The Pluribus multiprocessor was an early multi-processor computer designed by BBN for use as a packet switch in the ARPANET . Its design later influenced the BBN Butterfly computer.
54-553: The Pluribus had its beginnings in 1972 when the need for a second-generation interface message processor (IMP) became apparent. At that time, the BBN had already installed IMPs at more than thirty-five ARPANET sites. These IMPs were Honeywell 316 and 516 minicomputers. The network was growing rapidly in several dimensions: number of nodes, hosts, and terminals; volume of traffic; and geographic coverage (including plans, now realized, for satellite extensions to Europe and Hawaii). A goal
108-456: A login to the SRI machine was attempted, but only the first two letters could be transmitted. The SRI machine crashed upon reception of the 'g' character. A few minutes later, the bug was fixed and the login attempt was successfully completed. BBN developed a program to test the performance of the communication circuits. According to a report filed by Heart, a preliminary test in late 1969 based on
162-450: A serial number . Once assigned a number and published, an RFC is never rescinded or modified; if the document requires amendments, the authors publish a revised document. Therefore, some RFCs supersede others; the superseded RFCs are said to be deprecated , obsolete , or obsoleted by the superseding RFC. Together, the serialized RFCs compose a continuous historical record of the evolution of Internet standards and practices. The RFC process
216-557: A 27-hour period of activity on the UCSB-SRI line found "approximately one packet per 20,000 in error;" subsequent tests "uncovered a 100% variation in this number - apparently due to many unusually long periods of time (on the order of hours) with no detected errors." A variant of the IMP existed, called the TIP (Terminal IMP), which connected terminals (i.e., teletypes ) as well as computers to
270-526: A common set of terms such as "MUST" and "NOT RECOMMENDED" (as defined by RFC 2119 and 8174 ), augmented Backus–Naur form (ABNF) ( RFC 5234 ) as a meta-language, and simple text-based formatting, in order to keep the RFCs consistent and easy to understand. The RFC series contains three sub-series for IETF RFCs: BCP, FYI, and STD. Best Current Practice (BCP) is a sub-series of mandatory IETF RFCs not on standards track. For Your Information (FYI)
324-444: A multiprocessor approach because of its promising potential for modularity, for cost per performance advantages, for reliability, and because the IMP packet switch algorithms were clearly suitable for parallel processing by independent processors. A Pluribus consisted of two or more standard 19" electronic equipment racks, each divided into four bays. Each bay contained a backplane bus and an independent power supply. A bay might contain
378-527: A network of host computers . Wes Clark suggested inserting "a small computer between each host computer and the network of transmission lines", i.e. making the IMP a separate computer. The IMPs were built by the Massachusetts-based company Bolt Beranek and Newman (BBN) in 1969. BBN was contracted to build four IMPs, the first being due at UCLA by Labor Day; the remaining three were to be delivered in one-month intervals thereafter, completing
432-573: A new submission which will receive a new serial number. Standards track documents are further divided into Proposed Standard and Internet Standard documents. Only the IETF, represented by the Internet Engineering Steering Group (IESG), can approve standards-track RFCs. If an RFC becomes an Internet Standard (STD), it is assigned an STD number but retains its RFC number. The definitive list of Internet Standards
486-545: A processor bus, a shared memory bus, or an I/O bus. Custom-built bus couplers connected the bays to one another so that the processors could reach the shared memory and the I/O devices. A 6-processor Pluribus was used as a network switch to interconnect BBN's five Tenex /"Twenex" timesharing systems along with 378 terminals on direct serial and dial-in modem lines. The Pluribus used the Lockheed SUE as its processor. The SUE
540-423: A processor stopped running, another processor would detect it and initiate a recovery. The recovery process would unlock any locks placed on shared resources, release allocated storage, and restart all processing on all processors. This was acceptable on an ARPANET routing node, since any lost packets would eventually be retransmitted. Interface Message Processors The Interface Message Processor ( IMP )
594-587: A similar fashion; BCP n refers to a certain RFC or set of RFCs, but which RFC or RFCs may change over time). An informational RFC can be nearly anything from April 1 jokes to widely recognized essential RFCs like Domain Name System Structure and Delegation ( RFC 1591 ). Some informational RFCs formed the FYI sub-series. An experimental RFC can be an IETF document or an individual submission to
