FTP: the file transfer protocol

Save this PDF as:
 WORD  PNG  TXT  JPG

Size: px
Start display at page:

Download "FTP: the file transfer protocol"

Transcription

1 FTP: the file transfer protocol at host FTP interface FTP client local file system file transfer FTP remote file system transfer file to/from remote host client/ model client: side that initiates transfer (either to/from remote) : remote host ftp: RFC 959 ftp : port 21 2: Application Layer 1 FTP: separate control, data connections FTP client contacts FTP at port 21, specifying TCP as transport protocol Client obtains authorization over control connection Client browses remote directory by sending commands over control connection. When receives a command for a file transfer, the opens a TCP data connection to client After transferring one file, closes connection. FTP client TCP control connection port 21 TCP data connection port 20 FTP Control connection: out of band FTP maintains state : current directory, earlier authentication 2: Application Layer 2

2 FTP commands, responses Sample commands: sent as ASCII text over control channel USER name PASS password LIST return list of file in current directory RETR filename retrieves (gets) file STOR filename stores (puts) file onto remote host Sample return codes status code and phrase (as in HTTP) 331 Username OK, password required 125 data connection already open; transfer starting 425 Can t open data connection 452 Error writing file 2: Application Layer 3 Electronic Mail Four major components: s s simple transfer protocol: SMTP access protocols: POP3, IMAP User Agent a.k.a. reader composing, editing, reading messages e.g., Eudora, Outlook, elm, Netscape Messenger outgoing, incoming messages stored on SMTP SMTP SMTP SMTP/POP3 SMTP/POP3 outgoing message queue box SMTP/IMAP 2: Application Layer 4

3 Electronic Mail: s Mail Servers box contains incoming messages for message queue of outgoing (to be sent) messages SMTP protocol between s to send e messages client: sending : receiving SMTP SMTP SMTP 2: Application Layer 5 Electronic Mail: SMTP [RFC 2821] uses TCP to reliably transfer e message from client to, port 25 direct transfer: sending to receiving three phases of transfer handshaking (greeting) transfer of messages closure command/response interaction commands: ASCII text response: status code and phrase messages must be in 7-bit ASCII 2: Application Layer 6

4 Scenario: Alice sends message to Bob 1) Alice uses UA to compose message and to 2) Alice s UA sends message to her ; message placed in message queue using SMTP 3) Client side of SMTP opens TCP connection with Bob s 4) SMTP client sends Alice s message over the TCP connection 5) Bob s places the message in Bob s box 6) Bob invokes his to read message using POP3, IMAP : Application Layer 7 Sample SMTP interaction S: 220 hamburger.edu C: HELO crepes.fr S: 250 Hello crepes.fr, pleased to meet you C: MAIL FROM: S: 250 Sender ok C: RCPT TO: S: 250 Recipient ok C: DATA S: 354 Enter, end with "." on a line by itself C: Do you like ketchup? C: How about pickles? C:. S: 250 Message accepted for delivery C: QUIT S: 221 hamburger.edu closing connection 2: Application Layer 8

5 Try SMTP interaction for yourself: telnet name 25 see 220 reply from enter HELO, MAIL FROM, RCPT TO, DATA, QUIT commands above lets you send e without using e client (reader) 2: Application Layer 9 SMTP: final words SMTP uses persistent connections SMTP requires message (header & body) to be in 7- bit ASCII SMTP uses CRLF.CRLF to determine end of message Comparison with HTTP: HTTP: pull SMTP: push both have ASCII command/response interaction, status codes HTTP: each object encapsulated in its own response msg SMTP: multiple objects sent in multipart msg 2: Application Layer 10

6 Mail message format SMTP: protocol for exchanging e msgs RFC 822: standard for text message format: header lines, e.g., To: From: Subject: different from SMTP commands! body the message, ASCII characters only header body blank line 2: Application Layer 11 Message format: multimedia extensions MIME: multimedia extension, RFC 2045, 2056 additional lines in msg header declare MIME content type MIME version method used to encode data multimedia data type, subtype, parameter declaration encoded data From: To: Subject: Picture of yummy crepe. MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Type: image/jpeg base64 encoded data base64 encoded data 2: Application Layer 12

7 MIME types Content-Type: type/subtype; parameters Text example subtypes: plain, html Video example subtypes: mpeg, quicktime Image example subtypes: jpeg, gif Audio exampe subtypes: basic (8-bit mu-law encoded), 32kadpcm (32 kbps coding) Application other data that must be processed by reader before viewable example subtypes: msword, octet-stream 2: Application Layer 13 Multipart Type From: To: Subject: Picture of yummy crepe. MIME-Version: 1.0 Content-Type: multipart/mixed; boundary=startofnextpart --StartOfNextPart Dear Bob, Please find a picture of a crepe. --StartOfNextPart Content-Transfer-Encoding: base64 Content-Type: image/jpeg base64 encoded data base64 encoded data --StartOfNextPart Do you want the reciple? 2: Application Layer 14

8 Mail access protocols SMTP SMTP access protocol sender s receiver s SMTP: delivery/storage to receiver s Mail access protocol: retrieval from POP: Post Office Protocol [RFC 1939] authorization ( <-->) and download IMAP: Internet Mail Access Protocol [RFC 1730] more features (more complex) manipulation of stored msgs on HTTP: Hot, Yahoo! Mail, etc. 2: Application Layer 15 POP3 protocol authorization phase client commands: : declare name pass: password responses +OK -ERR transaction phase, client: list: list message numbers retr: retrieve message by number dele: delete quit S: +OK POP3 ready C: bob S: +OK C: pass hungry S: +OK successfully logged on C: list S: S: 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 signing off 2: Application Layer 16

