Sneakernet is an informal term for the transfer of electronic information by physically moving media such as magnetic tape, floppy disks, compact discs, USB flash drives or external hard drives from one computer to another; rather than transmitting the information over a computer network. The term, a tongue-in-cheek play on net(work) as in Internet or Ethernet, refers to walking in sneakers as the transport mechanism for the data.
Also known as trainnets or pigeonets, these types of physically mediated networks are in use throughout the world. Sneakernets are used when data transfer is impractical due to bandwidth limitations or other reasons such as data security. 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. The ease of this system has been facilitated by the availability of USB external hard drives, USB flash drives and portable music players.
The United States Postal Service also offers a Media Mail, a discounted shipping service for 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 online methods of data transfer.
From an information theory standpoint, sneakernets can achieve tremendous throughput (amount of data per unit time), but they suffer from high latency (low responsiveness). For example, if Alice requests Bob send her a DVD (4.7 GB) worth of information. Over the Internet, the latency for the file request may be milliseconds—Alice starts receiving the information nearly immediately—but at a modest download speed of 50 kB/s it may take up to a day to complete the transfer. On the other hand, Bob could burn a DVD and deliver it to Alice in an hour. The latency was an hour, but the throughput of the transfer is roughly equal to a transfer rate of 1305 kB/s.
If an Airbus A380 were filled with microSD cards each holding 512 gigabytes of storage capacity, the theoretical total storage space onboard would be approximately 91 million terabytes. A flight from New York to Los Angeles would work out to a data transport rate of well over 5 petabytes per second.
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.
Another way sneakernets are used together with network transfers is to provide an initial full backup as a base for incremental backups. In the case of a large (several terabyte) dataset that grows by just a few megabytes a day, the initial seeding of the data to be backed up would require an excessively long time upload over a network. One solution is to make a local copy of the data which is then physically relocated to the remote location and topped up with daily incremental backups over a network.
When Australia joined Usenet in 1983, it received articles via tapes sent from the United States to the University of Sydney, which disseminated data to dozens of other computers on the country’s Unix network. The 2011 raid of Osama bin Laden’s compound in Pakistan revealed that he used a series of USB thumb drives to store his email drafts. A courier of his would then take the saved emails to a nearby Internet cafe and send them out to the desired recipients.
In 2009, a South African company Unlimited IT pitted a messenger pigeon against rival ISP Telkom to transfer 4 GB of data 60 miles from Howick to Durban. The pigeon, carrying the data on a memory stick, arrived in one hour eight minutes, with the data taking another hour to read from the memory stick. During the same two-hour period, only about 4.2% of the data had been transferred over the ADSL link. A similar experiment was conducted in England in 2010; the ‘pigeonnet’ also proved superior the standard telecom data rates.
An Australian TV show repeated the experiment with a carrier pigeon with a microSD card, a car carrying a USB Stick, and an ADSL line. The data was to be transferred a distance of 132 km by road. The pigeon won the race with a time of approximately 1 hour 5 minutes, the car came in second at 2 hours 10 minutes, and the internet transfer did not finish, having dropped out a second time and not coming back.
Google has used a sneakernet to transport large datasets, such as the 120 TB of data from the Hubble Space Telescope. Users of Google Cloud can import their data into Google Cloud Storage through sneakernet. The SETI@home project uses a sneakernet to overcome bandwidth limitations: data recorded by the radio telescope in Arecibo, Puerto Rico is stored on magnetic tapes which are then shipped to Berkeley, California for processing. In 2005, Jim Gray reported sending hard drives and even ‘metal boxes with processors’ to transport large amounts of data by postal mail.
When home broadband access was less common, many people downloaded large files over their workplace networks and took them home by sneakernet. Today, as home broadband is more common, sometimes technical workers at institutions with congested WAN links do the reverse: downloading data at home in the evening and carrying the files to work on USB flash drives. In the early demoscene (a computer art subculture), the primary method of exchanging data was using snail mail to exchange floppies between groups. Each group usually had at least one person designated as a swapper, who would exchange news, data and productions with swappers from other groups this way. The best swappers were known to send and receive over 100 mails a month.
Online DVD rental services such as GameFly, or those formerly provided by Netflix, are effectively sneakernets. They deliver data, stored on DVDs and occasionally other forms of digital media, via regular postal mail.
North Korean dissidents have been known to smuggle flash drives filled with western movies and television shows, largely in an effort to inspire a cultural revolution ‘El Paquete Semanal’ is a roughly 1TB compilation of media, distributed weekly throughout Cuba via portable hard drives and USB memory sticks.
In 2015 Amazon Web Services launched AWS Snowball, a 50 lb (23 kg), 50 TB device for transporting data to the AWS cloud; and in 2016 AWS Snowmobile, a truck to transport up to 100 PB of data in one load. For similar reasons, there is also a Google Transfer Appliance and an IBM Cloud Mass Data Migration device.
American computer scientist Andrew Tanenbaum is quoted as saying: ‘Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.’ The original version of this quotation came from a problem in Tanenbaum’s 1981 textbook ‘Computer Networks’ that asks for the throughput of a St. Bernard carrying floppy disks (in 1981 the standard 8 inch floppy held 241 kilobytes of data per side, though various formatting and data blocking techniques could get that as high as 800 kilobytes per side, while the 5.25 inch floppy held 180 kilobytes per side).
The 1995 film ‘Johnny Mnemonic,’ based on the short story by William Gibson, stars Keanu Reeves as a digital courier with 320 GB of corporate data transported in his head. In the film ‘Snowden,’ the title character is seen evading security by carrying a data chip concealed in a Rubik’s Cube.
The Daily Omnivore 
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