2 Protocolli Applicativi

Protocolli Applicativi ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Alcune applicazioni di rete ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Creare un’applicazione di rete ,[object Object],[object Object],[object Object],[object Object],application transport network data link physical application transport network data link physical application transport network data link physical

Creare un’applicazione di rete ,[object Object],[object Object],[object Object],application transport network data link physical application transport network data link physical application transport network data link physical

Comunicazione tra processi ,[object Object],[object Object],[object Object]

Processi e Protocolli ,[object Object],[object Object],[object Object]

Interazione coi livelli inferiori ,[object Object],[object Object],[object Object],Presentazione Sessione WEB FTP Mail Trasporto Livello controllato dall’applicazione Livelli controllati dal sistema operativo

Interazione coi livelli inferiori ,[object Object],WEB FTP Mail Trasporto Livello controllato dall’applicazione Livelli controllati dal sistema operativo

Sockets ,[object Object],[object Object],[object Object],[object Object],Internet controlled by OS controlled by app developer ,[object Object],process TCP with buffers, variables socket host or server process TCP with buffers, variables socket host or server

Indirizzamento dei processi ,[object Object],[object Object],[object Object]

Indirizzamento dei processi ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Protocolli applicativi ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Requisiti del servizio di trasporto ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Requisiti del servizio di trasporto Application file transfer e-mail Web documents real-time audio/video stored audio/video interactive games instant messaging Data loss no loss no loss no loss loss-tolerant loss-tolerant loss-tolerant no loss Bandwidth elastic elastic elastic audio: 5kbps-1Mbps video:10kbps-5Mbps same as above few kbps up elastic Time Sensitive no no no yes, 100’s msec yes, few secs yes, 100’s msec yes and no

Servizi di trasporto in Internet ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Applicazioni e protocolli di trasporto Application e-mail remote terminal access Web file transfer streaming multimedia Internet telephony Application layer protocol SMTP [RFC 2821] Telnet [RFC 854] HTTP [RFC 2616] FTP [RFC 959] proprietary (e.g. RealNetworks) proprietary (e.g., Vonage,Dialpad) Underlying transport protocol TCP TCP TCP TCP TCP or UDP typically UDP

Comunicazione Client-Server ,[object Object],[object Object],[object Object],[object Object]

Comunicazione Client-Server ,[object Object],[object Object],[object Object],[object Object],client server request response

Processi Client-Server ,[object Object],[object Object],[object Object],[object Object]

Programmi Client-Server ,[object Object],[object Object],request response request response requests responses ... ...

Programmi Client e Server ,[object Object],[object Object],[object Object],[object Object],[object Object]

Architetture applicative ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Architettura client-server ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Architettura P2P (pura) ,[object Object],[object Object],[object Object],[object Object],Fortemente scalabile ma difficile da gestire

Architettura ibrida ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Web Browsing Hyper Text Transfer Protocol (HTTP)

HyperText Tranfer Protocol (HTTP) ,[object Object],[object Object],[object Object],[object Object],HTTP request HTTP response ,[object Object],[object Object],client server

Trasporto dei messaggi ,[object Object],[object Object],[object Object],[object Object],http ://www.polimi.it /index.html Indica il protocollo applicativo Indica l’indirizzo di rete del server Indica la pagina web richieste La porta TCP viene definita per default (80) Method Host :// : Port Path /

Trasporto dei messaggi ,[object Object],: ,[object Object],[object Object],[object Object],Altri oggetti Testo HTML

Non persistent ,[object Object],[object Object],[object Object],[object Object],Request (index.html) Response (index.html file) Request (image1.jpg) Request (image2.jpg)

Persistent connection ,[object Object],[object Object],[object Object],[object Object],[object Object]

Esempi di Methods ,[object Object],[object Object],E’ utilizzato per memorizzare un documento nel server. Il documento viene fornito nel corpo del messaggio e la posizione di memorizzazione nell’URL. PUT E’ usato quando il client non vuole scaricare il documento ma solo alcune informazioni sul documento (come ad esempio la data dell’ultima modifica). Nella risposta il server non inserisce il documento ma solo degli header informativi. HEAD E’ usato per fornire degli input al server da utilizzare per un particolare oggetto (di solito un applicativo) identificato nell’URL. POST E’ usato quando il client vuole scaricare un documento dal server. Il documento richiesto è specificato nell’URL. Il server normalmente risponde con il documento richiesto nel corpo del messaggio di risposta. GET

