{"id":16780,"date":"2021-10-26T15:48:33","date_gmt":"2021-10-26T10:18:33","guid":{"rendered":"https:\/\/networkinterview.com\/?p=16780"},"modified":"2021-10-26T15:48:33","modified_gmt":"2021-10-26T10:18:33","slug":"what-is-arq-automatic-repeat-request","status":"publish","type":"post","link":"https:\/\/networkinterview.com\/what-is-arq-automatic-repeat-request\/","title":{"rendered":"What is ARQ (Automatic Repeat Request)?"},"content":{"rendered":"<div class=\"netwo-in-between-content\" id=\"netwo-3995515627\"><script async src=\"\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-1375203873676133\" crossorigin=\"anonymous\"><\/script><ins class=\"adsbygoogle\" style=\"display:block;\" data-ad-client=\"ca-pub-1375203873676133\" \ndata-ad-slot=\"2134143805\" \ndata-ad-format=\"auto\"><\/ins>\n<script> \n(adsbygoogle = window.adsbygoogle || []).push({}); \n<\/script>\n<\/div><p><span style=\"font-weight: 400;\">Various techniques are used at the Data link layer to control errors to simply ensure and confirm that all the data frames or packets; i.e., bit streams of data are transmitted and transferred from sender to receiver with accuracy. Using or providing error control at the Data link layer is a feature of optimization rather than a requirement. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">Error control process tracks data frames that got lost or corrupted during transmission. The Data link layer follows a technique to retransmit frames to detect or identify transit errors and also take actions which are required to reduce or eliminate such errors.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">In this article we will learn more about a technique used at<span style=\"color: #0000ff;\"><a style=\"color: #0000ff;\" href=\"https:\/\/en.wikipedia.org\/wiki\/Data_link_layer\" target=\"_blank\" rel=\"noopener\"> Data link layer<\/a><\/span> protocols known as Automation Repeat Request (ARQ) to make an effort to detect loss of packets during transmission, its advantages and how it is performed.\u00a0\u00a0<\/span><\/p>\n<h1><b>What is ARQ (Automatic Repeat Request)?<\/b><\/h1>\n<p><span style=\"font-weight: 400;\">There are two ways of doing error control namely error detection and error correction. Error detection simply means detection or identification of error. These errors may cause the receiver to receive garbled or unclear or distorted messages. Error correction means correction or fixing errors. Reconstruction and rebuilding of original data which is error free.\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">The main function of ARQ protocol is send receives an acknowledgement from the receiver end suggesting that the frame or packet is received correctly before timeout is occurred, timeout defines a specific time window within which acknowledgement has to be sent by the receiver to the sender. <\/span><\/p>\n<p><span style=\"font-weight: 400;\">If timeout happens sender will not get acknowledgement within specific time, which implies that data packet or frame is either lost or got corrupted during its transmission hence sender will re-transmit the data frame or packet and ARQ protocol will ensure that process will be repeated until the right packet transmission is completed. \u00a0<\/span><\/p>\n<h2>Techniques of Error Control<\/h2>\n<p><span style=\"font-weight: 400;\">There are various techniques of error control such as:<\/span><\/p>\n<h3><strong>Stop and Wait ARQ \u2013<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">It is also known as alternating bit protocol. It is the simplest flow and error control mechanism. This is usually required in telecommunications to transmit data or information between two connected devices. Receiver signals its readiness to receive data for each frame, sender sends information or data packet to receiver. Sender will stop and wait for acknowledgement from the receiver.<\/span><\/p>\n<p><span style=\"font-weight: 400;\"> If acknowledgement is not received within a fixed time frame, the sender will resend the data frame and wait for acknowledgement. If the sender receives acknowledgement, it will send the next data frame and wait again. And this process will keep on repeating until send has left with no data frame or information to send to the receiver.\u00a0<\/span><\/p>\n<h3><strong>Sliding Window ARQ \u2013<\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">It is used for continuous transmission error control and it is categorized into Go Back N ARQ and Selective repeat ARQ.\u00a0<\/span><\/p>\n<h3><strong>Go Back N ARQ \u2013 <\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">It sends frames within a specified window frame even without receiving acknowledgement.<\/span><\/p>\n<h3><strong>Selective Repeat ARQ \u2013 <\/strong><\/h3>\n<p><span style=\"font-weight: 400;\">Only suspected or damaged or lost data frames are retransmitted. Sender only retransmits frames for which No acknowledgement is received. It is used however lesser because of more complexity at sender and receiver end as each packet must be acknowledged individually.