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#1732776110382648-591: Is a sub-series of informational RFCs promoted by the IETF as specified in RFC ; 1150 (FYI 1). In 2011, RFC 6360 obsoleted FYI 1 and concluded this sub-series. Standard (STD) used to be the third and highest maturity level of the IETF standards track specified in RFC 2026 (BCP 9). In 2011 RFC 6410 (a new part of BCP 9) reduced the standards track to two maturity levels. There are five streams of RFCs: IETF , IRTF , IAB , independent submission , and Editorial . Only
702-408: Is another of the four first of what were ARPANET nodes and the source of early RFCs. The ARC became the first network information center ( InterNIC ), which was managed by Elizabeth J. Feinler to distribute the RFCs along with other network information. From 1969 until 1998, Jon Postel served as the RFC editor . On his death in 1998, his obituary was published as RFC 2468 . Following
756-595: Is authored by individuals or groups of engineers and computer scientists in the form of a memorandum describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems. It is submitted either for peer review or to convey new concepts, information, or, occasionally, engineering humor. The IETF adopts some of the proposals published as RFCs as Internet Standards . However, many RFCs are informational or experimental in nature and are not standards. The RFC system
810-413: Is documented in RFC 2026 ( The Internet Standards Process, Revision 3 ). The RFC production process differs from the standardization process of formal standards organizations such as International Organization for Standardization (ISO). Internet technology experts may submit an Internet Draft without support from an external institution. Standards-track RFCs are published with approval from
864-602: Is now typical of Internet Draft documents, the precursor step before being approved as an RFC. In December 1969, researchers began distributing new RFCs via the newly operational ARPANET. RFC 1 , titled "Host Software", was written by Steve Crocker of the University of California, Los Angeles (UCLA), and published on April 7, 1969. Although written by Steve Crocker, the RFC had emerged from an early working group discussion between Steve Crocker, Steve Carr, and Jeff Rulifson . In RFC 3 , which first defined
918-502: Is obsoleted by various newer RFCs, but SMTP itself is still "current technology", so it is not in "Historic" status. However, since BGP version 4 has entirely superseded earlier BGP versions, the RFCs describing those earlier versions, such as RFC 1267 , have been designated historic. Status unknown is used for some very old RFCs, where it is unclear which status the document would get if it were published today. Some of these RFCs would not be published at all today; an early RFC
972-562: Is submitted as plain ASCII text and is published in that form, but may also be available in other formats . For easy access to the metadata of an RFC, including abstract, keywords, author(s), publication date, errata, status, and especially later updates, the RFC Editor site offers a search form with many features. A redirection sets some efficient parameters, example: rfc:5000. The official International Standard Serial Number (ISSN) of
1026-492: Is the Official Internet Protocol Standards. Previously STD 1 used to maintain a snapshot of the list. When an Internet Standard is updated, its STD number stays the same, now referring to a new RFC or set of RFCs. A given Internet Standard, STD n , may be RFCs x and y at a given time, but later the same standard may be updated to be RFC z instead. For example, in 2007 RFC 3700
1080-523: The Internet ) and a data field, and transmits the message across the 1822 interface to the IMP. The IMP routes the message to the destination host using protocols that were eventually adopted by Internet routers. Messages could store a total length of 8159 bits, of which the first 96 were reserved for the header ("leader"). While packets transmitted across the Internet are assumed to be unreliable, 1822 messages were guaranteed to be transmitted reliably to
1134-692: The Internet Research Task Force (IRTF), and an independent stream from other outside sources. A new model was proposed in 2008, refined, and published in August 2009, splitting the task into several roles, including the RFC Series Advisory Group (RSAG). The model was updated in 2012. The streams were also refined in December 2009, with standards defined for their style. In January 2010, the RFC Editor function
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#17327761103821188-525: The ARPANET was the one at the University of Maryland. BBN Report 1822 specifies the method for connecting a host computer to an IMP. This connection and protocol is generally referred to as 1822 , the report number. The specification was written by Bob Kahn . To transmit data, the host constructs a message containing the numeric address of another host on the network (similar to an IP address on
