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id="mw-head-base" class="noprint"></div> <div id="content" class="mw-body" role="main"> <a id="top"></a> <div id="siteNotice"></div> <div class="mw-indicators"> </div> <h1 id="firstHeading" class="firstHeading" lang="en">Interface Message Processor</h1> <div id="bodyContent" class="mw-body-content"> <div id="siteSub">From Wikipedia, the free encyclopedia</div> <div id="contentSub"></div> <div id="jump-to-nav" class="mw-jump"> Jump to: <a href="#mw-head">navigation</a>, <a href="#p-search">search</a> </div> <div id="mw-content-text" lang="en" dir="ltr" class="mw-content-ltr"><div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150322022520/http://en.wikipedia.org/wiki/File:Leonard-Kleinrock-and-IMP1.png" class="image"><img alt="" src="//web.archive.org/web/20150322022520im_/http://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Leonard-Kleinrock-and-IMP1.png/220px-Leonard-Kleinrock-and-IMP1.png" width="220" height="281" class="thumbimage" srcset="//web.archive.org/web/20150322022520im_/http://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Leonard-Kleinrock-and-IMP1.png/330px-Leonard-Kleinrock-and-IMP1.png 1.5x, //web.archive.org/web/20150322022520im_/http://upload.wikimedia.org/wikipedia/commons/thumb/6/68/Leonard-Kleinrock-and-IMP1.png/440px-Leonard-Kleinrock-and-IMP1.png 2x" data-file-width="444" data-file-height="568"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150322022520/http://en.wikipedia.org/wiki/File:Leonard-Kleinrock-and-IMP1.png" class="internal" title="Enlarge"></a></div> <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Leonard_Kleinrock" title="Leonard Kleinrock">Leonard Kleinrock</a> and the first IMP</div> </div> </div> <p>The <b>Interface Message Processor</b> (<b>IMP</b>) was the <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Packet-switching" title="Packet-switching" class="mw-redirect">packet-switching</a> <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Node_(networking)" title="Node (networking)">node</a> used to interconnect participant networks to the <a href="/web/20150322022520/http://en.wikipedia.org/wiki/ARPANET" title="ARPANET">ARPANET</a> from the late 1960s to 1989. It was the first generation of gateways, which are known today as <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Router_(computing)" title="Router (computing)">routers</a>.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span>[</span>1<span>]</span></a></sup><sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span>[</span>2<span>]</span></a></sup><sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span>[</span>3<span>]</span></a></sup> An IMP was a <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Rugged_computer" title="Rugged computer">ruggedized</a> <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Honeywell" title="Honeywell">Honeywell</a> <a href="/web/20150322022520/http://en.wikipedia.org/wiki/DDP-516" title="DDP-516" class="mw-redirect">DDP-516</a> <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Minicomputer" title="Minicomputer">minicomputer</a> with special-purpose interfaces and software.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span>[</span>4<span>]</span></a></sup> In later years the IMPs were made from the non-ruggedized <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Honeywell_316" title="Honeywell 316">Honeywell 316</a> which could handle two-thirds of the communication traffic at approximately one-half the cost.<sup id="cite_ref-5" class="reference"><a href="#cite_note-5"><span>[</span>5<span>]</span></a></sup> An IMP requires the connection to a host computer via a special bit-<a href="/web/20150322022520/http://en.wikipedia.org/wiki/Serial_communications" title="Serial communications" class="mw-redirect">serial</a> interface, defined in <a href="/web/20150322022520/http://en.wikipedia.org/wiki/BBN_Report_1822" title="BBN Report 1822">BBN Report 1822</a>. The IMP software and the ARPA network communications protocol running on the IMPs was discussed in <a class="external mw-magiclink-rfc" rel="nofollow" href="//web.archive.org/web/20150322022520/http://tools.ietf.org/html/rfc1">RFC 1</a>, the first of a <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Request_for_Comments" title="Request for Comments">series of standardization documents</a> published by the <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Internet_Engineering_Task_Force" title="Internet Engineering Task Force">Internet Engineering Task Force</a> (IETF).