1. Institute for Visualization and Perception Research 1 © Copyright 1998 Haim Levkowitz Introduction to the Internet Internet service concepts... Introduction to information services Finger-, Inetd-, and Telnet-based services FTP WAIS Gopher World-Wide Web Email services Security Future topics and research opportunities

2. Institute for Visualization and Perception Research 2 © Copyright 1998 Haim Levkowitz Internet service concepts … What is the Internet?... Internet services structure... TCP/IP... Info-clients info-servers comm.

3. Institute for Visualization and Perception Research 3 © Copyright 1998 Haim Levkowitz What is the Internet? … Federation of computer networks... Three roles... What does it mean to be on the Internet?... What is on the Internet?...

4. Institute for Visualization and Perception Research 4 © Copyright 1998 Haim Levkowitz Federation of computer networks... Speak same protocols Computer network protocols TCP/IP Connected with high-speed telephone circuits

5. Institute for Visualization and Perception Research 5 © Copyright 1998 Haim Levkowitz Three roles... Information providers Users (customers) Connection providers

6. Institute for Visualization and Perception Research 6 © Copyright 1998 Haim Levkowitz What does it mean to be on the Internet?... “Really” on the Internet On-demand; no Internet protocols Hybrid

7. Institute for Visualization and Perception Research 7 © Copyright 1998 Haim Levkowitz Full-time IP connection... IP protocol

8. Institute for Visualization and Perception Research 8 © Copyright 1998 Haim Levkowitz Dial-up access terminal emulation

9. Institute for Visualization and Perception Research 9 © Copyright 1998 Haim Levkowitz Hybrid... SLIP: Serial Line Internet Protocol PPP: Point-to-Point Protocol ISDN: Integrated Services Digital Network... Running Internet protocols over dial- up...

10. Institute for Visualization and Perception Research 10 © Copyright 1998 Haim Levkowitz ISDN: Integrated Services Digital Network... Voice, data, both On-demand, full-time Speed comparable to leased-line connection

11. Institute for Visualization and Perception Research 11 © Copyright 1998 Haim Levkowitz Running Internet protocols over dial-up... Dial-up hybrid

12. Institute for Visualization and Perception Research 12 © Copyright 1998 Haim Levkowitz What is on the Internet?... Computers: all kinds People: large number, variety Places

13. Institute for Visualization and Perception Research 13 © Copyright 1998 Haim Levkowitz Internet services structure … Client/server architecture... Information service client/server... Any computer can be a service provider Compare: commercial networks...

14. Institute for Visualization and Perception Research 14 © Copyright 1998 Haim Levkowitz Client/server architecture... Client: interact with user Server: perform tasks as directed by user Same/different computers

15. Institute for Visualization and Perception Research 15 © Copyright 1998 Haim Levkowitz Information service client/server … Client... Server...

16. Institute for Visualization and Perception Research 16 © Copyright 1998 Haim Levkowitz Client... Accept queries/other input from users Send queries/data to server Manage display of results

17. Institute for Visualization and Perception Research 17 © Copyright 1998 Haim Levkowitz Server... Receive queries/other data from clients Process Send results/status

18. Institute for Visualization and Perception Research 18 © Copyright 1998 Haim Levkowitz Compare: commercial networks... E.g., CompuServe All services from computers run by network No information by users (except e- mail)

19. Institute for Visualization and Perception Research 19 © Copyright 1998 Haim Levkowitz TCP/IP... Packets: data; acknowledge data received Layered protocols... inetd superserver... Stand-alone servers... Naming...

20. Institute for Visualization and Perception Research 20 © Copyright 1998 Haim Levkowitz Layered protocols … IP... TCP (connectio n-oriented)... UDP (connectio nless)...

21. Institute for Visualization and Perception Research 21 © Copyright 1998 Haim Levkowitz IP... Internet Protocol IP packet Addresses: 32-bit numbers... No guaranteed delivery No guaranteed serialization

22. Institute for Visualization and Perception Research 22 © Copyright 1998 Haim Levkowitz Addresses: 32-bit numbers... 0 to ~4.3 billion Dotted-octet notation... Net, subnet hierarchy

23. Institute for Visualization and Perception Research 23 © Copyright 1998 Haim Levkowitz Dotted-octet notation... 4 sets of 8 bits Convert to decimal Concatenate, separated by dots

24. Institute for Visualization and Perception Research 24 © Copyright 1998 Haim Levkowitz TCP (connection-oriented)... Transmission Control Protocol Two services IP doesn't Guaranteed delivery Serialization of data How?... ==> Mimic stream over dedicated line Also, port numbers...

