TLC p01 NetworkServices 2012

7/29/2019 TLC p01 NetworkServices 2012

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Telecomunicazioni

Docente: Andrea BaiocchiDIET - Stanza 35, 1 piano palazzina P. Piga

Sede Facolt S. Pietro in Vincoli

E-mail: [email protected]

University of RomaLa Sapienza

Corso di Laurea in Ingegneria Gestionale

A.A. 2011/2012

Telecomunicazioni - a.a. 2011/2012 - Prof. Andrea Baiocchi

2

Programma

1. SERVIZI E RETI DI TELECOMUNICAZIONE (KR-Cap. 1; GW-Cap. 1)

2. FONDAMENTI DI COMUNICAZIONI

3. ARCHITETTURE DI COMUNICAZIONE4. 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

9. CENNI SUI PROTOCOLLI APPLICATIVI


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Communication Networks andServices

Basic terminology and concepts


4

Communication

Network

The big picture

Communication

Network

Users

Users run applications and interact via acommunication network


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5

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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Examples: client-server apps

Email

FTP

SSH, Telnet

WWW

E-commerce

Audio & video streaming

Web 2.0


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Examples: p2p apps

Telephony, Voice/Telephony-over-Internet

Instant messaging: messenger, SMS

File sharing: eMule, BitTorrent,

Real-time P2P: Skype, IPTV

Network interactive games


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What is a communication network?

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

Virtually invisible to the user; represented by acloud

Communication

Network

Equipment

Routers, servers,switches, multiplexers,

hubs, modems,

Facilities

Copper wires, coaxialcables, optical fiber, radio

Ducts, conduits,telephone poles


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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

information


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Approaches to long-distancecommunications

Transfer ofmessages 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 oftransmission and reception ofsignals

Drums, beacons, mirrors, smoke, flags, semaphores,

Electromagnetic field

We focus on electrical communications


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11

Morse code converts text message into sequenceof dots and dashes

Use transmission system designed to convey dotsand dashes

0! 1! !R!!I

!9 !!Z ! Q!!!!H

!!8 ! Y! !P !G

!!!7 !! X O!! !F

!!!!6! W !N!E

!!!!!5!!! V M !!D

!!!! 4!! U! !!L ! !C

!!! 3T ! K !!!B

!! 2!!!S! J! A

MorseCode

MorseCode

MorseCode

MorseCode

Example of digital communications


12

Digital Transmission Evolution

1.0E+00

1.0E+02

1.0E+04

1.0E+06

1.0E+08

1.0E+10

1.0E+12

1.0E+14

1850 1875 1900 1925 1950 1975 2000

Morse

T-1 Carrier

SONET

Optical

CarrierInformationtransfer

persecond

Wavelength

Division

Multiplexing

Baudot


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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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The N2 Problem

For Nusers to be fullyconnected directly

Requires N(N 1)/2connections, i.e. 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 a

need ofintermediate 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 circtui networks known as exchange;

in LAN or ATM contexts known as switch.


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Switching: telephony example

Patchcord panel switch invented in 1877

Operators connect users on demand

Establish circuitto allow electrical current to flow from

inlet to outlet

Only Nconnections required to central office

1

23

N 1

N


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Circuit switching0

1

62

0

1

31

2

2

0

1

62

0

1

31

0

1

62

0

1

31

0

1

62

0

1

31

3161

0

1

62 31

0

1

0

1

31

0

1

62

A1

B1C1

A2

B2C2

0

1

62

C261

B

C

AA3

B3

C3


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Telephone subscribers connected to local CO (central office)

Tandem & Toll switches connect COs

Hierarchical Network Structure

Tandem

CO

Toll

CO COCO

CO

Tandem

CO = central office


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1

2

3

Routing

Store&Forward

Input

lines

Output

lines

Packet switching


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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


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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

Informationtransfer

Connection

release

Telephone

network

Example: telephone call


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Communication Network Architecture

Network architecture: the plan that specifieshow 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 overallcommunication process into separate functionalareas called layers

E.g. physical layer, end-to-end layer,


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Architecture layer view

Given a layer of the network architecture, the

communication network can be modeled by agraph Vertices are nodes that cooperate with neighboring nodes to

support upper layer service

Edges define (logical) direct communication links used bynodes to cooperate

Network topology

Interface (node-to-node)

Protocol(layer)


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Network topology

Refers to a givenarchitecture layer viewof the system

Specifies connectivity,i.e. capability of directinteraction betweenpeer entities

Topology model: agraph


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Connections of all Internetsub-networks in the world


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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 nodescorresponds to an interface

Entity: piece of sw/hw able to perform a task by co-operating with other remote,peerentities

An interface is defined by specification of thefollowing 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 morefunctions of the i/f: protocol)


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Example: ITU-T V.24

!

!