1242-627: The IETF creates BCPs and RFCs on the standards track. The IAB publishes informational documents relating to policy or architecture. The IRTF publishes the results of research, either as informational documents or as experiments. Independent submissions are published at the discretion of the Independent Submissions Editor. Non-IETF documents are reviewed by the IESG for conflicts with IETF work. IRTF and independent RFCs generally contain relevant information or experiments for
1296-568: The IETF, and are usually produced by experts participating in IETF Working Groups , which first publish an Internet Draft. This approach facilitates initial rounds of peer review before documents mature into RFCs. The RFC tradition of pragmatic, experience-driven, after-the-fact standards authorship accomplished by individuals or small working groups can have important advantages over the more formal, committee-driven process typical of ISO and national standards bodies. Most RFCs use
1350-404: The IMP simply as "a messenger" that would only "store-and-forward". BBN designed only the host-to-IMP specification, leaving host sites to build individual host-to-host interfaces. The IMP had an error-control mechanism that discarded packets with errors without acknowledging receipt; the source IMP, upon not receiving an acknowledging receipt, would subsequently re-send a duplicate packet. Based on
1404-577: The Internet at large not in conflict with IETF work. compare RFC 4846 , 5742 and 5744 . The Editorial Stream is used to effect editorial policy changes across the RFC series (see RFC 9280 ). The official source for RFCs on the World Wide Web is the RFC Datatracker. Almost any published RFC can be retrieved via a URL of the form https://datatracker.ietf.org/doc/html/rfc5000, shown for RFC 5000 . Every RFC
1458-755: The Internet community, other documents also called requests for comments have been published, as in U.S. Federal government work, such as the National Highway Traffic Safety Administration . The inception of the RFC format occurred in 1969 as part of the seminal ARPANET project. Today, it is the official publication channel for the Internet Engineering Task Force (IETF), the Internet Architecture Board (IAB), and – to some extent –
1512-627: The PID. The value was used to select the process to run. If a program or device needed to signal another process to run, it would write that process' number into the PID. The PID would emit the highest priority process that anyone had requested, and served them out to all processors. An important aspect of the Pluribus software was the "STAGE" system, which detected system errors and took steps to recover from them. The processor clocks had interrupt handlers which implemented watchdog timers on all processors. If
1566-436: The RFC Editor. A draft is designated experimental if it is unclear the proposal will work as intended or unclear if the proposal will be widely adopted. An experimental RFC may be promoted to standards track if it becomes popular and works well. The Best Current Practice subseries collects administrative documents and other texts which are considered as official rules and not only informational , but which do not affect over
1620-826: The RFC Series Approval Board (RSAB). It also established a new Editorial Stream for the RFC Series and concluded the RSOC. The role of the RSE was changed to the RFC Series Consulting Editor (RSCE). In September 2022, Alexis Rossi was appointed to that position. Requests for Comments were originally produced in non- reflowable text format. In August 2019, the format was changed so that new documents can be viewed optimally in devices with varying display sizes. The RFC Editor assigns each RFC
1674-451: The RFC series is 2070-1721. Not all RFCs are standards. Each RFC is assigned a designation with regard to status within the Internet standardization process. This status is one of the following: Informational , Experimental , Best Current Practice , Standards Track , or Historic . Once submitted, accepted, and published, an RFC cannot be changed. Errata may be submitted, which are published separately. More significant changes require
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1728-641: The RFC series, Crocker started attributing the RFC series to the Network Working Group. Rather than being a formal committee, it was a loose association of researchers interested in the ARPANET project. In effect, it included anyone who wanted to join the meetings and discussions about the project. Many of the subsequent RFCs of the 1970s also came from UCLA, because UCLA is one of the first of what were Interface Message Processors (IMPs) on ARPANET. The Augmentation Research Center (ARC) at Stanford Research Institute , directed by Douglas Engelbart ,