\u00a0<\/span><\/p>\n<p>&nbsp;<\/p>\n<h2><strong>Applications of Automatic Repeat Request<\/strong><\/h2>\n<p><span style=\"font-weight: 400;\">ARQ protocols have a wide range of applications to ensure they provide reliable transmissions over unreliable upstream sources. These protocols operate on short wave radio so as to ensure reliable delivery of signals.\u00a0\u00a0<\/span><\/p>\n<p><span style=\"font-weight: 400;\">For the same function of ARQ, there are various applications:\u00a0<\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Transmission Control Protocol (<span style=\"color: #0000ff;\"><a style=\"color: #0000ff;\" href=\"https:\/\/networkinterview.com\/introduction-to-tcp-ip\/\" target=\"_blank\" rel=\"noopener\">TCP<\/a><\/span>)<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Specific Service Orientation Protocol: Error-correction of message signals in ATM networks<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">High-Level Data Link protocol (HLDL)<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">IBM Binary synchronous Communications Protocol (IBSC)\u00a0<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Xmodem : modem file transfer protocol<\/span><\/li>\n<\/ul>\n<h2><strong>Pros and Cons of Automatic Repeat Request<\/strong><\/h2>\n<p><span style=\"color: #00ff00;\"><strong>PROS<\/strong><\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Quite simple error detection and error correction techniques<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Simple decoding equipment as compared to other techniques<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">ARQ is adaptive, as information is retransmitted only if error occurs\u00a0<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">Ideal for using noisy channels<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">It has both error flow and error control mechanism\u00a0<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">It has timer implementation\u00a0<\/span><\/li>\n<\/ul>\n<p><span style=\"color: #ff0000;\"><strong>CONS<\/strong><\/span><\/p>\n<ul>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">High error rate on a medium and channel could cause too much transmission of the frames or packets of information<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">High error rate in channel could lead to loss of information and lead to reduction in efficiency or productivity of the system\u00a0<\/span><\/li>\n<li style=\"font-weight: 400;\" aria-level=\"1\"><span style=\"font-weight: 400;\">System throughput is lowered by ARQ when channel error is high\u00a0<\/span><\/li>\n<\/ul>\n<h2><span style=\"color: #ff6600;\">Continue Reading:<\/span><\/h2>\n<p><span style=\"color: #0000ff;\"><em><strong><a style=\"color: #0000ff;\" href=\"https:\/\/networkinterview.com\/what-is-hot-standby-router-protocol-hsrp\/\" target=\"_blank\" rel=\"noopener\">What is HSRP (Hot Standby Router Protocol) ?<\/a><\/strong><\/em><\/span><\/p>\n<p><span style=\"color: #0000ff;\"><em><strong><a style=\"color: #0000ff;\" href=\"https:\/\/networkinterview.com\/what-is-netconf-protocol\/\" target=\"_blank\" rel=\"noopener\">What is NETCONF protocol?<\/a><\/strong><\/em><\/span><\/p>\n<p><em><strong><span style=\"color: #0000ff;\"><a style=\"color: #0000ff;\" href=\"https:\/\/networkinterview.com\/mpls-vs-ip-routing\/\" target=\"_blank\" rel=\"noopener\">What is MPLS and how is it different from IP Routing?<\/a><\/span><\/strong><\/em><\/p>\n<div class=\"netwo-after-content\" id=\"netwo-2229679883\"><script async src=\"\/\/pagead2.googlesyndication.com\/pagead\/js\/adsbygoogle.js?client=ca-pub-1375203873676133\" crossorigin=\"anonymous\"><\/script><ins class=\"adsbygoogle\" style=\"display:block;\" data-ad-client=\"ca-pub-1375203873676133\" \ndata-ad-slot=\"2134143805\" \ndata-ad-format=\"auto\"><\/ins>\n<script> \n(adsbygoogle = window.adsbygoogle || []).push({}); \n<\/script>\n<\/div>","protected":false},"excerpt":{"rendered":"<p>Various techniques are used at the Data link layer to control errors to simply ensure and confirm that all the data frames or packets; i.e., bit streams of data are transmitted and transferred from sender to receiver with accuracy. Using &hellip; <\/p>\n","protected":false},"author":146,"featured_media":16781,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[1,92],"tags":[6610],"class_list":["post-16780","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-techblog","category-protocol","tag-protocol"],"jetpack_featured_media_url":"https:\/\/networkinterview.com\/wp-content\/uploads\/2021\/10\/ARQ.jpg","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/posts\/16780","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/users\/146"}],"replies":[{"embeddable":true,"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/comments?post=16780"}],"version-history":[{"count":0,"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/posts\/16780\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/media\/16781"}],"wp:attachment":[{"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/media?parent=16780"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/categories?post=16780"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/networkinterview.com\/wp-json\/wp\/v2\/tags?post=16780"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}