Messaggi ,[object Object],[object Object],[object Object],[object Object],[object Object],Prima parte della richiesta accettata. 100 Continue: Servizio non disponibile 503 Service unavailable Funzione non implementata 501 Not implemented Errore o guasto nel server 500 Internal server error La richiesta ha avuto successo; l’informazione è inclusa 200 OK: L’oggetto è stato spostato nell’URL indicato 304 Moved Temporalily: L’oggetto è stato spostato nell’URL indicato 302 Moved Permanently: Accesso senza necessari account e passwd 401 Unauthorized: l’oggetto non esiste sul server 404 Not Found: errore generico 400 Bad Request:

Header ,[object Object],[object Object],[object Object],Header name Header value : Tipo di user agent User-agent Mostra i permessi del client Authorization Invia il doc. solo se modificato If-modified-since Linguaggio accettato Accept-language Formati accettati Accept Informazione sulla cache Cache-control

Scambio di messaggi: un esempio ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],HTTP è testuale (ASCII)

Cache locale: get condizionato ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Cache di rete: uso dei proxy ,[object Object],[object Object]

Proxy ,[object Object],[object Object],[object Object],LL IP TCP HTTP User Agent LL IP TCP HTTP Server LL IP TCP HTTP Proxy

Autenticazione ,[object Object],[object Object],[object Object],GET /ntw/index.html HTTP/1.1 401 Authorization Required WWW-Authenticate:[tipo di autenticazione] GET /ntw/index.html HTTP/1.1 Authorization: account, passwd GET image.gif HTTP/1.1 Authorization: account, passwd . . .

Cookie ,[object Object],[object Object],[object Object],GET /ntw/index.html HTTP/1.1 200 OK Set-cookie:18988466 GET /ntw/carrello/index.html HTTP/1.1 Cookie: 18988466 GET image.gif HTTP/1.1 Cookie: 18988466 . . .

HTML (HyperText Markup Language) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Pagine WEB dinamiche ,[object Object],[object Object],GET /cgi-bin/prog.pl HTTP/1.1 prog.pl 200 OK Pagina dinamica

Pagine WEB attive ,[object Object],[object Object],[object Object],GET /java/applet HTTP/1.1 200 OK programma

Trasferimento di informazione File Transfer Protocol (FTP)

File Transfer Protocol (FTP) ,[object Object],[object Object],[object Object]

File Transfer Protocol (FTP) ,[object Object],[object Object],User Interface Control process Data tranfer process LFS Control process Data tranfer process LFS client server Port 21 Port 20

FTP: connessione di controllo ,[object Object],[object Object],[object Object],[object Object],Control process Data tranfer process LFS LFS client server Passive open Port 21 Control process Data tranfer process Active open Port 66778

FTP: connessione dati ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

FTP: connessione dati ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

FTP: comandi ,[object Object],USER username PASS password QUIT log out Comandi di accesso CWD change directory DELE delete file LIST list files RETR retrive file STOR store file Gestione file TYPE file type MODE transfer mode PORT client port PASV server choose port Modalità di trasferimento Gestione delle porte

FTP: risposte 125 Data connection already open; transfer starting 200 Command OK 225 Data connection open 226 Closing data connection 227 Entering passive mode; srv. sends Ip_add.,port 230 User login OK 331 Username OK, password required 425 Can't open data connection 426 Connection closed; tranfer aborted 452 Error writing file 500 Syntax error; unrecognized command 501 Syntax error in parameters or arguments 502 Command not implemented

FTP: esempio trasferimento file Client Server 220 service ready USER matteo 331 username OK; password ? PASS pippo123 230 user login OK PORT 65667 150 opening data connection LIST /usr/pub 125 data connection OK 226 closing data connection Data

Servizio di E-mail Simple Mail Transfer Protocol (SMTP)

E-mail ,[object Object],[object Object]

SMTP ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],J.B. Postel, "Simple Mail Transfer Protocol," RFC 821, August 1982.

Colloquio tra client e server SMTP ,[object Object],Handshake

Formato dei messaggi ,[object Object],[object Object],D.H. Crocker, "Standard for the Format of ARPA Internet Text Messages," RFC 822, August 1982 . From: alice@crepes.fr To: bob@hamburger.edu Subject: Request of information <black line> <Body> .