</p> <p></p> <div id="toc" class="toc"> <div id="toctitle"> <h2>Contents</h2> </div> <ul> <li class="toclevel-1 tocsection-1"><a href="#History"><span class="tocnumber">1</span> <span class="toctext">History</span></a></li> <li class="toclevel-1 tocsection-2"><a href="#References"><span class="tocnumber">2</span> <span class="toctext">References</span></a></li> <li class="toclevel-1 tocsection-3"><a href="#Further_reading"><span class="tocnumber">3</span> <span class="toctext">Further reading</span></a></li> <li class="toclevel-1 tocsection-4"><a href="#External_links"><span class="tocnumber">4</span> <span class="toctext">External links</span></a></li> </ul> </div> <p></p> <h2><span class="mw-headline" id="History">History</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150322022520/http://en.wikipedia.org/w/index.php?title=Interface_Message_Processor&action=edit&section=1" title="Edit section: History">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <p>The idea of the IMP was first publicly discussed in early 1967 at a meeting of principal investigators for the Department of Defense's <a href="/web/20150322022520/http://en.wikipedia.org/wiki/DARPA" title="DARPA">Advanced Research Projects Agency</a> (ARPA) to discuss interconnecting machines across the country. <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Lawrence_Roberts_(scientist)" title="Lawrence Roberts (scientist)">Larry Roberts</a>, who led the ARPANET implementation, initially proposed a network of host computers. <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Wesley_A._Clark" title="Wesley A. Clark">Wes Clark</a> suggested inserting "a small computer between each host computer and the network of transmission lines",<sup id="cite_ref-Hafner_6-0" class="reference"><a href="#cite_note-Hafner-6"><span>[</span>6<span>]</span></a></sup> i.e. making the IMP a separate computer.</p> <p>The IMPs were built by the Massachusetts-based company <a href="/web/20150322022520/http://en.wikipedia.org/wiki/BBN_Technologies" title="BBN Technologies">Bolt Beranek and Newman</a> (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 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".<sup id="cite_ref-Hafner_6-1" class="reference"><a href="#cite_note-Hafner-6"><span>[</span>6<span>]</span></a></sup></p> <p>The team working on the IMP called themselves the "IMP Guys":<sup id="cite_ref-Hafner_6-2" class="reference"><a href="#cite_note-Hafner-6"><span>[</span>6<span>]</span></a></sup></p> <ul> <li>Team Leader: Frank Heart</li> <li>Software: <a href="/web/20150322022520/http://en.wikipedia.org/wiki/William_Crowther_(programmer)" title="William Crowther (programmer)">Willy Crowther</a>, <a href="/web/20150322022520/http://en.wikipedia.org/w/index.php?title=Dave_Walden&action=edit&redlink=1" class="new" title="Dave Walden (page does not exist)">Dave Walden</a>, Bernie Cosell</li> <li>Hardware: <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Severo_Ornstein" title="Severo Ornstein">Severo Ornstein</a>, Ben Barker</li> <li>Theory and collaboration with the above on the overall system design: <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Bob_Kahn" title="Bob Kahn">Bob Kahn</a></li> <li>Other: Hawley Rising</li> <li>Added to IMP team later: Marty Thrope (hardware), Jim Geisman, Truett Thach (installation), Bill Bertell (Honeywell)</li> </ul> <p>BBN began programming work in February 1969 on modified Honeywell DDP-516s. The completed code 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.