9 POP3 (more) and IMAP More about POP3 Previous example uses download and delete mode. Bob cannot re-read e- if he changes client (or location) Download-and-keep : copies of messages on different clients POP3 is stateless across sessions IMAP Keep all messages in one place: the Allows to organize messages in folders IMAP keeps state across sessions: names of folders and mappings between message IDs and folder name 2: Application Layer 17 DNS: Domain Name System People: many identifiers: SSN, name, passport # Internet hosts, routers: IP address (32 bit) - used for addressing datagrams name, e.g., gaia.cs.umass.edu - used by humans Q: map between IP addresses and name? Domain Name System: distributed database implemented in hierarchy of many name s application-layer protocol host, routers, name s to communicate to resolve names (address/name translation) note: core Internet function, implemented as application-layer protocol complexity at network s edge 2: Application Layer 18

10 DNS name s Why not centralize DNS? single point of failure traffic volume distant centralized database maintenance doesn t scale! no has all nameto-ip address mappings local name s: each ISP, company has local (default) name host DNS query first goes to local name authoritative name : for a host: stores that host s IP address, name can perform name/address translation for that host s name 2: Application Layer 19 DNS: Root name s contacted by local name that can not resolve name root name : contacts authoritative name if name mapping not known gets mapping returns mapping to local name a NSI Herndon, VA c PSInet Herndon, VA d U Maryland College Park, MD g DISA Vienna, VA h ARL Aberdeen, MD j NSI (TBD) Herndon, VA k RIPE London i NORDUnet Stockholm m WIDE Tokyo e NASA Mt View, CA f Internet Software C. Palo Alto, CA b USC-ISI Marina del Rey, CA l ICANN Marina del Rey, CA 13 root name s worldwide 2: Application Layer 20

11 Simple DNS example root name host surf.eurecom.fr wants IP address of gaia.cs.umass.edu 1. contacts its local DNS, dns.eurecom.fr 2. dns.eurecom.fr contacts root name, if necessary 3. root name contacts authoritative name, dns.umass.edu, if necessary local name dns.eurecom.fr requesting host surf.eurecom.fr authorititive name dns.umass.edu gaia.cs.umass.edu 2: Application Layer 21 DNS example root name Root name : may not know authoritative name may know intermediate name : who to contact to find authoritative name local name dns.eurecom.fr requesting host surf.eurecom.fr intermediate name dns.umass.edu 4 5 authoritative name dns.cs.umass.edu gaia.cs.umass.edu 2: Application Layer 22

12 DNS: iterated queries root name recursive query: puts burden of name resolution on contacted name heavy load? iterated query: contacted replies with name of to contact I don t know this name, but ask this local name dns.eurecom.fr requesting host surf.eurecom.fr iterated query intermediate name dns.umass.edu 5 6 authoritative name dns.cs.umass.edu gaia.cs.umass.edu 2: Application Layer 23 DNS: caching and updating records once (any) name learns mapping, it caches mapping cache entries timeout (disappear) after some time update/notify mechanisms under design by IETF RFC : Application Layer 24

13 DNS records DNS: distributed db storing resource records (RR) RR format: (name, value, type,ttl) Type=A name is hostname value is IP address Type=NS name is domain (e.g. foo.com) value is IP address of authoritative name for this domain Type=CNAME name is alias name for some cannonical (the real) name is really east.backup2.ibm.com value is cannonical name Type=MX value is name of associated with name 2: Application Layer 25 DNS protocol, messages DNS protocol : query and reply messages, both with same message format msg header identification: 16 bit # for query, reply to query uses same # flags: query or reply recursion desired recursion available reply is authoritative 2: Application Layer 26

14 DNS protocol, messages Name, type fields for a query RRs in reponse to query records for authoritative s additional helpful info that may be used 2: Application Layer 27 Web caches (proxy ) Goal: satisfy client request without involving origin sets browser: Web accesses via cache browser sends all HTTP requests to cache object in cache: cache returns object else cache requests object from origin, then returns object to client client client HTTP request HTTP response HTTP request HTTP response Proxy HTTP request HTTP response origin origin 2: Application Layer 28

15 Why Web Caching? Assume: cache is close to client (e.g., in same network) lower response time: cache closer to client decrease traffic to distant s link out of institutional/local ISP network often bottleneck institutional network public Internet 1.5 Mbps access link 10 Mbps LAN origin s institutional cache 2: Application Layer 29 More about Web caching Cache acts as both client and Cache can do up-to-date check using If-modifiedsince HTTP header Issue: should cache take risk and deliver cached object without checking? Heuristics are used Typically cache is installed by ISP (university, company, residential ISP) Where should caches be placed? institutional network public Internet 1.5 Mbps access link 10 Mbps LAN origin s institutional cache 2: Application Layer 30

Digital Communication in the Modern World Application Layer cont. DNS, SMTP

Digital Communication in the Modern World Application Layer cont. DNS, SMTP Digital Communication in the Modern World Application Layer cont. DNS, http://www.cs.huji.ac.il/~com com@cs.huji.ac.il Some of the slides have been borrowed from: Computer Networking: A Top Down Approach

More information

FTP: the file transfer protocol

FTP: the file transfer protocol File Transfer: FTP FTP: the file transfer protocol at host FTP interface FTP client local file system file transfer FTP remote file system transfer file to/from remote host client/ model client: side that