25. Institute for Visualization and Perception Research 25 © Copyright 1998 Haim Levkowitz How?... Sequence numbers for IP packets Check arriving packets for completeness, order Get missing packets resent

26. Institute for Visualization and Perception Research 26 © Copyright 1998 Haim Levkowitz Also, port numbers... Layer below IP address (computer) Identify services within computer 16-bit “Well known,” e.g.,...

27. Institute for Visualization and Perception Research 27 © Copyright 1998 Haim Levkowitz “Well known,” e.g.,... 25: Simple Mail Transfer Protocol (SMTP) mailer 23: Telnet “Privileged” ports (UNIX) Numbers < 1024 Only root can start Security Prevent “listening”

28. Institute for Visualization and Perception Research 28 © Copyright 1998 Haim Levkowitz UDP (connectionless)... User Datagram Protocol Two additional features to IP Port #s (16-bit, not same as TCP) Checksumming (optional) Detect modifications Avoid TCP for 1-packet q's / responses

29. Institute for Visualization and Perception Research 29 © Copyright 1998 Haim Levkowitz inetd superserver... Many servers, idle periods ==> waste inetd: Internet Superserver Listen to ports Start requested server Server talks directly to client inetd.conf...

30. Institute for Visualization and Perception Research 30 © Copyright 1998 Haim Levkowitz inetd.conf... Determine servers at start-up E.g.,:...

31. Institute for Visualization and Perception Research 31 © Copyright 1998 Haim Levkowitz E.g.,...

32. Institute for Visualization and Perception Research 32 © Copyright 1998 Haim Levkowitz To find... % grep telnet /etc/services telnet 23/tcp Connection request ==> transaction in syslog

33. Institute for Visualization and Perception Research 33 © Copyright 1998 Haim Levkowitz Stand-alone servers... inetd restarts servers whenever needed Auto handle of config change Inefficient for busy service Takes time for inetd to start server ==> Run server stand-alone

34. Institute for Visualization and Perception Research 34 © Copyright 1998 Haim Levkowitz Daemon... Listen to assigned port Spawn copy of self to handle ea. request + Fast – Crash unnoticed; explicit reread of config files when changed

35. Institute for Visualization and Perception Research 35 © Copyright 1998 Haim Levkowitz Naming... Domain names... Aliases...

36. Institute for Visualization and Perception Research 36 © Copyright 1998 Haim Levkowitz Domain names... cs.uml.edu (from specific to general).edu,.com,.gov,.org,.mil 2-letter country codes (ISO 3166) Servers: Domain Name Server (DNS) Clients: resolvers Send queries to DNS for IP addr. name

37. Institute for Visualization and Perception Research 37 © Copyright 1998 Haim Levkowitz Aliases... Pointers to other domain names Easier to remember E.g., ftp.uml.edu, www.cs.uml.edu

38. Institute for Visualization and Perception Research 38 © Copyright 1998 Haim Levkowitz Info-clients info-servers comm. Gopher... Web... FTP...

39. Institute for Visualization and Perception Research 39 © Copyright 1998 Haim Levkowitz Gopher... User request resource on Gopher server Client query... Gopher server response... Client stores file TCP connection torn down TCP up and down for each request

40. Institute for Visualization and Perception Research 40 © Copyright 1998 Haim Levkowitz Client query... Accept input & translate into query Send query to Gopher server Look in /etc/services to find port number gopher 70/tcp Query --> TCP packet(s) --> server (port 70)

41. Institute for Visualization and Perception Research 41 © Copyright 1998 Haim Levkowitz Gopher server response... Listen on port 70 / inetd listen inetd check destination /etc/services to find port number Map to service name Gopher Start server, gopherd Gopher interpret query Open, read file, send to client

42. Institute for Visualization and Perception Research 42 © Copyright 1998 Haim Levkowitz Web... Similar to Gopher Ea. doc. new TCP connection Ea. inline graphics ==> separate TCP connection With approp. server where graphics is

43. Institute for Visualization and Perception Research 43 © Copyright 1998 Haim Levkowitz FTP... Different from Gopher, Web 2 connections server client Control: up through time user logged in Data: up when needed

44. Institute for Visualization and Perception Research 44 © Copyright 1998 Haim Levkowitz Introduction to information services Overview of Internet information services... What to do with Internet Services, e.g.,... System and network requirements... Human requirements...