</p> <p>BBN designed the IMP simply as "a messenger" that would only "store-and-forward".<sup id="cite_ref-Hafner_6-3" class="reference"><a href="#cite_note-Hafner-6"><span>[</span>6<span>]</span></a></sup> 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 the requirements of ARPA's <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Request_for_proposal" title="Request for proposal">request for proposal</a>, the IMP used a 24-bit <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Checksum" title="Checksum">checksum</a> 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.</p> <p>The first IMP was delivered to <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Leonard_Kleinrock" title="Leonard Kleinrock">Leonard Kleinrock</a>'s group at UCLA on August 30, 1969. It used an SDS Sigma-7 host computer. <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Douglas_Engelbart" title="Douglas Engelbart">Douglas Engelbart</a>'s group at the Stanford Research Institute (SRI) received the second IMP on October 1, 1969. It was attached to an <a href="/web/20150322022520/http://en.wikipedia.org/wiki/SDS_940" title="SDS 940">SDS-940</a> host. The third IMP was installed in University of California, Santa Barbara on November 1, 1969. The fourth and final 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 a <i>login</i> 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.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span>[</span>7<span>]</span></a></sup> A few minutes later, the bug was fixed and the login attempt was successfully completed.</p> <p>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 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."<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span>[</span>8<span>]</span></a></sup></p> <p>A variant of the IMP existed, called the TIP, which connected terminals instead of computers to the network; it was based on the 316. Initially, some Honeywell-based IMPs were replaced with multiprocessing BBN <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Pluribus" title="Pluribus">Pluribus</a> IMPs, but ultimately BBN developed a microprogrammed clone of the Honeywell processor.</p> <p>IMPs were at the heart of the ARPANET until DARPA decommissioned ARPANET in 1989. Most IMPs were either taken apart, junked or transferred to <a href="/web/20150322022520/http://en.wikipedia.org/wiki/MILNET" title="MILNET">MILNET</a>. Some became artifacts in museums; Kleinrock placed IMP Number One on public view at UCLA.<sup id="cite_ref-Hafner_6-4" class="reference"><a href="#cite_note-Hafner-6"><span>[</span>6<span>]</span></a></sup> The last IMP on the ARPANET was the one at the University of Maryland.</p> <div class="thumb tright"> <div class="thumbinner" style="width:222px;"><a href="/web/20150322022520/http://en.wikipedia.org/wiki/File:Interface_Message_Processor_Front_Panel.jpg" class="image"><img alt="" src="//web.archive.org/web/20150322022520im_/http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Interface_Message_Processor_Front_Panel.jpg/220px-Interface_Message_Processor_Front_Panel.jpg" width="220" height="147" class="thumbimage" srcset="//web.archive.org/web/20150322022520im_/http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Interface_Message_Processor_Front_Panel.jpg/330px-Interface_Message_Processor_Front_Panel.jpg 1.5x, //web.archive.org/web/20150322022520im_/http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Interface_Message_Processor_Front_Panel.jpg/440px-Interface_Message_Processor_Front_Panel.jpg 2x" data-file-width="3872" data-file-height="2592"/></a> <div class="thumbcaption"> <div class="magnify"><a href="/web/20150322022520/http://en.wikipedia.org/wiki/File:Interface_Message_Processor_Front_Panel.jpg" class="internal" title="Enlarge"></a></div> The front panel of the same IMP as in the photo above, taken at the opening of the Kleinrock Internet Heritage Site and Archive</div> </div> </div> <h2><span class="mw-headline" id="References">References</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150322022520/http://en.wikipedia.org/w/index.php?title=Interface_Message_Processor&action=edit&section=2" title="Edit section: References">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <div class="reflist" style="list-style-type: decimal;"> <ol class="references"> <li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://www.livinginternet.com/i/ii_imp.htm">IMP -- Interface Message Processor</a>, LivingInternet Accessed June 22, 2007.