1782-423: The addressed destination. If the message could not be delivered, the IMP sent to the originating host a message indicating that the delivery failed. In practice, however, there were (rare) conditions under which the host could miss a report of a message being lost, or under which the IMP could report a message as lost when it had in fact been received. The specification incorporated an alternating bit protocol , of
1836-698: The communication traffic at approximately one-half the cost. An IMP requires the connection to a host computer via a special bit- serial interface, defined in BBN Report 1822 . The IMP software and the ARPA network communications protocol running on the IMPs was discussed in RFC 1 , the first of a series of standardization documents published by what later became the Internet Engineering Task Force (IETF). The concept of an interface computer for computer networking
1890-494: The entire network in a total of twelve months. When Massachusetts Senator Edward Kennedy learned of BBN's accomplishment in signing this million-dollar agreement, he sent a telegram congratulating the company for being contracted to build the "Interfaith Message Processor". The team working on the IMP called themselves the "IMP Guys": BBN began programming work in February 1969 on modified Honeywell DDP-516s. The completed code
1944-648: The expiration of the original ARPANET contract with the U.S. federal government, the Internet Society, acting on behalf of the IETF, contracted with the Networking Division of the University of Southern California (USC) Information Sciences Institute (ISI) to assume the editorship and publishing responsibilities under the direction of the IAB. Sandy Ginoza joined USC/ISI in 1999 to work on RFC editing, and Alice Hagens in 2005. Bob Braden took over
1998-490: The global community of computer network researchers in general. The authors of the first RFCs typewrote their work and circulated hard copies among the ARPA researchers. Unlike the modern RFCs, many of the early RFCs were actual Requests for Comments and were titled as such to avoid sounding too declarative and to encourage discussion. The RFC leaves questions open and is written in a less formal style. This less formal style
2052-567: The network; it was based on the Honeywell 316, a later version of the 516. Later, some Honeywell-based IMPs were replaced with multiprocessing BBN Pluribus IMPs, but ultimately BBN developed a microprogrammed clone of the Honeywell machine. IMPs were at the heart of the ARPANET until DARPA decommissioned the ARPANET in 1989. Most IMPs were either taken apart, junked or transferred to MILNET . Some became artifacts in museums; Kleinrock placed IMP Number One on public view at UCLA. The last IMP on
2106-689: The program were included the RFC Editor Model (Version 3) as defined in RFC 9280 , published in June 2022. Generally, the new model is intended to clarify responsibilities and processes for defining and implementing policies related to the RFC series and the RFC Editor function. Changes in the new model included establishing the position of the RFC Consulting Editor, the RFC Series Working Group (RSWG), and
2160-427: The recommendation to use source filtering to make DoS attacks more difficult ( RFC 2827 : " Network Ingress Filtering: Defeating Denial of Service Attacks which employ IP Source Address Spoofing ") is BCP 38 . A historic RFC is one that the technology defined by the RFC is no longer recommended for use, which differs from "Obsoletes" header in a replacement RFC. For example, RFC 821 ( SMTP ) itself
2214-471: The requirements of ARPA's request for proposal , the IMP used a 24-bit checksum for error correction. BBN chose to make the IMP hardware calculate the checksum, because it was a faster option than using a software calculation. The IMP was initially conceived as being connected to one host computer per site, but at the insistence of researchers and students from the host sites, each IMP was ultimately designed to connect to multiple host computers. The first IMP
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2268-429: The role of RFC project lead, while Joyce K. Reynolds continued to be part of the team until October 13, 2006. In July 2007, streams of RFCs were defined, so that the editing duties could be divided. IETF documents came from IETF working groups or submissions sponsored by an IETF area director from the Internet Engineering Steering Group . The IAB can publish its own documents. A research stream of documents comes from
2322-537: The type proposed by Donald Davies' team for the NPL network in 1968. Later versions of the 1822 protocol, such as 1822L, are described in RFC 802 and its successors. Request for Comments A Request for Comments ( RFC ) is a publication in a series from the principal technical development and standards-setting bodies for the Internet , most prominently the Internet Engineering Task Force (IETF). An RFC
