Editing Endianness (section)

=== Networking ===

Many [[IETF RFC]]s use the term ''network order'', meaning the order of transmission for bytes ''over the wire'' in [[network protocols]]. Among others, the historic {{IETF RFC|1700|link=no}} defines the network order for protocols in the [[Internet protocol suite]] to be big-endian.<ref>{{ cite IETF | title = Assigned Numbers | rfc = 1700 | std = 2 | sectionname = Data Notations | page = 3 | last1 = Reynolds | first1 = J. | author-link1 = Joyce K. Reynolds | last2 = Postel | first2 = J. | author-link2 = Jon Postel | date=October 1994 | publisher = [[IETF]] | access-date = 2012-03-02 }}</ref>

However, not all protocols use big-endian byte order as the network order. The [[Server Message Block]] (SMB) protocol uses little-endian byte order. In [[CANopen]], multi-byte parameters are always sent [[least significant byte]] first (little-endian). The same is true for [[Ethernet Powerlink]].<ref>Ethernet POWERLINK Standardisation Group (2012), ''EPSG Working Draft Proposal 301: Ethernet POWERLINK Communication Profile Specification Version 1.1.4'', chapter 6.1.1.</ref>

The [[Berkeley sockets]] [[API]] defines a set of functions to convert 16- and 32-bit integers to and from network byte order: the {{code|htons}} (host-to-network-short) and {{code|htonl}} (host-to-network-long) functions convert 16- and 32-bit values respectively from machine (''host'') to network order; the {{code|ntohs}} and {{code|ntohl}} functions convert from network to host order.<ref>{{cite book | title = The Open Group Base Specifications Issue 7 | author = IEEE and The Open Group | date = 2018 | volume = 2 | chapter = 3. System Interfaces | page = 1120 | url = https://pubs.opengroup.org/onlinepubs/9699919799/functions/htonl.html | access-date = 2021-04-09 | archive-date = 2021-04-18 | archive-url = https://web.archive.org/web/20210418041546/https://pubs.opengroup.org/onlinepubs/9699919799/functions/htonl.html | url-status = live }}</ref><ref>{{Cite web|title=htonl(3) - Linux man page|url=https://linux.die.net/man/3/htonl|access-date=2021-04-09|website=linux.die.net|archive-date=2021-04-18|archive-url=https://web.archive.org/web/20210418054331/https://linux.die.net/man/3/htonl|url-status=live}}</ref> These functions may be a [[no-op]] on a big-endian system.

While the high-level network protocols usually consider the byte (mostly meant as ''[[octet (computing)|octet]]'') as their atomic unit, the lowest layers of a [[network stack]] may deal with ordering of bits within a byte.