</span></li> <li id="cite_note-2"><span class="mw-cite-backlink"><b><a href="#cite_ref-2">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://www.livinginternet.com/i/ii_imp_walden.htm">Looking back at the ARPANET effort, 34 years later</a>, Dave Walden, Accessed June 22, 2007.</span></li> <li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://www.cs.utexas.edu/users/chris/think/ARPANET/Technical_Tour/imp-to-imp.shtml">A Technical History of the ARPANET - A Technical Tour</a>, THINK Protocols team, Accessed June 22, 2007.</span></li> <li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><span id="CITEREFHeartKahnOrnsteinCrowther1970" class="citation">Heart, F. E.; Kahn, R. E.; Ornstein, S. M.; Crowther, W. R.; Walden, D. C. (1970), <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://portal.acm.org/citation.cfm?id=1476936.1477021">"The interface message processor for the ARPA computer network"</a>, <i>Proceedings of the May 5–7, 1970, spring joint computer conference</i>: 551–567, <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a rel="nofollow" class="external text" href="//web.archive.org/web/20150322022520/http://dx.doi.org/10.1145%2F1476936.1477021">10.1145/1476936.1477021</a><span class="reference-accessdate">, retrieved <span class="nowrap">2009-07-19</span></span></span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInterface+Message+Processor&rft.atitle=The+interface+message+processor+for+the+ARPA+computer+network&rft.au=Crowther%2C+W.+R.&rft.aufirst=F.+E.&rft.au=Heart%2C+F.+E.&rft.au=Kahn%2C+R.+E.&rft.aulast=Heart&rft.au=Ornstein%2C+S.+M.&rft.au=Walden%2C+D.+C.&rft.date=1970&rft.genre=article&rft_id=http%3A%2F%2Fportal.acm.org%2Fcitation.cfm%3Fid%3D1476936.1477021&rft_id=info%3Adoi%2F10.1145%2F1476936.1477021&rft.jtitle=Proceedings+of+the+May+5%E2%80%937%2C+1970%2C+spring+joint+computer+conference&rft.pages=551-567&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-5"><span class="mw-cite-backlink"><b><a href="#cite_ref-5">^</a></b></span> <span class="reference-text"><span id="CITEREFOrnsteinHeartCrowtherRising1971" class="citation">Ornstein, S. M.; Heart, F. E.; Crowther, W. R.; Rising, H. K.; Russell, S. B.; Michel, A. (1971), <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://portal.acm.org/citation.cfm?id=1478873.1478906">"The terminal IMP for the ARPA computer network"</a>, <i>Proceedings of the November 16–18, 1971, fall joint computer conference</i>: 243–254, <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a rel="nofollow" class="external text" href="//web.archive.org/web/20150322022520/http://dx.doi.org/10.1145%2F1478873.1478906">10.1145/1478873.1478906</a></span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInterface+Message+Processor&rft.atitle=The+terminal+IMP+for+the+ARPA+computer+network&rft.au=Crowther%2C+W.+R.&rft.aufirst=S.+M.&rft.au=Heart%2C+F.+E.&rft.aulast=Ornstein&rft.au=Michel%2C+A.&rft.au=Ornstein%2C+S.+M.&rft.au=Rising%2C+H.+K.&rft.au=Russell%2C+S.+B.&rft.date=1971&rft.genre=article&rft_id=http%3A%2F%2Fportal.acm.org%2Fcitation.cfm%3Fid%3D1478873.1478906&rft_id=info%3Adoi%2F10.1145%2F1478873.1478906&rft.jtitle=Proceedings+of+the+November+16%E2%80%9318%2C+1971%2C+fall+joint+computer+conference&rft.pages=243-254&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-Hafner-6"><span class="mw-cite-backlink">^ <a href="#cite_ref-Hafner_6-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-Hafner_6-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-Hafner_6-2"><sup><i><b>c</b></i></sup></a> <a href="#cite_ref-Hafner_6-3"><sup><i><b>d</b></i></sup></a> <a