More information

FTP and email. Computer Networks. FTP: the file transfer protocol

FTP and email. Computer Networks. FTP: the file transfer protocol Computer Networks and email Based on Computer Networking, 4 th Edition by Kurose and Ross : the file transfer protocol transfer file to/from remote host client/ model client: side that initiates transfer

More information

FTP: the file transfer protocol

FTP: the file transfer protocol FTP: the file transfer protocol at host FTP interface FTP client local file system file transfer FTP remote file system transfer file to/from remote host client/ model client: side that initiates transfer

More information

CSCI-1680 SMTP Chen Avin

CSCI-1680 SMTP Chen Avin CSCI-1680 Chen Avin Based on Computer Networking: A Top Down Approach - 6th edition Electronic Three major components: s s simple transfer protocol: User Agent a.k.a. reader composing, editing, reading

More information

DNS: Distributed Name System

DNS: Distributed Name System Distributed Name System Slides adapted from: Computer Networking: A Top Down Approach Featuring the Internet, 2 nd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2002. All material copyright 1996-2002

More information

Chapter 2 Application Layer. Lecture 5 FTP, Mail. Computer Networking: A Top Down Approach

Chapter 2 Application Layer. Lecture 5 FTP, Mail. Computer Networking: A Top Down Approach Chapter 2 Application Layer Lecture 5 FTP, Mail Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March 2012 Application Layer 2-1 Chapter 2: outline 2.1 principles

More information

DATA COMMUNICATOIN NETWORKING

DATA COMMUNICATOIN NETWORKING DATA COMMUNICATOIN NETWORKING Instructor: Ouldooz Baghban Karimi Course Book: Computer Networking, A Top-Down Approach By: Kurose, Ross Introduction Course Overview Basics of Computer Networks Internet

More information

CPSC 360 - Network Programming. Email, FTP, and NAT. http://www.cs.clemson.edu/~mweigle/courses/cpsc360

CPSC 360 - Network Programming. Email, FTP, and NAT. http://www.cs.clemson.edu/~mweigle/courses/cpsc360 CPSC 360 - Network Programming E, FTP, and NAT Michele Weigle Department of Computer Science Clemson University mweigle@cs.clemson.edu April 18, 2005 http://www.cs.clemson.edu/~mweigle/courses/cpsc360

More information

Protocolo FTP. FTP: Active Mode. FTP: Active Mode. FTP: Active Mode. FTP: the file transfer protocol. Separate control, data connections

Protocolo FTP. FTP: Active Mode. FTP: Active Mode. FTP: Active Mode. FTP: the file transfer protocol. Separate control, data connections : the file transfer protocol Protocolo at host interface local file system file transfer remote file system utilizes two ports: - a 'data' port (usually port 20...) - a 'command' port (port 21) SISTEMAS

More information

Cours du 22 novembre

Cours du 22 novembre Cours du 22 novembre Couche application DNS Application Layer 2-2 DNS: domain name system people: many identifiers: SSN, name, passport # Internet hosts, routers: IP address (32 bit) - used for addressing

More information

The Application Layer: DNS

The Application Layer: DNS Recap SMTP and email The Application Layer: DNS Smith College, CSC 9 Sept 9, 0 q SMTP process (with handshaking) and message format q Role of user agent access protocols q Port Numbers (can google this)

More information

internet technologies and standards

internet technologies and standards Institute of Telecommunications Warsaw University of Technology 2015 internet technologies and standards Piotr Gajowniczek Andrzej Bąk Michał Jarociński Internet application layer the email service The

More information

Domain Name System (DNS)

Domain Name System (DNS) Chapter 18 CSC465 Computer Networks Spring 2004 Dr. J. Harrison These slides are based on the text TCP/IP Protocol Suite (2 nd Edition) Domain Name System (DNS) CONTENTS NAME SPACE DOMAIN NAME SPACE DISTRIBUTION

More information

Computer Networks. Instructor: Niklas Carlsson Email: niklas.carlsson@liu.se

Computer Networks. Instructor: Niklas Carlsson Email: niklas.carlsson@liu.se Computer Networks Instructor: Niklas Carlsson Email: niklas.carlsson@liu.se Notes derived from Computer Networking: A Top Down Approach, by Jim Kurose and Keith Ross, Addison-Wesley. The slides are adapted

More information

DNS: Domain Name System

DNS: Domain Name System DNS: Domain Name System People: many identifiers: SSN, name, passport # Internet hosts, routers: IP address (32 bit) - used for addressing datagrams name, e.g., ww.yahoo.com - used by humans Q: map between

More information

1 Introduction: Network Applications

1 Introduction: Network Applications 1 Introduction: Network Applications Some Network Apps E-mail Web Instant messaging Remote login P2P file sharing Multi-user network games Streaming stored video clips Internet telephone Real-time video

More information

CS43: Computer Networks Email. Kevin Webb Swarthmore College September 24, 2015

CS43: Computer Networks Email. Kevin Webb Swarthmore College September 24, 2015 CS43: Computer Networks Email Kevin Webb Swarthmore College September 24, 2015 Three major components: mail (MUA) mail transfer (MTA) simple mail transfer protocol: SMTP User Agent a.k.a. mail reader composing,

More information

Domain Name System (or Service) (DNS) Computer Networks Term B10

Domain Name System (or Service) (DNS) Computer Networks Term B10 Domain Name System (or Service) (DNS) Computer Networks Term B10 DNS Outline DNS Hierarchial Structure Root Name Servers Top-Level Domain Servers Authoritative Name Servers Local Name Server Caching and

