Tlc p01 network_services_2012

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Tlc p01 network_services_2012

  1. 1. University of Roma “La Sapienza” Telecomunicazioni Docente: Andrea Baiocchi DIET - Stanza 35, 1° piano palazzina “P. Piga” Sede Facoltà S. Pietro in Vincoli E-mail: andrea.baiocchi@uniroma1.it Corso di Laurea in Ingegneria Gestionale A.A. 2011/2012 2 Programma 1. SERVIZI E RETI DI TELECOMUNICAZIONE (KR- Cap. 1; GW-Cap. 1) 2. FONDAMENTI DI COMUNICAZIONI 3. ARCHITETTURE DI COMUNICAZIONE 4. SERVIZI DI RETE E MODI DI TRASFERIMENTO 5. STRATO DI COLLEGAMENTO E ACCESSO MULTIPLO 6. TECNOLOGIE DI STRATO DI COLLEGAMENTO 7. LO STRATO DI RETE IN INTERNET 8. LO STRATO DI TRASPORTO IN INTERNET 9. CENNI SUI PROTOCOLLI APPLICATIVITelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  2. 2. Communication Networks and Services Basic terminology and concepts 4 The big picture Users Communication Communication Network Network Users run applications and interact via a communication networkTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  3. 3. 5 Applications • Client-server – Few host (servers) have got information content, processing power or any needed facility and are ready to answer to service requests from a much larger number of hosts (clients) • Peer-to-peer – Many hosts (peers) cooperate to create service, with possibly small help from some centralized servers • Also: – Uni/bi-directional – Interactive or notTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 6 Examples: client-server apps • Email • FTP • SSH, Telnet • WWW • E-commerce • Audio & video streaming • Web 2.0Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  4. 4. 7 Examples: p2p apps • Telephony, Voice/Telephony-over-Internet • Instant messaging: messenger, SMS • File sharing: eMule, BitTorrent,… • Real-time P2P: Skype, IPTV • Network interactive gamesTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 8 What is a communication network? Communication Network • The equipment (hardware & software) and facilities that provide the basic communication service • Virtually invisible to the user; represented by a cloud • Equipment • Facilities – Routers, servers, – Copper wires, coaxial switches, multiplexers, cables, optical fiber, radio hubs, modems, … – Ducts, conduits, telephone poles …Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  5. 5. 9 Analogies • A communication network provides services – This is like utilities, e.g. water supply, electric supply,… • Flexible connectivity – This is like transportation systems Goods / people informationTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi Approaches to long-distance 10 communications • Transfer of messages made up of – parseable sequence of symbols (digital information) – continuously variable physical quantities (analog information) • Courier: physical transport of the message – Messenger pigeons, pony express, FedEx,… • Messages can be transferred by means of transmission and reception of signals – Drums, beacons, mirrors, smoke, flags, semaphores,… – Electromagnetic field • We focus on electrical communicationsTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  6. 6. 11 Example of digital communications • Morse code converts text message into sequence of dots and dashes • Use transmission system designed to convey dots and dashes Morse Morse Morse Morse Code Code Code Code A ! — J !——— S !!! 2 !!——— B —!!! K —!— T — 3 !!!—— C —!—! L !—!! U !!— 4 !!!!— D —!! M —— V !!!— 5 !!!!! E ! N —! W !—— 6 —!!!! F !!—! O ——— X —!!— 7 ——!!! G ——! P !——! Y —!—— 8 ———!! H !!!! Q ——!— Z ——!! 9 ————! I !! R !—! 1 !———— 0 —————Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 12 Digital Transmission Evolution Wavelength Division 1.0E+14 Multiplexing Information transfer 1.0E+12 per second 1.0E+10 1.0E+08 SONET 1.0E+06 T-1 Carrier Optical 1.0E+04 Carrier Baudot 1.0E+02 1.0E+00 1850 1875 1900 1925 1950 1975 2000 MorseTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  7. 7. 13 Multiplexing • Point-to-point communication systems: – tx + communication link + rx • Usually much more capacity available than useful/affordable for single user pair • Natural approach: put multiple information flows of different user pairs onto the same shared communication system • Generalizable to point-to-multipoint communicationsTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 14 The N2 Problem • For N users to be fully 1 connected directly – Requires N(N – 1)/2 connections, i.e. scales N 2 with square of number of users .. . – Requires too much communication resources, 4 3 often underutilized: inefficient & costly • Basic idea to improve: resource sharing N = 1000 N(N – 1)/2 = 499500Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  8. 