Internet Applications Lynn Bashaw Manager, Network Engineering.

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1 Internet Applications Lynn Bashaw Manager, Network Engineering

2 Applications DNS Telnet FTP WWW Email News

3 Internet Architecture

4 Private Peering Public Peering

5 Internet Architecture

6

7 Domain Name Service Machines talk in numbers; 192.54.81.2 01111011001100010101000100100101 Humans can’t remember numbers Map names to numbers –www.microsoft.com = 193.204.22.10

8 Domain Name Service Enter destination in browser www.microsoft.com

9 Domain Name Service DNS Resolver DNS Server

10 Domain Name Service DNS Resolver DNS Server Root Name Server

11 Domain Name Service DNS Server Root Name Server DNS Server

12 Domain Name Service DNS Resolver DNS Server

13 Domain Name Service DNS Resolver DNS Server

14 Domain Name Service

15 Telnet

16 Telnet Client Telnet Server Initially Support NVT NVT - Network Virtual Terminal

17 Telnet Telnet Client Telnet Server Negotiate Terminal Options

18 File Transfer Protocol Provides a service for applications that want to move files between networked computers It does NOT define the user interface What you know as FTP is really an application designed to provide a friendly interface to the FTP application. Primary function of FTP is to reduce or remove incompatabilities between the handling of files on different operating systems Uses a set of defined network standard commands

19 File Transfer Protocol FTP Client FTP Application FTP Server IP Network User “double clicks” on a folder on “Formus” List MAC OS ls SunOS Formus

20 File Transfer Protocol FTP Client FTP Application FTP Server MAC OS SunOS Control Data Port 21 Port 20

21 World Wide Web Originated at European Particle Physics Laboratory (CERN) Hypertext system modified for use on the Internet Hypertext is a another method of organization unlike a traditional hierarchial tree Three key specifications of a WWW implementation are; –URL (Universal Resource Locator) –HTTP (HyperText Transfer Protocol) –HTML (HyperText Mark-up Language)

22 Universal Resource Locator Intended to be a method of identifying a specific resource on a specific host protocol://server/directory/filname http: ftp: telnet: Host Indicator carl.org www.carl.org /pub/carlweb/pa ges index.html jobs.html

23 HyperText Transfer Protocol Client Server TCP 803089

24 HyperText Transfer Protocol Client Server Request Chain

25 HyperText Transfer Protocol Client Server Response Chain

26 WWW Browser WWW Browser WWW Server WWW Server User requests a resource

27 WWW Browser WWW Browser WWW Server WWW Server Browser (Client) requests resource from server

28 WWW Browser WWW Browser WWW Server WWW Server Server provides the resource

29 WWW Browser WWW Browser WWW Server WWW Server 1. Browser decodes document to present final document to user 2. Browser determines it needs additional resources to complete the document

30 WWW Browser WWW Browser WWW Server WWW Server Browser (Client) requests resources from server

31 WWW Browser WWW Browser WWW Server WWW Server Server provides the resources

32 WWW Browser WWW Browser WWW Server WWW Server Browser finishes decoding the document and presents to the user

33 Electronic Mail Most popular form of traffic on the Internet Two protocols of interest –Simple Mail Transfer Protocol –Post Office Protocol Originator does not discard mail until target acknowledges receipt

34 Electronic Mail System User Interface User Interface Outgoing Mail Spool Area Outgoing Mail Spool Area Mailboxes for Incoming Mail Mailboxes for Incoming Mail SMTP Client SMTP Client SMTP Server SMTP Server User Reads Mail User Sends Mail TCP Connection

35 Electronic Mail System User Interface User Interface Outgoing Mail Spool Area Outgoing Mail Spool Area Mailboxes for Incoming Mail Mailboxes for Incoming Mail SMTP Client SMTP Client SMTP Server SMTP Server User Reads Mail User Sends Mail TCP Connection Alias Expansion & Fowarding Alias Expansion & Fowarding Alias Database