More information

Application layer Protocols application transport

Application layer Protocols application transport Application layer Protocols application transport data link physical Network Applications and Application Layer Protocols Network applications: running in end systems (hosts) distributed, communicating

More information

CMPE 80N: Introduction to Networking and the Internet

CMPE 80N: Introduction to Networking and the Internet CMPE 80N: Introduction to Networking and the Internet Katia Obraczka Computer Engineering UCSC Baskin Engineering Lecture 11 CMPE 80N Spring'10 1 Announcements Guest lecture on intellectual property and

More information

Application Layer. Abusayeed Saifullah. CS 5600 Computer Networks. These slides are adapted from Kurose and Ross

Application Layer. Abusayeed Saifullah. CS 5600 Computer Networks. These slides are adapted from Kurose and Ross Application Layer Abusayeed Saifullah CS 5600 Computer Networks These slides are adapted from Kurose and Ross Web caches (proxy server) goal: satisfy client request without involving origin server v user

More information

CMPE 80N: Introduction to Networking and the Internet

CMPE 80N: Introduction to Networking and the Internet CMPE 80N: Introduction to Networking and the Internet Katia Obraczka Computer Engineering UCSC Baskin Engineering Lecture 10 CMPE 80N Fall'10 1 Announcements Forum assignment #2 posted. Due Nov. 5 th.

More information

Domain Name System Richard T. B. Ma

Domain Name System Richard T. B. Ma Domain Name System Richard T. B. Ma School of Computing National University of Singapore CS 3103: Compute Networks and Protocols Names Vs. Addresses Names are easier for human to remember www.comp.nus.edu.sg

More information

Domain Name System (DNS) RFC 1034 RFC 1035 http://www.ietf.org

Domain Name System (DNS) RFC 1034 RFC 1035 http://www.ietf.org Domain Name System (DNS) RFC 1034 RFC 1035 http://www.ietf.org TCP/IP Protocol Suite Application Layer DHCP DNS SNMP HTTP SMTP POP Transport Layer UDP TCP ICMP IGMP Network Layer IP Link Layer ARP ARP

More information

Application-layer protocols

Application-layer protocols Application layer Goals: Conceptual aspects of network application protocols Client server paradigm Service models Learn about protocols by examining popular application-level protocols HTTP DNS Application-layer

More information

Chapter 2 Application Layer

Chapter 2 Application Layer Chapter 2 Application Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations;

More information

Chapter 2: outline. 2.6 P2P applications 2.7 socket programming with UDP and TCP

Chapter 2: outline. 2.6 P2P applications 2.7 socket programming with UDP and TCP Chapter 2: outline 2.1 principles of network applications app architectures app requirements 2.2 Web and HTTP 2.3 FTP 2.4 electronic mail SMTP, POP3, IMAP 2.5 DNS 2.6 P2P applications 2.7 socket programming

More information

Review of Previous Lecture

Review of Previous Lecture Review of Previous Lecture Principles of app layer protocols clients and servers app requirements Web and HTTP FTP Some slides are in courtesy of J. Kurose and K. Ross Announcement All got partners and

More information

CS 355. Computer Networking. Wei Lu, Ph.D., P.Eng.

CS 355. Computer Networking. Wei Lu, Ph.D., P.Eng. CS 355 Computer Networking Wei Lu, Ph.D., P.Eng. Chapter 2: Application Layer Overview: Principles of network applications? Introduction to Wireshark Web and HTTP FTP Electronic Mail: SMTP, POP3, IMAP

More information

Computer Networks: Domain Name Service (DNS)

Computer Networks: Domain Name Service (DNS) Computer Networks: Domain Name Service (DNS) CS 3516 D- term 2013 Instructor: Krishna Venkatasubramanian Quiz 2 DNS: domain name system people: many identifiers: SSN, name, passport # Internet hosts, routers:

More information

DNS and electronic mail. DNS purposes

DNS and electronic mail. DNS purposes DNS and electronic mail Section 9.1.3 in the textbook DNS purposes Originally purpose was to translate hostnames into IP addresses www.csd. is easier to remember than 129.100.23.247 Lets us do load balancing

More information

Internet Technology 2/13/2013

Internet Technology 2/13/2013 Internet Technology 03r. Application layer protocols: email Email: Paul Krzyzanowski Rutgers University Spring 2013 1 2 Simple Mail Transfer Protocol () Defined in RFC 2821 (April 2001) Original definition

More information

DNS: Domain Names. DNS: Domain Name System. DNS: Root name servers. DNS name servers

DNS: Domain Names. DNS: Domain Name System. DNS: Root name servers. DNS name servers DNS: Domain Name System DNS: Domain Names People: many identifiers: SSN, name, Passport # Internet hosts, routers: Always: IP address (32 bit) - used for addressing datagrams Often: name, e.g., nifc14.wsu.edu

More information

DNS and P2P File Sharing

DNS and P2P File Sharing Computer Networks DNS and P2P File Sharing Based on Computer Networking, 4 th Edition by Kurose and Ross DNS: Domain Name System People: many identifiers: SSN, name, passport # Internet hosts, routers:

More information

File Transfer Protocol (FTP)

File Transfer Protocol (FTP) COM 362 Computer Networks I. FTP Lecture Outline Lec 4: Applicatin Layer: FTP, E-Mail and P2P Applications 2. Electronic Mail:, POP3, IMAP 3. P2P Applications Prof. Dr. Halûk Gümüşkaya haluk.gumuskaya@gediz.edu.tr

