1.6 Delay() P29-31 in packet-switched networkspackets experience delay on end-to-end pathP29

nodal processing delay ()queueing delay ()Transmission delay ()Propagation delay ()

Delay in packet-switched networksnodal processing(): check bit errorsdetermine routequeueing()time waiting at output link for transmission depends on congestion level of router

Delay in packet-switched networksTransmission delay():R=link bandwidth (bps)L=packet length (bits)time to send bits into link = L/RPropagation delay () :d = length of physical links = propagation speed in medium (~2x108 m/sec)propagation delay = d/sNote: s and R are very different quantities!

end-to-end delay nodal processing delayqueueing delayTransmission delayPropagation delay

packet lost()

Internet delays and routes1 cs-gw (128.119.240.254) 1 ms 1 ms 2 ms2 border1-rt-fa5-1-0.gw.umass.edu (128.119.3.145) 1 ms 1 ms 2 ms3 cht-vbns.gw.umass.edu (128.119.3.130) 6 ms 5 ms 5 ms4 jn1-at1-0-0-19.wor.vbns.net (204.147.132.129) 16 ms 11 ms 13 ms 5 jn1-so7-0-0-0.wae.vbns.net (204.147.136.136) 21 ms 18 ms 18 ms 6 abilene-vbns.abilene.ucaid.edu (198.32.11.9) 22 ms 18 ms 22 ms7 nycm-wash.abilene.ucaid.edu (198.32.8.46) 22 ms 22 ms 22 ms8 62.40.103.253 (62.40.103.253) 104 ms 109 ms 106 ms9 de2-1.de1.de.geant.net (62.40.96.129) 109 ms 102 ms 104 ms10 de.fr1.fr.geant.net (62.40.96.50) 113 ms 121 ms 114 ms11 renater-gw.fr1.fr.geant.net (62.40.103.54) 112 ms 114 ms 112 ms12 nio-n2.cssi.renater.fr (193.51.206.13) 111 ms 114 ms 116 ms13 nice.cssi.renater.fr (195.220.98.102) 123 ms 125 ms 124 ms14 r3t2-nice.cssi.renater.fr (195.220.98.110) 126 ms 126 ms 124 ms15 eurecom-valbonne.r3t2.ft.net (193.48.50.54) 135 ms 128 ms 133 ms16 194.214.211.25 (194.214.211.25) 126 ms 128 ms 126 ms17 *fantasia.eurecom.fr (193.55.113.142) 132 ms 128 ms traceroute: routers, rt delays on source-dest path also: pingplotter, various windows programs P33 tracert

1.7 Protocol Layers() P34-39Networks are complex! many pieces:hostsrouterslinks of various mediaapplicationsprotocolshardware, softwareQuestion: Is there any hope of organizing structure of network?

Organization of air travela series of steps P35

Organization of air travel: a different viewLayers: each layer implements a servicevia its own internal-layer actionsrelying on services provided by layer below

Distributed implementation of layer functionalityticket (purchase)

baggage (check)

gates (load)

runway takeoff

airplane routingticket (complain)

baggage (claim)

gates (unload)

runway landing

airplane routingDeparting airportarriving airportintermediate air traffic sites

12345P22

OSI()

(network architecture)

Internet protocol stackapplication(): supporting network applicationsftp, smtp, httptransport () : transfer application data between client and server.tcp, udpnetwork () : routing of datagrams from source to destinationip, routing protocolslink () : data transfer between neighboring network elementsppp, ethernetphysical () : transfer bits on the wire

P38

Layering: logical communication Each layer:distributedentities() implement layer functions at each nodeentities perform actions, exchange messages with peers ()

Layering: logical communication E.g.: transporttake data from applicationadd addressing, reliability check information to form datagramsend datagram to peer()wait for peer to ack receipt

transporttransport

Layering: physical communication routerreceiversender

Protocol layering and dataEach layer takes data from aboveadds header() information to create new data unitpasses new data unit to layer below

sourcedestinationmessagesegmentdatagramframe

function of layerEach layer may have functions as folllows:error control()flow control()segmentation and reassembly()multiplexing()connection setup()

P37

HTTPFTPSMTPTELNETDNSSNMPTCP UDP ICMPIPARPRARPvarious data link protocols TCP/IP Protocol Stackvarious physical protocols

1.8 Internet History P40()1961: Kleinrock - queueing theory shows effectiveness of packet-switching1964: Baran - packet-switching in military nets1967: ARPAnet conceived by Advanced Research Projects Agency1969: first ARPAnet node operational

1972: ARPAnet demonstrated publiclyNCP (Network Control Protocol) first host-host protocol first e-mail programARPAnet has 15 nodes1961-1972: Early packet-switching principles

Internet History1970: ALOHAnet satellite network in Hawaii1973: Metcalfes PhD thesis proposes Ethernet1974: Cerf and Kahn - architecture for interconnecting networkslate70s: proprietary architectures: DECnet, SNA, XNAlate 70s: switching fixed length packets (ATM precursor)1979: ARPAnet has 200 nodesCerf and Kahns internetworking principles:minimalism, autonomy - no internal changes required to interconnect networksbest effort service modelstateless routersdecentralized controldefine todays Internet architecture1972-1980: Internetworking, new and proprietary nets

Internet History1983: deployment of TCP/IP1982: smtp e-mail protocol defined 1983: DNS defined for name-to-IP-address translation1985: ftp protocol defined1988: TCP congestion controlnew national networks: Csnet, BITnet, NSFnet, Minitel100,000 hosts connected to confederation of networks

1980-1990: new protocols, a proliferation of networks

Internet HistoryEarly 1990s: ARPAnet decommissioned1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995)early 1990s: WWWhypertext [Bush 1945, Nelson 1960s]HTML, http: Berners-Lee1994: Mosaic, later Netscapelate 1990s: commercialization of the WWW

Late 1990s:est. 50 million computers on Internetest. 100 million+ usersbackbone links running at 1 Gbps

1990s: commercialization, the WWW

Introduction: SummaryCovered a ton of material!Internet overviewwhats a protocol?network edge, core, access networkpacket-switching versus circuit-switchingperformance: loss, delaylayering and service modelsbackbones, NAPs, ISPshistoryYou now have: context, overview, feel of networkingmore depth, detail later in course