Computer Networking Yao Liang, Professor [email protected] Dept. of Computer Science IUPUI Fall 2020 Introduction 1-1 Roadmap Computer networking is the area in Computer Science studying the principles of connecting computer devices via communication networks (e.g., Internet) 1.1 what is the Internet? 1.2 network edge 1.3 network core 1.4 protocol layers, service models 1.5 history Introduction 1-2 What’s the Internet: “nuts and bolts” view PC millions of connected mobile network server computing devices: wireless . hosts = end systems global ISP laptop smartphone . running network apps home network communication links regional ISP wireless . fiber, copper, radio, links satellite wired links . transmission rate: bandwidth Packet switches: forward router packets (chunks of data) institutional network . routers and switches Introduction 1-3 “Fun” internet appliances Fitbit Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ Tweet-a-watt: monitor energy use Slingbox: watch, control cable TV remotely Internet Internet phones refrigerator Introduction 1-4 What’s the Internet: a service view mobile network Infrastructure that provides services to applications: global ISP . Web, VoIP, email, games, e- commerce, social nets, … home network provides programming regional ISP interface to apps . hooks that allow sending and receiving app programs to “connect” to Internet . provides service options, analogous to postal service institutional network Introduction 1-6 What’s a protocol? protocols control network protocols: sending, receiving of machines rather than msgs humans all communication activity human protocols: in Internet governed by protocols “what’s the time?” “I have a question” introductions protocols define format, order of msgs sent and received … specific msgs sent among network entities, … specific actions taken and actions taken on msg when msgs received, or other events transmission, receipt Introduction 1-7 What’s a protocol? a human protocol and a computer network protocol: Hi TCP connection request Hi TCP connection response Got the time? Get http://www.awl.com/kurose-ross 2:00 <file> time Q: other human protocols? Introduction 1-8 A closer look at network structure: network edge: mobile network . hosts: clients and servers global ISP . servers often in data centers home access networks, physical network media: wired, wireless regional ISP communication links network core: . interconnected routers . network of networks institutional network Introduction 1-9 Access networks Q: How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks Introduction 1-10 Enterprise access networks (Ethernet) institutional link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers typically used in companies, universities, etc 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates today, end systems typically connect into Ethernet switch Introduction 1-14 Wireless access networks shared wireless access network connects end system to router . via base station aka “access point” wireless LANs: wide-area wireless access . within building (100 ft) . provided by telco (cellular) . 802.11b/g (WiFi): 11, 54 Mbps operator, 10’s km transmission rate . between 1 and 10 Mbps . 3G, 4G: LTE to Internet to Internet Introduction 1-15 The network core mesh of interconnected routers packet-switching: hosts break application-layer messages into packets . forward packets from one router to the next, across links on path from source to destination . each packet transmitted at full link capacity Introduction 1-18 Packet Switching: queueing delay, loss C A R = 100 Mb/s D R = 1.5 Mb/s B queue of packets E waiting for output link queuing and loss: If arrival rate (in bits) to link exceeds transmission rate of link for a period of time: . packets will queue, wait to be transmitted on link . packets can be dropped (lost) if memory (buffer) fills up Introduction 1-19 Two key network-core functions routing: determines source- forwarding: move packets from destination route taken by router’s input to appropriate packets router output . routing algorithms routing algorithm local forwarding table header value output link 0100 3 1 0101 2 0111 2 3 2 1001 1 dest address in arriving packet’s header Network Layer 4-20 Internet structure: network of networks Question: given millions of access ISPs, how to connect them together? access access net net access net access access net net access access net net access access net net access net access net access net access net access access net access net net Internet structure: network of networks Option: connect each access ISP to every other access ISP? access access net net access net access access net net access access