549534&wpFormIdentifier=titleform" title="Information on how to cite this page"><span>Cite this page</span></a></li><li id="t-urlshortener" class="mw-list-item"><a href="/w/index.php?title=Special:UrlShortener&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FConsistent_Overhead_Byte_Stuffing"><span>Get shortened URL</span></a></li><li id="t-urlshortener-qrcode" class="mw-list-item"><a href="/w/index.php?title=Special:QrCode&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FConsistent_Overhead_Byte_Stuffing"><span>Download QR code</span></a></li> </ul> </div> </div> <div id="p-coll-print_export" class="vector-menu mw-portlet mw-portlet-coll-print_export" > <div class="vector-menu-heading"> Print/export </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="coll-download-as-rl" class="mw-list-item"><a href="/w/index.php?title=Special:DownloadAsPdf&page=Consistent_Overhead_Byte_Stuffing&action=show-download-screen" title="Download this page as a PDF file"><span>Download as PDF</span></a></li><li id="t-print" class="mw-list-item"><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&printable=yes" title="Printable version of this page [p]" accesskey="p"><span>Printable version</span></a></li> </ul> </div> </div> <div id="p-wikibase-otherprojects" class="vector-menu mw-portlet mw-portlet-wikibase-otherprojects" > <div class="vector-menu-heading"> In other projects </div> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li id="t-wikibase" class="wb-otherproject-link wb-otherproject-wikibase-dataitem mw-list-item"><a href="https://www.wikidata.org/wiki/Special:EntityPage/Q5163224" title="Structured data on this page hosted by Wikidata [g]" accesskey="g"><span>Wikidata item</span></a></li> </ul> </div> </div> </div> </div> </div> </div> </nav> </div> </div> </div> <div class="vector-column-end"> <div class="vector-sticky-pinned-container"> <nav class="vector-page-tools-landmark" aria-label="Page tools"> <div id="vector-page-tools-pinned-container" class="vector-pinned-container"> </div> </nav> <nav class="vector-appearance-landmark" aria-label="Appearance"> <div id="vector-appearance-pinned-container" class="vector-pinned-container"> <div id="vector-appearance" class="vector-appearance vector-pinnable-element"> <div class="vector-pinnable-header vector-appearance-pinnable-header vector-pinnable-header-pinned" data-feature-name="appearance-pinned" data-pinnable-element-id="vector-appearance" data-pinned-container-id="vector-appearance-pinned-container" data-unpinned-container-id="vector-appearance-unpinned-container" > <div class="vector-pinnable-header-label">Appearance</div> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-pin-button" data-event-name="pinnable-header.vector-appearance.pin">move to sidebar</button> <button class="vector-pinnable-header-toggle-button vector-pinnable-header-unpin-button" data-event-name="pinnable-header.vector-appearance.unpin">hide</button> </div> </div> </div> </nav> </div> </div> <div id="bodyContent" class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Algorithm for encoding data bytes</div> <p><b>Consistent Overhead Byte Stuffing</b> (<b>COBS</b>) is an <a href="/wiki/Algorithm" title="Algorithm">algorithm</a> for encoding data bytes that results in efficient, reliable, unambiguous <a href="/wiki/Packet_(information_technology)#Packet_framing" class="mw-redirect" title="Packet (information technology)">packet framing</a> regardless of packet content, thus making it easy for receiving applications to recover from malformed packets. It employs a particular byte value, typically zero, to serve as a <i>packet <a href="/wiki/Delimiter" title="Delimiter">delimiter</a></i> (a special value that indicates the boundary between packets). When zero is used as a delimiter, the algorithm replaces each zero data byte with a non-zero value so that no zero data bytes will appear in the packet and thus be misinterpreted as packet boundaries. </p><p><b>Byte stuffing</b> is a process that transforms a sequence of data bytes that may contain 'illegal' or 'reserved' values (such as packet delimiter) into a potentially longer sequence that contains no occurrences of those values. The extra length of the transformed sequence is typically referred to as the <a href="/wiki/Overhead_(computing)" title="Overhead (computing)">overhead</a> of the algorithm. <a href="/wiki/High-Level_Data_Link_Control#Asynchronous_framing" title="High-Level Data Link Control">HDLC framing</a> is a well-known example, used particularly in <a href="/wiki/Point-to-point_protocol" class="mw-redirect" title="Point-to-point protocol">PPP</a> (see <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/rfc1662#section-4.2">RFC 1662 § 4.2</a>). Although HDLC framing has an overhead of <1% in the <i>average</i> case, it suffers from a very poor <i>worst</i>-case overhead of 100%; for inputs that consist entirely of bytes that require escaping, HDLC byte stuffing will double the size of the input. </p><p>The COBS algorithm, on the other hand, tightly bounds the worst-case overhead. COBS requires a minimum of 1 byte overhead, and a maximum of ⌈<i>n</i>/254⌉ bytes for <i>n</i> data bytes (one byte in 254, rounded up). Consequently, the time to transmit the encoded byte sequence is highly predictable, which makes COBS useful for real-time applications in which jitter may be problematic. The algorithm is computationally inexpensive, and in addition to its desirable <i>worst</i>-case overhead, its <i>average</i> overhead is also low compared to other unambiguous framing algorithms like HDLC.