More information

Applications and Application Level Protocols

Applications and Application Level Protocols ECE453 Introduction to Computer Networks Lecture 16 Application Layer (DNS, E-mail, Web, FTP) Applications and Application Level Protocols application transport network data link physical application transport

More information

Domain Name System (DNS)

Domain Name System (DNS) Domain Name System (DNS) Instructor: Anirban Mahanti Office: ICT 745 Email: mahanti@cpsc.ucalgary.ca Class Location: ICT 121 Lectures: MWF 12:00 12:50 Notes derived from Computer Networking: A Top Down

More information

2- Electronic Mail (SMTP), File Transfer (FTP), & Remote Logging (TELNET)

2- Electronic Mail (SMTP), File Transfer (FTP), & Remote Logging (TELNET) 2- Electronic Mail (SMTP), File Transfer (FTP), & Remote Logging (TELNET) There are three popular applications for exchanging information. Electronic mail exchanges information between people and file

More information

Evolution of the WWW. Communication in the WWW. WWW, HTML, URL and HTTP. HTTP Abstract Message Format. The Client/Server model is used:

Evolution of the WWW. Communication in the WWW. WWW, HTML, URL and HTTP. HTTP Abstract Message Format. The Client/Server model is used: Evolution of the WWW Communication in the WWW World Wide Web (WWW) Access to linked documents, which are distributed over several computers in the History of the WWW Origin 1989 in the nuclear research

More information

Computer Networks 1 (Mạng Máy Tính 1) Lectured by: Dr. Phạm Trần Vũ MEng. Nguyễn CaoĐạt

Computer Networks 1 (Mạng Máy Tính 1) Lectured by: Dr. Phạm Trần Vũ MEng. Nguyễn CaoĐạt Computer Networks 1 (Mạng Máy Tính 1) Lectured by: Dr. Phạm Trần Vũ MEng. Nguyễn CaoĐạt 1 Lecture 10: Application Layer 2 Application Layer Where our applications are running Using services provided by

More information

Names vs. Addresses. Flat vs. Hierarchical Space. Domain Name System (DNS) Computer Networks. Lecture 5: Domain Name System

Names vs. Addresses. Flat vs. Hierarchical Space. Domain Name System (DNS) Computer Networks. Lecture 5: Domain Name System Names vs. Addresses Computer Networks Lecture 5: Domain Name System Names are easier for human to remember www.umich.edu vs. 141.213.4.4 Addresses can be changed without changing names move www.umich.edu

More information

Email Electronic Mail

Email Electronic Mail Email Electronic Mail Electronic mail paradigm Most heavily used application on any network Electronic version of paper-based office memo Quick, low-overhead written communication Dates back to time-sharing

More information

Email. Daniel Zappala. CS 460 Computer Networking Brigham Young University

Email. Daniel Zappala. CS 460 Computer Networking Brigham Young University Email Daniel Zappala CS 460 Computer Networking Brigham Young University How Email Works 3/25 Major Components user agents POP, IMAP, or HTTP to exchange mail mail transfer agents (MTAs) mailbox to hold

More information

Evolution of the WWW. Communication in the WWW. WWW, HTML, URL and HTTP. HTTP - Message Format. The Client/Server model is used:

Evolution of the WWW. Communication in the WWW. WWW, HTML, URL and HTTP. HTTP - Message Format. The Client/Server model is used: Evolution of the WWW Communication in the WWW World Wide Web (WWW) Access to linked documents, which are distributed over several computers in the History of the WWW Origin 1989 in the nuclear research

More information

CS 43: Computer Networks Naming and DNS. Kevin Webb Swarthmore College September 17, 2015

CS 43: Computer Networks Naming and DNS. Kevin Webb Swarthmore College September 17, 2015 CS 43: Computer Networks Naming and DNS Kevin Webb Swarthmore College September 17, 2015 Agenda Identifiers and addressing Domain Name System History Query sequences Record types Load balancing Recall:

More information

CS 348: Computer Networks. - DNS; 22 nd Oct 2012. Instructor: Sridhar Iyer IIT Bombay

CS 348: Computer Networks. - DNS; 22 nd Oct 2012. Instructor: Sridhar Iyer IIT Bombay CS 348: Computer Networks - DNS; 22 nd Oct 2012 Instructor: Sridhar Iyer IIT Bombay Domain Name System Map between host names and IP addresses People: many identifiers: name, Passport #, Internet hosts:

More information

DATA COMMUNICATOIN NETWORKING

DATA COMMUNICATOIN NETWORKING DATA COMMUNICATOIN NETWORKING Instructor: Ouldooz Baghban Karimi Course Book: Computer Networking, A Top-Down Approach By: Kurose, Ross Introduction Course Overview Basics of Computer Networks Internet

More information

Application Example: WWW. Communication in the WWW. WWW, HTML, URL and HTTP. Loading of Web Pages. The Client/Server model is used in the WWW

Application Example: WWW. Communication in the WWW. WWW, HTML, URL and HTTP. Loading of Web Pages. The Client/Server model is used in the WWW Application Example WWW Communication in the WWW In the following application protocol examples for WWW and E-Mail World Wide Web (WWW) Access to linked documents, which are distributed over several computers

More information

Communicating Applications

Communicating Applications Communicating Applications Network Applications The raison d'être of computer networks Innovation happens in the application layer There is always a killer application Remote login -> Email -> Web -> P2P

More information

Domain Name System DNS

Domain Name System DNS CE443 Computer Networks Domain Name System DNS Behnam Momeni Computer Engineering Department Sharif University of Technology Acknowledgments: Lecture slides are from Computer networks course thought by

