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Store and forward is a
telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
technique in which
information Information is an abstract concept that refers to that which has the power to inform. At the most fundamental level information pertains to the interpretation of that which may be sensed. Any natural process that is not completely random ...
is sent to an intermediate station where it is kept and sent at a later time to the final destination or to another intermediate station. The intermediate station, or
node In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics *Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines, ...
in a networking context, verifies the
integrity Integrity is the practice of being honest and showing a consistent and uncompromising adherence to strong moral and ethical principles and values. In ethics, integrity is regarded as the honesty and truthfulness or accuracy of one's actions. Inte ...
of the message before forwarding it. In general, this technique is used in networks with intermittent connectivity, especially in the wilderness or environments requiring high mobility. It may also be preferable in situations when there are long delays in transmission and variable and high error rates, or if a direct, end-to-end connection is not available.


Modern store and forward networking

* Store and forward originates with delay-tolerant networks. No real-time services are available for these kinds of networks. * Logistical Networking is a scalable form of store and forward networking that exposes network-embedded buffers on intermediate nodes and allows flexible creation of services by higher-level managers including caching, point-to-multipoint communication (or
multicast In computer networking, multicast is group communication where data transmission is addressed to a group of destination computers simultaneously. Multicast can be one-to-many or many-to-many distribution. Multicast should not be confused with ...
),
content delivery Digital distribution, also referred to as content delivery, online distribution, or electronic software distribution, among others, is the delivery or distribution of digital media content (media), content such as Sound recording and reproductio ...
and many other stateful distributed services.Beck, M.; Moore, T.; Plank, J.; Swany, M.:"Logistical Networking", Active Middleware Services, pp. 141-154. Springer US, 2000 Real time services can be created using logistical networking when data transfer connectivity permits. A store-and-forward switching center is a
message switching In telecommunications, message switching involves messages routed in their entirety, one hop at a time. It evolved from circuit switching and was the precursor of packet switching. History Western Union operated a message switching system, Plan ...
center in which a message is accepted from the originating user, ''i.e.,'' sender, when it is offered, held in a physical storage, and forwarded to the destination user, ''i.e.,'' receiver, in accordance with the priority placed upon the message by the originating user and the
availability In reliability engineering, the term availability has the following meanings: * The degree to which a system, subsystem or equipment is in a specified operable and committable state at the start of a mission, when the mission is called for at a ...
of an outgoing
channel Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Country, region of outback Austral ...
. Store and forward switching centers are usually implemented in mobile service stations where the messages that are sent from the sender is first sent to these centers. If the destination address isn't available, then the center stores this message and tries sending it later. This improves the probability of the message to be delivered. In the other case, if the destination is available at that time, then the message is immediately sent.


Manually operated relay

Store and forward networks predate the use of computers. Point-to-point
teleprinter A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
equipment was used to send messages which were stored at the receiving end on punched
paper tape Five- and eight-hole punched paper tape Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated paper tape is a form of data storage ...
at a relay center. A human operator at the center removed the message tape from the receiving machine, read the addressing information, and then sent it toward its destination on appropriate outbound point-to-point teleprinter link. If the outbound link was in use, the operator placed the message in tape in a physical queue, usually consisting of a set of clips or hooks. A major relay center in the mid 1900s might have dozens of inbound and outbound teleprinters, scores of operators, and thousands of messages in the queues during peak periods. Operators referred to these centers as "torn-
tape relay A tape relay is a method of retransmitting teletypewriter traffic from one communication channel to another, in which messages arriving on an incoming channel are recorded in the form of perforated tape, this punched tape then being either fed dire ...
centers," a reference to removing the received message from the inbound teleprinter by tearing the paper tape to separate one message from the next. The
U.S. military The United States Armed Forces are the military forces of the United States. The armed forces consists of six service branches: the Army, Marine Corps, Navy, Air Force, Space Force, and Coast Guard. The president of the United States is the ...
term for such a center was "Non-Automated Relay Center" (NARC).


Automatic relay

In 1948,
Western Union The Western Union Company is an American multinational financial services company, headquartered in Denver, Colorado. Founded in 1851 as the New York and Mississippi Valley Printing Telegraph Company in Rochester, New York, the company chang ...
introduced Plan 55-A, the first automatic electromechanical store and forward message switching system. All message storage was performed by
paper tape Five- and eight-hole punched paper tape Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated paper tape is a form of data storage ...
punches paired with paper tape readers, with a bin in between.