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup> COBS does, however, require up to 254 bytes of <i>lookahead</i>. Before transmitting its first byte, it needs to know the position of the first zero byte (if any) in the following 254 bytes. </p><p>A 1999 <a href="/wiki/Internet_Draft" title="Internet Draft">Internet Draft</a> proposed to standardize COBS as an alternative for HDLC framing in <a href="/wiki/Point-to-point_protocol" class="mw-redirect" title="Point-to-point protocol">PPP</a>, due to the aforementioned poor worst-case overhead of HDLC framing.<sup id="cite_ref-ietf-draft_3-0" class="reference"><a href="#cite_note-ietf-draft-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup> </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Packet_framing_and_stuffing">Packet framing and stuffing</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit&section=1" title="Edit section: Packet framing and stuffing"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>When packetized data is sent over any serial medium, some <a href="/wiki/Communications_protocol" class="mw-redirect" title="Communications protocol">protocol</a> is required to demarcate packet boundaries. This is done by using a framing marker, a special bit-sequence or character value that indicates where the boundaries between packets fall. Data stuffing is the process that transforms the packet data before transmission to eliminate all occurrences of the framing marker, so that when the receiver detects a marker, it can be certain that the marker indicates a boundary between packets. </p><p>COBS transforms an arbitrary string of bytes in the range [0,255] into bytes in the range [1,255]. Having eliminated all zero bytes from the data, a zero byte can now be used to unambiguously mark the end of the transformed data. This is done by appending a zero byte to the transformed data, thus forming a packet consisting of the COBS-encoded data (the <i><a href="/wiki/Payload_(computing)" title="Payload (computing)">payload</a></i>) to unambiguously mark the end of the packet. </p><p>(Any other byte value may be reserved as the packet delimiter, but using zero simplifies the description.) </p> <figure class="mw-halign-center" typeof="mw:File/Frameless"><a href="/wiki/File:Cobs_encoding_with_example.png" class="mw-file-description" title="Consistent Overhead Byte Stuffing (COBS) encoding process"><img alt="Consistent Overhead Byte Stuffing (COBS) encoding process" src="//upload.wikimedia.org/wikipedia/commons/thumb/5/50/Cobs_encoding_with_example.png/800px-Cobs_encoding_with_example.png" decoding="async" width="800" height="123" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/5/50/Cobs_encoding_with_example.png/1200px-Cobs_encoding_with_example.png 1.5x, //upload.wikimedia.org/wikipedia/commons/5/50/Cobs_encoding_with_example.png 2x" data-file-width="1532" data-file-height="235" /></a><figcaption>Consistent Overhead Byte Stuffing (COBS) encoding process</figcaption></figure> <p>There are two equivalent ways to describe the COBS encoding process: </p> <dl><dt>Prefixed block description</dt> <dd>To encode some bytes, first append a zero byte, then break them into groups of either 254 non-zero bytes, or 0–253 non-zero bytes followed by a zero byte. Because of the appended zero byte, this is always possible.</dd> <dd>Encode each group by deleting the trailing zero byte (if any) and prepending the number of non-zero bytes, plus one. Thus, each encoded group is the same size as the original, except that 254 non-zero bytes are encoded into 255 bytes by prepending a byte of 255.</dd> <dd>As a special exception, if a packet ends with a group of 254 non-zero bytes, it is not necessary to add the trailing zero byte. This saves one byte in some situations.</dd> <dt>Linked list description</dt> <dd>First, insert a zero byte at the beginning of the packet, and after every run of 254 non-zero bytes. This encoding is obviously reversible. It is not necessary to insert a zero byte at the end of the packet if it happens to end with exactly 254 non-zero bytes.</dd> <dd>Second, replace each zero byte with the offset to the next zero byte, or the end of the packet. Because of the extra zeros added in the first step, each offset is guaranteed to be at most 255.</dd></dl> <div class="mw-heading mw-heading2"><h2 id="Encoding_examples">Encoding examples</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit&section=2" title="Edit section: Encoding examples"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>These examples show how various data sequences would be encoded by the COBS algorithm. In the examples, all bytes are expressed as <a href="/wiki/Hexadecimal" title="Hexadecimal">hexadecimal</a> values, and encoded data is shown with text formatting to illustrate various features: </p> <ul><li><b>Bold</b> indicates a data byte which has not been altered by encoding. All non-zero data bytes remain unaltered.