Composizionenumero

telefonico

DTR ON

RI ON

RTS ON

CTS ON

Tono

Audio

Cifre di

selezione

T x D

RTS OFF

CTS OFF

Toni Audio

(Dati)

Toni Audio

(OFF)

Toni Audio

(Dati)R x D

RTS OFF

CTS OFF

CD OFFCD OFF

CTS OFF

RTS OFF

T x D

CTS ON

Breve

Ritardo

Breve

Ritardo

RTS ON

CD OFF

R x D

DSR ON

DTR ON

ModalitDati

CD ON

Fasedi

trasferimentodati

Fasedi

Instaurazione

Fasedi

abbattimento

Toni Audio

(OFF)

DCE

(Modem)

DTE

(Terminale)

DCE

(Modem)

DTE

(Terminale)

InterfacciaDTE/DCE

InterfacciaDTE/DCE

Linea

telefonica

commutata

! Spia luminosa accesa Spia luminosa spenta

DCE

Ring Indication

Data Terminal Ready

Carrier Detect

Signal Ground

Data Set Ready

Clear To Send

Request To SendReceive Data

Transmit Data

Shield Ground

22

20

8

7

6

5

4

3

2

1

DTE

Connettore 25 pinISO 2110

RI

DTR

CD

SIG

DSR

CTS

RTSRxD

TxD

SHG

25 24 23 22 21 20 19 18 17 16 15 14

47.17mm

13 12 11 10 9 8 7 6 5 2 134


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Example: Ethernet

Specification of electrical quantities (current, voltage) andwaveforms (sync pulse trains, pulse shape)

Specification of access procedures: Medium Access Control (MAC)protocol


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Whats a protocol?

a human protocol and a computer network protocol:

Hi

Hi

Got thetime?

2:00

TCP connectionrequest

TCP connectionresponse

Get http://net.infocom.uniroma1.it

time


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Protocol elements

A protocol is a set of rules that governs how two ormore parties communicating over an interface areto interact

Examples Internet Protocol (IP), Transmission Control Protocol

(TCP), HyperText Transfer Protocol (HTTP), Simple MailTransfer Protocol (SMTP)

Key elements of a protocol

Syntax

Semanthics

Timing


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Protocols A protocol can be described by means of state

machines

State is the set of variables whose value issufficient to decide next transition given input andinternal events

E.g. message receipts, timer expiration

Given state at time t,X(t)=a, any event occurringin the interface at a subsequent time t+h makesthe state evolve to b

Actions are associated to transition a->b.

Protocols define format, order of msgs sent and receivedamong network entities, and actions taken on msg send/rcv


Internet at large


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Packet Switching

Internet is but one example of apacket switched

network 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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First packet switching ideasPaul Baran, 1964


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A closer look at network structure:

network edge

applications and hosts

access networks

wired/wirelesscommunication links

large number of smallrouters

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

Dialup modem

xDSL - Digital Subscriber Line

wirelessaccesspoint

wirelesslaptops

router/

firewall

modemto/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

basestation

mobilehosts

router

Access networks


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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 is

customeroftier-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 arecustomersofhigher 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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Hourglass model (H. Schulzrinne)


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Outlook


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Trends in Network Evolution

Its all about services

Building networks involves huge investment

Services that generate revenues drive the networkarchitecture

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-commerce


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Declination on 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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Evolution of services

Yesterday,call switching

today,call center


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Network models:intelligent vs dumb

Source: M. Dcina, 2006


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Network models: flat Mesh, ad hoc networks

IEEE 802.11 e 802.16

Pervasive andubiquitous computing

Domotics,embedded/wearablecomputing

event-driven, context-aware, communicating,networked smart objects

Wireless sensor

networks ZigBee, RFID Source: M. Dcina, 2006


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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, privacy


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ICT security attributes


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TCP/IP stack & security


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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 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 networks


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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 (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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History


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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 traffic


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Internet History (1/5)

1961: Kleinrock - queueing theory shows effectiveness ofpacket-switching

1964: Baran - packet-switching in military nets

1967: ARPAnet conceived by Advanced Research ProjectsAgency

1969: first ARPAnet node operational

1972:

ARPAnet public demonstration

NCP (Network Control Protocol) first host-host protocol

first e-mail program

ARPAnet has 15 nodes

1961-1972: Early packet-switching principles


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ARPANET - September 1971


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1970: ALOHAnet satellite network in Hawaii

1974: Cerf and Kahn - architecture for interconnecting nets

1976: Ethernet at Xerox PARC

Late 70s: proprietary architectures: DECnet, SNA, XNA

Late 70s: switching fixed length packets (ATM precursor)

1979: ARPAnet has 200 nodes

Cerf and Kahns internetworking principles: minimalism, autonomy - no internal changes required to interconnect nets

best effort service model

stateless routers

decentralized control

1972-1980: Internetworking, new and proprietary nets


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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 networks

1980-1990: new protocols, a proliferation of networks


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Early 1990s: ARPAnet decommissioned 1991: NSF lifts restrictions on commercial use of NSFnet

(decommissioned, 1995)

Early 1990s: Web

hypertext [Bush 1945, Nelson 1960s]

HTML, HTTP: Berners-Lee, 1989

1993: Mosaic, later Netscape

Late 1990s

commercialization of the Web network security to forefront

estimated 50 million host, 100 million+ users

backbone links running at Gbps

1990, 2000s: commercialization, the Web, new apps


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2000s

more killer apps:

instant messaging

P2P applications (BitTorrent - file sharing; Skype - VoIP;PPLive - video)

YouTube

Gaming

E-commerce

wireless, mobility

tens/hundreds Gbps backbone


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The Internet gotha


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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 246countries

End of 2009:

234 million websites

247 billion emails sent daily on the average

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

YouTube serves 1 billion videos per day


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Host count

TLC p01 NetworkServices 2012

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Transcript of TLC p01 NetworkServices 2012