Metalink is a cross-platform and cross-application Internet standard In computer network engineering, an Internet Standard is a normative specification of a technology or methodology applicable to the Internet. Internet Standards are created and published by the Internet Engineering Task Force (IETF)/framework/file format for programs that download, including download managers A download manager is a computer program dedicated to the task of downloading possibly unrelated stand-alone files from (and sometimes to) the Internet for storage. This is unlike a World Wide Web browser, which is mainly intended to browse web pages, composed of a multitude of smaller files, where error-free moving of files for permanent storage, BitTorrent A BitTorrent client is a computer program that manages downloads and uploads using the BitTorrent protocol clients, Web browsers, FTP clients, and P2P A peer-to-peer, commonly abbreviated to P2P, is any distributed network architecture composed of participants that make a portion of their resources directly available to other network participants, without the need for central coordination instances (such as servers or stable hosts). Peers are both suppliers and consumers of resources, in programs. For increased convenience, it stores the multiple download locations for a file (FTP File Transfer Protocol is a standard network protocol used to copy a file from one host to another over a TCP/IP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server applications, which solves the problem of different end host/HTTP The Hypertext Transfer Protocol is an Application Layer protocol for distributed, collaborative, hypermedia information systems/P2P A peer-to-peer, commonly abbreviated to P2P, is any distributed network architecture composed of participants that make a portion of their resources directly available to other network participants, without the need for central coordination instances (such as servers or stable hosts). Peers are both suppliers and consumers of resources, in) and other metadata Metadata is loosely defined as data about data. Though this definition is easy to remember, it is not very precise. The strength of this definition is in recognizing that metadata is data. As such, metadata can be stored and managed in a database, often called a registry or repository. However, it is impossible to identify metadata just by looking in an XML XML is a set of rules for encoding documents electronically. It is defined in the XML 1.0 Specification produced by the W3C and several other related specifications; all are fee-free open standards file with the extension .meta4 or .metalink. This provides reliability in case one method fails. Some clients also achieve faster download speeds by allowing different chunks/segments of each file to be downloaded from multiple resources at the same time (segmented downloading Segmented downloading can be a more efficient way of downloading files from many peers at once. The one single file is downloaded, in parallel, from several distinct sources or uploaders of the file. This can help a group of users with asymmetric connections, such as ADSL to provide a high total bandwidth to one downloader, and to handle peaks in).

Other features include automatic hash verification of finished downloads, automatic repair of downloads with errors, listing multiple files to be added to a download queue, and automatic OS/language selection.

Metalink is extensible, and supports listing multiple partial and full file hashes A cryptographic hash function is a deterministic procedure that takes an arbitrary block of data and returns a fixed-size bit string, the hash value, such that an accidental or intentional change to the data will change the hash value. The data to be encoded is often called the "message", and the hash value is sometimes called the along with PGP Pretty Good Privacy is a computer program that provides cryptographic privacy and authentication. PGP is often used for signing, encrypting and decrypting e-mails to increase the security of e-mail communications. It was created by Philip Zimmermann in 1991 signatures. Most clients only support verifying MD5 In cryptography, MD5 is a widely used cryptographic hash function with a 128-bit hash value. Specified in RFC 1321, MD5 has been employed in a wide variety of security applications, and is also commonly used to check the integrity of files. However, it has been shown that MD5 is not collision resistant; as such, MD5 is not suitable for, SHA-1 The SHA hash functions are a set of cryptographic hash functions designed by the National Security Agency and published by the NIST as a U.S. Federal Information Processing Standard. SHA stands for Secure Hash Algorithm. The three SHA algorithms are structured differently and are distinguished as SHA-0, SHA-1, and SHA-2. The SHA-2 family uses an, & SHA-256, however. Besides FTP and HTTP mirror In computing, a mirror is an exact copy of a data set. On the Internet, a mirror site is an exact copy of another Internet site. Mirror sites are most commonly used to provide multiple sources of the same information, and are of particular value as a way of providing reliable access to large downloads. Mirroring is a type of file synchronization locations and rsync rsync is a software application for Unix systems which synchronizes files and directories from one location to another while minimizing data transfer using delta encoding when appropriate. An important feature of rsync not found in most similar programs/protocols is that the mirroring takes place with only one transmission in each direction. rsync, it also supports listing the P2P methods BitTorrent BitTorrent is a peer-to-peer file sharing protocol used for distributing large amounts of data. BitTorrent is one of the most common protocols for transferring large files, and it has been estimated that it may account for as much as 43 % of all Internet traffic as of February 2009, ed2k, magnet link The magnet: URI scheme is a draft open standard defining a URI scheme for magnet links, which are mainly used to reference resources available for download via peer-to-peer networks. Such a link typically identifies a file not by location or name, but by content; more precisely, by the content's hash value or any other that uses a URI In computing, a Uniform Resource Identifier is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network (typically the World Wide Web) using specific protocols. Schemes specifying a concrete syntax and associated protocols define each.