</li> <li><span style="color:green;">Green</span> indicates a zero data byte that was altered by encoding. All zero data bytes are replaced during encoding by the offset to the following zero byte (i.e. one plus the number of non-zero bytes that follow). It is effectively a pointer to the next packet byte that requires interpretation: if the addressed byte is non-zero then it is the following <span style="color:green;">group header byte zero data byte</span> that points to the next byte requiring interpretation; if the addressed byte is zero then it is the <span style="color:blue">end of packet</span>.</li> <li><span style="color: red;">Red</span> is an overhead byte which is also a group header byte containing an offset to a following group, but does not correspond to a data byte. These appear in two places: at the beginning of every encoded packet, and after every group of 254 non-zero bytes.</li> <li>A <span style="color:blue">blue</span> zero byte appears at the end of every packet to indicate end-of-packet to the data receiver. This packet delimiter byte is not part of COBS proper; it is an additional framing byte that is appended to the encoded output.</li></ul> <table class="wikitable"> <tbody><tr> <th>Example</th> <th>Unencoded data (hex)</th> <th>Encoded with COBS (hex) </th></tr> <tr> <td>1</td> <td><style data-mw-deduplicate="TemplateStyles:r886049734">.mw-parser-output .monospaced{font-family:monospace,monospace}</style><span class="monospaced">00</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">01</span> <span style="color:green;">01</span> <span style="color:blue">00</span></span> </td></tr> <tr> <td>2</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">00 00</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">01</span> <span style="color:green;">01 01</span> <span style="color:blue">00</span></span> </td></tr> <tr> <td>3</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">00 11 00</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">01</span> <span style="color:green;">02 </span> <b>11</b> <span style="color:green;">01 </span> <span style="color:blue">00</span></span> </td></tr> <tr> <td>4</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">11 22 00 33</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">03</span> <b>11 22</b> <span style="color:green;">02</span> <b>33</b> <span style="color:blue">00</span></span> </td></tr> <tr> <td>5</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">11 22 33 44</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">05</span> <b>11 22 33 44</b> <span style="color:blue">00</span></span> </td></tr> <tr> <td>6</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">11 00 00 00</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">02</span> <b>11</b> <span style="color:green;">01 01 01</span> <span style="color:blue">00</span></span> </td></tr> <tr> <td>7</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">01 02 03 ... FD FE</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">FF</span> <b>01 02 03 ... FD FE</b> <span style="color:blue">00</span></span> </td></tr> <tr> <td>8</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">00 01 02 ... FC FD FE</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">01</span> <span style="color:green;">FF</span> <b>01 02 ... FC FD FE</b> <span style="color:blue">00</span></span> </td></tr> <tr> <td>9</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">01 02 03 ... FD FE FF</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">FF</span> <b>01 02 03 ... FD FE</b> <span style="color: red;">02</span> <b>FF</b> <span style="color:blue">00</span></span> </td></tr> <tr> <td>10</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">02 03 04 ... FE FF 00</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">FF</span> <b>02 03 04 ... FE FF</b> <span style="color: red;">01</span> <span style="color:green;">01</span> <span style="color:blue">00</span></span> </td></tr> <tr> <td>11</td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced">03 04 05 ... FF 00 01</span></td> <td><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r886049734"><span class="monospaced"><span style="color: red;">FE</span> <b>03 04 05 ... FF</b> <span style="color:green;">02</span> <b>01</b> <span style="color:blue">00</span></span> </td></tr></tbody></table><p> Below is a diagram using example 4 from above table, to illustrate how each modified data byte is located, and how it is identified as a data byte or an end of frame byte.</p><pre> [OHB]  : Overhead byte (Start of frame) 3+ -------------->|  : Points to relative location of first zero symbol 2+-------->|  : Is a zero data byte, pointing to next zero symbol [EOP] : Location of end-of-packet zero symbol. 