8. 15 Switching • Since information flows share same link, there is a need of intermediate dispatching – Analogous to railway or bus stations • A system where more links converge (input) and from which more links depart (output) is defined as a switching node if it has the task of deciding and actuating the correct output for each piece of information coming from an input – In Internet context known as router; – in telephone circtui networks known as exchange; – in LAN or ATM contexts known as switch.Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 16 Switching: telephony example • Patchcord panel switch invented in 1877 • Operators connect users on demand – Establish circuit to allow electrical current to flow from inlet to outlet • Only N connections required to central office N 1 N–1 2 3Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  9. 9. 17 A Circuit switching A3 0 0 0 0 1 1 1 1 2 2 31 62 62 31 A1 A2 B B3 B1 B2 C1 C2 0 0 0 0 0 1 1 1 1 1 61 C2 31 62 62 31 62 C C3 0 0 0 0 1 1 1 1 61 31 31 62 62 31Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 18 Hierarchical Network Structure Toll CO = central office Tandem Tandem CO CO CO CO CO Telephone subscribers connected to local CO (central office) Tandem & Toll switches connect COsTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  10. 10. 19 Packet switching Input lines 1 2 Routing Output lines 3 Store&ForwardTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 20 Communications modes • With connection – Two or more parties – Stateful – Three phases: Set up, Data transfer, Tear down • Connectionless – Two or more parties – Stateless – Single phase: Data transferTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  11. 11. Example: telephone call 1. Telephone Pick up phone network Dial tone. 2. Telephone network Connection set up Dial number 3. Telephone network Network selects route; 4. Telephone Sets up connection; network Called party alerted Information transfer 5. Telephone network Exchange voice signals Connection 6. Telephone release network Hang up. 22 Communication Network Architecture • Network architecture: the plan that specifies how the network is built and operated – Architecture is driven by network services and relies on available technology • Overall communication process is complex: therefore network architecture partitions overall communication process into separate functional areas called layers – E.g. physical layer, end-to-end layer,…Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  12. 12. 23 Architecture layer view • Given a layer of the network architecture, the communication network can be modeled by a graph – Vertices are nodes that cooperate with neighboring nodes to support upper layer service – Edges define (logical) direct communication links used by nodes to cooperate • Network topology • Interface (node-to-node) • Protocol (layer)Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 24 Network topology • Refers to a given architecture layer view of the system • Specifies connectivity, i.e. capability of direct interaction between peer entities • Topology model: a graphTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  13. 13. Connections of all Internet 25 sub-networks in the worldTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 26 What is an interface?• Contact point between two entities at a given level of abstraction (layer) – In the graph model of the layer, an edge between two nodes corresponds to an interface• Entity: piece of sw/hw able to perform a task by co- operating with other remote, peer entities• An interface is defined by specification of the following aspects: – Mechanical (only for physical interfaces) – Electrical (only for physical interfaces) – Functional (role played by any part of the interface) – Procedural (sequence of events that involve one or more functions of the i/f: protocol)Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  14. 14. 