Development History

Metalink 3.0 was publicly released in 2005. It was designed to aid in downloading Linux ISO images An ISO image is an archive file of an optical disc in a format defined by the International Organization for Standardization (ISO). This format is supported by many software vendors. ISO image files typically have a file extension of .ISO. The name ISO is taken from the ISO 9660 file system used with CD-ROM media, but an ISO image can also contain and other large files on release day, when servers would be overloaded (each server would have to be tried manually) and to repair large downloads instead of fully re-downloading them. It was initially adopted by download managers A download manager is a computer program dedicated to the task of downloading possibly unrelated stand-alone files from (and sometimes to) the Internet for storage. This is unlike a World Wide Web browser, which is mainly intended to browse web pages, composed of a multitude of smaller files, where error-free moving of files for permanent storage, and was used by open source Open source describes practices in production and development that promote access to the end product's source materials. Some consider open source a philosophy, others consider it a pragmatic methodology. Before the term open source became widely adopted, developers and producers used a variety of phrases to describe the concept; open source projects such as OpenOffice.org OpenOffice.org, commonly known as OOo or OpenOffice, is an open-source software application suite available for a number of different computer operating systems. It is distributed as free software and written using its own GUI toolkit. It supports the ISO/IEC standard OpenDocument Format for data interchange as its default file format, as well as and Linux distributions A Linux distribution is a member of the family of Unix-like software distributions built on top of the Linux kernel. Such distributions (often called distros for short) consist of a large collection of software applications such as word processors, spreadsheets, media players and database applications. The operating system will consist of the. A community developed around it, more download programs supported it (including proprietary ones) and it saw commercial adoption. In 2008, the community took their work to the Internet Engineering Task Force The Internet Engineering Task Force develops and promotes Internet standards, cooperating closely with the W3C and ISO/IEC standards bodies and dealing in particular with standards of the TCP/IP and Internet protocol suite. It is an open standards organization, with no formal membership or membership requirements. All participants and managers are which resulted in Metalink 4.0 in 2010, described in a Standards Track RFC In computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force (IETF) describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems. Metalink 3.0 (with the extension .metalink) and Metalink 4.0 (with the extension .meta4) are incompatible because they have a slightly different format.

