TLC p01 NetworkServices 2014 - uniroma1.itnetlab.uniroma1.it/.../default/files/TLC_p01_NetworkServices_2014.pdf · Telecomunicazioni - a.a. 2013/2014 - Prof. Andrea Baiocchi 3 Programma

Telecomunicazioni

Docente: Andrea BaiocchiDIET - Stanza 107, 1° piano palazzina “P. Piga”

Sede Facoltà S. Pietro in Vincoli

E-mail: [email protected]

University of Roma

“La Sapienza”

Corso di Laurea in Ingegneria Gestionale

A.A. 2013/2014

Telecomunicazioni - a.a. 2013/2014 - Prof. Andrea Baiocchi

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About applications and services…

It will be possible for a business man in New York to dictate instructions, and have theminstantly appear in type at his office in London or elsewhere. He will be able to call up, fromhis desk, and talk to any telephone subscriber on the globe.... An inexpensive instrument,not bigger than a watch, will enable its bearer to hear anywhere, on sea or land, music orsong, the speech of a political leader, the address of an eminent man of science, or thesermon of an eloquent clergyman, delivered in some other place, however distant. In thesame manner any picture, character, drawing, or print can be transferred from one toanother place…

[Nicolas Tesla, 1908]

I do not think that the wireless waves I have discovered will have any practical application.

[Heinrich Hertz, end of XIX century]

That’s an amazing invention, but who would ever want to use one of them?

[President Rutherford B. Hayes to Alexander Graham Bell in 1876 on viewing the telephonefor the first time]

I think there is a world market for maybe five computers.

[Thomas Watson, chairman of IBM, 1943]

There is no reason anyone would want a computer in their home.

[Ken Olson, president, chairman, and founder of Digital Equipment Corp., 1977]


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Programma

1. SERVIZI E RETI DI TELECOMUNICAZIONE

2. FONDAMENTI DI COMUNICAZIONI

3. ARCHITETTURE DI COMUNICAZIONE

4. SERVIZI DI RETE E MODI DI TRASFERIMENTO

5. STRATO DI COLLEGAMENTO E ACCESSOMULTIPLO

6. TECNOLOGIE DI STRATO DI COLLEGAMENTO

7. LO STRATO DI RETE IN INTERNET

8. LO STRATO DI TRASPORTO IN INTERNET


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L’ICT è pervasiva…

• Multimedia

• Green networking

• Data & network security

• Nano-scale systems/nets

• Data mining, big data

• Computationalintelligence

• Smart grids

• E-Government

• Aeronautical Tlc Network(ATN)

• Intelligent TransportationSystem (ITS)

– Vehicular communications

• Context awareness, smartspaces

• Sensors, Internet of Things

(IoT)

• Cloud computing

• Bio-inspired systems/nets

• E-commerce

Communication Networks andServices

Basic terminology and concepts


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Communication

Network

The big picture

Communication

Network

Users

Users run applications and interact via acommunication network


7

Applications

• Client-server

– Few host (servers) have got information content,processing power or any needed facility and are ready toanswer to service requests from a much larger number ofhosts (clients)

• Peer-to-peer

– Many hosts (peers) cooperate to create service, withpossibly small help from some centralized servers

• Also:

– Uni/bi-directional

– Interactive or not


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Tanenbaum, Wetherall, Reti di calcolatori © Pearson 20128

Una rete con due client e un server


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Il modello client-servercomprende richieste e risposte


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Sistema peer-to-peer


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Examples: client-server apps

• Email

• FTP

• SSH, Telnet

• WWW

• E-commerce

• Audio & video streaming

• Web 2.0

• Gaming on line


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Examples: p2p apps

• Telephony

• Instant messaging: WhatsApp, SMS,…

• File sharing: eMule, BitTorrent,…

• Real-time P2P: Skype, IPTV, TeamSpeak,…

• Network interactive games: CoD,…


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What is a communication network?

