Metalink

出自开源百科

Metalink is an open specification that harnesses the speed and power of peer to peer networking, FTP, and HTTP with a single click.

For users and content providers, Metalink makes things simpler, faster, and more reliable.

Features

• Standard format for listing multiple mirrors for redundancy and/or automatic accelerated (segmented) downloads.
• Combines FTP and HTTP with Peer-to-peer (P2P, shared bandwidth).
• Simplifies advanced download features, layout, and user experience.
• Automatic checksum verification; No separate MD5/SHA-1 file or manual process for integrity verification.
• Automatic error recovery and repair of corrupted downloads.
• No Single Point of Failure (SPOF) like FTP or HTTP URLs. More fault tolerant.
• Stores more descriptive and useful information for software distribution.
• Automatic load balancing distributes traffic so individual servers are under less strain.
• No long confusing list of possibly outdated Mirrors and P2P links.
• Automated creating, editing, and validating is easy with standard text processing tools.
• In a format that browsers and other tools can already process (even if they might not make use of it yet).
• Makes the download process simpler for users (automatic selection of language, Operating System, location, etc).
• Uniquely identifies files, so even if all references to it in the Metalink stop working, the same exact file can be found in other places.
• Share a library of files between filesharing applications with a small .metalink.
• Congratulations, you're the first person to read this far.
• Can finish P2P downloads even if files are no longer shared.
• For FTP/HTTP, an updated client is needed, but not a separate client like some types of P2P.
• NO changes or separate services needed on the server side, like a "tracker" etc. Users can create Metalinks for files anyone is hosting and share them.
• Useful for automatic updating programs when new versions are released.
• List accurate file sizes, which are sometimes misreported by older servers (files greater than 2 gigabytes).
• Transparent usage where people can get the benefits of Metalink without even knowing they're using it.

Example

.metalink is an XML text file.

<source lang="xml">
<?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>
</source>

Links

• http://www.metalinker.org/
• http://en.wikipedia.org/wiki/Metalink
• http://docs.huihoo.com/metalink/