Multipurpose Internet Mail Extensions (MIME) ,[object Object],[object Object],[object Object],From: alice@crepes.fr To: bob@hamburger.edu Subject: Picture of yummy crepe. MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Type: image/jpeg base64 encoded data ..... ........................ .....base64 encoded data .

Multipurpose Internet Mail Extensions (MIME) ,[object Object],[object Object],[object Object],[object Object],[object Object],11001100 10000001 00111001 110011 001000 000100 111001 0110011 0001000 0000100 0111001 Z I E 5 base64

Multipurpose Internet Mail Extensions (MIME) ,[object Object],[object Object],[object Object],[object Object],00100110 & 01001100 L 10011101 Non-ASCII Quotable-printable 00111001 9 00100110 & 01001100 L 00111101 = 00111001 9 1001 9 1101 D

Multipurpose Internet Mail Extensions (MIME) ,[object Object],From: alice@crepes.fr To: bob@hamburger.edu Subject: Picture of yummy crepe with commentary MIME-Version: 1.0 Content-Type: multipart/mixed; Boundary=StartOfNextPart --StartOfNextPart Dear Bob, Please find a picture of an absolutely scrumptious crepe. --StartOfNextPart Content-Transfer-Encoding: base64 Content-Type: image/jpeg base64 encoded data ..... --StartOfNextPart Let me know if you would like the recipe. .

Protocolli di accesso al mailbox ,[object Object],[object Object],[object Object],[object Object]

POP3 ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],C: list S: 1 498 S: 2 912 S: . C: retr 1 S: <message 1 contents> S: . C: dele 1 C: retr 2 S: <message 1 contents> S: . C: dele 2 C: quit S: +OK POP3 server signing off S: +OK POP3 server ready C: user bob S: +OK C: pass hungry S: +OK user successfully logged on

Case History ,[object Object],[object Object],[object Object],[object Object],[object Object]

TELNET (TErminaL NETwork) ,[object Object],[object Object],Terminal driver Telnet client Pseudo-terminal driver Telnet server Internet TCP IP LL TCP IP LL

TELNET (TErminaL NETwork) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],c a t f i l e a IAC EC 1

Indirizzamento simbolico dei domini Domani Name System (DNS)

Domain Name System (DNS) ,[object Object],[object Object],[object Object],[object Object],[object Object],131.175.21.1 morgana.elet.polimi.it

Domain Name System (DNS) ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],"Domain Names - Concepts and Facilities," RFC 1034, Nov. 1987. "Domain Names - Implementation and Specification," RFC 1035, Nov. 1987.

Indirizzamento simbolico ,[object Object],[object Object],[object Object],com edu org gov mil it fr jp de ... ucla columbia polimi elet cs virgilio rett yahoo morgana morgana.elet.polimi.it

Tipi di NS ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Gerarchia DNS ,[object Object],Source: Computer Networking, J. Kurose

Root NS nel 2004 http://www.wia.org/

Come ottenere un mappaggio ,[object Object],[object Object],[object Object],[object Object],HOST Local NS DNS request DNS response DNS Network

Informazioni memorizzate ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],Name, Value, Type , TTL

Organizzazione del database ,[object Object],[object Object],[object Object],[object Object],com edu org gov mil it fr jp de ... ucla columbia polimi elet cs virgilio rett yahoo morgana

Reperire informazioni ,[object Object],[object Object],[object Object],Source: Computer Networking, J. Kurose

Reperire informazioni ,[object Object],[object Object]

Caching ,[object Object],[object Object],[object Object],[object Object]

Messaggi DNS ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],sono in binario (non ASCII)

P2P file sharing ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

P2P: directory centralizzata ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],centralized directory server peers Alice Bob 1 1 1 1 2 3

P2P: directory centralizzata ,[object Object],[object Object],[object Object],[object Object],[object Object]

P2P: completamente distribuita ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

P2P: completamente distribuita ,[object Object],[object Object],[object Object],[object Object],File transfer: HTTP Query QueryHit Query Query QueryHit Query Query QueryHit

P2P: completamente distribuita ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

P2P: architettura ibrida ,[object Object],[object Object],[object Object],[object Object],[object Object]

2 Protocolli Applicativi

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2 Protocolli Applicativi