More information

INF3190 Application Layer DNS, Web, Mail

INF3190 Application Layer DNS, Web, Mail INF3190 Application Layer DNS, Web, Mail Carsten Griwodz Email: griff@ifi.uio.no Application layer Introduction What is it? Internet view everything above the socket interface is application layer function

More information

2- Electronic Mail (SMTP), File Transfer (FTP), & Remote Logging (TELNET)

2- Electronic Mail (SMTP), File Transfer (FTP), & Remote Logging (TELNET) 2- Electronic Mail (SMTP), File Transfer (FTP), & Remote Logging (TELNET) There are three popular applications for exchanging information. Electronic mail exchanges information between people and file

More information

Naming and the DNS. Focus. How do we name hosts etc.? Application Presentation Topics. Session Domain Name System (DNS) Email/URLs

Naming and the DNS. Focus. How do we name hosts etc.? Application Presentation Topics. Session Domain Name System (DNS) Email/URLs Naming and the DNS Focus How do we name hosts etc.? Application Presentation Topics Session Domain Name System (DNS) Email/URLs Transport Network Data Link Physical Ldns.1 Names and Addresses 43 name address

More information

Distributed Systems. Naming

Distributed Systems. Naming Distributed Systems Naming Some slides here are adapted from DNS slide material by Kurose and Ross for their textbook: Computer Networking: A Top Down Approach Featuring the Internet Any problem in computer

More information

CSE 677: Introduction to Computer Networking. Application Layer. Presentation H. Domain Name System DNS

CSE 677: Introduction to Computer Networking. Application Layer. Presentation H. Domain Name System DNS CSE 677: Introduction to Computer Networking Application Layer Presentation H Study: 22.1, 23.1 Kannan Srinivasan 11-01-2012 Domain Name System DNS To identify a remote computer, TCP/IP protocols use the

More information

DNS: Domain Name System

DNS: Domain Name System DNS: Domain Name System CMPSCI 491G: Computer Networking Lab V. Arun Slides adapted from Liebeherr & Zarki, Kurose & Ross, Kermani DNS: domain name system people: many identifiers: SSN, name, passport

More information

Networking Applications

Networking Applications Networking Dr. Ayman A. Abdel-Hamid College of Computing and Information Technology Arab Academy for Science & Technology and Maritime Transport Electronic Mail 1 Outline Introduction SMTP MIME Mail Access

More information

Review of Networking Basics. Yao Wang Polytechnic University, Brooklyn, NY11201 yao@vision.poly.edu

Review of Networking Basics. Yao Wang Polytechnic University, Brooklyn, NY11201 yao@vision.poly.edu Review of Networking Basics Yao Wang Polytechnic University, Brooklyn, NY11201 yao@vision.poly.edu These slides are extracted from the slides made by authors of the book (J. F. Kurose and K. Ross), available

More information

NET0183 Networks and Communications

NET0183 Networks and Communications NET0183 Networks and Communications Lecture 25 DNS Domain Name System 8/25/2009 1 NET0183 Networks and Communications by Dr Andy Brooks DNS is a distributed database implemented in a hierarchy of many

More information

DNS. Spring 2016 CS 438 Staff 1

DNS. Spring 2016 CS 438 Staff 1 DNS Spring 2016 CS 438 Staff 1 Host Names vs. IP addresses Host names Mnemonic name appreciated by humans Variable length, full alphabet of characters Provide little (if any) information about physical

More information

FTP Protocol Secure Shell (SSH) and Secure FTP (SFTP) Components of an Email System Simple Mail Transfer Protocol Mail Access Protocols

FTP Protocol Secure Shell (SSH) and Secure FTP (SFTP) Components of an Email System Simple Mail Transfer Protocol Mail Access Protocols 5. File Transfer and Electronic Mail in the Internet FTP Protocol Secure Shell (SSH) and Secure FTP (SFTP) Components of an Email System Simple Mail Transfer Protocol Mail Access Protocols From Jon Turner

More information

Ch 6: Networking Services: NAT, DHCP, DNS, Multicasting

Ch 6: Networking Services: NAT, DHCP, DNS, Multicasting Ch 6: Networking Services: NAT, DHCP, DNS, Multicasting Magda El Zarki Prof. of CS Univ. of CA, Irvine Email: elzarki@uci.edu http: www.ics.uci.edu/~magda Overivew of NAT NAT: Network Address Translation

More information

Email, SNMP, Securing the Web: SSL

Email, SNMP, Securing the Web: SSL Email, SNMP, Securing the Web: SSL 4 January 2015 Lecture 12 4 Jan 2015 SE 428: Advanced Computer Networks 1 Topics for Today Email (SMTP, POP) Network Management (SNMP) ASN.1 Secure Sockets Layer 4 Jan

More information

Overview of Computer Networks

Overview of Computer Networks Overview of Computer Networks Client-Server Transaction Client process 4. Client processes response 1. Client sends request 3. Server sends response Server process 2. Server processes request Resource

More information

Application Layer, Client/Server Computing and Socket Programming (II)

Application Layer, Client/Server Computing and Socket Programming (II) CS 455/555 / Spring 2014 Intro to Networks and Communications Application Layer, Client/Server Computing and Socket Programming (II) Dr. Tamer Nadeem http://www.cs.odu.edu/~nadeem/classes/cs455-s14/ The