href="#cite_ref-Hafner_6-4"><sup><i><b>e</b></i></sup></a></span> <span class="reference-text"><span id="CITEREFHafnerLyon1996" class="citation">Hafner, K.; Lyon, M. (1996), <i>Where Wizards Stay Up Late</i>, <a href="/web/20150322022520/http://en.wikipedia.org/wiki/New_York_City" title="New York City">New York City</a>: <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Simon_%26_Schuster" title="Simon & Schuster">Simon & Schuster</a>, <a href="/web/20150322022520/http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Special:BookSources/0-684-83267-4" title="Special:BookSources/0-684-83267-4">0-684-83267-4</a></span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInterface+Message+Processor&rft.aufirst=K.&rft.au=Hafner%2C+K.&rft.aulast=Hafner&rft.au=Lyon%2C+M.&rft.btitle=Where+Wizards+Stay+Up+Late&rft.date=1996&rft.genre=book&rft.isbn=0-684-83267-4&rft.place=New+York+City&rft.pub=Simon+%26+Schuster&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><span id="CITEREFHambling2005" class="citation">Hambling, David (2005), <i>Weapons Grade</i>, <a href="/web/20150322022520/http://en.wikipedia.org/wiki/New_York_City" title="New York City">New York City</a>: <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Carroll_%26_Graf" title="Carroll & Graf" class="mw-redirect">Carroll & Graf</a>, <a href="/web/20150322022520/http://en.wikipedia.org/wiki/International_Standard_Book_Number" title="International Standard Book Number">ISBN</a> <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Special:BookSources/0-7867-1769-6" title="Special:BookSources/0-7867-1769-6">0-7867-1769-6</a></span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInterface+Message+Processor&rft.aufirst=David&rft.au=Hambling%2C+David&rft.aulast=Hambling&rft.btitle=Weapons+Grade&rft.date=2005&rft.genre=book&rft.isbn=0-7867-1769-6&rft.place=New+York+City&rft.pub=Carroll+%26+Graf&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook" class="Z3988"><span style="display:none;"> </span></span></span></li> <li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><span id="CITEREFHeart1970" class="citation">Heart, F. E. (1970), <a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://dtic.mil/dtic/tr/fulltext/u2/699946.pdf">"Interface message processors for the ARPA computer network"</a>, <i>Quarterly Technical Report No. 4</i>: 7<span class="reference-accessdate">, retrieved <span class="nowrap">2013-03-05</span></span></span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInterface+Message+Processor&rft.atitle=Interface+message+processors+for+the+ARPA+computer+network&rft.aufirst=F.+E.&rft.au=Heart%2C+F.+E.&rft.aulast=Heart&rft.date=1970&rft.genre=article&rft_id=http%3A%2F%2Fdtic.mil%2Fdtic%2Ftr%2Ffulltext%2Fu2%2F699946.pdf&rft.jtitle=Quarterly+Technical+Report+No.+4&rft.pages=7&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal" class="Z3988"><span style="display:none;"> </span></span></span></li> </ol> </div> <h2><span class="mw-headline" id="Further_reading">Further reading</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150322022520/http://en.wikipedia.org/w/index.php?title=Interface_Message_Processor&action=edit&section=3" title="Edit section: Further reading">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <ul> <li><span class="citation news">Walden, David; IMP Software Guys (Apr–June 2014). "The Arpanet IMP Program: Retrospective and Resurrection". <i>IEEE Annals of the History of Computing</i> <b>36</b> (2). pp. 28–39. <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Digital_object_identifier" title="Digital object identifier">doi</a>:<a rel="nofollow" class="external text" href="//web.archive.org/web/20150322022520/http://dx.doi.org/10.1109%2FMAHC.2014.30">10.1109/MAHC.2014.30</a>.