0 1 2 3 4 5  : Byte Position 03 11 22 02 33 00  : COBS Data Frame 11 22 00 33  : Extracted Data OHB = Overhead Byte (Points to next zero symbol) EOP = End Of Packet </pre> <p>Examples 7 through 10 show how the overhead varies depending on the data being encoded for packet lengths of 255 or more. </p> <div class="mw-heading mw-heading2"><h2 id="Implementation">Implementation</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit&section=3" title="Edit section: Implementation"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The following code implements a COBS encoder and decoder in the C programming language: </p> <div class="mw-highlight mw-highlight-lang-c mw-content-ltr" dir="ltr"><pre><span></span><span class="cp">#include</span><span class="w"> </span><span class="cpf"><stddef.h></span> <span class="cp">#include</span><span class="w"> </span><span class="cpf"><stdint.h></span> <span class="cp">#include</span><span class="w"> </span><span class="cpf"><assert.h></span> <span class="cm">/** COBS encode data to buffer</span> <span class="cm"> @param data Pointer to input data to encode</span> <span class="cm"> @param length Number of bytes to encode</span> <span class="cm"> @param buffer Pointer to encoded output buffer</span> <span class="cm"> @return Encoded buffer length in bytes</span> <span class="cm"> @note Does not output delimiter byte</span> <span class="cm">*/</span> <span class="kt">size_t</span><span class="w"> </span><span class="nf">cobsEncode</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">data</span><span class="p">,</span><span class="w"> </span><span class="kt">size_t</span><span class="w"> </span><span class="n">length</span><span class="p">,</span><span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="n">buffer</span><span class="p">)</span> <span class="p">{</span> <span class="w"> </span><span class="n">assert</span><span class="p">(</span><span class="n">data</span><span class="w"> </span><span class="o">&&</span><span class="w"> </span><span class="n">buffer</span><span class="p">);</span> <span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="n">encode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buffer</span><span class="p">;</span><span class="w"> </span><span class="c1">// Encoded byte pointer</span> <span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="n">codep</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">encode</span><span class="o">++</span><span class="p">;</span><span class="w"> </span><span class="c1">// Output code pointer</span> <span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="n">code</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">;</span><span class="w"> </span><span class="c1">// Code value</span> <span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="n">byte</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="p">)</span><span class="n">data</span><span class="p">;</span><span class="w"> </span><span class="n">length</span><span class="o">--</span><span class="p">;</span><span class="w"> </span><span class="o">++</span><span class="n">byte</span><span class="p">)</span> <span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">*</span><span class="n">byte</span><span class="p">)</span><span class="w"> </span><span class="c1">// Byte not zero, write it</span> <span class="w"> </span><span class="o">*</span><span class="n">encode</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">byte</span><span class="p">,</span><span class="w"> </span><span class="o">++</span><span class="n">code</span><span class="p">;</span> <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!*</span><span class="n">byte</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">code</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mh">0xff</span><span class="p">)</span><span class="w"> </span><span class="c1">// Input is zero or block completed, restart</span> <span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="o">*</span><span class="n">codep</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">code</span><span class="p">,</span><span class="w"> </span><span class="n">code</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">1</span><span class="p">,</span><span class="w"> </span><span class="n">codep</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">encode</span><span class="p">;</span> <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!*</span><span class="n">byte</span><span class="w"> </span><span class="o">||</span><span class="w"> </span><span class="n">length</span><span class="p">)</span> <span class="w"> </span><span class="o">++</span><span class="n">encode</span><span class="p">;</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="o">*</span><span class="n">codep</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">code</span><span class="p">;</span><span class="w"> </span><span class="c1">// Write final code value</span> <span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="kt">size_t</span><span class="p">)(</span><span class="n">encode</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="n">buffer</span><span class="p">);</span> <span class="p">}</span> <span class="cm">/** COBS decode data from buffer</span> <span class="cm"> @param buffer Pointer to encoded input bytes</span> <span class="cm"> @param length Number of bytes to decode</span> <span class="cm"> @param data Pointer to decoded output data</span> <span