Napster
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Napster is a popular p2p application based in the centralized model. In Napster, a central directory server maintains an index on the metadata of all the files in the network. The metadata might include file names, creation dates, and copyright information . The server also maintain a table of user connection information including user’s IP address and line speed. A file query is sent to the server first. A query consists of a list of desired words. When the server receives a query, it searches for matches in its index. The query results including a list of users who hold the file are sent back to the user who initiated the query. The user then opens a direct connection with the peer that has the requested file for downloading.
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Technical issues
The Napster model creates certain issues like:
- Many clients just aren’t accessible.
- Firewalls can limit incoming connections to clients.
- Many client systems come and go (churn).
- Round trip times to certain world locations can be slow.
- Slow 'upload' speeds are common in nowadays connections.
- Clients might withdraw a file unexpectedly causing the download to break. E.g: if low on disk space, or if they download something on top of a song they aren’t listening to anymore.
- If we assume clients serve up the same stuff people download, the number of sources for a less popular item will be very small.
- Under assumption that churn is a constant, these less popular items will generally not be accessible or have slow download speeds.
Napster refinements
Early Napster just listed anything. Later it adds improvements such as:
- Enhanced directory servers appear to probe clients, track their health. Uses an automated reporting of download problems to trim 'bad sources' from list.
- Incentives by ranking data sources to preferentially list clients who:
- Have been up for a long time.
- Seem to have fast connections.
- Appear to be “close” to the client doing the download (uses notion of 'Internet distance').
- Implement parallel downloads and even an experimental method for doing 'striped' downloads (first block from source A, second from source B, third from C, etc).
- Leverages asymmetric download/uplink speeds.
Legal challenges
Heavy metal band Metallica discovered that a demo of their song ‘I Disappear’ had been circulating across the Napster network, even before it was released. This eventually led to the song being played on several radio stations across America and brought to Metallica’s attention that their entire back catalogue of studio material was also available. The band responded in 2000 by filing a lawsuit against the service offered by Napster. A month later, rapper Dr. Dre shared a litigator and legal firm with Metallica, and filed a similar lawsuit after Napster wouldn't remove his works from their service, even after he issued a written request. Separately, both Metallica and Dr. Dre later delivered thousands of usernames to Napster who they believed were pirating their songs. One year later, Napster settled both suits, but this came after being shut down by the Ninth Circuit Court in a separate lawsuit from several major record labels (see below).
In 2000, A&M records and several other recording companies sued Napster for contributory and vicarious copyright infringement under the US Digital Millennium Copyright Act (DMC Act). The music industry made the following claims against Napster:
(1) That its users were directly infringing the plaintiff's copyright;
(2) That Napster was liable for contributory infringement of the plaintiff's copyright;
(3) That Napster was liable for vicarious infringement of the plaintiff's copyright.
The court found Napster guilty on all three claims.
Napster lost the case in the District Court and appealed to the U.S. Court of Appeals for the Ninth Circuit. Although the Ninth Circuit found that Napster was capable of commercially significant non-infringing uses, it affirmed the District Court's decision. On remand, the District Court ordered Napster to monitor the activities of its network and to block access to infringing material when notified of that material's location. Napster was unable to do this, and so shut down its service in July 2001. Napster finally declared itself bankrupt in 2002 and sold its assets. It had already been offline since the previous year owing to the effect of the court rulings.
References
- Peer to peer systems and applications. Steinmetz R, Wehrle K. Springer, 2005.
- Wikipedia.