net net connecting each access ISP to each other directly doesn’t access access net scale: O(N2) connections. net access net access net access net access net access access net access net net Internet structure: network of networks Option: connect each access ISP to a global transit ISP? Customer and provider ISPs have economic agreement. access access net net access net access access net net access access net net global access access net ISP net access net access net access net access net access access net access net net Internet structure: network of networks But if one global ISP is viable business, there will be competitors …. access access net net access net access access net net access access net net ISP A access access net ISP B net access ISP C net access net access net access net access access net access net net Internet structure: network of networks But if one global ISP is viable business, there will be competitors …. which must be interconnected Internet exchange point access access net net access net access access net net IXP access access net net ISP A access IXP access net ISP B net access ISP C net access net access peering link net access net access access net access net net Internet structure: network of networks … and regional networks may arise to connect access nets to ISPS access access net net access net access access net net IXP access access net net ISP A access IXP access net ISP B net access ISP C net access net access net regional net access net access access net access net net Tier-1 ISP Network map: Sprint (2019) POP: point-of-presence to/from other Sprint PoPS links to peering networks … … … … … links to/from Sprint customer networks Protocol “layers” Networks are complex, with many “pieces”: . hosts Question: . routers is there any hope of . links of various organizing structure of media network? . applications . protocols …. or at least our . hardware, discussion of networks? software Introduction 1-33 Internet protocol stack application: supporting network applications . FTP, SMTP, HTTP application transport: process-process data transfer transport . TCP, UDP network network: routing of datagrams from source to destination link . IP, routing protocols link: data transfer between physical neighboring network elements . Ethernet, 802.111 (WiFi), PPP physical: bits “on the wire” Introduction 1-34 source message M applicatio Encapsulation segment Ht M n datagram Hn Ht M transport frame Hl Hn Ht M network link physical link physical switch destination Hn Ht M network H H H M M applicatio l n t link Hn Ht M physical Ht M n Hn Ht M transport Hl Hn Ht M network router link physical Internet history 1961-1972: Early packet-switching principles 1961: Kleinrock - 1972: queueing theory shows . ARPAnet public demo effectiveness of packet- . NCP (Network Control switching Protocol) first host-host 1964: Baran - packet- protocol switching in military nets . first e-mail program 1967: ARPAnet . ARPAnet has 15 nodes conceived by Advanced Research Projects Agency 1969: first ARPAnet node operational . https://www.youtube.com/watch?v=kh ajeqHUQ7Q . https://www.youtube.com/watch?v=vu iBTJZfeo8 Introduction 1-37 Internet history 1972-1980: Internetworking, new and proprietary nets 1970: ALOHAnet satellite network in Hawaii Cerf and Kahn’s 1974: Cerf and Kahn - internetworking principles: architecture for interconnecting . minimalism, autonomy - no networks internal changes required to 1976: Ethernet at Xerox PARC interconnect networks . best effort service model late70’s: proprietary architectures: DECnet, SNA, . stateless routers XNA . decentralized control late 70’s: switching fixed length define today’s Internet packets (ATM precursor) architecture 1979: ARPAnet has 200 nodes Introduction 1-38 Internet history 1980-1990: new protocols, a proliferation of networks 1983: deployment of new national networks: TCP/IP Csnet, BITnet, NSFnet, 1982: smtp e-mail Minitel protocol defined 100,000 hosts connected 1983: DNS defined for to confederation of name-to-IP-address networks translation 1985: ftp protocol defined 1988: TCP congestion control Introduction 1-39 Internet history 1990, 2000’s: commercialization, the Web, new apps early 1990’s: ARPAnet late 1990’s – 2000’s: decommissioned more killer apps: instant 1991: NSF lifts restrictions on messaging, P2P file sharing commercial use of NSFnet network security to (decommissioned, 1995) forefront early 1990s: Web est. 50 million host, 100 . hypertext [Bush 1945, million+ users Nelson 1960’s] backbone links running at . HTML, HTTP: Berners-Lee Gbps . 1994: Mosaic, later Netscape . late 1990’s: commercialization of the Web Introduction 1-40 Internet history 2005-present: