Sneakernet

In a non-network environment, the floppy disk was once the primary means of transferring data between computers. Today, portable flash drives or memory cards are more practical.

Sneakernet is a tongue-in-cheek term used to describe the transfer of electronic information, especially computer files, by physically carrying removable media such as magnetic tape, floppy disks, compact discs, USB flash drives, or external hard drives from one computer to another. This is usually in lieu of transferring the information over a computer network. This mode of data transport is often used as an academic example to illustrate the trade-off between latency and bandwidth.

Summary and background

Sneakernets are in use throughout the computer world. Sneakernets may be used when computer networks are prohibitively expensive for the owner to maintain, in high-security environments where manual inspection (for re-classification of information) is necessary, where information needs to be shared between networks with different levels of security clearance, when data transfer is impractical due to bandwidth limitations, when a guest laptop is incompatible with the local network, or simply when two computers are not powered up at the same time or lack the correct interconnecting cabling. Because sneakernets take advantage of physical media, different security measures must be taken into account for the transfer of sensitive information.

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.^[1]

The United States Postal Service also offers a Media Mail 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 other methods of data transfer.

Theory

From an information theory standpoint, sneakernets can achieve tremendous throughput, but they suffer from high latency (see Comparison of latency and throughput). 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's (4.7 GB) worth of information. Over the Internet the latency for the file request may be milliseconds, but at a modest broadband download speed of 50 kB/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 1305 kB/s.

The theoretical capacity of a Boeing 747 filled with Blu-Ray discs is 595,520,000 Gigabits, resulting in a 37,034.826 Gb/s flight from New York to Los Angeles. ^[2]

Similarly, as of 2006^[update] the largest backup tape available is the DLT-S4, with a capacity of 800 GB. 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 Mbit/s. With current networking technology, this magnitude of speed over this distance would be very difficult to attain without a costly dedicated connection.^{[original research?]}

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.

Usage examples

• In September 2009, Durban company Unlimited IT reportedly pitted a carrier pigeon against South African 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 upload: during the same two-hour period, only about 4% of the data had been transferred over the ADSL link.^[3]
• Google has reportedly used a sneakernet to transport datasets too large for current computer networks, up to 120TB in size.^[4]
• 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.^[5]
• Many film editing and visual effects companies transfer large film-scans using hard drives shipped via courier (to reduce bandwidth bills, and to reserve bandwidth for more time-critical transfers)^{[citation needed]}
• Wizzy Digital Courier provides Internet access to schools with poor or no network connectivity by implementing UUCP on USB memory sticks. This allows email transport and scoops of web pages that back-fill a web cache.
• When home broadband access was less common, many people downloaded large files over their workplace networks and took them home by sneakernet. Today when 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.^{[citation needed]}
• In the Amiga demoscene the primary method of exchanging data was using snail mail to exchange floppies between groups. Each group 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.^{[citation needed]}
• Online DVD rental services such as Netflix and GameFly are effectively sneakernets, as they deliver data on DVDs and other media via regular mail.
• Petroleum seismic surveys routinely record field data many Terabytes in size. A cluster computer is required to process these data, and may take a year or more, during which time the field crew will wish to work in other areas. The field data are generally hand-carried on tape, and increasingly on hard disk inserts, to the processing centre.^{[citation needed]}
• Data analytics teams in the financial services sector often use sneakernets to transfer sensitive corporate information, such as ledger entries, customer data and financial statistics. There are several reasons for this: firstly, sneakernets can provide very high security (and possibly more importantly, they are perceived to be secure); secondly, the volumes of data concerned are often extremely high; and thirdly, setting up secure network links between the client business and the analytics team's facilities is often either impossible or an extremely convoluted process.

In media

Non-fiction

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. pp. 83. 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^{[citation needed]}. 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.

Fiction

The Terry Pratchett novel Going Postal includes a contest between a horse-back courier and the "Grand Trunk Clacks" (a semaphore line) to see which is faster to transmit the contents of a book to a remote destination.

The "valuable data file" has become a common MacGuffin in action films and television programs, and indeed the motif of the "valuable letter or documents" (pre-electronic information storage technology) dates back hundreds of years.

• The film Live Free or Die Hard depicts a digital thief attempting to download 500TB of financial data to a suitcase sized package(s).

• The 1995 film Johnny Mnemonic, based on the short story by William Gibson, stars Keanu Reaves as a digital courier with data transported in his head. Gibson's 2007 novel Spook Country also featured sneakernets, with iPods being the storage device used to clandestinely move information.^[6]

Similar concepts

• IP over Avian Carriers (RFC 1149), transmission of messages via homing pigeon.
• Delay-tolerant networks, such as the Haggle project at Cambridge University

Copyright concerns

This section needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (August 2008)

There have been many steps to inhibit the use of sneakernet techniques to prevent copyright infringement of information, most notably copy protection placed on audio files as well as physical media to prevent the user from copying and distributing that data.

In 1992 the Software Publisher Association (now known as the SIIA) produced a PSA campaign titled Don't Copy That Floppy.

SD Cards, as well as DVD-R/-RAM/-RW disks use "Content Protection for Recordable Media (CPRM)." ^{[7] [8]}

Memory_Stick Cards use a different form of DRM.

See also

Computer Science portal

• Pod slurping
• Darknet (file sharing)
• Jargon File
• Wizzy Digital Courier is a project to distribute data like email to places with no Internet connection, via USB flash drive.
• Meatspace (tongue-in-cheek implication of the real world as a similar analogue to cyberspace writ large)

References

1. ^ Sneakernet Redux: Walk Your Data
2. ^ Galore and Bandwidth that May Rival Your Stationwagon
3. ^ BBC NEWS | Africa | SA Pigeon 'Faster than broadband'
4. ^ BBC NEWS | Technology | Google helps terabyte data swaps
5. ^ ACM Queue - A Conversation with Jim Gray: Who would ever, in this time of the greatest interconnectivity in human history, go back to shipping bytes around via snail mail as a preferred means of data transfer?
6. ^ Poole, Steven (August 18, 2007). "Sign language". The Guardian (Guardian Media Group). http://www.guardian.co.uk/books/2007/aug/18/sciencefictionfantasyandhorror.fiction?gusrc=rss&feed=books. Retrieved September 24, 2009. 
7. ^ DTCP Overview (page 8)
8. ^ SD Technology - SD Card Association

External links

• "Don't Copy That Floppy" in Internet Archive
• Entry for "sneakernet" in the Jargon File
• Security risk of sneaker nets and USB devices
• Sneaker Net 2.0