More information

Domain Name System (DNS) Reading: Section in Chapter 9

Domain Name System (DNS) Reading: Section in Chapter 9 Domain Name System (DNS) Reading: Section in Chapter 9 RFC 1034, STD 13 Name Syntax and rules for delegating authority over names Specify implementation of a distributed system that maps names to addresses

More information

Security Analysis of DNS & Applications/Email

Security Analysis of DNS & Applications/Email Security Analysis of DNS & Applications/Email EE 122: Intro to Communication Networks Fall 2007 (WF 4-5:30 in Cory 277) Vern Paxson TAs: Lisa Fowler, Daniel Killebrew & Jorge Ortiz http://inst.eecs.berkeley.edu/~ee122/

More information

Applications and Services. DNS (Domain Name System)

Applications and Services. DNS (Domain Name System) Applications and Services DNS (Domain Name Service) File Transfer Protocol (FTP) Simple Mail Transfer Protocol (SMTP) Malathi Veeraraghavan Distributed database used to: DNS (Domain Name System) map between

More information

Introduction to Computer Networks

Introduction to Computer Networks Introduction to Computer Networks Chen Yu Indiana University Basic Building Blocks for Computer Networks Nodes PC, server, special-purpose hardware, sensors Switches Links: Twisted pair, coaxial cable,

More information

Ch 6: Networking Services: NAT, DHCP, DNS, Multicasting, NTP

Ch 6: Networking Services: NAT, DHCP, DNS, Multicasting, NTP Ch 6: Networking Services: NAT, DHCP, DNS, Multicasting, NTP Magda El Zarki Prof. of CS Univ. of CA, Irvine Email: elzarki@uci.edu http: www.ics.uci.edu/~magda Network Address Translation - NAT Private

More information

The Application Layer. CS158a Chris Pollett May 9, 2007.

The Application Layer. CS158a Chris Pollett May 9, 2007. The Application Layer CS158a Chris Pollett May 9, 2007. Outline DNS E-mail More on HTTP The Domain Name System (DNS) To refer to a process on the internet we need to give an IP address and a port. These

More information

The Web: some jargon. User agent for Web is called a browser: Web page: Most Web pages consist of: Server for Web is called Web server:

The Web: some jargon. User agent for Web is called a browser: Web page: Most Web pages consist of: Server for Web is called Web server: The Web: some jargon Web page: consists of objects addressed by a URL Most Web pages consist of: base HTML page, and several referenced objects. URL has two components: host name and path name: User agent

More information

CSE 461 Naming and DNS. David Wetherall

CSE 461 Naming and DNS. David Wetherall CSE 461 Naming and DNS David Wetherall djw@cs.washington.edu Naming and DNS Focus: How do we resolve names to addresses Names and addresses Application DNS as a system design Transport Network Link Physical

More information

Computer Networks & Security 2014/2015

Computer Networks & Security 2014/2015 Computer Networks & Security 2014/2015 IP Protocol Stack & Application Layer (02a) Security and Embedded Networked Systems time Protocols A human analogy All Internet communication is governed by protocols!

More information

2.5 DNS The Internet s Directory Service

2.5 DNS The Internet s Directory Service 130 CHAPTER 2 APPLICATION LAYER e-mail is also provided by Google, Yahoo!, as well as just about every major university and corporation. With this service, the user agent is an ordinary Web browser, and

More information

Network Technologies

Network Technologies Network Technologies Glenn Strong Department of Computer Science School of Computer Science and Statistics Trinity College, Dublin January 28, 2014 What Happens When Browser Contacts Server I Top view:

More information

Network Services. Email SMTP, Internet Message Format. Johann Oberleitner SS 2006

Network Services. Email SMTP, Internet Message Format. Johann Oberleitner SS 2006 Network Services Email SMTP, Internet Message Format Johann Oberleitner SS 2006 Agenda Email SMTP Internet Message Format Email Protocols SMTP Send emails POP3/IMAPv4 Read Emails Administrate mailboxes

More information

Introduction to LAN/WAN. Application Layer (Part II)

Introduction to LAN/WAN. Application Layer (Part II) Introduction to LAN/WAN Application Layer (Part II) Application Layer Topics Domain Name System (DNS) (7.1) Electronic Mail (Email) (7.2) World Wide Web (WWW) (7.3) Electronic Mail (Email) Mostly used

More information

Electronic Mail: SMTP

Electronic Mail: SMTP 1 Electronic Mail: SMTP Electronic mail Asynchronous exchange of data sender does not know when (if) data reaches receiver mail user agent (MUA) outgoing mail queue client message transfer agent (MTA)

More information

Solutions to the Sample Questions on Application Layer

Solutions to the Sample Questions on Application Layer Solutions to the Sample Questions on Application Layer 1) Why is SMTP not used for transferring e-mail messages from the recipient s mail server to the recipient s personal computer? Answer: Whereas SMTP

More information

Applications & Application-Layer Protocols: The Domain Name System and Peerto-Peer

Applications & Application-Layer Protocols: The Domain Name System and Peerto-Peer CPSC 360 Network Programming Applications & Application-Layer Protocols: The Domain Name System and Peerto-Peer Systems Michele Weigle Department of Computer Science Clemson University mweigle@cs.clemson.edu

More information

Configuring your email client to connect to your Exchange mailbox

Configuring your email client to connect to your Exchange mailbox Configuring your email client to connect to your Exchange mailbox Contents Use Outlook Web Access (OWA) to access your Exchange mailbox... 2 Use Outlook 2003 to connect to your Exchange mailbox... 3 Add

