{"id":378,"date":"2026-09-05T06:52:44","date_gmt":"2026-09-05T06:52:44","guid":{"rendered":"https:\/\/neodata.com.uy\/labs\/127-bytes\/"},"modified":"2026-09-07T13:51:28","modified_gmt":"2026-09-07T13:51:28","slug":"127-bytes","status":"publish","type":"post","link":"https:\/\/neodata.com.uy\/labs\/127-bytes\/","title":{"rendered":"127 bytes."},"content":{"rendered":"<p><!--\nWORDPRESS CONTENT: NEODATA Labs Marginalia\n--><\/p>\n<p class=\"nlabs-kicker\">MARGINALIA &middot; ONE NUMBER<\/p>\n<h2 id=\"the-physical-frame-before-cryptography-takes-its-share\">The physical frame, before cryptography takes its share.<\/h2>\n<p><strong>127 octets<\/strong><\/p>\n<p>That is the maximum physical-layer packet size used in the IEEE 802.15.4 calculation set out by RFC 4944.<\/p>\n<p>The number is only the beginning. The RFC subtracts a maximum frame overhead of 25 octets, leaving 102 at the media-access layer. In its largest AES-CCM-128 security case, another 21 octets are consumed. What remains is 81 octets, before an adaptation layer and the application have expressed anything.<\/p>\n<p>At this scale, a nonce, authentication tag, key identifier, counter and algorithm indication are not negligible metadata. They compete directly with the message. A construction that is compact in an API can require fragmentation, new state and new failure paths on the wire.<\/p>\n<p>The number is useful because it moves the security discussion from algorithm names to complete encodings.<\/p>\n<p class=\"nlabs-source\">Source: <a href=\"https:\/\/www.rfc-editor.org\/rfc\/rfc4944.html#section-4\">RFC 4944, Section 4<\/a>.<\/p>\n<p>Related research: <a href=\"https:\/\/neodata.com.uy\/labs\/the-handshake-has-a-budget-of-fourteen-kilobytes\/\">The handshake has a budget of fourteen kilobytes.<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>An IEEE 802.15.4 calculation begins with 127 octets. After framing and link security, only 81 may remain.<\/p>\n","protected":false},"author":2,"featured_media":400,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[35],"tags":[24],"nlabs_article_type":[],"class_list":["post-378","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-marginalia","tag-marginalia"],"_links":{"self":[{"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/posts\/378","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/comments?post=378"}],"version-history":[{"count":1,"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/posts\/378\/revisions"}],"predecessor-version":[{"id":401,"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/posts\/378\/revisions\/401"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/media\/400"}],"wp:attachment":[{"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/media?parent=378"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/categories?post=378"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/tags?post=378"},{"taxonomy":"nlabs_article_type","embeddable":true,"href":"https:\/\/neodata.com.uy\/labs\/wp-json\/wp\/v2\/nlabs_article_type?post=378"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}