• The equipment (hardware & software) and facilitiesthat provide the basic communication service

Communication

Network

• Equipment

– Routers, servers,switches, multiplexers,hubs, modems, …

• Facilities

– Copper wires, coaxialcables, optical fiber, radio

– Ducts, conduits,telephone poles …


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The essence of communications

• Transfer of messages made up of

– parseable sequence of symbols (digital information)

– continuously variable physical quantities (analoginformation)

• Messages can be transferred by means oftransmission and reception of signals

– Drums, beacons, mirrors, smoke, flags, semaphores,…

– Electromagnetic field

• We focus on electrical communications


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Multiplexing

• Point-to-point communication systems:

– tx + communication link + rx

• Usually much more capacity available thanuseful/affordable for single user pair

• Natural approach: put multiple information flowsof different user pairs onto the same sharedcommunication system

• Generalizable to point-to-multipointcommunications


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Digression: graphs

• Let V be a finite set. We call an element of V“node” or “vertex”

– E.g., V={1,2,…,n}.

• Let A be a subset of the cartesian product VxV. Wecall an element of A “arc” or “edge”

– The ordered couple (i,j) is an arc from node i to node j.

• A graph is a couple G={V,A}

– Undirected graph: if (i,j) belongs to A, then (j,i) belongsto A as well.

– Directed graph: the condition above does not hold.


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The N2 Problem

• For N users to be fullyconnected directly

– Requires N(N – 1)/2connections, i.e., it scaleswith square of number ofusers

– Requires too muchcommunication resources,often underutilized:inefficient & costly

• Basic idea to improve:resource sharing

N = 1000

N(N – 1)/2 = 499500

1

2

34

N

. . .


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Switching

• Since information flows share same link, there is aneed of intermediate dispatching

– Analogous to railway or bus stations

• A system where more links converge (input) andfrom which more links depart (output) is definedas a switching node if it has the task of decidingand actuating the correct output for each piece ofinformation coming from an input

– In Internet context known as router;

– in telephone circuit networks known as exchange;

– in LAN context known as switch.


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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 transfer

Network selects route;

Sets up connection;

Called party alerted

Telephone

network

Pick up phone

Dial tone.

Dial number

Exchange voice

signals

1.

2.

3.

4.

5.

Telephone

network

Telephone

network

Telephone

network

Telephone

network

Hang up.6.

Connection

set up

Information

transfer

Connection

release

Telephone

network

Example: telephone call


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Operations, Administration,Maintenance, and Billing

• Communication like transportation networks

– Traffic flows need to be monitored and controlled, QoSand security must be guaranteed, possibly at differentlevels

– Tolls have to be collected

– Roads have to be maintained

– Need to forecast traffic and plan network growth

• Highly-developed in tlc networks

– Entire organizations address OAM & Billing

– Becoming automated for flexibility & reduced cost


Internet at large


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Packet Switching

• Internet is but one example of a packet switchednetwork

• Basic ideas:

– Information is segmented into “small”, self-containedchunks (smaller than typical amount of information to betransferred) -> PACKETS

– Packets hop from one node to another until they find theirway to the destination -> STORE & FORWARD

– Hop can be realized by ANY underlying communicationtechnology -> INTERNETWORKING

– Improvement of QoS demanded to end-to-end protocols(e.g., error recovery, flow/congestion control)


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High-level view of Internet• Hosts, routers and inter-networking

G

G

G

G

G

G

Net 1

Net 5

Net 3

Net 4Net 2

H

HH

H


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A closer look at network structure:

• network edge

– applications and hosts

• access networks

– wired/wirelesscommunication links

– large number of “small”routers

• network core

– interconnected routers

– network of networks


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Q: How to connect end systems to edge router?

• residential access nets

• institutional access networks (school, company)

• mobile access networks

xDSL - Digital Subscriber Line

wirelessaccess point

wirelesslaptops

routermodemto/fromCO

Access networks


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Q: How to connect end systems to edge router?