27 Example: ITU-T V.24 Linea Interfaccia telefonica Interfaccia 47.17 DTE/DCE commutata DTE/DCE mm DTE DCE DCE DTE (Terminale) (Modem) (Modem) (Terminale) 13 12 11 10 9 8 7 6 5 4 3 2 1 Composizione numero Cifre di DTR ON 25 24 23 22 21 20 19 18 17 16 15 14 telefonico selezione RI ON RTS ON CD ON Instaurazione Tono Fase di Modalità Audio Breve Dati DTR ON Ritardo DTE DCE ! DSR ON Toni Audio CTS ON (Dati) TxD RxD 22 Ring Indication RI RTS OFF 20 Data Terminal Ready CD OFF DTR trasferimento dati RTS ON Toni Audio CTS OFF 8 (OFF) CD Carrier Detect Fase di 7 SIG Signal Ground Breve 6 Ritardo DSR Data Set Ready 5 CTS ON CTS Clear To Send ! TxD Toni Audio (Dati) 4 RxD RTS Request To Send 3 RxD Receive Data Toni Audio abbattimento RTS OFF (OFF) RTS OFF 2 Fase di TxD Transmit Data CTS OFF CTS OFF 1 Shield Ground SHG CD OFF CD OFF Connettore 25 pin ISO 2110 ! Spia luminosa accesa Spia luminosa spentaTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 28 Example: Ethernet • Specification of electrical quantities (current, voltage) and waveforms (sync pulse trains, pulse shape) • Specification of access procedures: Medium Access Control (MAC) protocolTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  15. 15. 29 What’s a protocol? a human protocol and a computer network protocol: Hi TCP connection request Hi TCP connection Got the response time? Get http://net.infocom.uniroma1.it 2:00 <file> timeTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 30 Protocol elements • A protocol is a set of rules that governs how two or more parties communicating over an interface are to interact • Examples – Internet Protocol (IP), Transmission Control Protocol (TCP), HyperText Transfer Protocol (HTTP), Simple Mail Transfer Protocol (SMTP) • Key elements of a protocol – Syntax – Semanthics – TimingTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  16. 16. 31 Protocols • A protocol can be described by means of state machines • State is the set of variables whose value is sufficient to decide next transition given input and internal events – E.g. message receipts, timer expiration • Given state at time t, X(t)=a, any event occurring in the interface at a subsequent time t+h makes the state evolve to b • Actions are associated to transition a->b. Protocols define format, order of msgs sent and received among network entities, and actions taken on msg send/rcvTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi Communication Networks and Services Internet at large
  17. 17. 33 Packet Switching • Internet is but one example of a packet switched network • Basic ideas: – Information is segmented into “small”, self-contained chunks (smaller than typical amount of information to be transferred) -> PACKETS – Packets hop from one node to another until they find their way to the destination -> STORE & FORWARD – Hop can be realized by ANY underlying communication technology -> INTERNETWORKING – Improvement of QoS demanded to end-to-end protocols (e.g. error recovery, flow/congestion control)Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 34 High-level view of Internet • Hosts, routers and inter-networking H H Net 3 G Net 1 G G G Net 5 Net 2 Net 4 H G G HTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  18. 18. 35 First packet switching ideas Paul Baran, 1964Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 36 A closer look at network structure: • network edge – applications and hosts • access networks – wired/wireless communication links – large number of “small” routers • network core – interconnected routers – network of networksTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  19. 19. 37 Access networks Q: How to connect end systems to edge router? • residential access nets • institutional access networks (school, company) • mobile access networks wireless xDSL - Digital Subscriber Line laptopsDialup modem to/from modem router/ CO firewall wireless access pointTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 38 Access networks Q: How to connect end systems to edge router? • residential access nets • institutional access networks (school, company) • mobile access networks Wireless LAN - Local Area Network router base station mobile hostsTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  20. 20. 39 Internet structure: network of networks • roughly hierarchical • at center: “tier-1” ISPs (e.g., Verizon, Sprint, AT&T, Cable and Wireless), national/international coverage – treat each other as equals Tier-1 providers Tier 1 ISP interconnect (peer) privately Tier 1 ISP Tier 1 ISPTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 40 Tier-1 ISP: e.g., Sprint POP: point-of-presence to/from backbone peering … … . … … … to/from customersTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  21. 21. 