45. Institute for Visualization and Perception Research 45 © Copyright 1998 Haim Levkowitz Overview of Internet information services … Mail-based... FTP: file transfer protocol... Telnet & finger... Gopher... WAIS: Wide Area Information Servers... WWW: The World-Wide Web...

46. Institute for Visualization and Perception Research 46 © Copyright 1998 Haim Levkowitz Mail-based... Reach largest population Get quickest response Grab attention Compare: Gopher, WWW User has to check Two types...

47. Institute for Visualization and Perception Research 47 © Copyright 1998 Haim Levkowitz Two types … Mailing lists... Archive servers...

48. Institute for Visualization and Perception Research 48 © Copyright 1998 Haim Levkowitz Mailing lists... List of e-mail addresses Reach all with one address E-mail list server programs Majordomo Listserv listproc, e.g.,...

49. Institute for Visualization and Perception Research 49 © Copyright 1998 Haim Levkowitz listproc, e.g.,... To: listproc@online.ora.com -------- subscribe ora-news John Q. User of Some Organization

50. Institute for Visualization and Perception Research 50 © Copyright 1998 Haim Levkowitz Archive servers... Send out files by e-mail Response to users' e-mail requests Also on-the-fly First index, then file name Archive: encodes, splits to pieces, sends User: reassembles, decodes ftpmail: xfer files from other hosts & deliver by e-mail

51. Institute for Visualization and Perception Research 51 © Copyright 1998 Haim Levkowitz FTP: file transfer protocol... Restricted login Limited set of commands (all) Limited set of files Anonymous...

52. Institute for Visualization and Perception Research 52 © Copyright 1998 Haim Levkowitz Anonymous... Public access User: anonymous Password: user's e-mail address (convention) Supports almost all platforms, all file formats Can define privileged access, limit # of users – Slow to browse, no file description Read README while logged in: get README -

53. Institute for Visualization and Perception Research 53 © Copyright 1998 Haim Levkowitz Telnet & finger... On most OSs Fairly primitive Telnet: login over net E.g., DUATS: weather briefing for pilots duats.gtefsd.com (student), duat.gtefsd.com Finger: info on users of remote system Also other short info, e.g., stock quotes, weather report

54. Institute for Visualization and Perception Research 54 © Copyright 1998 Haim Levkowitz Gopher... Text-labeled menus Can be cascaded Advantages... Limitations...

55. Institute for Visualization and Perception Research 55 © Copyright 1998 Haim Levkowitz Advantages... Easy navigation Simple, powerful, easy to administer Organize directory where server runs Subdirectories become menu items Files in directories become available Text oriented ==> good for slow links, dial-ups

56. Institute for Visualization and Perception Research 56 © Copyright 1998 Haim Levkowitz Limitations... Text only display Can xfer binary Display with other software Link only from menu Compare WWW: from within document Links to FTP, WAIS, Telnet But not same variety as WWW

57. Institute for Visualization and Perception Research 57 © Copyright 1998 Haim Levkowitz WAIS: Wide Area Information Servers... Search data... Minimal support for browsing Gopher, WWW assume user knows where to look WAIS doesn't ==> Good complement to WWW, Gopher Requires graphical browser, IP connectivity...

58. Institute for Visualization and Perception Research 58 © Copyright 1998 Haim Levkowitz Search data... Start at Directory of Servers Index of all servers... Real search in most approp. servers Search documents for keywords Similar (but not sufficient) documents: add entire document to keyword list Relevance feedback: match & similar documents

59. Institute for Visualization and Perception Research 59 © Copyright 1998 Haim Levkowitz Index of all servers... Indexing beforehand ==> quick search Support many data types ASCII, LaTeX, PostScript, GIF, TIFF, mail digests, NetNews archives Easy to add data types

60. Institute for Visualization and Perception Research 60 © Copyright 1998 Haim Levkowitz Requires graphical browser, IP connectivity... Text-based, pretty difficult Most WAIS clients provide viewers for basic formats Allow specify external programs to process & present more types Works best with formats w / lots of words Big database indexes ==> need lots of disk space

61. Institute for Visualization and Perception Research 61 © Copyright 1998 Haim Levkowitz WWW: The World-Wide Web... Most powerful, many features of its own Integrates most other info services ==> Simple to use & understand Web browser: GUI-based access to FTP, WAIS, Gopher, etc. Format: HyperText Markup Language (HTML)... Protocol: HyperText Transfer Protocol (HTTP)...