Client programs

• aria2 (GPL), in the Debian repositories, is a Unix/Windows command line download utility that supports BitTorrent and Metalink (HTTP/FTP/BitTorrent)
• DownThemAll (GPL The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU project), a Firefox extension and download manager that has basic Metalink support.
• FlashGot FlashGot is a free and open source Mozilla extension meant to handle single and massive downloads with several external download managers (GPL The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU project), a Firefox extension for integrating with many Download Managers, supports Metalink.
• Free Download Manager Free Download Manager is a free open source graphical download manager for the Microsoft Windows operating system (GPL The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU project), a Windows Download Manager, supports Metalink (HTTP/FTP) in version 2.5.
• GetRight GetRight is able to pause and resume downloads, download from multiple servers to speed up download time , scheduling the starting and stopping of downloads and shutting off the computer or disconnecting the modem when the downloads have finished. It is also able to integrate with Microsoft's Internet Explorer, and Mozilla Firefox with the 6, a Windows Download Manager, supports Metalink (HTTP/FTP/BitTorrent).
• jDownloader JDownloader is an open source download manager, written in Java, which allows the automatic download of files and split files from one-click hosting sites such as Rapidshare and Megaupload. JDownloader supports the use of premium accounts is an open source download manager written in Java Java refers to a number of proprietary computer software products and specifications from Sun Microsystems, a subsidiary of Oracle Corporation, that together provide a system for developing application software and deploying it in a cross-platform environment. Java is used in a wide variety of computing platforms from embedded devices and mobile.
• KGet KGet is a free download manager for KDE. By default it is the download manager used for Konqueror, but can also be used with Mozilla Firefox. KGet is part of the KDE Network package, and was featured by Tux Magazine and Free Software Magazine (GPL The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU project), KDE KDE is an international free software community producing an integrated set of cross-platform applications designed to run on Linux, FreeBSD, Windows, Solaris and Mac OS X systems. It is best known for its Plasma Desktop workspace, a desktop environment provided as the default working environment on many Linux distributions, such as openSUSE,'s native download manager, supports Metalink in KDE 4.
• Net Transport Net Transport is a shareware (with 30 day trial) download manager and stream ripper for Windows made by Xi Software, a Windows Download Manager, supports Metalink.
• Orbit Downloader Orbit Downloader is a freeware graphical download manager for the Microsoft Windows operating system. One of the main features of the program is its ability to grab and download embedded Flash Video files from sites like YouTube, Dailymotion, Metacafe etc. Orbit Downloader also accelerates downloads by acting as a peer-to-peer client, utilizing, a Windows Download Manager, supports Metalink (HTTP/FTP).
• Phex (GPL The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU project), a Mac/Unix/Windows gnutella Gnutella was the first decentralized file sharing network. It celebrated a decade of existence on March 14, 2010 and has a user base in the millions. In late 2007, it was the most popular file sharing network on the Internet with an estimated market share of more than 40%. In June 2005, gnutella's population was 1.81 million computers increasing client, supports Metalink downloads along with exporting a library to Metalink for sharing between users.
• Retriever is a closed source cross platform Java download manager that supports Metalink and BitTorrent.
• SmartFTP, a Windows GUI FTP client, supports Metalink for adding files to an FTP transfer queue and hash verification.
• VeryCD's easyMule (version 1 is GPLed The GNU General Public License is the most widely used free software license, originally written by Richard Stallman for the GNU project, ver.2 may be GPL-Violation) is a version of eMule eMule is a free peer-to-peer file sharing application for Microsoft Windows. Started in May 2002 as an alternative to eDonkey2000, eMule now connects to both the eDonkey network and the Kad network. The distinguishing features of eMule are the direct exchange of sources between client nodes, fast recovery of corrupted downloads, and the use of a with Metalink support.
• wxDownload Fast wxDownload Fast is a free/open source download manager. It was created to be multi-platform, so at the moment it builds on Windows (2000, XP), Linux, BSD, and Mac OS X. Besides that, it is a multi-threaded (aka accelerated or segmented) download manager. This means that it can split a file into several pieces and download the pieces simultaneously (GPL) is a Mac/Unix/Windows download manager that supports Metalink (HTTP/FTP).
• yum, an open source Open-source software is computer software that is available in source code form for which the source code and certain other rights normally reserved for copyright holders are provided under a software license that permits users to study, change, and improve the software. Open source licenses often meet the requirements of the Open Source command line A command-line interface is a mechanism for interacting with a computer operating system or software by typing commands to perform specific tasks. This text-only interface contrasts with the use of a mouse pointer with a graphical user interface (GUI) to click on options, or menus on a text user interface (TUI) to select options. This method of package management utility for RPM-compatible Linux Linux refers to the family of Unix-like computer operating systems using the Linux kernel. Linux can be installed on a wide variety of computer hardware, ranging from mobile phones, tablet computers and video game consoles, to mainframes and supercomputers. Linux is predominantly known for its use in servers; in 2009 it held a server market share operating systems An operating system is the software on a computer that manages the way different programs use its hardware, and regulates the ways that a user controls the computer. Operating systems are found on almost any device that contains a computer with multiple programs—from cellular phones and video game consoles to supercomputers and web servers. Some, uses Metalink internally, invisible to the user.
• ZYpp ZYpp is a package management engine that powers Linux applications like YaST, Zypper and the openSUSE/SUSE Linux Enterprise implementation of PackageKit. Unlike other common package managers, it provides a powerful satisfiability solver to compute package dependencies and a convenient package management API. It is an open source and free software, the package management engine that powers YaST2 and Zypper ZYpp is a package management engine that powers Linux applications like YaST, Zypper and the openSUSE/SUSE Linux Enterprise implementation of PackageKit. Unlike other common package managers, it provides a powerful satisfiability solver to compute package dependencies and a convenient package management API. It is an open source and free software, supports Metalink for downloading. It uses aria2 internally.

In use

Mandriva Linux has integrated Metalink into package management with urpmi and aria2. Fedora has integrated Metalink into package management with yum. openSUSE has integrated Metalink into package management with ZYpp and aria2.

Wubi, the Windows-based Ubuntu installer, uses Metadl (LGPL) to download Ubuntu ISO images and takes advantage of Metalink's features of higher availability and increased reliability. If there are errors in the download, they are repaired, instead of restarting the large download.

Appupdater (GPL) for Windows "is similar to apt-get or yum on Linux. It automates the process of installing and maintaining up to date versions of programs."

Currently, OpenOffice.org uses Metalinks to distribute their free office suite. cURL offers Metalinks of their downloads. UniProt Consortium also provides a Metalink for their large protein database. Dofus, a Flash MMORPG uses Metalinks for downloads and so does Sage, the open-source mathematical software.