</span><span title="ctx_ver=Z39.88-2004&rfr_id=info%3Asid%2Fen.wikipedia.org%3AInterface+Message+Processor&rft.atitle=The+Arpanet+IMP+Program%3A+Retrospective+and+Resurrection&rft.au=IMP+Software+Guys&rft.aulast=Walden%2C+David&rft.au=Walden%2C+David&rft.date=Apr%E2%80%93June+2014&rft.genre=article&rft_id=info%3Adoi%2F10.1109%2FMAHC.2014.30&rft.issue=2&rft.jtitle=IEEE+Annals+of+the+History+of+Computing&rft.pages=28-39&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.volume=36" class="Z3988"><span style="display:none;"> </span></span> <span style="font-size:100%" class="error citation-comment">Check date values in: <code style="color:inherit; border:inherit; padding:inherit;">|date=</code> (<a href="/web/20150322022520/http://en.wikipedia.org/wiki/Help:CS1_errors#bad_date" title="Help:CS1 errors">help</a>)</span></li> </ul> <h2><span class="mw-headline" id="External_links">External links</span><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/web/20150322022520/http://en.wikipedia.org/w/index.php?title=Interface_Message_Processor&action=edit&section=4" title="Edit section: External links">edit</a><span class="mw-editsection-bracket">]</span></span></h2> <ul> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://computer.howstuffworks.com/arpanet.htm/printable">A Technical History of the ARPANET with photos of IMP</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://www.livinginternet.com/i/ii_imp.htm">IMP history with photo of developers</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://www.livinginternet.com/i/ii_imp_walden.htm">Dave Walden's memories of the IMP and ARPANET</a></li> <li><a rel="nofollow" class="external text" href="https://web.archive.org/web/20150322022520/http://purl.umn.edu/107591">Oral history interview with Severo Ornstein</a>, <a href="/web/20150322022520/http://en.wikipedia.org/wiki/Charles_Babbage_Institute" title="Charles Babbage Institute">Charles Babbage Institute</a>, University of Minnesota. Ornstein was principal hardware designer of the IMP.</li> <li>Internet STD 39, also known as <a href="/web/20150322022520/http://en.wikipedia.org/wiki/BBN_Report_1822" title="BBN Report 1822">BBN Report 1822</a>, "Specification for the Interconnection of a Host and an IMP".</li> </ul>    <noscript><img src="//web.archive.org/web/20150322022520im_/http://en.wikipedia.org/wiki/Special:CentralAutoLogin/start?type=1x1" alt="" title="" width="1" height="1" style="border: none; position: absolute;"/></noscript></div> <div class="printfooter"> Retrieved from "<a dir="ltr" href="https://web.archive.org/web/20150322022520/http://en.wikipedia.org/w/index.php?title=Interface_Message_Processor&oldid=648317580">http://en.wikipedia.org/w/index.php?title=Interface_Message_Processor&oldid=648317580</a>" </div> <div id="catlinks" class="catlinks"><div id="mw-normal-catlinks" class="mw-normal-catlinks"><a href="/web/20150322022520/http://en.wikipedia.org/wiki/Help:Category" title="Help:Category">Categories</a>: <ul><li><a href="/web/20150322022520/http://en.wikipedia.org/wiki/Category:Networking_hardware" title="Category:Networking hardware">Networking hardware</a></li><li><a href="/web/20150322022520/http://en.wikipedia.org/wiki/Category:ARPANET" title="Category:ARPANET">ARPANET</a></li></ul></div><div id="mw-hidden-catlinks" class="mw-hidden-catlinks mw-hidden-cats-hidden">Hidden categories: <ul><li><a href="/web/20150322022520/http://en.wikipedia.org/wiki/Category:CS1_errors:_dates" title="Category:CS1 errors: dates">CS1 errors: dates</a></li></ul></div></div> <div class="visualClear"></div> </div> </div> <div id="mw-navigation"> <h2>Navigation menu</h2> <div id="mw-head"> <div id="p-personal" role="navigation" class="" aria-labelledby="p-personal-label"> <h3 id="p-personal-label">Personal tools</h3> <ul> <li id="pt-createaccount"><a href="/web/20150322022520/http://en.wikipedia.org/w/index.php?title=Special:UserLogin&returnto=Interface+Message+Processor&type=signup" title="You are encouraged to create an account and log in; however, it is not mandatory">Create account</a></li><li id="pt-login"><a href="/web/20150322022520/http://en.wikipedia.org/w/index.php?title=Special:UserLogin&returnto=Interface+Message+Processor" title="You're encouraged to log in; however, it's not mandatory. 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