62. Institute for Visualization and Perception Research 62 © Copyright 1998 Haim Levkowitz Format: HyperText Markup Language (HTML)... Commands to format document, specify hyperlinks Browser formats, marks hyperlinks Follow links, format according to type Fire off other programs (e.g., xv to view images) Must have IP connectivity

63. Institute for Visualization and Perception Research 63 © Copyright 1998 Haim Levkowitz Protocol: HyperText Transfer Protocol (HTTP)... http:// / ftp://, gopher:// Local: file://

64. Institute for Visualization and Perception Research 64 © Copyright 1998 Haim Levkowitz What to do with Internet Services, e.g.,... Internal... External... Commercial transactions; charging money...

65. Institute for Visualization and Perception Research 65 © Copyright 1998 Haim Levkowitz Internal... Corporate info Forms, logos, style sheets Timecards Home-grown software archives Employee directory Workgroup mailing lists “Intranet”

66. Institute for Visualization and Perception Research 66 © Copyright 1998 Haim Levkowitz External... Electronic magazine / newsletter Manual pages (e.g., BSDI) Product, support, price info Press releases Software product distribution Bug reports Contributed public domain software archives

67. Institute for Visualization and Perception Research 67 © Copyright 1998 Haim Levkowitz Commercial transactions; charging money... Billing Authentication and secure transactions Unauthorized “sharing” “Eavesdropping” Free to use but not to resell Future versions at a price

68. Institute for Visualization and Perception Research 68 © Copyright 1998 Haim Levkowitz System and network requirements... Network connection type... Network load... Computational load... Disk space...

69. Institute for Visualization and Perception Research 69 © Copyright 1998 Haim Levkowitz Network connection type... Full-time IP connection Limited Gopher, Telnet, Finger, WAIS Minimum 28.8 Kbaud PPP connection Standard modem, phone line Most services Minimum 56 Kbaud Serious service ISDN or T1

70. Institute for Visualization and Perception Research 70 © Copyright 1998 Haim Levkowitz Network load... Queries (usually small)... Responses (bulk of traffic)...

71. Institute for Visualization and Perception Research 71 © Copyright 1998 Haim Levkowitz Queries (usually small)... Mailing lists: short modification messages Mail archive: request index / file FTP: download short; upload can be long Gopher: short menu item / document name WAIS: long if doc’s added for relevance feedback, but use IDs WWW: short strings identifying doc’s

72. Institute for Visualization and Perception Research 72 © Copyright 1998 Haim Levkowitz Responses (bulk of traffic)... Estimate size of avg. reply Size of files; likelihood of retrieval If know frequency of files / menu items ==> better prediction For WWW: inline images increase avg. size Network tracing, monitoring Monitoring devices Usage logs: well-known ports... Mailing-lists, mail archives...

73. Institute for Visualization and Perception Research 73 © Copyright 1998 Haim Levkowitz Usage logs: well-known ports... FTP (data connection): 20 FTP (control connection): 21 Gopher: 70 Z39.50 (WAIS protocol): 210 HTTP (WWW protocol): 80

74. Institute for Visualization and Perception Research 74 © Copyright 1998 Haim Levkowitz Mailing-lists, mail archives... Hard to predict size No dedicated out port: unreserved, > 1023 Hard to monitor Hard to separate In port 25, but can't separate types Best way: syslog file Mailing-lists... Archives...

75. Institute for Visualization and Perception Research 75 © Copyright 1998 Haim Levkowitz Mailing-lists... Very little reply traffic Other traffic can be substantial

76. Institute for Visualization and Perception Research 76 © Copyright 1998 Haim Levkowitz Archives... Huge amounts of reply No effective limit No good way to predict avg. response size

77. Institute for Visualization and Perception Research 77 © Copyright 1998 Haim Levkowitz Computational load... More guessing game Monitor trend in peak load average As service grows in popularity Predict need for faster machine early Mailing-list... Mail-based archive... FTP, Gopher, WWW... WAIS...