• residential access nets

• institutional access networks (school, company)

• mobile access networks

LAN - Local Area NetworkWireless / Cellular

Base station

mobilehosts

router

Access networks

switch

router


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Internet structure: network of networks

• roughly hierarchical

• at center: “tier-1” ISPs (e.g., Verizon, Sprint, AT&T, Cableand Wireless), national/international coverage

– treat each other as equals

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier-1providersinterconnect(peer)privately


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Tier-1 ISP: e.g., Sprint

…

to/from customers

peering

to/from backbone

…

.

………

POP: point-of-presence


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• “Tier-2” ISPs: smaller (often regional) ISPs

– Connect to one or more tier-1 ISPs, possibly other tier-2 ISPs

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

Tier-2 ISP paystier-1 ISP forconnectivity torest of Internet! tier-2 ISP iscustomer oftier-1 provider

Tier-2 ISPsalso peerprivately witheach other.


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• “Tier-3” ISPs and local ISPs

– last hop (“access”) network (closest to end systems)

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP



Tier-2 ISP

localISPlocal

ISPlocalISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP

Local and tier-3 ISPs arecustomers ofhigher tierISPsconnectingthem to restof Internet


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• a packet passes through many networks!

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP



Tier-2 ISP

localISPlocal

ISPlocalISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP



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Schema dell’architettura di Internet


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Il progetto originale di ARPANET


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Crescita di ARPANET(a) Dicembre 1969. (b) Luglio 1970. (c) Marzo

1971. (d) Aprile 1972. (e) Settembre 1972.


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Internet statistics

• ~908 million hosts (July 2012)

• ~2.4 billion users (June 2012)

• As of Feb. 27rd, 2012: 138,143,921 Top Level Domains

• As of Feb. 1st, 2012: 3,479,770,880 IP addresses assigned in 246countries

End of 2009:

• 234 million websites

• 247 billion emails sent daily on the average (~90% is spam!)

• Facebook serves 260 billion page views per month (6 millions permin)

• YouTube serves 1 billion videos per day

http://www.internetworldstats.com/stats.htm


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Host count


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Log-scale host count


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Fixed broadband Internet

2012 - Subscriptions as a percentage of population


Outlook


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Trends in Network Evolution

• It’s all about services

– Building networks involves huge investment

– Services that generate revenues drive the networkarchitecture

• Current trends and issues

– Multimedia applications

– Info-centric communications

– Security and legal issues (laws are local, network isglobal)

– Overlay networks

– Nano-networks


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Declinations of Internet

• Internet of Communities: organization of people activitiesthrough the Internet, on the basis of common interests andlikings.

• Internet of Services: interconnection of providers andconsumers of any type of service that can be accessedthrough the Internet.

• Internet of Media: network supporting media search,delivery, and integration, regardless their format, providingsuitable storage and quick access.

• Internet of Things: pervasive network, capable ofconnecting all devices that can generate, transmit, or receivecontents, including sensors, cameras, wearable devices.


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Example of IoT: V2V

Feb 4, 2014

• The U.S. Department of Transportation's (DOT) NationalHighway Traffic Safety Administration (NHTSA) announcedtoday that it will begin taking steps to enable vehicle-to-vehicle (V2V) communication technology for light vehicles.


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Evolution of services

Yesterday,call switching…

…today,call center


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Success Factors for New Services

• Technology not only factor in success of a newservice

• Three factors considered in new telecom services

TechnologyMarket

Regulation

Can it be

implemented cost-

effectively?

Can there be

demand for the

service?

Is the service

allowed/somehow

constrained?

New

Service


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Role of regulation

• Public regulation is fundamental as communicationservices become a commodity

• Minimum service access to be guaranteed

– Universal service

• Digital divide

• Also fundamental for

– unique resources (e.g., radio spectrum)

– protection of public interests (e.g., health)


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Standards

• New technologies very costly and risky

• Standards allow players to share risk and benefitsof 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 products


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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,Bluetooth


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Prefissi metrici principali

Documents

TLC p01 NetworkServices 2014 - uniroma1.itnetlab.uniroma1.it/.../default/files/TLC_p01_NetworkServices_2014.pdf · Telecomunicazioni - a.a. 2013/2014 - Prof. Andrea Baiocchi 3 Programma