class="cm"> @return Number of bytes successfully decoded</span> <span class="cm"> @note Stops decoding if delimiter byte is found</span> <span class="cm">*/</span> <span class="kt">size_t</span><span class="w"> </span><span class="nf">cobsDecode</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="n">buffer</span><span class="p">,</span><span class="w"> </span><span class="kt">size_t</span><span class="w"> </span><span class="n">length</span><span class="p">,</span><span class="w"> </span><span class="kt">void</span><span class="w"> </span><span class="o">*</span><span class="n">data</span><span class="p">)</span> <span class="p">{</span> <span class="w"> </span><span class="n">assert</span><span class="p">(</span><span class="n">buffer</span><span class="w"> </span><span class="o">&&</span><span class="w"> </span><span class="n">data</span><span class="p">);</span> <span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="n">byte</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">buffer</span><span class="p">;</span><span class="w"> </span><span class="c1">// Encoded input byte pointer</span> <span class="w"> </span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="n">decode</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="p">(</span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="p">)</span><span class="n">data</span><span class="p">;</span><span class="w"> </span><span class="c1">// Decoded output byte pointer</span> <span class="w"> </span><span class="k">for</span><span class="w"> </span><span class="p">(</span><span class="kt">uint8_t</span><span class="w"> </span><span class="n">code</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mh">0xff</span><span class="p">,</span><span class="w"> </span><span class="n">block</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span><span class="w"> </span><span class="n">byte</span><span class="w"> </span><span class="o"><</span><span class="w"> </span><span class="n">buffer</span><span class="w"> </span><span class="o">+</span><span class="w"> </span><span class="n">length</span><span class="p">;</span><span class="w"> </span><span class="o">--</span><span class="n">block</span><span class="p">)</span> <span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">block</span><span class="p">)</span><span class="w"> </span><span class="c1">// Decode block byte</span> <span class="w"> </span><span class="o">*</span><span class="n">decode</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">byte</span><span class="o">++</span><span class="p">;</span> <span class="w"> </span><span class="k">else</span> <span class="w"> </span><span class="p">{</span> <span class="w"> </span><span class="n">block</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="o">*</span><span class="n">byte</span><span class="o">++</span><span class="p">;</span><span class="w"> </span><span class="c1">// Fetch the next block length</span> <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="n">block</span><span class="w"> </span><span class="o">&&</span><span class="w"> </span><span class="p">(</span><span class="n">code</span><span class="w"> </span><span class="o">!=</span><span class="w"> </span><span class="mh">0xff</span><span class="p">))</span><span class="w"> </span><span class="c1">// Encoded zero, write it unless it's delimiter.</span> <span class="w"> </span><span class="o">*</span><span class="n">decode</span><span class="o">++</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">0</span><span class="p">;</span> <span class="w"> </span><span class="n">code</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n">block</span><span class="p">;</span> <span class="w"> </span><span class="k">if</span><span class="w"> </span><span class="p">(</span><span class="o">!</span><span class="n">code</span><span class="p">)</span><span class="w"> </span><span class="c1">// Delimiter code found</span> <span class="w"> </span><span class="k">break</span><span class="p">;</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="p">}</span> <span class="w"> </span><span class="k">return</span><span class="w"> </span><span class="p">(</span><span class="kt">size_t</span><span class="p">)(</span><span class="n">decode</span><span class="w"> </span><span class="o">-</span><span class="w"> </span><span class="p">(</span><span class="kt">uint8_t</span><span class="w"> </span><span class="o">*</span><span class="p">)</span><span class="n">data</span><span class="p">);</span> <span class="p">}</span> </pre></div> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit&section=4" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Bit_stuffing" title="Bit stuffing">Bit stuffing</a></li> <li><a href="/wiki/Serial_Line_Internet_Protocol" title="Serial Line Internet Protocol">Serial Line Internet Protocol</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit&section=5" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist"> <div class="mw-references-wrap"><ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"> <style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite id="CITEREFCheshireBaker1999" class="citation journal cs1"><a