78. Institute for Visualization and Perception Research 78 © Copyright 1998 Haim Levkowitz Mailing-list... Servers don’t require much CPU Simple op’s on aliases file Not much network traffic Lists can be CPU intensive, depending on size of list and message sendmail: no efficient sending of thousands of messages at same time

79. Institute for Visualization and Perception Research 79 © Copyright 1998 Haim Levkowitz Mail-based archive... Lots of CPU time in File transfers Processing of files transferred Mailing those files

80. Institute for Visualization and Perception Research 80 © Copyright 1998 Haim Levkowitz FTP, Gopher, WWW... CPU consumption proportional to Number of queries received Size of files processed FTP bogging down processors Wash U. FTP: special features to limit access, set of number users WWW demanding because of inline images

81. Institute for Visualization and Perception Research 81 © Copyright 1998 Haim Levkowitz WAIS... Most demanding Search Open index files Compute scores (match search criteria) Other non-trivial tasks ==> Per-query load high No way to control access based on sys load Need fast processor to save large WAIS db

82. Institute for Visualization and Perception Research 82 © Copyright 1998 Haim Levkowitz Disk space... At least enough for all files offered Extra overhead WAIS... Mail server... Other services requirements insignificant But if multiple, might need as many copies of data as number of services FTP copy, Gopher copy, WWW copy, etc.

83. Institute for Visualization and Perception Research 83 © Copyright 1998 Haim Levkowitz WAIS... Index files as large as data files ==> Consume 2 x data

84. Institute for Visualization and Perception Research 84 © Copyright 1998 Haim Levkowitz Mail server... Header + bodies in mail queue directory ==> Lots of space More significant with mail-based archive servers Large mail messages E.g., uuencoded split binaries

85. Institute for Visualization and Perception Research 85 © Copyright 1998 Haim Levkowitz Human requirements... Understand material offered How to structure intuitively and effectively Constantly update, add new, check integrity of links “System guru” not necessarily same as “contents guru” (librarian) Librarian’s duties... Librarian’s desirable qualifications...

86. Institute for Visualization and Perception Research 86 © Copyright 1998 Haim Levkowitz Librarian’s duties... Author & format info Meta-info: FTP README, Gopher menus,... Collect & distribute info from other sources Keep up-to-date Provide & maintain links to other info resources Respond to user requests for help

87. Institute for Visualization and Perception Research 87 © Copyright 1998 Haim Levkowitz Librarian’s desirable qualifications... User-interface experience Familiarity with subject & audience Ability to navigate the Internet Find new info resources to point to Check integrity of links Good people skills for customer service

88. Institute for Visualization and Perception Research 88 © Copyright 1998 Haim Levkowitz Finger-, Inetd-, and Telnet- based services

89. Institute for Visualization and Perception Research 89 © Copyright 1998 Haim Levkowitz FTP Setting up an FTP archive The WU archive FTP daemon Maintaining and FTP archive

90. Institute for Visualization and Perception Research 90 © Copyright 1998 Haim Levkowitz WAIS Creating and Internet database server with WAIS Creating WAIS sources with waisindex

91. Institute for Visualization and Perception Research 91 © Copyright 1998 Haim Levkowitz Gopher Introduction Compiling the server Managing the server Preparing Information Linking services together Incorporating databases Veronica and jughead Gopher+ forms and other new features

92. Institute for Visualization and Perception Research 92 © Copyright 1998 Haim Levkowitz World-Wide Web Introduction to the World-Wide Web Setting up a Web server Authoring for the Web Gateways and forms Access control and security

93. Institute for Visualization and Perception Research 93 © Copyright 1998 Haim Levkowitz Email services Introduction Simple mailing lists Automating mailing list with majordomo The majordomo list owner and moderator

94. Institute for Visualization and Perception Research 94 © Copyright 1998 Haim Levkowitz Security Firewalls and information services xinetd Legal issues Protecting intellectual property

95. Institute for Visualization and Perception Research 95 © Copyright 1998 Haim Levkowitz Future topics and research opportunities New & improved Authentication, verification, and other security schemes Information encryption/decryption Secure fund transfers Etc. Contents quality visualization and assessment New and improved information search and exploration schemes Image and other high bandwidth transfer New interaction paradigms Automatic contents control E.g., parents' control of children's access Web site traffic assessment (beyond simplistic ``hit'' counts). Other topics