Chapter 1: IntroductionChapter 1: roadmapWhat’s the Internet: “nuts and bolts” viewWhat’s the Internet: “nuts and bolts” viewWhat’s the Internet: a service viewWhat’s a protocol?What’s a protocol?Chapter 1: roadmapA closer look at network structure:The network edge:Network edge: connection-oriented serviceNetwork edge: connectionless serviceChapter 1: roadmapThe Network CoreNetwork Core: Circuit SwitchingNetwork Core: Circuit SwitchingCircuit Switching: FDM and TDMNumerical exampleNetwork Core: Packet SwitchingPacket Switching: Statistical MultiplexingPacket switching versus circuit switchingPacket switching versus circuit switchingPacket-switching: store-and-forwardPacket-switched networks: forwardingNetwork TaxonomyChapter 1: roadmapAccess networks and physical mediaResidential access: point to point accessResidential access: cable modemsResidential access: cable modemsCable Network Architecture: OverviewCable Network Architecture: OverviewCable Network Architecture: OverviewCable Network Architecture: OverviewCompany access: local area networksWireless access networksHome networksPhysical MediaPhysical Media: coax, fiberPhysical media: radioChapter 1: roadmapInternet structure: network of networksTier-1 ISP: e.g., SprintInternet structure: network of networksInternet structure: network of networksInternet structure: network of networksChapter 1: roadmapHow do loss and delay occur?Four sources of packet delayDelay in packet-switched networksNodal delayQueueing delay (revisited)“Real” Internet delays and routes“Real” Internet delays and routesPacket lossChapter 1: roadmapProtocol “Layers”Why layering?Internet protocol stackEncapsulationChapter 1: roadmapInternet HistoryInternet HistoryInternet HistoryIntroduction: SummaryChapter 1: IntroductionOur goal: get “feel” and terminology more depth, detail laterin course approach: use Internet as exampleOverview: what’s the Internet what’s a protocol? network edge network core access net, physical media Internet/ISP structure performance: loss, delay protocol layers, service models network modelingIntroduction1-1Chapter 1: roadmap1.1 What isthe Internet?1.2 Network edge1.3 Network core1.4 Network access and physical media1.5 Internet structure and ISPs1.6 Delay & loss in packet-switched networks1.7 Protocol layers, service models1.8 HistoryIntroduction1-2What’s the Internet: “nuts and bolts” viewlocal ISPcompanynetworkregional ISProuterworkstationservermobile millions of connected computing devices: hosts = end systems running network appscommunication links fiber, copper, radio, satellite transmission rate = bandwidthrouters:forward packets (chunks of data)Introduction1-3What’s the Internet: “nuts and bolts” viewlocal ISPcompanynetworkregional ISProuterworkstationservermobileprotocolscontrol sending, receiving of msgs e.g., TCP, IP, HTTP, FTP, PPPInternet: “network of networks” loosely hierarchical public Internet versus private intranetInternet standards RFC: Request for comments IETF: Internet Engineering Task ForceIntroduction1-4What’s the Internet: a service view communication infrastructure enables distributed applications: Web, email, games, e-commerce, file sharingcommunication services provided to apps: Connectionless unreliable connection-oriented reliableIntroduction1-5What’s a protocol?network protocols: machines rather than humans all communication activity in Internet governed by protocolshuman protocols: “what’s the time?” “I have a question” introductions… specific msgs sent… specific actions taken when msgs received, or other eventsprotocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receiptIntroduction1-6What’s a protocol?a human protocol and a computer network protocol:Introduction1-7Q: Other human protocols? HiHiGot thetime?2:00TCP connectionreqTCP connectionresponseGet http://www.awl.com/kurose-ross<file>timeChapter 1: roadmap1.1 What isthe Internet?1.2 Network edge1.3 Network core1.4 Network access and physical media1.5 Internet structure and ISPs1.6 Delay & loss in packet-switched networks1.7 Protocol layers, service models1.8 HistoryIntroduction1-8A closer look at network structure: network edge:applications and hosts network core: routers network of networksaccess networks, physical media:communication linksIntroduction1-9The network edge: end systems (hosts): run application programs e.g. Web, email at “edge of network” client/server model client host requests, receives service from always-on server e.g. Web browser/server; email client/server peer-peer model: minimal (or no) use of dedicated servers e.g. Gnutella, KaZaAIntroduction1-10Network edge: connection-oriented serviceGoal:data transfer between end systemshandshaking:setup (prepare for) data transfer ahead of time Hello, hello back human protocolset up “state”in two communicating hostsTCP - Transmission Control Protocol Internet’s connection-oriented serviceTCP service [RFC 793]reliable, in-orderbyte-stream data transfer loss: acknowledgements and retransmissionsflow control: sender won’t overwhelm receivercongestion control: senders “slow down sending rate” when network congestedIntroduction1-11Network edge: connectionless serviceGoal:data transfer between end systems same as before!UDP - User Datagram Protocol [RFC 768]: connectionless unreliable data transfer no flow control no congestion controlApp’s using TCP: HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email)App’s using UDP: streaming media, teleconferencing, DNS, Internet telephonyIntroduction1-12Chapter 1: roadmap1.1 What isthe Internet?1.2 Network edge1.3 Network core1.4 Network access and physical media1.5 Internet structure and ISPs1.6 Delay & loss in packet-switched networks1.7 Protocol layers, service models1.8 HistoryIntroduction1-13The Network Core mesh of interconnected routersthefundamental question: how is data transferred through net? circuit switching:dedicated circuit per call: telephone net packet-switching: data sent thru net in discrete “chunks”Introduction1-14Network Core: Circuit SwitchingEnd-end resources reserved for “call” link bandwidth, switch capacity
View Full Document