href="/wiki/Stuart_Cheshire" title="Stuart Cheshire">Cheshire, Stuart</a>; Baker, Mary (April 1999). <a rel="nofollow" class="external text" href="http://www.stuartcheshire.org/papers/COBSforToN.pdf">"Consistent Overhead Byte Stuffing"</a> <span class="cs1-format">(PDF)</span>. <i><a href="/wiki/IEEE/ACM_Transactions_on_Networking" title="IEEE/ACM Transactions on Networking">IEEE/ACM Transactions on Networking</a></i>. <b>7</b> (2): <span class="nowrap">159–</span>172. <a href="/wiki/CiteSeerX_(identifier)" class="mw-redirect" title="CiteSeerX (identifier)">CiteSeerX</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.108.3143">10.1.1.108.3143</a></span>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1109%2F90.769765">10.1109/90.769765</a>. <a href="/wiki/S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:47267776">47267776</a><span class="reference-accessdate">. Retrieved <span class="nowrap">November 30,</span> 2015</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=IEEE%2FACM+Transactions+on+Networking&rft.atitle=Consistent+Overhead+Byte+Stuffing&rft.volume=7&rft.issue=2&rft.pages=%3Cspan+class%3D%22nowrap%22%3E159-%3C%2Fspan%3E172&rft.date=1999-04&rft_id=https%3A%2F%2Fciteseerx.ist.psu.edu%2Fviewdoc%2Fsummary%3Fdoi%3D10.1.1.108.3143%23id-name%3DCiteSeerX&rft_id=https%3A%2F%2Fapi.semanticscholar.org%2FCorpusID%3A47267776%23id-name%3DS2CID&rft_id=info%3Adoi%2F10.1109%2F90.769765&rft.aulast=Cheshire&rft.aufirst=Stuart&rft.au=Baker%2C+Mary&rft_id=http%3A%2F%2Fwww.stuartcheshire.org%2Fpapers%2FCOBSforToN.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AConsistent+Overhead+Byte+Stuffing" class="Z3988"></span></span> </li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCheshireBaker1997" class="citation conference cs1"><a href="/wiki/Stuart_Cheshire" title="Stuart Cheshire">Cheshire, Stuart</a>; Baker, Mary (17 November 1997). <a rel="nofollow" class="external text" href="http://conferences.sigcomm.org/sigcomm/1997/papers/p062.pdf"><i>Consistent Overhead Byte Stuffing</i></a> <span class="cs1-format">(PDF)</span>. <a href="/wiki/Association_for_Computing_Machinery" title="Association for Computing Machinery">ACM</a> <a href="/wiki/SIGCOMM" title="SIGCOMM">SIGCOMM</a> '97. <a href="/wiki/Cannes" title="Cannes">Cannes</a><span class="reference-accessdate">. Retrieved <span class="nowrap">November 23,</span> 2010</span>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=conference&rft.btitle=Consistent+Overhead+Byte+Stuffing&rft.place=Cannes&rft.date=1997-11-17&rft.aulast=Cheshire&rft.aufirst=Stuart&rft.au=Baker%2C+Mary&rft_id=http%3A%2F%2Fconferences.sigcomm.org%2Fsigcomm%2F1997%2Fpapers%2Fp062.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AConsistent+Overhead+Byte+Stuffing" class="Z3988"></span></span> </li> <li id="cite_note-ietf-draft-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-ietf-draft_3-0">^</a></b></span> <span class="reference-text"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFCarlsonCheshireBaker1997" class="citation cs1">Carlson, James; <a href="/wiki/Stuart_Cheshire" title="Stuart Cheshire">Cheshire, Stuart</a>; Baker, Mary (November 1997). <a rel="nofollow" class="external text" href="https://datatracker.ietf.org/doc/html/draft-ietf-pppext-cobs-00.txt"><i>PPP Consistent Overhead Byte Stuffing (COBS)</i></a>. I-D draft-ietf-pppext-cobs-00.txt.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=PPP+Consistent+Overhead+Byte+Stuffing+%28COBS%29&rft.date=1997-11&rft.aulast=Carlson&rft.aufirst=James&rft.au=Cheshire%2C+Stuart&rft.au=Baker%2C+Mary&rft_id=https%3A%2F%2Fdatatracker.ietf.org%2Fdoc%2Fhtml%2Fdraft-ietf-pppext-cobs-00.txt&rfr_id=info%3Asid%2Fen.wikipedia.org%3AConsistent+Overhead+Byte+Stuffing" class="Z3988"></span></span> </li> </ol></div></div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Consistent_Overhead_Byte_Stuffing&action=edit&section=6" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a rel="nofollow" class="external text" href="https://pypi.python.org/pypi/cobs">Python implementation</a></li> <li><a rel="nofollow" class="external text" href="https://github.com/cmcqueen/cobs-c">Alternate C implementation</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20180719005741/http://www.jacquesf.com/2011/03/consistent-overhead-byte-stuffing/">Another implementation in C</a></li> <li><a rel="nofollow" class="external text" href="https://pythonhosted.org/cobs/cobsr-intro.html">Consistent Overhead Byte Stuffing—Reduced (COBS/R)</a></li> <li><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US9438411B1">A patent describing a scheme with a similar result but using a different method</a></li></ul>    </div><noscript><img src="https://login.wikimedia.org/wiki/Special:CentralAutoLogin/start?useformat=desktop&type=1x1&usesul3=0" alt="" width="1" height="1" style="border: none; position: absolute;"></noscript> <div class="printfooter" data-nosnippet="">Retrieved from "<a dir="ltr" href="https://en.wikipedia.org/w/index.php?title=Consistent_Overhead_Byte_Stuffing&oldid=1244549534">https://en.wikipedia.org/w/index.php?title=Consistent_Overhead_Byte_Stuffing&oldid=1244549534</a>"</div></div> <div