World Library  
Flag as Inappropriate
Email this Article

Dot-decimal notation

Article Id: WHEBN0000436706
Reproduction Date:

Title: Dot-decimal notation  
Author: World Heritage Encyclopedia
Language: English
Subject: Open Shortest Path First, WikiProject Spam, Network addressing, Common Gateway Interface, IPv6 address
Collection: Network Addressing
Publisher: World Heritage Encyclopedia
Publication
Date:
 

Dot-decimal notation

Dot-decimal notation is a presentation format for numerical data. It consists of a string of decimal numbers, each pair separated by a full stop (dot).

A common use of dot-decimal notation is in information technology where it is a method of writing numbers in octet-grouped base-10 (decimal) numbers separated by dots (full stops). In computer networking, Internet Protocol Version 4 addresses are commonly written using the quad-dotted notation of four decimal integers, ranging from 0 to 255 each.

Contents

  • Definition and use 1
  • IPv4 address 2
  • See also 3
  • Notes 4
  • References 5

Definition and use

Dot-decimal notation is a presentation format for numerical data expressed as a string of decimal numbers each separated by a full stop. In computer networking, the term is often used as a synonym of dotted quad notation,[1] or quad-dotted notation, a specific use to represent Internet Protocol Version 4 addresses. [2]

For example, the hexadecimal number 0xFF0000 may be expressed in dot-decimal notation as 255.0.0.

Object identifiers use a style of dot-decimal notation to represent an arbitrarily deep hierarchy of objects identified by decimal numbers.

IPv4 address

An IP address (version 4) in both dot-decimal notation and binary code

An Internet Protocol Version 4 (IPv4) address consists of 32 bits, which may be divided into four octets. These four octets are written in decimal numbers, ranging from 0 to 255, and are concatenated as a character string with full stop delimiters between each number.

For example, the address of the loopback interface, usually assigned the host name localhost, is 127.0.0.1. It consists of the four binary octets 01111111, 00000000, 00000000, and 00000001, forming the full 32-bit address.

There is no official specification for this textual IP address representation. The first mention of this format in RFC documents was in Mail Transfer Protocol’s (a predecessor to SMTP) RFC 780 from May 1981, where the IP address was supposed to be enclosed by brackets. (And an alternate representation was a decimal integer prefixed by a pound sign.) A table in the “Assigned Numbers” RFC 790 used the dotted decimal format, zero-padding each number to three digits.[3]

A popular implementation of IP networking, originating in 4.2BSD, contains a function inet_aton() for converting IP addresses in character strings representation to internal binary storage. In addition to the basic four-decimals format and full 32-bit addresses, it also supported intermediate syntaxes of octet.24bits (e.g. 10.1234567; for Class A addresses) and octet.octet.16bits (e.g. 172.16.12345; for Class B addresses). It also allowed the numbers to be written in hexadecimal and octal, by prefixing them with 0x and 0, respectively. These features continue to be supported by software until today, even though they are seen as non-standard.[3] But this also means addresses where an IP address component is written with a leading zero digit may be interpreted differently by different programs: some will ignore the leading zero, some will interpret the number as octal.[4]

IP addresses in the dot-decimal notation are sometimes suffixed with a slash and a number, which is used to specify the length of the associated routing prefix. This is called CIDR notation. For example, 127.0.0.1/8 indicates that the IP address has a 24-bit routing prefix.

See also

Notes

References

  1. ^ "Dotted Decimal Notation". encyclopedia.com. 
  2. ^ "Dot address". TechTarget. Retrieved 2010-11-18. 
  3. ^ a b Main, Andrew (23 February 2005). Textual Representation of IPv4 and IPv6 Addresses.  
  4. ^ "Ping and FTP resolve IP address with leading zero as octal". Microsoft Support. Retrieved 2010-03-01. 
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.
 


Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.