Anthony Bryan wrote: > Abstract > > This document specifies Metalink, an XML-based download description > format. Metalink describes alternate download locations (mirrors), > checksums, and other information. Clients can transparently use this > information to reliably transfer files. > > 1. Introduction > > Metalink is an XML-based document format that describes a file or > lists of files to be added to a download queue. Metalinks can list a > I think this should be "a file or list of files", so that both are in the singular (both "file" and "list of files"). > number of files, each with an extensible set of attached metadata. For > example, each file can have a description, checksum, and list of URIs > that it is available from. > > Identical copies of a file are frequently accessible in multiple > locations on the Internet over a variety of protocols (FTP, HTTP, and > Peer-to-Peer). Users are shown a list of these multiple download > locations (mirrors) and must manually select a single one on the basis > of geographical location, priority, or bandwidth. This distributes the > load across multiple servers. At times, individual servers can be > slow, outdated, or unreachable, but this can not be determined until > the download has been initiated. This can lead to the user canceling > the download and needing to restart it. During downloads, errors in > transmission can corrupt the file. There are no easy ways to repair > these files. For large downloads this can be extremely troublesome. > Any of the number of problems that can occur during a download lead to > frustration on the part of users. > > All the information about a download, including mirrors, checksums, > digital signatures, and other information can be stored in a > machine-readable Metalink file. This Metalink file transfers the > knowledge of the download server (and mirror database) to the client. > With this knowledge, the client is enabled to work its way to a > successful download even under adverse circumstances. All this is done > transparently to the user and the download is much more reliable and > efficient. In contrast, a traditional HTTP redirect to a mirror > conveys only extremely minimal information - one link to one server, > and there is no provision in the HTTP protocol to handle failures. > Other features that some clients provide include multi-source > downloads, where chunks of a file are downloaded from multiple mirrors > (and optionally, Peer-to-Peer) simultaneously which frequently results > in a faster download. > Apart from that small detail (above), I think it's good. It points out the advantages with metalinks and why/how to use them very well.
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