id="catlinks" class="catlinks" data-mw="interface"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/wiki/Help:Category" title="Help:Category">Category</a>: <ul><li><a href="/wiki/Category:Encodings" title="Category:Encodings">Encodings</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/wiki/Category:Articles_with_short_description" title="Category:Articles with short description">Articles with short description</a></li><li><a href="/wiki/Category:Short_description_matches_Wikidata" title="Category:Short description matches Wikidata">Short description matches Wikidata</a></li></ul></div></div> </div> </main> </div> <div class="mw-footer-container"> <footer id="footer" class="mw-footer" > <ul id="footer-info"> <li id="footer-info-lastmod"> This page was last edited on 7 September 2024, at 19:35<span class="anonymous-show"> (UTC)</span>.</li> <li id="footer-info-copyright">Text is available under the <a href="/wiki/Wikipedia:Text_of_the_Creative_Commons_Attribution-ShareAlike_4.0_International_License" title="Wikipedia:Text of the Creative Commons Attribution-ShareAlike 4.0 International License">Creative Commons Attribution-ShareAlike 4.0 License</a>; additional terms may apply. By using this site, you agree to the <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Terms_of_Use" class="extiw" title="foundation:Special:MyLanguage/Policy:Terms of Use">Terms of Use</a> and <a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy" class="extiw" title="foundation:Special:MyLanguage/Policy:Privacy policy">Privacy Policy</a>. Wikipedia® is a registered trademark of the <a rel="nofollow" class="external text" href="https://wikimediafoundation.org/">Wikimedia Foundation, Inc.</a>, a non-profit organization.</li> </ul> <ul id="footer-places"> <li id="footer-places-privacy"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Privacy_policy">Privacy policy</a></li> <li id="footer-places-about"><a href="/wiki/Wikipedia:About">About Wikipedia</a></li> <li id="footer-places-disclaimers"><a href="/wiki/Wikipedia:General_disclaimer">Disclaimers</a></li> <li id="footer-places-contact"><a href="//en.wikipedia.org/wiki/Wikipedia:Contact_us">Contact Wikipedia</a></li> <li id="footer-places-wm-codeofconduct"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Universal_Code_of_Conduct">Code of Conduct</a></li> <li id="footer-places-developers"><a href="https://developer.wikimedia.org">Developers</a></li> <li id="footer-places-statslink"><a href="https://stats.wikimedia.org/#/en.wikipedia.org">Statistics</a></li> <li id="footer-places-cookiestatement"><a href="https://foundation.wikimedia.org/wiki/Special:MyLanguage/Policy:Cookie_statement">Cookie statement</a></li> <li id="footer-places-mobileview"><a href="//en.m.wikipedia.org/w/index.php?title=Consistent_Overhead_Byte_Stuffing&mobileaction=toggle_view_mobile" class="noprint stopMobileRedirectToggle">Mobile view</a></li> </ul> <ul id="footer-icons" class="noprint"> <li id="footer-copyrightico"><a href="https://wikimediafoundation.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><picture><source media="(min-width: 500px)" srcset="/static/images/footer/wikimedia-button.svg" width="84" height="29"><img src="/static/images/footer/wikimedia.svg" width="25" height="25" alt="Wikimedia Foundation" lang="en" loading="lazy"></picture></a></li> <li id="footer-poweredbyico"><a href="https://www.mediawiki.org/" class="cdx-button cdx-button--fake-button cdx-button--size-large cdx-button--fake-button--enabled"><picture><source media="(min-width: 500px)" srcset="/w/resources/assets/poweredby_mediawiki.svg" width="88" height="31"><img src="/w/resources/assets/mediawiki_compact.svg" alt="Powered by MediaWiki" width="25" height="25" loading="lazy"></picture></a></li> </ul> </footer> </div> </div> </div> <div class="vector-header-container vector-sticky-header-container"> <div id="vector-sticky-header" class="vector-sticky-header"> <div class="vector-sticky-header-start"> <div class="vector-sticky-header-icon-start vector-button-flush-left vector-button-flush-right" aria-hidden="true"> <button class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-sticky-header-search-toggle" tabindex="-1" data-event-name="ui.vector-sticky-search-form.icon"><span class="vector-icon mw-ui-icon-search mw-ui-icon-wikimedia-search"></span> <span>Search</span> </button> </div> <div role="search" class="vector-search-box-vue vector-search-box-show-thumbnail vector-search-box"> <div class="vector-typeahead-search-container"> <div class="cdx-typeahead-search cdx-typeahead-search--show-thumbnail"> <form action="/w/index.php" id="vector-sticky-search-form" class="cdx-search-input cdx-search-input--has-end-button"> <div class="cdx-search-input__input-wrapper" data-search-loc="header-moved"> <div class="cdx-text-input cdx-text-input--has-start-icon"> <input class="cdx-text-input__input" type="search" name="search" placeholder="Search Wikipedia"> <span class="cdx-text-input__icon cdx-text-input__start-icon"></span> </div> <input type="hidden" name="title" value="Special:Search"> </div> <button class="cdx-button cdx-search-input__end-button">Search</button> </form> </div> </div> </div> <div