The software hosting and collaboration platform Origo generates Metalinks for all hosted releases.

The following Linux distributions use Metalink for ISO image distribution: 64 Studio, Adios, Bayanihan Linux, BeleniX, Berry Linux, BLAG Linux and GNU, Bluewhite64 Linux, Damn Small Linux, Fedora, GoboLinux, Granular Linux, KateOS, Linux Mint, openSUSE, Pardus Linux, PCLinuxOS, PuppyLinux, Sabayon Linux, StartCom Enterprise Linux, SUSE Linux, Ubuntu.

The following FreeBSD based distributions use Metalink for ISO image distribution: DesktopBSD, MidnightBSD, PC-BSD and TrueBSD.

File based search engine findthatfile provides search for Metalinks.

Metalink client feature comparison

A guide to which clients support which Metalink features:

No clients support rsync at this time.

Metalink generation

Metalink is XML so they can be hand crafted or XML tools can be used for automation. These tools are specifically for Metalink.

• Bouncer is "database driven mirror management app that has three main components - a bounce script, a sentry script to check mirrors and files for integrity and a set of web-based administration tools." Bouncer supports Metalink via a patch that has not yet been integrated upstream.
• Geo McFly (GPL) is an on the fly generator of metalinks based on the downloader's geographical location, written in Python.
• Metalink Editor (GPL) is a Cross Platform GUI Metalink editor written in Python which allows you to create and edit Metalinks.
• Metalink Library (GPL) is a Cross Platform Metalink library for Python and PHP based on Metalink Editor with many automatic features and an easy command-line interface to generate Metalink and Torrent files.
• Metalink Generator can also be used to create Metalinks by filling out a Web form.
• Metalink tools (GPL) Unix/Windows command line tools for generating Metalinks with hashes and mirror/p2p lists.
• Dynamic online metalinks based on metadata. Automatically created metalinks based on metadata published by each mirror.
• MirrorManager (MIT X11 license) is used by the Fedora Project for dynamically listing mirrors.
• The MirrorBrain (GPL, Apache License) is a real-time Metalink generator and download redirector. It can either return Metalinks, or automatically redirect non-Metalink clients (per HTTP redirection) to a mirror server near them. Advanced features, as transparent negotiation of Metalinks, or embedding of PGP signatures, are fully supported. It is used by openSUSE, OpenOffice.org, and other projects.
• Origo is a new and easy to use software development and hosting platform for open and closed source projects. Among many features, it has easy release management and mirroring with automatic metalink generation.

Example Metalink 4.0 .meta4 file

Metalink 4.0 files have the extension .meta4 and are XML text files. They are served with the application/metalink4+xml Internet media type.

<?xml version="1.0" encoding="UTF-8"?>
<metalink xmlns="urn:ietf:params:xml:ns:metalink">
<published>2009-05-15T12:23:23Z</published>
<file name="example.ext">
<size>14471447</size>
<identity>Example</identity>
<version>1.0</version>
<language>en</language>
<description>
A description of the example file for download.
</description>
<hash type="sha-256">3d6fece8033d146d8611eab4f032df738c8c1283620fd02a1f2bfec6e27d590d</hash>
<url location="de" priority="1">ftp://ftp.example.com/example.ext</url>
<url location="fr" priority="1">http://example.com/example.ext</url>
<metaurl mediatype="torrent" priority="2">http://example.com/example.ext.torrent</metaurl>
</file>
</metalink>

Example Metalink 3.0 .metalink file

Metalink 3.0 files have the extension .metalink and are XML text files.

<?xml version="1.0" encoding="UTF-8"?>
<metalink version="3.0" xmlns="http://www.metalinker.org">
<files>
<file name="example.ext">
<verification>
<hash type="md5">example-md5-hash</hash>
<hash type="sha1">example-sha1-hash</hash>
<signature type="pgp"/>
</verification>
<resources>
<url type="ftp" location="us" preference="90">ftp://ftp.example.com/example.ext</url>
<url type="ftp" location="uk" preference="90">ftp://ftp.example.net/example.ext</url>
<url type="http" location="us" preference="90">http://example.com/example.ext</url>
<url type="http" location="de" preference="90">http://example.net/example.ext</url>
<url type="bittorrent" preference="100">http://example.org/example.ext.torrent</url>
<url type="rsync"/>
<url type="magnet"/>
<url type="ed2k"/>
</resources>
</file>
</files>
</metalink>

See also

• Magnet URI scheme

References

External links

• Metalink project official homepage
• Making Metalinks article

Metalink standard

• RFC 5854 - "The Metalink Download Description Format"
• Metalink 3.0 Specification

Categories: Distributed data storage | Download managers | Network-related software | XML-based standards

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