More information

MIME and Transfer Encoding

MIME and Transfer Encoding E-Mail Message Format MIME and Transfer Encoding MIME 1 Message Format: Multimedia Extensions MIME: Multimedia Internet Mail Extension, RFC 2045-49, 2056 ~ an extension of RFC 822 for resolving prob. in

More information

Application Layer Protocols

Application Layer Protocols Application Layer Protocols Network Applications Requirements Application Layer Protocol Functions. Sample Internet Applications & Protocols: File Transfer Protocol (FTP). Sending E-Mail: SMTP. HyperText

More information

Chapter 2 Application Layer

Chapter 2 Application Layer Chapter 2 Application Layer All material copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Addison-Wesley March

More information

Chapter 26 Remote Logging, Electronic Mail, 26.1 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Chapter 26 Remote Logging, Electronic Mail, 26.1 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 26 Remote Logging, Electronic Mail, and File Transfer 26.1 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 26-1 REMOTE LOGGING It would be impossible

More information

Application-layer Protocols and Internet Services

Application-layer Protocols and Internet Services Application-layer Protocols and Internet Services Computer Networks Lecture 8 http://goo.gl/pze5o8 Terminal Emulation 2 Purpose of Telnet Service Supports remote terminal connected via network connection

More information

loss-tolerant and time sensitive loss-intolerant and time sensitive loss-intolerant and time insensitive

loss-tolerant and time sensitive loss-intolerant and time sensitive loss-intolerant and time insensitive CS326e Quiz 5 The first correct 10 answers will be worth 1 point each. Each subsequent correct answer will be worth 0.2 points. Circle the correct answer. UTEID The transfer of an html file from one host

More information

Domain Name System (DNS)

Domain Name System (DNS) Application Layer Domain Name System Domain Name System (DNS) Problem Want to go to www.google.com, but don t know the IP address Solution DNS queries Name Servers to get correct IP address Essentially

More information

File Transfer Protocol (FTP) & SSH

File Transfer Protocol (FTP) & SSH http://xkcd.com/949/ File Transfer Protocol (FTP) & SSH Computer Networking: A Top Down Approach 6 th edition Jim Kurose, Keith Ross Some materials copyright 1996-2012 Addison-Wesley J.F Kurose and K.W.

More information

Electronic Mail. 4: Application Protocols: SMTP and others. SMTP History. Electronic Mail: mail servers. Electronic Mail

Electronic Mail. 4: Application Protocols: SMTP and others. SMTP History. Electronic Mail: mail servers. Electronic Mail Electronic Mail 4: Application Protocols: SMTP and others Last Modified: 2/3/2003 8:07:08 PM 2: Application Layer 1 2: Application Layer 2 Electronic Mail Three major components: s s simple transfer protocol:

More information

Lecture 2 CS 3311. An example of a middleware service: DNS Domain Name System

Lecture 2 CS 3311. An example of a middleware service: DNS Domain Name System Lecture 2 CS 3311 An example of a middleware service: DNS Domain Name System The problem Networked computers have names and IP addresses. Applications use names; IP uses for routing purposes IP addresses.

More information

Application Level Protocols

Application Level Protocols Application Level Protocols Nixu Oy PL 21 (Mäkelänkatu 91) 00601 Helsinki, Finland tel. +358 9 478 1011 fax. +358 9 478 1030 info@nixu.fi http://www.nixu.fi Contents Client-Server Store and Forward Push

More information

Thomas G. Broxholm. Setting Up Outlook Mail Accounts

Thomas G. Broxholm. Setting Up Outlook Mail Accounts Thomas G. Broxholm Setting Up Outlook Mail Accounts Outlook Open the Windows Control Panel and double click on the Mail icon. Note! For 64 bit Windows users. The mail icon could be found inside a folder

More information

Midterm Exam CMPSCI 453: Computer Networks Fall 2011 Prof. Jim Kurose

Midterm Exam CMPSCI 453: Computer Networks Fall 2011 Prof. Jim Kurose Midterm Exam CMPSCI 453: Computer Networks Fall 2011 Prof. Jim Kurose Instructions: There are 4 questions on this exam. Please use two exam blue books answer questions 1, 2 in one book, and the remaining

More information

Domain Name System E-mail WWW. Application Layer. Mahalingam Ramkumar Mississippi State University, MS. September 15, 2014.

Domain Name System E-mail WWW. Application Layer. Mahalingam Ramkumar Mississippi State University, MS. September 15, 2014. Application Layer Mahalingam Mississippi State University, MS September 15, 2014 Outline 1 DNS Records DNS Components 2 Message Transfer Fetching Emails 3 Applications We will focus on 3 applications DNS

More information

Electronic mail security. MHS (Message Handling System)

Electronic mail security. MHS (Message Handling System) Electronic mail security Diana Berbecaru < diana.berbecaru @ polito.it> Politecnico di Torino Dip. Automatica e Informatica MHS (Message Handling System) MS MS MUA MUA (Message Transfer ) MS (Message Store)

More information

Owner of the content within this article is Written by Marc Grote

Owner of the content within this article is  Written by Marc Grote Owner of the content within this article is www.msexchange.org Written by Marc Grote www.it-training-grote.de Microsoft Exchange 2003 Using Telnet to connect to Exchange 2003 POP3 mailboxes and using SMTP

More information

Understanding the Outlook Configurations

Understanding the Outlook  Configurations LESSON 3 Understanding the Outlook E-mail Configurations In this lesson, you learn how to set up Outlook for different types of electronic mail. TYPES OF OUTLOOK E-MAIL CONFIGURATIONS The type or flavor

More information