2376-572: The wire data . The border between standards track and BCP is often unclear. If a document only affects the Internet Standards Process, like BCP 9, or IETF administration, it is clearly a BCP. If it only defines rules and regulations for Internet Assigned Numbers Authority (IANA) registries it is less clear; most of these documents are BCPs, but some are on the standards track. The BCP series also covers technical recommendations for how to practice Internet standards; for instance,
2430-449: Was an Internet Standard—STD 1—and in May 2008 it was replaced with RFC 5000 , so RFC 3700 changed to Historic , RFC 5000 became an Internet Standard, and as of May 2008 STD 1 is RFC 5000 . as of December 2013 RFC 5000 is replaced by RFC 7100 , updating RFC 2026 to no longer use STD 1. (Best Current Practices work in
2484-610: Was delivered to Leonard Kleinrock 's group at UCLA on August 30, 1969. It used an SDS Sigma 7 host computer. Douglas Engelbart 's group at the Stanford Research Institute (SRI) received the second IMP on October 1, 1969. It was attached to an SDS 940 host. The third IMP was installed in University of California, Santa Barbara on November 1, 1969. The fourth IMP was installed in the University of Utah in December 1969. The first communication test between two systems (UCLA and SRI) took place on October 29, 1969, when
2538-401: Was established to design a modular machine which, at its lower end, would be smaller and less expensive than the 316's and 516's while being expandable in capacity to provide ten times the bandwidth of, and capable of servicing five times as many input-output (I/O) devices as, the 516. Related goals included greater memory addressing capability and increased reliability. The designers decided on
2592-531: Was first proposed in 1966 by Donald Davies for the NPL network in England and implemented there in 1968-9. The same idea was independently developed in early 1967 at a meeting of principal investigators for the Department of Defense's Advanced Research Projects Agency (ARPA) to discuss interconnecting machines across the country. Larry Roberts , who led the ARPANET implementation, initially proposed
2646-416: Was invented by Steve Crocker in 1969 to help record unofficial notes on the development of ARPANET . RFCs have since become official documents of Internet specifications , communications protocols , procedures, and events. According to Crocker, the documents "shape the Internet's inner workings and have played a significant role in its success," but are not widely known outside the community. Outside of
2700-493: Was moved to a contractor, Association Management Solutions, with Glenn Kowack serving as interim series editor. In late 2011, Heather Flanagan was hired as the permanent RFC Series Editor (RSE). Also at that time, an RFC Series Oversight Committee (RSOC) was created. In 2020, the IAB convened the RFC Editor Future Development program to discuss potential changes to the RFC Editor model. The results of
2754-458: Was often just that: a simple Request for Comments, not intended to specify a protocol, administrative procedure, or anything else for which the RFC series is used today. The general rule is that original authors (or their employers, if their employment conditions so stipulate) retain copyright unless they make an explicit transfer of their rights. An independent body, the IETF Trust, holds
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#17327761103822808-419: Was similar to DEC's PDP-11 . The Pluribus software implemented MIMD symmetric multiprocessing. Software processes were implemented using non-preemptive multiprogramming . Process scheduling used a hardware device, called the pseudo-interrupt device or PID, that was accessible to both programs and to I/O devices. Each processor ran its own copy of the process scheduler, which would read an integer value from
2862-575: Was six thousand words long, and was written in the Honeywell 516 assembly language. The IMP software was produced primarily on a PDP-1, where the IMP code was written and edited, then run on the Honeywell. There was considerable technical interchange with the British team building the NPL network and Paul Baran at RAND but the BBN team independently developed significant aspects of the network's internal operation, such as routing, flow control, software design, and network control. BBN designed
2916-476: Was the packet switching node used to interconnect participant networks to the ARPANET from the late 1960s to 1989. It was the first generation of gateways , which are known today as routers . An IMP was a ruggedized Honeywell DDP-516 minicomputer with special-purpose interfaces and software. In later years the IMPs were made from the non-ruggedized Honeywell 316 which could handle two-thirds of
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