class="vector-sticky-header-context-bar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-sticky-header-toc" class="vector-dropdown mw-portlet mw-portlet-sticky-header-toc vector-sticky-header-toc vector-button-flush-left" > <input type="checkbox" id="vector-sticky-header-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-sticky-header-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-sticky-header-toc-label" for="vector-sticky-header-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-sticky-header-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <div class="vector-sticky-header-context-bar-primary" aria-hidden="true" ><span class="mw-page-title-main">Consistent Overhead Byte Stuffing</span></div> </div> </div> <div class="vector-sticky-header-end" aria-hidden="true"> <div class="vector-sticky-header-icons"> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-talk-sticky-header" tabindex="-1" data-event-name="talk-sticky-header"><span class="vector-icon mw-ui-icon-speechBubbles mw-ui-icon-wikimedia-speechBubbles"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-subject-sticky-header" tabindex="-1" data-event-name="subject-sticky-header"><span class="vector-icon mw-ui-icon-article mw-ui-icon-wikimedia-article"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-history-sticky-header" tabindex="-1" data-event-name="history-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-history mw-ui-icon-wikimedia-wikimedia-history"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only mw-watchlink" id="ca-watchstar-sticky-header" tabindex="-1" data-event-name="watch-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-star mw-ui-icon-wikimedia-wikimedia-star"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-edit-sticky-header" tabindex="-1" data-event-name="wikitext-edit-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-wikiText mw-ui-icon-wikimedia-wikimedia-wikiText"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-ve-edit-sticky-header" tabindex="-1" data-event-name="ve-edit-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-edit mw-ui-icon-wikimedia-wikimedia-edit"></span> <span></span> </a> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only" id="ca-viewsource-sticky-header" tabindex="-1" data-event-name="ve-edit-protected-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-editLock mw-ui-icon-wikimedia-wikimedia-editLock"></span> <span></span> </a> </div> <div class="vector-sticky-header-buttons"> <button class="cdx-button cdx-button--weight-quiet mw-interlanguage-selector" id="p-lang-btn-sticky-header" tabindex="-1" data-event-name="ui.dropdown-p-lang-btn-sticky-header"><span class="vector-icon mw-ui-icon-wikimedia-language mw-ui-icon-wikimedia-wikimedia-language"></span> <span>2 languages</span> </button> <a href="#" class="cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive" id="ca-addsection-sticky-header" tabindex="-1" data-event-name="addsection-sticky-header"><span class="vector-icon mw-ui-icon-speechBubbleAdd-progressive mw-ui-icon-wikimedia-speechBubbleAdd-progressive"></span> <span>Add topic</span> </a> </div> <div class="vector-sticky-header-icon-end"> <div class="vector-user-links"> </div> </div> </div> </div> </div> <div class="vector-settings" id="p-dock-bottom"> <ul></ul> </div><script>(RLQ=window.RLQ||[]).push(function(){mw.config.set({"wgHostname":"mw-web.codfw.main-d8647bfd6-mjqws","wgBackendResponseTime":101,"wgPageParseReport":{"limitreport":{"cputime":"0.180","walltime":"0.237","ppvisitednodes":{"value":1443,"limit":1000000},"postexpandincludesize":{"value":17391,"limit":2097152},"templateargumentsize":{"value":3556,"limit":2097152},"expansiondepth":{"value":16,"limit":100},"expensivefunctioncount":{"value":2,"limit":500},"unstrip-depth":{"value":1,"limit":20},"unstrip-size":{"value":28478,"limit":5000000},"entityaccesscount":{"value":0,"limit":400},"timingprofile":["100.00% 203.817 1 -total"," 55.15% 112.411 1 Template:Reflist"," 34.52% 70.348 1 Template:Cite_journal"," 32.84% 66.925 1 Template:Short_description"," 20.18% 41.139 2 Template:Pagetype"," 11.88% 24.212 1 Template:Cite_ietf"," 7.35% 14.989 3 Template:Main_other"," 6.84% 13.940 22 Template:Mono"," 6.37% 12.974 1 Template:SDcat"," 4.48% 9.132 22 Template:Ifsubst"]},"scribunto":{"limitreport-timeusage":{"value":"0.087","limit":"10.000"},"limitreport-memusage":{"value":3997300,"limit":52428800}},"cachereport":{"origin":"mw-web.codfw.main-84b999ff94-cqknl","timestamp":"20250204104240","ttl":2592000,"transientcontent":false}}});});</script> <script type="application/ld+json">{"@context":"https:\/\/schema.org","@type":"Article","name":"Consistent Overhead Byte Stuffing","url":"https:\/\/en.wikipedia.org\/wiki\/Consistent_Overhead_Byte_Stuffing","sameAs":"http:\/\/www.wikidata.org\/entity\/Q5163224","mainEntity":"http:\/\/www.wikidata.org\/entity\/Q5163224","author":{"@type":"Organization","name":"Contributors to Wikimedia projects"},"publisher":{"@type":"Organization","name":"Wikimedia Foundation, Inc.","logo":{"@type":"ImageObject","url":"https:\/\/www.wikimedia.org\/static\/images\/wmf-hor-googpub.png"}},"datePublished":"2010-11-23T16:25:38Z","dateModified":"2024-09-07T19:35:43Z"}</script> </body> </html>