41 Internet structure: network of networks • “Tier-2” ISPs: smaller (often regional) ISPs – Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs Tier-2 ISPsTier-2 ISP pays Tier-2 ISP also peer Tier-2 ISP privately withtier-1 ISP forconnectivity to Tier 1 ISP each other.rest of Internet! tier-2 ISP iscustomer oftier-1 provider Tier 1 ISP Tier 1 ISP Tier-2 ISP Tier-2 ISP Tier-2 ISPTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 42 Internet structure: network of networks • “Tier-3” ISPs and local ISPs – last hop (“access”) network (closest to end systems) local ISP Tier 3 local local local ISP ISP ISP ISPLocal and tier- Tier-2 ISP Tier-2 ISP3 ISPs arecustomers of Tier 1 ISPhigher tierISPsconnectingthem to rest Tier 1 ISPof Internet Tier 1 ISP Tier-2 ISP local Tier-2 ISP Tier-2 ISP ISP local local local ISP ISP ISPTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  22. 22. 43 Internet structure: network of networks • a packet passes through many networks! local ISP Tier 3 local local local ISP ISP ISP ISP Tier-2 ISP Tier-2 ISP Tier 1 ISP Tier 1 ISP Tier 1 ISP Tier-2 ISP local Tier-2 ISP Tier-2 ISP ISP local local local ISP ISP ISPTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 44 Hourglass model (H. Schulzrinne)Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  23. 23. Communication Networks and Services Outlook 46 Trends in Network Evolution • It’s all about services – Building networks involves huge investment – Services that generate revenues drive the network architecture • Current trends and issues – Multimedia applications – Info-centric communications – End of trust – Legal issues (laws are local, network is global) – Overlay networks – Nano-networks – E-government, e-business, e-commerceTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  24. 24. 47 Declination on Internet • Internet of Communities: organization of people activities through the Internet, on the basis of common interests and likings. • Internet of Services: interconnection of providers and consumers of any type of service that can be accessed through the Internet. • Internet of Media: network supporting media search, delivery, and integration, regardless their format, providing suitable storage and quick access. • Internet of Things: pervasive network, capable of connecting all devices that can generate, transmit, or receive contents, including sensors, cameras, wearable devices.Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 48 Evolution of services Yesterday, …today, call switching… call centerTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  25. 25. 49 Network models: intelligent vs dumb Source: M. Dècina, 2006Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 50 Network models: flat • Mesh, ad hoc networks – IEEE 802.11 e 802.16 • Pervasive and ubiquitous computing – Domotics, embedded/wearable computing – event-driven, context- aware, communicating, networked smart objects • Wireless sensor networks – ZigBee, RFID Source: M. Dècina, 2006Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  26. 26. 51 End of Trust • Security Attacks – Spam, Phishing, Pharming – Denial of Service, DDoS – Viruses – Impersonators • Firewalls & Filtering – Control flow of traffic/data from/to Internet • Confidentiality, integrity and authentication; authorization; traffic monitoring • Anonymity, privacyTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 52 ICT security attributesTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  27. 27. 53 TCP/IP stack & securityTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 54 Operations, Administration, Maintenance, and Billing • Communication like transportation networks – Traffic flows need to be monitored and controlled, QoS and security must be guaranteed, possibly at different levels – Tolls have to be collected – Roads have to be maintained – Need to forecast traffic and plan network growth • Highly-developed in telephone network – Entire organizations address OAM & Billing – Becoming automated for flexibility & reduced cost • Under development for IP networksTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  28. 28. 55 Success Factors for New Services • Technology not only factor in success of a new service • Three factors considered in new telecom services New Market Service Technology Can there be Can it be demand for the implemented cost- service? effectively? Regulation Is the service allowed/somehow constrained?Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 56 Role of regulation • Public regulation is fundamental as communication services become a commodity • Minimum service access to be guaranteed – Universal service • Digital divide • Also fundamental for – unique resources (radio spectrum) – protection of public interests (e.g. health)Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  29. 