* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Part I: Introduction
Net neutrality law wikipedia , lookup
Distributed firewall wikipedia , lookup
Multiprotocol Label Switching wikipedia , lookup
Zero-configuration networking wikipedia , lookup
Deep packet inspection wikipedia , lookup
Piggybacking (Internet access) wikipedia , lookup
Cracking of wireless networks wikipedia , lookup
Computer network wikipedia , lookup
Network tap wikipedia , lookup
List of wireless community networks by region wikipedia , lookup
Airborne Networking wikipedia , lookup
Routing in delay-tolerant networking wikipedia , lookup
Internet protocol suite wikipedia , lookup
Asynchronous Transfer Mode wikipedia , lookup
UniPro protocol stack wikipedia , lookup
Recursive InterNetwork Architecture (RINA) wikipedia , lookup
Protocol “Layers” Networks are complex! r many “pieces”: m hosts m routers m links of various media m applications m protocols m hardware, software Question: Is there any hope of organizing structure of network? Or at least our discussion of networks? 1: Introduction 1 Organization of air travel ticket (purchase) ticket (complain) baggage (check) baggage (claim) gates (load) gates (unload) runway takeoff runway landing airplane routing airplane routing airplane routing r a series of steps 1: Introduction 2 Organization of air travel: a different view ticket (purchase) ticket (complain) baggage (check) baggage (claim) gates (load) gates (unload) runway takeoff runway landing airplane routing airplane routing airplane routing Layers: each layer implements a service m via its own internal-layer actions m relying on services provided by layer below 1: Introduction 3 Layered air travel: services Counter-to-counter delivery of person+bags baggage-claim-to-baggage-claim delivery people transfer: loading gate to arrival gate runway-to-runway delivery of plane airplane routing from source to destination 1: Introduction 4 ticket (purchase) ticket (complain) baggage (check) baggage (claim) gates (load) gates (unload) runway takeoff runway landing airplane routing airplane routing arriving airport Departing airport Distributed implementation of layer functionality intermediate air traffic sites airplane routing airplane routing airplane routing 1: Introduction 5 Why layering? Dealing with complex systems: explicit structure allows identification, relationship of complex system’s pieces m layered reference model for discussion r modularization eases maintenance, updating of system m change of implementation of layer’s service transparent to rest of system m e.g., change in gate procedure doesn’t affect rest of system r layering considered harmful? r 1: Introduction 6 Internet protocol stack r application: supporting network applications m r transport: host-host data transfer m r ip, routing protocols link: data transfer between neighboring network elements m r tcp, udp network: routing of datagrams from source to destination m r ftp, smtp, http application transport network link physical ppp, ethernet physical: bits “on the wire” 1: Introduction 7 Layering: logical communication Each layer: r distributed r “entities” implement layer functions at each node r entities perform actions, exchange messages with peers application transport network link physical application transport network link physical network link physical application transport network link physical application transport network link physical 1: Introduction 8 Layering: logical communication E.g.: transport r r r r r take data from app add addressing, reliability check info to form “datagram” send datagram to peer wait for peer to ack receipt analogy: post office data application transport transport network link physical application transport network link physical ack data network link physical application transport network link physical data application transport transport network link physical 1: Introduction 9 Layering: physical communication data application transport network link physical application transport network link physical network link physical application transport network link physical data application transport network link physical 1: Introduction 10 Protocol layering and data Each layer takes data from above r adds header information to create new data unit r passes new data unit to layer below source M Ht M Hn Ht M Hl Hn Ht M application transport network link physical destination application Ht transport Hn Ht network Hl Hn Ht link physical M message M segment M M datagram frame 1: Introduction 11 Internet structure: network of networks roughly hierarchical r national/international backbone providers (NBPs) r m m r regional ISPs m r e.g. BBN/GTE, Sprint, AT&T, IBM, UUNet interconnect (peer) with each other privately, or at public Network Access Point (NAPs) connect into NBPs local ISP, company m local ISP regional ISP NBP B NAP NAP NBP A regional ISP local ISP connect into regional ISPs 1: Introduction 12 National Backbone Provider e.g. BBN/GTE US backbone network 1: Introduction 13 Internet History 1961-1972: Early packet-switching principles r r r r 1961: Kleinrock - queueing theory shows effectiveness of packetswitching 1964: Baran - packetswitching in military nets 1967: ARPAnet conceived by Advanced Reearch Projects Agency 1969: first ARPAnet node operational r 1972: m ARPAnet demonstrated publicly m NCP (Network Control Protocol) first hosthost protocol m first e-mail program m ARPAnet has 15 nodes 1: Introduction 14 Internet History 1972-1980: Internetworking, new and proprietary nets r r r r r r 1970: ALOHAnet satellite network in Hawaii 1973: Metcalfe’s PhD thesis proposes Ethernet 1974: Cerf and Kahn architecture for interconnecting networks late70’s: proprietary architectures: DECnet, SNA, XNA late 70’s: switching fixed length packets (ATM precursor) 1979: ARPAnet has 200 nodes Cerf and Kahn’s internetworking principles: m minimalism, autonomy no internal changes required to interconnect networks m best effort service model m stateless routers m decentralized control define today’s Internet architecture 1: Introduction 15 Internet History 1980-1990: new protocols, a proliferation of networks r r r r r 1983: deployment of TCP/IP 1982: smtp e-mail protocol defined 1983: DNS defined for name-to-IPaddress translation 1985: ftp protocol defined 1988: TCP congestion control new national networks: Csnet, BITnet, NSFnet, Minitel r 100,000 hosts connected to confederation of networks r 1: Introduction 16 Internet History 1990’s: commercialization, the WWW r r r Early 1990’s: ARPAnet decomissioned 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) early 1990s: WWW m hypertext [Bush 1945, Nelson 1960’s] m HTML, http: Berners-Lee m 1994: Mosaic, later Netscape m late 1990’s: commercialization of the WWW Late 1990’s: r r r est. 50 million computers on Internet est. 100 million+ users backbone links runnning at 1 Gbps 1: Introduction 17 ATM: Asynchronous Transfer Mode nets Internet: r today’s de facto standard for global data networking 1980’s: r telco’s develop ATM: competing network standard for carrying high-speed voice/data r standards bodies: m m ATM Forum ITU ATM principles: r small (48 byte payload, 5 byte header) fixed length cells (like packets) m m r r fast switching small size good for voice virtual-circuit network: switches maintain state for each “call” well-defined interface between “network” and “user” (think of telephone company) 1: Introduction 18 ATM layers r ATM Adaptation Layer (AAL): interface to upper layers m m r r end-system segmentation/rea ssembly ATM Layer: cell switching Physical application TCP/UDP IP AAL ATM physical application TCP/UDP IP AAL ATM physical Where’s the application? r ATM: lower layer r functionality only r IP-over ATM: later ATM physical application TCP/UDP IP AAL ATM physical application TCP/UDP IP AAL ATM physical 1: Introduction 19 Chapter 1: Summary Covered a “ton” of material! r r r r r r r r Internet overview what’s a protocol? network edge, core, access network performance: loss, delay layering and service models backbones, NAPs, ISPs history ATM network You now hopefully have: r context, overview, “feel” of networking r more depth, detail later in course 1: Introduction 20