Sneaker refers to the shoes of the person carrying the media. This is usually in lieu of transferring the information over a computer network. Sneakernets are often used as an academic example to illustrate the trade-off between latency and bandwidth.
This form of data transfer is also used for peer-to-peer (or friend-to-friend) file sharing and has grown in popularity in metropolitan areas and college communities, sometimes for the purpose of distributing copyrighted material. The ease of this system has been facilitated by the availability of USB external hard drives, USB flash drives and portable music players such as Apple's iPod.
The United States Postal Service also offers a Media Mail service for computer hard drives and compact discs among other items. This provides a viable mode of transport for long distance sneakernet use. In fact, when mailing a sufficiently large hard drive or a spindle of DVDs, the throughput (amount of data per unit time) may compete favorably with other methods of data transfer.
The throughput of the network is directly proportional to the size of the transmitted file(s). Latency is based on the amount of time it takes to fully process the request for information. Latency would include the time it takes to write the storage media and the time to travel from point A to point B.
For example: Person A requested Person B to send him a DVD (4.7GB) worth of information. Over the Internet the latency for the file request may be milliseconds but at a modest broadband download speed of 50kB/s it may take up to a day to complete the transfer. On the other hand Person B could burn a DVD and deliver it to Person A in an hour. The latency was an hour but the throughput of the transfer is roughly equal to a transfer rate of 1305kB/s.
Similarly, as of 2006 the largest backup tape available is the DLT-S4, with a capacity of 800GB. If a tape of this capacity were sent by overnight mail and were to arrive around 20 hours after it was sent, the effective data rate would be 89 Mb/s. This magnitude of speed would be very difficult to attain without a costly dedicated connection.
Sneakernets may also be used in tandem with computer network data transfer to increase data security. For example, a file or collection of files may be encrypted and sent over the Internet while the encryption key is printed and hand delivered or mailed. This method greatly reduces the possibility of an individual intercepting both the key and encrypted data.
There is also the limitation of read/write speeds on a computer. There are three ways disk speed can be increased. The speed of the drive and/or the media may be increased, multiple disks may be used (one disk may be read as another is written to), or simultaneous use of multiple disks.
Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.
—Tanenbaum, Andrew S. (1996). Computer Networks. New Jersey: Prentice-Hall. ISBN 0-13-349945-6.
The original version of this quotation came much earlier; the very first problem in Tanenbaum's 1981 textbook Computer Networks asks the student to calculate the throughput of a St. Bernard carrying floppy disks (which are said to hold 250 kilobytes of data). The first USENET citation is July 16, 1985, and it was widely considered a chestnut already, possibly dating from the 1970s . Other alleged speakers included Tom Reidel, Warren Jackson, or Bob Sutterfield. The station wagon transporting magnetic tapes is the canonical version, but variants using trucks or Boeing 747s and later storage technologies such as CD-ROMs have frequently appeared.
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