29. 57 Standards • New technologies very costly and risky • Standards allow players to share risk and benefits of a new market – Reduced cost of entry – Interoperability and network effect – Compete on innovation – Completing the value chain • Chips, systems, equipment vendors, service providers • Example – 802.11 wireless LAN productsTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 58 Standards Bodies • Internet Engineering Task Force (IETF) – Internet standards development – Request for Comments (RFCs): www.ietf.org • International Telecommunications Union (ITU) – International telecom standards • International Standardization Organization (ISO) • IEEE 802 Committee – Local area and metropolitan area network standards • Regional bodies (ETSI, ANSI) • Industry Organizations and Fora – 3GPP, MPLS Forum, WiFi Alliance, World Wide Web Consortium, BluetoothTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  30. 30. Communication Networks and Services History 60 Computer Network Evolution Overview • 1950s: Telegraph technology adapted to computers • 1960s: Dumb terminals access shared host computer – SABRE airline reservation system • 1970s & 1980s: Computers connect directly to each other – ARPANET packet switching network – TCP/IP based internetworking – Ethernet local area network • 1990s & 2000s: New applications and Internet growth – Commercialization of Internet – E-mail, file transfer, web, P2P, streaming . . . – Internet traffic surpasses voice trafficTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  31. 31. 61 Internet History (1/5) 1961-1972: Early packet-switching principles • 1961: Kleinrock - queueing theory shows effectiveness of packet-switching • 1964: Baran - packet-switching in military nets • 1967: ARPAnet conceived by Advanced Research Projects Agency • 1969: first ARPAnet node operational • 1972: – ARPAnet public demonstration – NCP (Network Control Protocol) first host-host protocol – first e-mail program – ARPAnet has 15 nodesTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 62 ARPANET - September 1971Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  32. 32. 63 Internet History (2/5) 1972-1980: Internetworking, new and proprietary nets • 1970: ALOHAnet satellite network in Hawaii • 1974: Cerf and Kahn - architecture for interconnecting nets • 1976: Ethernet at Xerox PARC • Late 70’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: – minimalism, autonomy - no internal changes required to interconnect nets – best effort service model – stateless routers – decentralized controlTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 64 Internet History (3/5) 1980-1990: new protocols, a proliferation of networks • 1983: deployment of TCP/IP • 1982: smtp e-mail protocol defined • 1983: DNS defined for name-to-IP-address translation • 1985: ftp protocol defined • 1988: TCP congestion control • new national networks: Csnet, BITnet, NSFnet, Minitel • 100,000 hosts connected to confederation of networksTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  33. 33. 65 Internet History (4/5) 1990, 2000’s: commercialization, the Web, new apps • Early 1990’s: ARPAnet decommissioned • 1991: NSF lifts restrictions on commercial use of NSFnet (decommissioned, 1995) • Early 1990s: Web – hypertext [Bush 1945, Nelson 1960’s] – HTML, HTTP: Berners-Lee, 1989 – 1993: Mosaic, later Netscape • Late 1990’s – commercialization of the Web – network security to forefront – estimated 50 million host, 100 million+ users – backbone links running at GbpsTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 66 Internet History (5/5) • 2000’s – more killer apps: • instant messaging • P2P applications (BitTorrent - file sharing; Skype - VoIP; PPLive - video) • YouTube • Gaming • E-commerce – wireless, mobility – tens/hundreds Gbps backboneTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  34. 34. 67 The Internet gothaTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi 68 Internet statistics • ~769 million hosts (July 2010) • ~2 billion users • As of Feb. 27rd, 2012: 138,143,921 Top Level Domains • As of Feb. 1st, 2012: 3,479,770,880 IP addresses assigned in 246 countries End of 2009: • 234 million websites • 247 billion emails sent daily on the average • Facebook serves 260 billion page views per month (6 millions per min) • YouTube serves 1 billion videos per dayTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi
  35. 35. 69 Host countTelecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi

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