36 Electronic Mail System Outgoing Mail Spool Area Outgoing Mail Spool Area Mailboxes for Incoming Mail Mailboxes for Incoming Mail SMTP Client SMTP Client SMTP Server SMTP Server TCP Connection Alias Expansion & Fowarding Alias Expansion & Fowarding Alias Database POP Server POP Server Outgoing Mail Spool Area Outgoing Mail Spool Area Mailboxes for Incoming Mail Mailboxes for Incoming Mail POP Client POP Client Alias Expansion & Fowarding Alias Expansion & Fowarding Alias Database Email Mgmt & Editing Application TCP Connection SMTP Client SMTP Client SMTP Relay SMTP Relay

37 Email Addressing lbashaw@formus.pl account host

38 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw

39 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw Composes email message from president@whitehouse.gov to lbashaw@carl.org

40 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw Completed email message is sent to spooler on PC spool

41 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw At predefined interval SMTP client logs on to SMTP Host and following successful login establishes a TCP session with mail server spool

42 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw SMTP client transfers all waiting mail in mail spool to mail server spool

43 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashawspool Mail from bigguy.whitehouse.gov is processed and sent to mail spool to await pick-up

44 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashawspool SMTP client checks spool and notes message from president@whitehouse.gov to lbashaw@carl.org

45 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashawspool SMTP client requests IP address of carl.org from DNS resolver

46 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashawspool DNS resolver requests IP address of carl.org from domain name server

47 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashawspool Domain Name Server determines that IP address of carl.org is 192.54.81.3

48 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashawspool SMTP client establishes a TCP session to 192.54.81.3 port 25 (SMTP Server)

49 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashawspool SMTP client transfers message from whitehouse.gov to SMTP Server on denver.carl.org

50 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashawspool SMTP server acknowledges receipt of message to SMTP client on whitehouse.gov

51 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw SMTP server puts message from president in mailbox for account lbashaw SMTP client discards message and tears down TCP connection

52 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw POP client in lynn.carl.org logs on to denver.carl.org and upon successful login establishes a TCP session with the POP server on denver.carl.org SMTP client discards message and tears down TCP connection

53 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw POP client uses POP to download all mail messages from mailbox for account lbashaw on denver.carl.org to mailbox on lynn.carl.org. Upon successful receipt POP client acknowledges receipt and POP server deletes messages from mailbox on denver.carl.org SMTP client discards message and tears down TCP connection

54 Email Example Internet denver.carl.org lynn.carl.org whitehouse.gov bigguy.whitehouse.gov lbashaw I read my email message from the President SMTP client discards message and tears down TCP connection

55 List Server Outgoing Mail Spool Area Outgoing Mail Spool Area Mailboxes for Incoming Mail Mailboxes for Incoming Mail SMTP Client SMTP Client SMTP Server SMTP Server TCP Connection Alias Expansion & Fowarding Alias Expansion & Fowarding Alias Database Administration Program Administration Program Relay Program Relay Program

56 List Server Outgoing Mail Spool Area Outgoing Mail Spool Area Mailboxes for Incoming Mail Mailboxes for Incoming Mail SMTP Client SMTP Client SMTP Server SMTP Server TCP Connection Alias Expansion & Fowarding Alias Expansion & Fowarding Alias Database Administration Program Administration Program Relay Program Relay Program Digest Program Digest Program

57 Usenet News Usenet News is a distributed computer conferencing system Conferences in Usenet News are called newsgroups, and messages are called articles Each server can download as much as it wants of what is available on any of the adjacent servers "Pouring water" principle of Usenet News distribution

58 Usenet News

59

60 References Internet RFC/STD/FYI/BCP Archives –http://www.faqs.org/rfcs/ –Repository of Internet Specifications STD 13 - Domain Name System STD 8 - TELNET Protocol Specification STD 9 - File Transfer Protocol (FTP)

61 References RFC 2068 - Hypertext Transfer Protocol -- HTTP/1.1 STD 10 - Simple Mail Transfer Protocol STD 53 - Post Office Protocol - Ver. 3 RFC 977 - Network News Transfer Protocol

62 References FYI 4 - FYI on Questions and Answers Answers to Commonly asked "New Internet User" Questions FYI 7 - FYI on Questions and Answers Answers to Commonly asked "Experienced Internet User" Questions FYI 34 - Users' Security Handbook