Email

It is very common for an
email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" meant ...
system using
SMTP The Simple Mail Transfer Protocol (SMTP) is an Internet standard communication protocol for electronic mail transmission. Mail servers and other message transfer agents use SMTP to send and receive mail messages. User-level email clients typical ...
to accept a message, store it and then forward it on elsewhere. Although fully
open mail relay An open mail relay is a Simple Mail Transfer Protocol (SMTP) server configured in such a way that it allows anyone on the Internet to send e-mail through it, not just mail destined to or originating from known users. This used to be the default con ...
s are no longer common, not only does simple server-based forwarding work this way, but also many
email filtering Email filtering is the processing of email to organize it according to specified criteria. The term can apply to the intervention of human intelligence, but most often refers to the automatic processing of messages at an SMTP server, possibly appl ...
and automated
electronic mailing lists A mailing list is a collection of names and addresses used by an individual or an organization to send material to multiple recipients. The term is often extended to include the people subscribed to such a list, so the group of subscribers is re ...
services.


UUCP

Prior to the deployment of the
Internet The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a '' network of networks'' that consists of private, pub ...
, computers were connected via a variety of point-to-point techniques, with many smaller computers using dial-up connections. The UUCP store-and-forward protocols allowed a message (typically e-mail) to move across the collection of computers and eventually reach its destination. Late in the 20th century, store and forward techniques evolved into
packet switching In telecommunications, packet switching is a method of grouping Data (computing), data into ''network packet, packets'' that are transmitted over a digital Telecommunications network, network. Packets are made of a header (computing), header and ...
which replaced it for most purposes.


FidoNet

FidoNet was an email store-and-forward system for
bulletin board system A bulletin board system (BBS), also called computer bulletin board service (CBBS), is a computer server running software that allows users to connect to the system using a terminal program. Once logged in, the user can perform functions such as ...
s that peaked at 45,000 systems with millions of users across the world. The system was highly efficient, using the latest
file compression In information theory, data compression, source coding, or bit-rate reduction is the process of encoding information using fewer bits than the original representation. Any particular compression is either lossy or lossless. Lossless compression ...
and
file transfer File transfer is the transmission of a computer file through a communication channel from one computer system to another. Typically, file transfer is mediated by a communications protocol. In the history of computing, numerous file transfer protocol ...
systems to aggressively drive down the cost of transmission on what was largely a hobby network. The system was later modified to support public messages ( forums) called EchoMail, which grew to about 8 MB a day, compressed.


See also

*
Best-effort delivery Best-effort delivery describes a network service in which the network does ''not'' provide any guarantee that data is delivered or that delivery meets any quality of service. In a best-effort network, all users obtain best-effort service. Under b ...
*
Cut-through switching Rat running (also known as rodent running, cut-through driving, or dive-bombing) is the practice by motorists of using residential side streets or any unintended short cut such as a parking lot, delivery service lane or cemetery road instead o ...
*
Delay-tolerant networking Delay-tolerant networking (DTN) is an approach to computer network architecture that seeks to address the technical issues in heterogeneous networks that may lack continuous network connectivity. Examples of such networks are those operating in mo ...
*
Email forwarding Email forwarding generically refers to the operation of re-sending an email message delivered to one email address to one or more different email addresses. The term ''forwarding'', used for mail since long before electronic communications, has no ...
*
Fragment free Fragment may refer to: Entertainment Television and film * "Fragments" (''Torchwood''), an episode from the BBC TV series * "Fragments", an episode from the Canadian TV series ''Sanctuary'' * "Fragments" (Steven Universe Future), an episode f ...
*
Hop-by-hop transport Hop-by-hop transport is a principle of controlling the flow of data in a network. With hop-by-hop transport, chunks of data are forwarded from node to node in a store-and-forward manner. As hop-by-hop transport involves not only the source and d ...
*
Internet fax Internet fax, e-fax, or online fax is the use of the internet and internet protocols to send a fax (facsimile), rather than using a standard telephone connection and a fax machine. A distinguishing feature of Internet fax, compared to other Intern ...
* Logistical Networking *
Network switch A network switch (also called switching hub, bridging hub, and, by the IEEE, MAC bridge) is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device. A netw ...
*
Packet radio In digital radio, packet radio is the application of packet switching techniques to digital radio communications. Packet radio uses a packet switching protocol as opposed to circuit switching or message switching protocols to transmit digital dat ...
* Stofor * Store and forward delay *
Wormhole routing Wormhole flow control, also called wormhole switching or wormhole routing, is a system of simple flow control in computer networking based on known fixed links. It is a subset of flow control methods called Flit-Buffer Flow Control. Switching is ...


References

*{{cite web, url=http://support.intel.com/support/express/switches/sb/cs-014410.htm, title=Switches — What Are Forwarding Modes and How Do They Work?, archive-url=https://web.archive.org/web/20140419110752/http://www.intel.com/support/express/switches/sb/cs-014410.htm, archive-date=2014-04-19, url-status=dead Network protocols