Early Internet History and How Urban Legends are BornOn the Internet cultural evolutionIntermission 1977-1983On the Internet and the ARPAnet life cycleARPANet/MILnet topology circa 1983Packet loss at GGP ARPAnet/MILnet gatewaysInternet measurements and performance evaluationNTP scatter diagramsAutonomous system modelIntermission 1983-1990ARPAnet topology August 1986NSF 1986 backbone networkSeptic routing – a dose of realityFallback routing principleFuzzball selective preemption strategyNSFnet 1988 backbone physical topologyNSFnet 1988 backbone logical topologyThings learned from the early NSFnet experienceThe FuzzballInternet time synchronizationA brief history of network timeLessons learned from NTP development programJan 14, 2019 1“When you are up to your ass in alligators, it is wiseto remember you are there to drain the swamp.”- R.M. NixonEarly Internet History and How Urban Legends are BornDavid L. MillsUniversity of Delawarehttp://www.eecis.udel.edu/[email protected] 14, 2019 2On the Internet cultural evolution“We have met the enemy and he is us.” – Walt KellyMaybe the most important lesson of the Internet was that the technology was developed and refined by its own users–There was a certain ham-radio mentality where users/developers had great fun making new protocols to work previously unheard applications–The developers were scattered all over the place, but they had a big, expensive sandbox with little parental supervision–There is no doubt that the enthusiasm driving the developers was due to the urgent need to communicate with each other without wasting trees or airplane fuelThe primary motivation for the Internet model was the need for utmost reliability in the face of untried hardware, buggy programs and lunch–The most likely way to lose a packet is a program bug, rather than a transmission error–Something somewhere was/is/will always be broken at every moment–The most trusted state is in the endpoints, not the networkJan 14, 2019 3Intermission 1977-1983Getting the word outThe ARPAnet as the first Internet backbone networkInternet measurements and performance evaluationThe GGP routing eraEvolution of the autonomous system modelBobJonVintJan 14, 2019 4On the Internet and the ARPAnet life cycleThe original ARPAnet was actually a terminal concentrator network so lots of dumb terminals could use a few big, expensive machinesIn the early Internet, the ARPAnet became an access network for little IP/TCP clients to use a few big, expensive IP/TCP serversIn the adolescent Internet, the ARPAnet became a transit network for widely distributed IP/TCP local area networksIn the mature Internet, the ARPAnet faded to the museums, but MILnet and clones remain for IP/TCP and ITU-T legacy stuffJan 14, 2019 5ARPANet/MILnet topology circa 1983Jan 14, 2019 6Packet loss at GGP ARPAnet/MILnet gatewaysAs time went on and traffic increased dramatically, the performance of the Internet paths that spanned the gateways deteriorated badlyJan 14, 2019 7Internet measurements and performance evaluation While ARPAnet measurement tools had been highly developed, the Internet model forced many changesThe objects to be measured and the measurement tools could be in far away places like foreign countriesFour example programs are discussed–Atlantic Satellite Network (SATNET) measurement program–IP/TCP reassembly scheme–TCP retransmission timeout estimator–NTP scatter diagramsThese weren’t the last word at all, just steps along the wayTCP a fine mouthwash available in BritainJan 14, 2019 8NTP scatter diagramsThese wedge diagrams show the time offset plotted against delay for individual NTP measurementsFor a properly operating measurement host, all points must be within the wedge (see proof elsewhere)The top diagram shows a typical characteristic with no route flappingThe bottom diagram shows route flapping, in this case due to a previously unsuspected oscillation between landline and satellite linksJan 14, 2019 9Autonomous system modelThere was every expectation that many incompatible routing protocols would be developed with different goals and reliability expectationThere was great fear that gateway interoperability failures could lead to wide scale network meltdownThe solution was thought to be a common interface protocol that could be used between gateway cliques, called autonomous systems–An autonomous system is a network of gateways operated by a responsible management entity and (at first) assumed to use a single routing protocol–The links between the gateways must be managed by the same entityThus the Exterior Gateway Protocol (EGP), documented in rfc904–Direct and indirect (buddy) routing data exchange–Compressed routing updates scalable to 1000 networks or more–Hello neighbor reachability scheme modeled on new ARPAnet scheme –Network reachability field, later misused as routing metricJan 14, 2019 10Intermission 1983-1990Cloning the technologyDecline of the ARPAnetINTELPOST as the first commercial IP/TCP networkEvolution to multicore routingThe NSFnet 1986 backbone network at 56 kbThe NSFnet 1998 backbone network at 1.5 MbThe FuzzballInternet time synchronizationJan 14, 2019 11ARPAnet topology August 1986ARPAnet was being phased out, but continued for awhile as NSFnet was established and expandedJan 14, 2019 12NSF 1986 backbone networkThe NSFnet phase-I backbone network (1986-1988) was the first large scale deployment of interdomain routingNSF supercomputing sites connected to the ARPAnet exchanged ICCB core routes using EGPOther NSF sites exchanged routes with backbone routers using Fuzzball Hello protocol and EGPAll NSF sites used mix-and-match interior gateway protocolsSee: Mills, D.L., and H.-W. Braun. The NSFNET backbone network. Proc. ACM SIGCOMM 87, pp. 191-196Jan 14, 2019 13Septic routing – a dose of realityThe NSF Internet was actually richly interconnected, but the global routing infrastructure was unaware of itIn fact, the backbone was grossly overloaded, so routing operated something like a septic system–Sites not connected in any other way flushed packets to the backbone septic tank–The tank drained through the nearest site connected to the ARPAnet–Sometimes the tank or drainage field backed up and emitted a stench–Sites connected to the ARPAnet casually leaked backdoor networks via EGP, breaking the