A Global Network of Networks

     Began with Defense Dept. ARPANET (Advanced Research Projects Agency)

          Designed to survive bomb attacks

          Distributed control, Expandable

     Now contains many more networks:

                                     EARN (European)
                                     NYSERNET (New York)

     Millions of Computers, Hundreds of millions of Users (and growing fast!)

A Packet Switched Network--
                           Like Postal System

                           Not Like Telephone System (Circuit Switched)

     Messages broken up into packets (like envelopes)

     |  Err. Detect |       Data             |   Header    |
     |  (Chk. Sum)  |                        | (Addresses) |

Computer Node Addresses:

  IP (Internet Protocol): 32 bit numeric address in 4 fields:   (HCI Risc Machine)
           |      |
       network  computer
    (City/State) (Street)

  TCP (Transmission Control Protocol):

         Send Site--Breaks message into packets

         Receive Site--Collects & Reassembles packets in proper order

                       2                      4
          1-------------\                     |


Domain Names: Synonyms for IP Addresses
         |                    |
    individual              largest
     machine                 domain

  Common High-level domain names:
                               com: commercial
                               edu: educational
                               gov: government
                               mil: military
                               org: other organization
                               net: network resources
                               -- : country name

Programs (Network Software):

  Client/Server Model

      Client Program -- seeks a service from remote computer
      Server Pgm. -- provides a service to a client running on a remote comp.

           Print Server
           File Server
           X Server (different)

  Information Server:

           Program that handles requests for information
                e-mail:   mail service
                telnet:   remote logon service
                ftp:      file transfer service
                gopher:   net browsing service
                archie/veronica: automated net search services
                WAIS:     automated file content search service
                Net News: network bulletin board service
                WWW:      hypermedia access to internet
                Mosaic:   graphical browser of WWW

E-mail--electronic mail client/server

     % elm
     % mail
     % pine

telnet--a remote logon client (you need an account on remote machine):

     % telnet  domain-name-or-address

        Provide logon ID & password
        session with remote machine

     % logout

ftp--file transfer protocol (many "anonymous" ftp servers
---                          provide access to public files)

     % ftp  domain-name-or-IP-address

     ftp>  name (anonymous)
     ftp>  password (your e-mail address if anonymous)


                ls     short remote directory listing
                dir    long remote directory listing
                cd     ;change remote directory
                lcd    ;change local directory
                !      ;"Bang"--rest of command interpreted as local command
                bin    ;set file transfer mode to binary
                ascii  ;set file transfer mode to text (default)
                get source-file [dest.-file]   ;download
                put source-file [dest.-file]   ;upload
                mget list-of files             ;download multiple files
                mput list-of files             ;upload multiple files
                pwd     ;display current remote directory
                help command-name
                close/quit/bye                 ;terminate ftp session

  Compressed files and ftp:

     File Extension      compress pgm.      uncompress pgm.

         .Z                compress             uncompress
         .gz               gzip                 gunzip
         .z                pack                 unpack
         .ZIP (DOS)        pkzip                pkunzip

  Moving directories (many files):

        %  tar -cf  xxx.tar       ;create archive of child directory
        %  compress xxx.tar       ;replace with compressed file xxx.tar.Z

        %  ftp machine-that-has-compressed-file
        ftp> get xxx.tar.Z
        ftp> quit

        %  uncompress xxx.tar.Z   ;uncompress the file
        %  tar -tf xxx.tar        ;display table of contents of archived file
        %  tar -xf xxx.tar        ;extract directory from archived file

  Sending Binary Files (executables, images, etc.) by e-mail

        %  uuencode filename < filename > temp   ; encode as text file
        Mail it
        Save it from your mailer (s command) & quit
        %  uudecode temp                         ; decode back to original

Gopher--a network browsing service

    Navigate through menus
    Response to an entry--a new menu or a text file of information
                          Each item may be a menu or file
                          suffix specifies what
                                / ==> directory
                                <?> ==> searchable


    gopher              ;gives menu of local gopher server
    gopher server-name  ;connect with a known gopher server

    =     ;reveal ftp site of current item
    s     ;save
    u     ;up to previous menu
    q     ;quit
    >     ;next page (multiple page menus)
    <     ;previous page (multiple page menus)
    a     ;add bookmark (to get to current menu fast in future)
    v     ;view bookmarks

Archie--An automated network search tool
            Search all directories of files available by ftp
            25 archie servers worldwide

  Use of archie:

      (a) use binghamton gopher menu (7 --> 5 ---> to archie server)
      (b) telnet to an archie server (logon: archie)
      (c) e-mail to archie@archie-server; search commands in message

           show [variable-name]
           set variable-name value
           find search-string       ;searches for file-name w/ search-string
           prog search-string       ;same as find
           whatis search-string     ;searches descriptive database (keywords)
                                    ;returns file name

  Important variable:
           'search' (type of search)--default is usually 'exact';
           better to use 'substring' search;

           archie> set search sub
           archie> find search-string

Veronica--Very Easy Rodent-Oriented Net-wide Index to Computerized Archives

  Automated searches of all menu items on all Gopher servers

        archie           veronica
      -----------  =  --------------
       ftp files       gopher menus

  Use of Veronica:

       binghamton gopher menu (7 --> 5 ---> to veronica server)

       prompts for a search string

       enter search-string and embedded commands

       returns a gopher menu

       can do Boolean searches (AND, OR, NOT, combinations)

WAIS--World Area Information Service
      Search full text of all documents (files) in a data base
      Examine CONTENTS of files


    Need to connect to a WAIS server with a WAIS client

    Binghamton gopher menu (7 --> 5 --> 1)

Network News--Subscribe to news groups & participate in discussions

    Thousands of news groups covering many areas of interest

    Some major news groups:

       Use a newsreader client--
                          tin (bingsuns)
                          xrn (hcirisc)

       First time you run client, a .newsrc file is set up for you
       specifies available newsgroups
       After newsgroup name:
                             ! ==> unsubscribed
                             : ==> subscribed